Progress in the control of viral hepatitis: Memorandum from a WHO Meeting*

Memorandarare state- Les Mimorandw I ments concerning the exposent les conclu- MemtZGltloranda conclusions or recom- sions et recomman- mendations of certain dations de certaines WHO scientific meet- reunions scientifiquesM~~~m~orandu s ings: they are signed de l'OMS; ils sontby the participants in signe s par les partici- the meeting. pants d ces riunions. Bulletin of the World Health Organization, 66 (4): 443-455 (1988) © World Health Organization 1988 Progress in the control of viral hepatitis: Memorandum from a WHO Meeting* Viral hepatitis is a major public health problem in all parts of the world, with hepatitis B (HB) as the most important of all the viral hepatitides. It is estimated that worldwide there are nearly 300 million carriers ofHB markers of active infection. More than 40% of persistently infected persons who survive into adult life will die of the consequences of HB, such as cirrhosis and hepatocellular carcinoma. The vaccines available against HB have an impressive record ofsafety and efficacy, and the best means ofcontrolling the infecion on a global scale, including the reduction ofmortality due to its sequelae, will be by mass immunization of infants. In areas where most infections are acquired early in life the vaccine should be administered shortly after birth, and HB immunization should be integrated into the Expanded Programme on Immunization. Progress has been made also in developing hepatitis A vaccines and in isolating the agents that induce hepatitis non-A non-B. The third meeting of the WHO Technical Advisory Group on Viral Hepatitis was held in Geneva from 2 to 5 November 1987. The purpose of the meeting was to review the WHO programme on control of viral hepatitis and the progress made in implementing the recommendations of the second meeting of the Group held in Geneva, in December 1985 as well as to formulate a plan of further action. WHO REGIONAL REPORTS African Region The epidemiology of hepatitis A (HA) and hepatitis B (HB) in Africa is sufficiently well understood to allow the establishment of nationally based control * This Memorandum is based on a report (document WHO/ MIM/HEP/87. 1) which was drafted by the participants at a meeting of the Technical Advisory Group on Viral Hepatitis. The names of the participants are listed on pages 453-454. Requests for reprints should be sent to: Chief, Microbiology and hmmunology Support Services, World Health Organization, 1211 Geneva 27, Switzer- land. A French translation of this Memorandum will appear in a later issue of the Bulktin. programmes. Infection with HA virus (HAV) usually occurs early in life and is subclinical; although the majority of the population is exposed to the virus before the age of 10 years, the symptomatic disease is relatively uncommon. Since HA is an acute self- limiting disease, immunization is likely to have a low priority in Africa, and the major emphasis of control programmes is on traditional public health measures, such as provision of clean water and adequate dis- posal of sewage. Viral HB is hyperendemic in Africa, where an estimated 50 million people are chronically infected, and many studies indicate that chronic in- fection with HB virus (HBV) is frequently associated with the development of chronic liver disease and hepatocellular carcinoma. Recently a number of studies have been undertaken in Africa to assess: -the optimal doses and routes of administration of HB vaccine; -the most cost-effective means of controlling infec- tion; and -whether HB vaccine can be administered simul- taneously with diphtheria-pertussis-tetanus (DPT), 4900 443- MEMORANDUM polio, and yellow fever vaccines, and whether it can be incorporated into the activities of the Expanded Programme on Immunization (EPI). With the exception of an externally funded scheme in Gambia, HB immunization programmes are vir- tually non-existent in Africa, and, in an attempt to stimulate activity, a WHO Task Force on Viral Hepatitis in Africa has been established. There is relatively little information on the epi- demiology of hepatitis delta (HD) and hepatitis non-A non-B (HNANB) infections in Africa. In five countries, among 1000 individuals who were positive for hepatitis B virus surface antigens (HBsAg) (most of whom were asymptomatic) the prevalence of HD markers ranged from 3% to 31 %. Also, HNANB is estimated to account for 8-38% ofcases of acute viral hepatitis throughout Africa. In contrast, the propor- tion of enterically and parenterally transmitted viral hepatitis is unknown. Enterically transmitted viral hepatitis non-A non-B has been reported from several countries of the African Region. Region of the Americas Although viral hepatitis is a major public health problem in the Americas, in many countries the full impact of the disease has not been determined. Throughout the Region, HA is generally a disease of childhood, with the exception of Canada, some of the Caribbean Islands, Chile, and the USA, where infection tends to be acquired during early adult life and is associated with significant morbidity. Outbreaks of HA have been reported from several countries, including Argentina, Brazil, Costa Rica, and Panama. The prevalence ofHB infection in the Region varies from low, in temperate North and South America, to moderate in tropical Central and South America, and is high in most parts of the Amazon Basin, His- paniola, Saint Kitts and Nevis, and in parts of Colombia, Peru, and Venezuela. In these areas, transmission presumably occurs during the perinatal period and childhood. Fulminant and chronic hepatitis caused by hepatitis delta virus (HDV) produces high mortality in some areas of Brazil (Amazon Basin), Colombia (Santa Marta region), Venezuela (Yucpa Indians), and Peru. Parenterally transmitted hepatitis non-A non-B (HNANB(P)) is present throughout the Region and is an important cause of acute hepatitis in adults. Two outbreaks of enterically transmitted hepatitis non-A non-B (HNANB(E)) occurred in neighbouring rural towns of Mexico in 1986, and immune electron microscopy studies of the virus-like particles re- covered from the stools of the Mexican patients indicated that they were similar to those isolated from Asian and African patients with the same disease. National hepatitis committees have been estab- lished in several countries of the Region to assist the health authorities to identify priorities and monitor control activities. Two vaccination projects will begin soon in HB- hyperendemic areas, one of which, in Saint Kitts and Nevis, will include evaluation of the immuno- genicity of alternative dosages and routes of admini- stering HB vaccine among infants and children. The second such immunization programme will be in the region of Sierra Nevada de Santa Marta, Colombia. Eastern Mediterranean Region In this Region, progress has been made in defining the epidemiology of viral hepatitis and the extent of the problem, but control programmes are either non- existent or in the early stages of development. HA appears to be hyperendemic, but as in many other Regions, infections are acquired early in life and are usually subclinical. HB is also hyperendemic, with HBsAg being detected