Recent developments in production and purification of malaria antigens: Soluble antigens released in vitro from erythrocytes infected with Plasmodium berghei*

Butletn of the World Health Organization. 57 (Suppl 1): 83 (1979) Soluble antigens released in vitro from erythrocytes infected with Plasmodium berghei* H. WEISSBERGER,' J. GOLENSER, & D. T. SPIRA' Rat erythrocyies parasitized with Plasmodiurn berghei were fozund to release soluble antigenic products in vitro. The supernatants obtained by centriJugation of the disrupted cells induced specific transformation of non-adherent spkeen lymphocytes of convalescent rats and produced precipitation lines with antiplasmodial antibodies. In a preliminary experiment they also immu7unized young rats against a viable challenge of P. berghei. It is suggested that the sohible material couldservefor the purification ofan effective protective antigen. Soluble products released in vitro from rat erythro- cytes parasitized with Plasmodiurn berghei have been proved to be antigenic. The optimal conditions under which the most effi- cient supernatant is produced were investigated (Table 1). The active product is released from the infected erythrocytes either spontaneously during incubation, or as the result of physical treatment. Five hundred million parasitized erythrocytes were incubated in 10 mlofRPMI-1640for 18-21 hat37°C,in 50 CO2 in air. The supernatants were centrifuged at 27 000 g for 30 min, concentrated J0-fold, and passed through a 0.45-pm filter. The same quantity of infected cells disrupted by 3 cycles of freezing and thawing or by sonication for I min repeated 3 times, produced a supernatant of comparable activity. The resulting supernatants: (1) induced a specific transformation of nonadherent spleen lymphocytes of convalescent rats; (2) produced precipitation lines with antiplasmodial antibodies, and (3) in a prelimi- nary expenment immunized young rats against a viable challenge of P. berghei. The fact that the soluble material is also recognized by sensitized lymphocytes suggests that it could be purified to serve as an effective protective antigen. Table 1. Conditions under which specific lymphocyte- stimulating products are released from erythrocytes parasit- ized with P. berghei Time of Infectivity of incubation incubated Stimulating (hours) Treatment erylhrocytes activity O _ + _ 5 - + _ 18 - _- O Freezing and thmwing - + 0 Sonication - + RPSUML ANTIGtNES SOLUBLES LIBERES iNt VITRo PAR DES tRYTHROCYTES INFECTES AVEC PLASMODIUM BERGHE! On a constate que des mrythrocytes de rats infectes par Plasmodium bergher liberaient in vitro du materiel anti- g6nique soluble. Le surnageant obtenu par centrifugation des celules eclat&es a 6t. utilise pour indduire chez des rats conmalescents une modification specifique des lymphocytes spleniques non adherents. Mis en presence d'anticorps contre Plasmiodium, iI a egalemenr determnine la formation de lignes de precipitines. EnfiIn, une experience prE1iminaire faite sur de jeunes rats a permis d'immuniser ceux-ci contre l'infection expirnmentale par du materiel parasitaire P. berghtei viable- On peutdoncpenser quelemat6riel soluble recolte pourrait etre purifie en vue d'obtenir un antigene capable de susciter une protection efficace. PFrom the Departmcnt of Protozoology, The Hebrew University -Hadassah Medica. School, Jerusalem 91000. Israel This work was supported by the Dutch Governmcnt through the International Collaborative Research Project on Mialaria Immunology and Immuno- pathology (ICRP/M[I). I Instructor. ' Scicntist. I Head, Department of Protozoology. 3872 -83-