in 2-10% of adults. The sequelae of chronic HB infection (chronic liver dis- ease and hepatocellular carcinoma) are common and well recognized. Infection with HDV is also wide- spread and thought to play an important role in the etiology of chronic liver disease in some countries. In recent years, HNANB(E) has been recognized and two major outbreaks have occurred among Ethiopian refugees in Somalia and among Eritrean and Tigrian refugees in eastern Sudan. Also, between January 1985 and September 1986, some 2000 cases occurred in refugee camps in Somalia, mainly among adults, resulting in 87 deaths, almost half of which were of pregnant women. The pattern was similar in the Sudan, beginning about 6 months after the onset of the rainy season. European Region In the European Region, viral hepatitis continues to be a serious public health problem and it is estimated that there are more than 600 000 cases per year, with an incidence ranging from 10 to 300 per 100 000. Despite this and the availability of safe, effective vaccines against HB, few countries take the problem seriously and fewer still have implemented control strategies. Different patterns of infection are seen in different parts of the Region, e.g., whereas antibodies to HAV are almost universal among adults in southern and eastern Europe, infection is relatively uncommon in northern and western Europe. In Scandinavia, HA is almost unknown except among travellers, whilst in 444 CONTROL OF VIRAL HEPATITIS parts of southern Europe the annual incidence of the disease is 100 cases per 100 000 people. The pattern of HB infection has not changed sig- nificantly over the past 2 years. In particular, the availability of HB vaccines has not resulted in a marked reduction in the incidence or distribution of cases, largely because the vaccine has not been administered to those most at risk. It is probable that some of the measures being introduced to reduce the transmission of AIDS (acquired immunodeficiency syndrome), e.g., improved quality of blood and blood products, use of sterile needles and syringes, and more frequent use of condoms, will reduce also the transmission of other blood-borne infections such as HB and HNANB(P). While approximately 15% of all hepatitis cases admitted to hospital in the Euro- pean Region appear to be caused by HNANB, the proportions transmitted enterically or parenterally are not known. Reduction in the incidence of HB has occurred in some countries following the introduction of immuni- zation programmes for risk groups. Furthermore, at least one country has set up a public sector pro- gramme to test all pregnant women for HBsAg and immunize all babies born to HBsAg-positive mothers with human HB immunoglobulin and vaccine, as well as offering, free of charge, testing for HB immunity and immunization of risk groups, including medical and dental personnel and students. South-East Asia Region While infection with HA is endemic throughout countries of the Region, the disease is relatively uncommon except among visitors. In contrast, HB is a major public health problem in most parts of the Region and a significant cause of morbidity and mortality. Indonesia and Thailand have begun to develop national programmes and are about to com- mence pilot immunization projects. A regional meeting held in New Delhi in December 1986 re- viewed the available information and made a number of recommendations. Several outbreaks of HNANB(E) have been docu- mented in Burma, India, and Nepal over the last 10 years, while sporadic cases, with the same epidemi- ological and clinical characteristics, have been recognized during the interepidemic periods. This type of hepatitis is common in India, accounting for the majority of the epidemics of the disease recorded since 1955 and for more than 50% of sporadic outbreaks in adults and about 25% of those in chil- dren. Outbreaks ofHNANB(E) have also been identi- fied in Indonesia and Nepal, and a WHO-supported multicentre study on the epidemiology of this type of hepatitis has just commenced. Western Pacific Region This Region has an active programme for the con- trol of viral hepatitis, focused mainly on efforts to control infection with HBV. Catalysed by a Regional Task Force, which has met annually since 1983, control programmes have been commenced in 14 countries of the Region and HB vaccine is being produced locally. Also, the WHO Regional Office is examining ways in which it can facilitate buying large quantities of HB vaccine so that Member countries can obtain the benefits of bulk purchasing. In some countries where local production of the vaccine is not feasible, a pilot project has been developed in which HBsAg-positive plasma is collected and forwarded to the WHO Collaborating Centre for Reference and Research on Viral Hepa- titis, Tokyo, Japan, to be made into vaccine. This process also provides a means of transferring tech- nology on blood collection, blood testing, and sterile procedures to developing countries. Because of similarities in the epidemiology of HB and infection with human immunodeficiency virus (HIV) and human T-cell lymphotropic virus type 1 (HTLV-1), and since each resultant disease requires common epidemiological skills, surveillance systems and laboratory support, the Regional Office is attempting to develop common strategies for sur- veillance and diagnosis. The first laboratory training programme for the diagnosis of HBV, HIV and HTLV-1 infections was held in Tonga in November 1987. HEPATITIS A VIRUS HAV is a picornavirus that is difficult to isolate in cell culture, grows poorly in early in vitro passages, and generally is not cytopathogenic. The genome of the virus has been cloned and sequenced, and only! one serotype has been identified. The virus has a worldwide but nonuniform distribution, and gen- erally causes less severe disease than some of the other hepatitis viruses, e.g., HBV. Although infec- tion with HAV never becomes chronic, it is the cause of significant human morbidity and loss of productivity, and approximately 25% of cases of clinical hepatitis in many developed countries and up to 80% in certain areas are caused by such infections. HA infection has diminished in importance in many industrialized countries, largely as a result of im- proved sanitation, but it remains a problem among certain groups. These include the staff of day-care centres and nurseries that care for infants, the parents of such infants, residents of institutions, the military, and travellers to regions where HAV is endemic, male homosexuals who change sexual partners frequently, 445 MEMORANDUM and users of intravenous drugs. In contrast, the infection continues to be endemic in many developing countries and, like other enterically transmitted viruses, infects almost 100% of the population aged 5-10 years in some countries. Such infections are often unrecognized, because HA is milder in infants and children than in older individuals. However, as sanitary conditions improve in such countries and the average age ofexposure to HAV increases, a para- doxical increase in clinical HA is usually observed. For these reasons, there will be a need for pro- phylaxis against HA for the forseeable future. Passive immunoprophylaxis (administration of human im- munoglobulin prior to or shortly after exposure) is effective, but of only temporary benefit, and active immunization would be a more practical approach to the control of the infection. Considerable progress has been made in the devel- opment of HA vaccines and conventional inactivated and live-attenuated vaccines have been prepared from HAV replicated cell culture. The safety and efficacy of both types of vaccines have been demon- strated in nonhuman primates and preliminary clini- cal trials in man have begun. Inactivated vaccines are likely to be the first to be available for general use. Unfortunately, however, markers of attenuation do not exist for candidate live virus vaccine strains, since these would be helpful for monitoring safety and transmissability during field studies. Recombinant DNA technology is being applied to develop alternative approaches to the development of HA vaccines. These approaches include expression of viral antigens in vitro, the use of live virus vectors for expression of viral antigens in vivo, and the production of synthetic peptides representing gene products of the virus. Because the important epitopes for neutralization of the virus appear to be conforma- tional rather than linear, further research will be necessary before hepatitis A vaccines based upon these new technologies become available. The HAV genome has been cloned and sequenced, infectious cDNA clones prepared, and the molecular basis of virulence and attenuation of such cloned viruses is currently being examined. In the future, it may be possible to further modify conventional live vaccines by recombinant DNA technology to yield virus strains with the desired characteristics. HEPATITIS B VIRUS HB infection and its sequelae, which include chronic persistent HB, chronic lobular HB, chronic active HB, cirrhosis, and hepatocellular carcinoma, remain a major public health problem. Persistent infection (the carrier state) constitutes the infectious reservoir or pool, with 0.1 % to 15% or more of the general population being involved in some Regions. It is estimated that worldwide there are nearly 300 million actively infective carriers of HB markers. The importance ofHB is stressed by the fact that more than 40% of persistently infected persons who survive into adult life will die as a consequence of their infection. Furthermore, more than one million children born in 1985 in HB-endemic areas will probably die from liver disease sequelae. 7he role of the pre-S domain of hepatitis B virus in the pathogenesis of liver damage and in protective immunization Studies of small laboratory animals have shown that the pre-S2 sequences of HBV can be more im- munogenic than the S-protein and that the antibody to pre-S sequences is elicited more rapidly than the response to S-protein. In addition, immunization of chimpanzees with a pre-S2 peptide resulted in protection to challenge with live HBV. Approximately equal levels ofantibodies to the pre- S2 region of the HBV envelope protein and to human serum albumin (HSA) have been reported in the sera of patients with acute or chronic HB infection. It has been proposed that anti-HSA antibodies arise as a result of an immune response to the pre-S2 sequences and that these antibodies are involved in hepato- cellular damage during HB infection. However, im- munization with the native pre-S2 sequence or with unconjugated synthetic peptides derived from that sequence does not result in the production of anti- HSA. In addition, when linked to certain carriers, but not to others, some synthetic peptides, irrespective of whether or not they are derived from the pre-S2 sequence, elicited an anti-HSA response in rabbits. These anti-HSA antibodies can be separated from anti-pre-S-specific antibodies by affinity chromato- graphy. The production of anti-HSA was restricted to certain synthetic peptide-linked-carrier combinations but not to the pre-S2 regions of the HBV envelope protein reported to be involved in the recognition of glutaraldehyde-polymerized serum albumin. The results of many studies indicate that glutaral- dehyde-polymerized HSA is not a host "self" com- ponent, although HSA and polymerized HSA (pHSA) have been considered to be associated with liver cell receptor sites for HBV; however, such an association cannot be relevant to the biology of HBV because of the need for the polymerization step. Indeed, studies indicate that the viral binding site for host cellular receptors is located in the pre-Sl domains. It has been suggested that the specificity of the assay for the detection of anti-HSA in serum is an artefact that arises because of the presence of IgG-coated virions 446 CONTROL OF VIRAL HEPATITIS in serum that can bind to solid-phase albumin. Fur- thermore, the association between anti-pre-S2 anti- bodies and persistent carriage of HBV has not been confirmed independently. In conclusion, there are no valid reasons for omitting pre-S2 proteins from future HB vaccines, which must be evaluated in controlled clinical trials. Hepatitis B virus and hepatocellular carcinoma Hepatocellular carcinoma is one of the 10 most common cancers in the world, and one of the most prevalent in developing countries. For example, in some parts of Asia and Africa, the age-adjusted incidence of the condition is over 30 cases per 100 000 population per year, whereas it is less than 5 cases per 100 000 per year throughout most of Australia, Europe, and North America. The disease is more common in males than females and its incidence increases with age. However, in certain populations, it also occurs in younger age groups. Hepatocellular carcinoma is strongly associated with chronic HB infection, and in a prospective study of Taiwanese men the relative risk of the carcinoma was 100 times greater for carriers than for non- carriers. The association between hepatocellular carcinoma and HBsAg is especially strong in areas where the HBsAg carrier rate is high, such as in Asia and Africa, and where infection occurs early in life. Macronodular cirrhosis also follows chronic infection with HBV and approximately 85% of cases of hepatocellular carcinoma involve individuals with cirrhotic livers. The seroepidemiological associ- ation ofHBV and hepatocellular carcinoma has been supported by laboratory studies of cell lines devel- oped from such tumours and by investigation of the tumours themselves using molecular biology techniques. Integrated HBV viral genome has been detected in liver tissue obtained from patients with hepatocellular carcinomas from many parts of the world. In areas with a high prevalence of both HBsAg carriers and hepatocellular carcinoma, at least 80% of tumours from HBsAg-positive patients contain integrated hepatitis B virus DNA sequences. Non-tumorous liver tissue from patients with hepatocellular carci- noma may also contain such integrated viral DNA sequences, with or without replicative forms, sug- gesting that integration precedes the development of neoplasia. Hepadnaviruses have been found in at least three groups of animals, and such animal models provide further strong evidence that hepadnaviruses are onco- genic. Woodchuck hepatitis virus, ground squirrel hepatitis virus, and duck hepatitis virus are all trans- missible from mother to offspring and have a chronic carrier state. Furthermore, a high proportion of carrier woodchucks and ground squirrels develop hepatocellular carcinoma, a condition that also occurs in carrier ducks but at a lower frequency. Viral DNA is integrated into the tumour cells of all these animals. Although it is clear that the hepadnaviruses cause hepatocellular carcinoma, the mechanism of onco- genesis is not clear. Especially perplexing is the fact that integration sequences in hepatocellular carci- noma do not show any regular pattern. Important questions that remain to be answered include whether integration of the viral genome occurs during acute infection with HBV and whether the carrier state is a prerequisite for progression to hepatocellular carcinomas. Irrespective of the mol- ecular basis of the involvement of HBV in causing hepatocellular carcinoma, it is clear that a period of persistent virus infection along with the associated chronic liver disease induces the process leading to neoplasia. Thus, vaccination against HBV, an action which prevents both primary and persistent infection, is likely also to prevent hepatocellular carcinoma. Hepatitis B virus and AIDS Although human immunodeficiency virus (HIV) is the etiological agent of the acquired immunodefi- ciency syndrome (AIDS), other factors may enhance infection or the progression of the disease. Extrachromosomal sequences of HBV-related DNA have been detected in peripheral blood mono- nuclear cells (PBMC) ofHBsAg carriers, particularly those who are also positive for hepatitis B virus envelope antigen (HBeAg), a marker that correlates with virus replication. In addition, extrachromosomal molecules of HBV-related DNA of high relative mol- ecular mass have been detected in the PBMC of some HBsAg carriers and individuals who are immune to HBV. These extrachromosomal molecules appeared to be multimers of the intact HBV genome that were not undergoing active replication at the time the cells were taken from the patient. These results, as well as the similarities in the epidemiological patterns of HB infection and AIDS, have recently led to the investigation of PBMC- associated hepatitis B virus DNA in patients with AIDS and AIDS-related disorders. In the USA, HIV- infected patients have a high prevalence of PBMC- associated hepatitis B virus DNA, and investigations are under way to determine whether HBV might act as a co-factor in the development of AIDS. While there are no contraindications for immuni- zing with HB vaccine individuals who are infected with HIV, the vaccine has proved to be less immuno- genic in this group. 447 MEMORANDUM Hepatitis B vaccines and immunization strategies Over 30 million doses of plasma-derived HB vac- cine produced by more than 12 manufacturers have been distributed worldwide over the last 2-3 years. The vaccines have an impressive record of safety. In addition, several vaccines manufactured by re- combinant DNA technology are now available and additional manufacturers are expected to enter the market in the next 2 or 3 years. These recombinant DNA vaccines are equivalent to plasma-derived vac- cines in respect of safety, immunogenicity, and efficacy, and neither vaccine currently offers any advantage over the other in these respects. Plasma- derived vaccines will therefore continue to play an essential role in control programmes worldwide for the forseeable future. The price of hepatitis B vaccines has now decreased to the level where countries in hyperendemic areas can begin to develop large-scale immunization programmes. The Technical Advisory Group encourages the establishment of programmes and liaison with rel- evant groups both within and outside WHO as well as the continued and increasing close collaboration betweenWHO and such bodies in developing and im- plementing the global programme on control of HB. It was reiterated that the most important means of controlling HB on a global scale and of reducing mortality from its sequelae is mass immunization of infants. The optimal strategy for this will vary from country to country, depending on the pattern of transmission. For example, in hyperendemic regions where most infections are acquired early in life, the vaccine should be administered shortly after birth and HB immunization integrated into the EPI. Immuni- zation of all infants should be considered for popu- lation groups with chronic HBV carrier rates greater than 2% and also should be a major public health priority for all infants in populations with carrier rates greater than 10%. Some countries with a lower carrier rate might opt to test all pregnant women for HBsAg and to immunize only the newborns of HBsAg-positive mothers. If use of HB vaccine is integrated into EPI, three doses should be injected intramuscularly into the thigh, the first dose being given as soon as possible after birth, concomitantly with the first EPI immuni- zation. The second dose of the vaccine should be given 4-12 weeks after the first, the timing being chosen to fit into the EPI schedule in operation. Cur- rently, administration of a third dose ofHB vaccine is recommended to achieve high levels of antibody and prolonged protection against infection. There is con- siderable latitude regarding the timing of this dose, which can be administered 2 to 12 months after the second, depending on the EPI schedule in the country. Simultaneous administration of hepatitis B IgG together with the first dose of HB vaccine results in better protection against infection than the use of the vaccine alone. However, the additional cost and logistic difficulties preclude the use of this combi- nation in most countries. The duration of protection from infection after primary immunization is not known. Although it is generally assumed that immunity persists provided the level of anti-HBsAg is at least 10 IU/1, this is probably an underestimate because immediate anam- nestic responses have been demonstrated after re- vaccination, even when anti-HBsAg was no longer detectable. The persistence of anti-HBsAg after primary immunization can be predicted from the titres of this antigen produced by the initial dose, and this is determined for members of high-risk groups in some countries. Further studies are needed to determine if and when booster immunizations should be given. The Technical Advisory Group encourages the application of operational research methods to define the optimum way of integrating HB immunization into EPI. In this respect, model immunization pro- jects, the results of which should be monitored by WHO, should be established in selected countries in hyperendemic areas in order to define the effective- ness of HB immunization in a variety of settings where different EPI schedules are used. Finally, the stability of HB vaccines should be evaluated to determine whether they can be incorporated into the EPI cold chain. Model immunization projects in China, Indonesia, and Thailand are being established in collaboration with the International Task Force on HB Immuni- zation, and WHO should assist in the evaluation of these projects on a continuing basis. International reference reagent for hepatitis B vac- cine (plasma-derived) and international standard for HBsAg (subtype ad) The international reference reagent for plasma- derived HB vaccine was established in 1986. This material is a liquid, alum-adsorbed HB vaccine that contains HBsAg purified from human plasma. The reference reagent is intended for use in immuno- genicity tests in small animals and can be used in potency tests of HB vaccine, provided parallel dose- response curves are obtained. No unitage is assigned to this preparation, but, when assayed in a suitable test, plasma-derived or recombinant vaccines from individual manufacturers should exhibit consistent potencies relative to the reference reagent. 448 CONTROL OF VIRAL HEPATMS The international standard for HBsAg (subtype ad) was established in 1985. This material contains diluted serum from a symptom-free donor who was HBsAg-positive. The serum was diluted and heated to reduce infectivity prior to freeze drying. The standard has been assigned a potency of 100 units per ampoule and can be used to determine the sensitivity of kits for the detection of HBsAg (subtype ad). In addition, the antigen content of individual sera can be expressed in IU. Also, the antigen content ofvaccines prior to adsorption to adjuvant can be expressed in IU, provided parallel dose-response curves are obtained. The above-mentioned international reference re- agents and standards are available on request from the WHO Collaborating Centre for Biological Standardi- zation, National Institute for Biological Standards and Control (NIBSC), Potters Bar EN6 3QG, Hert- fordshire, England. The NIBSC is also able to give advice on the preparation of candidate reference reagents and on the organization of appropriate col- laborative studies, which must be carried out prior to establishing international standards or reference reagents. A list of monoclonal antibodies to HBV available for collaborative research programmes is shown in Annex 1. HEPATITIS DELTA VIRUS Hepatitis delta virus (HDV) is a defective virus that requires the presence ofHBV as an obligatory helper. The HD virion measures about 36 nm in diameter, has an outer HBsAg coat, a small linear RNA genome, and a unique antigen (HDAg). The relative molecular mass of the genome is low and is similar to that of the satellite RNA viruses of plants. Diagnosis of HDV infection is based on detection ofHDAg, anti-HD, or anti-HD IgM. The presence of intrahepatic antigen can be demonstrated in liver specimens by immunohistochemical methods. The release of antigen into the blood is an event limited to the early stage of primary infection, and as a rule, HDAg cannot be detected in patients who are chronically infected with the virus. In practice, the diagnosis rests primarily on antibody testing. Two types of antibody assays have been developed, one of which is available commercially and measures the total antibody by a competitive blocking assay, while the other determines the level of specific IgM. Since the IgM assay detects antibody that does not com- pete in the blocking assay, the latter method is assumed to determine predominantly the IgG anti- body component. Since HDV requires the helper functions of HBV, individuals who are immune to the latter as a result of past infection or immunization are not susceptible to HDV. Two modes of infection are known-coinfec- tion and superinfection-and these have different clinical courses and outcomes. Coinfection occurs when there is simultaneous infection with HBV and HDV and usually results in a mild illness that does not differ clinically from infection with HB. Occasion- ally, however, coinfection may result in severe, even fulminant, hepatitis. Superinfection occurs when a carrier of HBsAg becomes infected also with HDV, and the clinical outcome is often more severe than in coinfection. Since the majority of liver cells of car- riers are colonized with HBsAg, superinfection may result in severe or fulminant hepatitis. There are several possible outcomes of superin- fection: resolution with clearance ofHDV; resolution with clearance of HDV and of HBsAg; chronic car- riage ofHDV and HBsAg -such individuals have an increased risk of developing chronic liver disease. The relative incidence of the different outcomes is unknown. Originally, infection with HDV was thought to be a regional phenomenon that was restricted to southern Italy, some other parts of Europe, and the USA. However, it has recently been recognized that such infections occur in all continents, but their frequency varies widely. Although the epidemiology of HDV infection is incomplete, the virus appears to be endemic in the Mediterranean basin, the Middle East, parts of South America, the USSR, Romania, and some Pacific islands. The southern European reservoir ofHDV infection extends from the Balkan peninsula through the east- ern Mediterranean countries to the Middle East, while in Africa the distribution appears to be irreg- ular, with high prevalences in Senegal, Gabon, Egypt, and Kenya and low prevalences in Nigeria and southern Africa. However, these differences may simply reflect limited sampling. In northern Europe, the USA, and Australia, in contrast, HDV infection appears to be confined to parenteral drug addicts, haemophiliacs and other recipients ofblood and blood products, and to be a relatively recent phenomenon. In South America, infection with HDV has been associated with severe and often fatal hepatitis. This was first demonstrated among the Yucpa Indians of western Venezuela, an indigenous population living between Lake Maracaibo and the Colombian border, and the severe hepatitis seen among these Indians appears to be due to both coinfection and superin- fection with the virus. In the Brazilian part of the Amazon basin, HDV appears to be the cause of Labrea fever, a form of fulminant hepatitis that affects children and adults. More recently, the virus has also been identified as 449 MEMORANDUM the etiological factor responsible for the fulminant hepatitis in a number of communities in the Sierra Nevada de Santa Marta of northern Colombia. PARENTERALLY TRANSMITrED HEPATITIS NON-A NON-B This infection is probably very common in devel- oped countries and is estimated to account for more than 70% of post-transfusion hepatitis in many countries. The agent or agents responsible have, nevertheless, not been identified. Acute infection is usually associated with mild (or subclinical) disease, with an incubation period of 5-12 weeks, and is frequently followed by development ofa carrier state. Prospective studies of patients who have developed parenteral hepatitis non-A non-B (HNANB(P)) fol- lowing blood transfusion suggest that chronic ALT elevations may occur in up to 40-50% of them, while 10-25% may develop cirrhosis. No specific diag- nostic tests exist, and there is no good evidence for the value of hepatitis non-A non-B IgG in prophylaxis. HNANB(P) is the commonest form of post-trans- fusion hepatitis in most developed countries and may account for more than 90% of cases. Prospective studies in the USA in the 1970s and in Europe in the 1980s indicated that 6-12%96 of recipients of multiple units of volunteer donor blood developed post-trans- fusion hepatitis. In the USA alone, some 150 000 to 300 000 infections are estimated to occur annually, while the prevalence of chronic carriers of the etiologic agent may exceed 1 %. In some countries, most haemophiliacs who require regular infusions of clotting factors also appear to have been infected with the virus. The risk is highest with commercial Factor vm concentrates, but exists even with con- centrates and cryoprecipitates prepared from volun- tary donors. The annual attack rate in haemophiliacs is 2-6%, while second attacks have been documented and may represent re-infection. Many of the episodes of HNANB(P) among dialysis and transplant patients are probably trans- fusion-related, but, once infection is established in a hospital unit, there is considerable potential for spread. The annual incidence of such acute infections among U.S. dialysis patients is 3-6%, while the incidence among staff is 1%. HNANB(P) probably causes the majority of episodes of acute and chronic hepatitis among renal transplant patients. The existence of multiple agents for HNANB(P) is suggested by the occurrence of multiple episodes of biopsy-proven acute hepatitis in some patients, and by the variation in incubation periods observed in some studies of chimpanzees. However, the results of challenge studies are difficult to interpret in the absence of specific laboratory tests. One presumed agent for HNANB(P) is chloroform sensitive and appears to have a diameter of 30- 60 nm, suggesting that it may be a togavirus, hep- adnavirus, delta-like virus, or a new class of agent. The agent has a buoyant density of approximately 1.12-1.14 g/cm3 in sucrose, which is consistent with it being a member of the non-anthropod-borne toga- viruses, a diverse group of small, lipid-containing RNA viruses. Nucleic acid hybridization assays have largely excluded the possibility that the major agent of the infection is either hepadnavirus-like or closely related to HDV. So far, a laboratory assay has not been developed that is capable of distinguishing HNANB(P)-infec- tious sera from control sera in coded panels, because either the level of HNANB(P) antigen present is too low to be detected (in chimpanzee studies, most infec- ted sera have infectivity titres < 102) or most persons develop chronic infection owing to the lack of anti- body production. Two surrogate markers have been proposed to detect HNANB(P)-carriers-ALT and anti-hepatitis B core antigen (anti-HBcAg) -and two U.S. studies have demonstrated a significant association between elevated donor ALT levels and the occurrence of HNANB(P) in recipients. Both of the latter studies predicted an approximate 30% reduction in the number of cases of HNANB(P) if blood from donors with elevated ALT levels were rejected; this would, however, reduce the donor population by 2-3 %. A similar analysis showed a relationship between the presence of donor anti-HBcAg and the occurrence of recipient HNANB(P). It appears that such testing for anti-HBcAg can detect populations that are also at increased risk of infection with HNANB(P); how- ever, screening for anti-HBcAg would exclude 2-6% of the blood donor population in developed countries. Stimulated by increasing evidence for the severity of chronic HNANB(P) infection and fear of patient litigation, a major debate in many countries centres on whether one or both these tests should be adopted until a specific HNANB(P) virus assay is available. In this respect, prospective studies of the incidence of HNANB(P), which are under way, should demon- strate whether screening donors for anti-HBcAg and for anti-HIV antigen results in a significant reduction in the incidence of HNANB(P). ENTERICALLY TRANSMITTED HEPATITIS NON-A NON-B This form of viral hepatitis, which has caused large outbreaks of disease in Africa, the Indian subconti- 450 CONTROL OF VIRAL HEPATITIS nent and other parts of Asia, and North America, is serologically unrelated to infection with the more commonly described HAV and HBV. The term "enterically transmitted HNANB" (HNANB(E)) derives from the waterborne or faecal-oral route and presumed enteric route of natural infection in man. HNANB(E) was first documented in New Delhi in 1955-56, when 29 000 cases of icteric hepatitis were estimated to have occurred after widespread faecal contamination of the city's drinking water. HNANB(E) has subsequently been shown to occur in epidemic or sporadic endemic forms in many countries. Characteristic clinical features of this disease include a high attack rate among adults and a high case fatality rate (average 20%) among pregnant women. Several laboratories have detected 27-34-nm diameter virus-like particles in the faeces of patients with HNANB(E). The specificity of these particles for HNANB(E) has been inferred from the results of immune electron microscopy studies on pre-infec- tion, acute-phase, and convalescent-phase sera from humans and experimentally infected primates (see below). The major agent of human HNANB(E) appears to be a virus-like particle that is approxi- mately 32 nm in diameter that sediments in sucrose gradients at 183 S. Furthermore, immune electron microscopy studies conducted in several laboratories suggest that acute-phase sera from patients with HNANB(E) readily aggregate these virus-like par- ticles; however, less consistent aggregation of the particles is observed when early or late convalescent- phase sera are used. These findings suggest that, whereas in most cases a vigorous acute-phase (IgM) antibody response is observed, in some convalescent- phase sera the antibody may be less avid. Also, cross- reactivity with acute-phase sera obtained from patients involved in outbreaks in Algeria, Burma, Gambia, India, Nepal, North America, Pakistan, Somalia, Sudan, and the USSR has been demon- strated for virus-like particles recovered from the stools of patients in Burma, India, Mexico, Pakistan, Somalia, and the USSR. These data strongly suggest that one virus or virus class is responsible for most cases of HNANB(E) observed worldwide. Primate-transmission studies indicate that about a dozen species, including tamarins, cynomolgus macaques, African green monkey, and possibly chimpanzees and rhesus monkeys, are susceptible to infection with the virus(es) that cause human HNANB(E). Also, immune electron microscopy studies of early- or pre-acute phase stools from some infected primates have revealed virus-like particles of 27-34 nm diameter, while cynomolgus, African green monkeys, tamarins, and chimpanzees develop antibodies to such particles in inocula -a finding that is consistent with an etiological relationship between these particles and the human disease. Serial passage of disease has been accomplished with cynomolgus monkeys and tamarins, and a serological relationship to disease-associated virus-like particles of27-34-nm diameter has been demonstrated by immune electron microscopy using pre-inoculation and acute or con- valescent sera. Antibodies have also been detected in some wild-caught cynomolgus monkeys. Preliminary studies indicate that convalescent serum can be used to develop a direct immunofluor- escent assay for HNANB(E)-associated antigen in infected primate liver tissue. The results suggest that maximum synthesis or accumulation of antigen occurs just prior to the peak of liver enzyme activity. A test based on this finding is currently being used to identify high-titre convalescent sera in order to develop improved serological assays for the detection of HNANB(E) antigen in stool suspensions, liver tissue, cell culture, and recombinant expression vector systems. PROSPECTS FOR THE PROGRAMME Technological factors Hepatitis A. Significant progress has been made over the past 2 years towards the development ofHA vaccines, and both killed and live vaccines have undergone preliminary clinical testing. It is likely that vaccines will be ready for expanded field trials within the next 2-5 years. Vaccines based upon recombinant DNA technology are, however, still at the research stage. The development and evaluation of candidate HA vaccines should continue. Enterically transmitted hepatitis non-A non-B. The agent of HNANB(E) hepatitis has been tentatively identified and partially characterized: there appears to be only one serotype or group of serologically related viruses. Standardized reagents and serological tests are needed in order to better delineate the epidemiology of HNANB(E). Partial control of the disease could be achieved now by means of improved sanitation, particularly the purity of potable water. The question of whether locally produced immune serum globulin can protect against the disease could be answered by WHO-sponsored trials in endemic regions. Active immunoprophylaxis is not feasible at present, but research on the etiological agent could be furthered by encouraging collaboration between laboratories active in this area. Hepatitis B. Many of the technological impedi- ments to the control of HB have been overcome. Highly effective vaccines have been developed and 451 MEMORANDUM licensed and are now in use in many countries. Strategies for their administration on a regional basis are understood, but substantial vaccine delivery problems still remain. Although, because of tech- nological advances and competition, the price of vaccine has fallen dramatically, recognition of the need for such vaccines and for the implementation of immunization programmes, particularly through EPI, is required. Hepatitis delta. At present, control of HDV depends on control of infection with HBV, since the former virus is defective and requires the presence of the latter as a helper. If immunization against HDV can be achieved, perhaps by vaccinating susceptible persons, i.e., HBsAg carriers, with hepatitis delta antigen, WHO could be instrumental in furthering the development of practical vaccines and assisting in efficacy trials. Parenterally transmitted hepatitis non-A non-B. Control of HNANB(P) has not yet reached a suffi- cient level of technological development for WHO to make a valuable contribution. WHO operational concerns A carefully planned and innovative programme for the control of viral hepatitis will only be effective if it can be implemented. Effective implementation requires a functioning infrastructure, adequate fund- ing, and appreciation of the problem at the local level, as outlined below. Infrastructure. The following aspects were high- lighted: -Headquarters: WHO's viral disease effort is cur- rently too small to provide the personnel or financial support necessary for a viable programme. -Regional Offices: there are marked differences in the effectiveness of Regional Offices in implementing the hepatitis programmes. The reasons for this need to be determined and corrected and more efficient coordination encouraged with other priority pro- grammes e.g., Global Programme on AIDS (GPA). -Collaborating Centres: these should be re-evalu- ated in light of changing priorities and additions and deletions made as necessary. Economics and funding. Additional mechanisms for acquiring extrabudgetary funds must be found if the hepatitis programme is going to accomplish its goals. Innovative approaches to financing the pro- gramme, such as contracting for fund-raising, seem essential for its success, if not its survival. Priorities. The limited nature of WHO's current viral diseases effort (other than GPA) dictates setting rigid priorities for the hepatitis programme and limiting it initially to a small number of achievable goals as set out in the recommendations given below. Once these are selected and implemented, there must be a system of monitoring and accountability that will ensure continuing progress by identifying and removing impediments as soon as they appear. CONCLUSIONS AND RECOMMENDATIONS Following is a summary of the principal con- clusions and recommendations made by the Technical Advisory Group. 1. The Group reiterated its support for the WHO viral hepatitis programme and expressed concern that the funds which had been provided to establish the programme were exhausted. It considered it import- ant that additional funds be mobilized and that more personnel be recruited to administer the programme. In particular, the duties of the programme manager should be to: -coordinate the activities of the various Regions; -facilitate gathering and exchange of information; -assist in mobilizing funds; -liaise with other units in WHO and with groups having similar aims; and -ensure that the programme is regularly evaluated. 2. The programme manager and the WHO Re- gional Advisers in Communicable Diseases should work closely to ensure that interaction and collabor- ation occur at the regional and national levels. Whenever possible, programmes should involve two or more Regions. 3. The Group recommended further that a Steering Committee be established comprising a small number of scientists involved in HB immunization studies and WHO staff from Headquarters and the Regions. This committee would assist the WHO Secretariat in im- plementing the programme of HB control, in raising appropriate funds, and in coordinating the pro- gramme activities. 4. WHO should play a leading role in attempts to control viral hepatitis by encouraging its Regional Offices to develop programmes and by liaising with relevant groups within and outside the Organization. With regard to HB immunization, the Group stated that: -the major emphasis of the WHO programme for viral hepatitis should be prevention of infection with HBV (and hence of hepatocellular carcinoma) by immunization; 452 CONTROL OF VIRAL HEPATITIS -use ofHB vaccine should be incorporated into EPI activities; -existing HB vaccines had an excellent safety record; -a sterile syringe and sterile needle should be used with each injection of vaccine; and -because of concerns that jet injectors could act as vehicles for transmission of blood-borne infections, the use of such injectors for mass immunization should be discouraged. 5. The Group believes that WHO has a special responsibility to: -review data and issue authoritative statements that will assist public health authorities to develop rational policies for control of hepatitis; -stimulate and support operational research that would not otherwise be undertaken; -identify the need for and develop standards and requirements for hepatitis antigens, antibodies, and vaccines; -assist Member countries in obtaining or producing diagnostic reagents for hepatitis; -develop mechanisms for bulk purchase of hepatitis vaccines and diagnostic reagents; and -assist in the transfer of technology. 6. The Group recommended that WHO: -locate and obtain access to extrabudgetary funds that can be used to assist the development of control programmes; -encourage interregional cooperation either through the WHO network or by collaboration with other bodies with common aims; -sensitize key personnel in national health authori- ties about the importance ofHB control programmes; -identify and work with key people in each Region who can assist in the development and implemen- *tation of control programmes; and -regularly analyse the impact of the programmes, identifying the reasons for success and causes of failure, and review its strategies accordingly. 7. The Group identified several projects in which WHO could play a coordinating role. These include: -organizing studies to determine whether locally produced human normal immunoglobulin can prevent HNANB(E) and/or reduce the impact of this disease in pregnant women; - arranging and coordinating studies to evaluate the importance of new candidate HNANB agents (when- ever possible, these studies should be undertaken through the existing network of collaborating centres and national reference laboratories); -developing protocols for the control and evaluation of hepatitis vaccines; -determining whether self-exclusion and screening of blood donors for anti-HIV antibodies has had any impact on the incidence of post-transfusion HNANB(P); and -encouraging studies to define the natural history ofHNANB(P), in particular the conditions leading to the development of clinically important chronic liver disease and/or hepatocellular carcinoma. * LIST OF PARTICIPANTS Technical Advisory Group E. A. Ayoola, College ofHealth Sciences, University of Sokoto, Sokoto, Nigeria (Vice-Chairman) M. S. Balayan, Institute of Poliomyelitis and Viral Encephalitides, Moscow, USSR F. Deinhardt, Max von Pettenkofer Institute for Hygiene and Medical Microbiology, Munich, Federal Republic of Germany (Chairman) I. Gust, Virus Laboratory, Fairfield Hospital, Mel- bourne, Victoria, Australia (Rapporteur) A. W. Kureshi, Departnent of Paediatrics, Rawal- pindi Medical College and General Hospital, Rawalpindi, Pakistan J. E. Maynard, International Task Force on Hepatitis B Immunization, PATH, Seattle, WA, USA N. C. Nayak, Department of Pathology, All India Institute of Medical Sciences, New Delhi, India H. G. Schatzmayr, Department of Virology, Instituto Oswaldo Cruz, Rio de Janeiro, Brazil Hui Zhuang, Department of Epidemiology, School of Public Health, Beijing Medical University, Beijing, China Temporary Advisers R. P. Beasley, School of Public Health, University of Texas, Houston, TX, USA A. F. Blueger, Riga Medical Institute, Riga, USSR 453 MEMORANDUM D. W. Bradley, Hepatitis Branch, Division of Viral Diseases, Centers for Disease Control, Atlanta, GA, USA M. Ferguson, National Institute for Biological Stan- dards and Control, Potters Bar, England J. Melnick, Department of Virology and Epidemi- ology, Baylor College of Medicine, Houston, TX, USA R. H. Purcell, NIAID, National Institutes of Health, Bethesda, MD, USA A. J. Zuckerman, London School of Hygiene and Tropical Medicine, London, England (Rap- porteur) WHO Secretariat B. Bytchenko, WHO Regional Office for Europe, Copenhagen, Denmark C. J. Clements, Expanded Programme on Immuni- zation, WHO, Geneva, Switzerland A. Deria, WHO Regional Office for the Eastern Mediterranean, Alexandria, Egypt J. Esparza, Microbiology and Immunology Support Services, WHO, Geneva, Switzerland K. Esteves, Division of Communicable Diseases, WHO, Geneva, Switzerland Y. Ghendon, Microbiology and Immunology Support Services, WHO, Geneva, Switzerland (Secretary) V. Grachev, Biologicals, WHO, Geneva, Switzer- land P.-H. Lambert, Microbiology and Immunology Sup- port Services, WHO, Geneva, Switzerland G. M. R. Manube, representing WHO Regional Office for Africa, Brazzaville, Congo B. Parra, Division of Communicable Diseases, WHO, Geneva, Switzerland Y. Pervikov, Microbiology and Immunology Sup- port Services, WHO, Geneva, Switzerland F. Pinheiro, WHO Regional Office for the Americas, Washington, DC, USA J. Stjernsward, Cancer Unit, WHO, Geneva, Switz- erland G. Torrigiani, Division of Communicable Diseases, WHO, Geneva, Switzerland T. Umenai, Disease Prevention and Control, WHO Regional Office for the Western Pacific, Manila, Philippines nex 1 List of monoclonal antibodies to hepatitis B virus available for collaborative research programmes Monoclonal Class of antibody antibody Test Specificity Laboratorya HBs1C6B12 IgGl EIAb HBs (a-determinant) HBs2E4G8 IgGl EIA HBs (a-determinant) HBs4A7E3 IgGl EIA HBs (a-determinant) HBs2E4E2 IgGl EIA HBs (a-determinant) HBc13YF9C7 IgG2A HBc HBc1-8E111B12 IgG3 EIA HBc HBc18H5G1 IgG2A EIA HBc HBeB7G5F1 1gM EIA HBe HBeA2C12F9B1 IgG2B EIA HBe Contact addresses: 1. Dr 1. Hiozanek, Institute of Molecular Genetics, Prague, Czechoslovakia. 2. Dr J. Pillot, Institut Pasteur, Paris, France. 3. Dr P. Swenson, Seattle-King County Department of Public Health, Laboratory Section, Seattle, WA, USA. 4. Dr E. Ren, WHO Collaborating Centre for Research and Training in Immunology, Faculty of Medicine, National University of Singapore, Singapore. 5. Dr P. Mancal,WHO Collaborating Centre for Reference and Research on Rapid Viral Diagnosis, Institute of Sera and Vaccines, Prague, Czechoslovakia. b EIA - enzyme immunoassay. 454 CONTROL OF VIRAL HEPATITIS Annex I (continued) Monoclonal Class of antibody antibody Test Specificity Laboratory' 20/12 IgGl IF,c EIA HBs (a-determinant) 2 57/5 IgGl IF, EIA HBs (a-determinant) 80/9 IgGl IF, EIA HBs (a-determinant) 10/13 IgGl IF, EIA HBs (a-determinant) 4.21.31 IgGl IF, EIA HBs (a-determinant) 39/10 IgGl IF, EIA HBs (a-determinant) 5.28.6 IgGl IF, EIA HBs (a-determinant) 27.A.13 IgGl IF, EIA HBs (a-determinant) 14.C.9 IgGl IF, EIA HBs (a-determinant) 51.B.10 IgGl IF, EIA HBs (a-determinant) 38.B.10 IgGl IF, EIA HBs (a-determinant) 616 IgGl IF, EIA HBs (a-determinant) F124 IgGl IF, EIA pre-S2a F376 IgGl IF, EIA pre-S2b F52 1gM IF, EIA pre-S 2H1 IgGl EIA, RIAd HBs (react with all HBsAg subtypes) 3 3B8 IgGl EIA, RIA, WBe HBs (react with all HBsAg subtypes) 3E7 IgGl EIA, RIA HBs (react with all HBsAg subtypes) lElOF10 IgGl EIA, RIA HBs (react with all HBsAg subtypes) 1 F6 IgGl EIA HBs (react with all HBsAg subtypes) iC1o IgGl EIA, WB pre-S2 (ayw 2, ayw 3, ayw 4, adw 2) lHl IgG2b EIA, RIA HBs (ayw 1, ayw 2, ayw 3, ayw 4, ayr, adw 2) 2D1 1 IgGl EIA, WB HBs (y-determinant) 1C4 IgGl EIA, WB pre-S2 (ayr, adw 4, adr) lElOG5 IgG2b EIA HBs (w-determinant) 2C6 IgGl EIA HBs (ayw 4, adw 4, adr) 2D2 IgGl EIA HBs (adw 4, adr) 2D3 IgGl EIA, WB pre-S2 (ayr, adw 4, adr) 3A5 IgGl EIA HBs (ayw 3, ayw 4, adw 4) 3A6 IgGl EIA HBs (adw 4, adr) 3C3 IgGl EIA HBs (d-determinant) 3D9 IgGl EIA, WB HBs (ayw 4, ayr, adw 4, adr) 3E2 IgG2a EIA, WB HBs (ayw 1, ayw 2, adw 2, adw 4, adr) 3F7 IgGl EIA HBs (ayw 1, ayw 2, ayw 4, adw 2, adw 4, adr) WiCS-101 IgG IF, EIA HBs (a-determinant) 4 WlCS-1 15 IgG2b IF, EIA HBs (d-determinant) WlCS-119 IgG EIA HBc W1CS-120 IgG EIA HBc HBsOl IgGl IF, EIA HBs (a-determinant) 5 HBsO2 IgGl IF, EIA HBs (d-determinant) HBsO3 IgGl IF, EIA HBs (a-determinant) IF - immunofluorescence. d RIA - radioimmunoassay. WB - Westem blot. 455