Irradiated sporozoites prime mice to produce high antibody titres upon viable Plasmodium berghei sporozoite challenge, which act upon liver-stage development.
C57BL6 mice were protected against Plasmodium berghei sporozoite challenge by immunization with live 12 krad dose-irradiated sporozoites, but not by 20 krad dose-irradiated sporozoites. Immunization with 12 krad irradiated sporozoites generated low levels of antibody reactive to liver-stage parasites (titres of 1/100). Inoculation of as few as 100 live P. berghei sporozoites induced complete host protection accompanied by a very quick and high boost of antibody titres up to 1/4000. This sporozoite challenge-drive antibody boost was absent in mice immunized by 20 krad sporozoites and in non-protected, and non-immunized mice. Antibody was mainly liver-stage (LS) specific and due to an increase of IgG2a and IgG2b. The in vitro effect of pre- and post-challenge sera upon either sporozoite invasion or LS development was assessed in Hep-G2 cultures. Both were found to have a strong effect upon LS development even at 1/2500 dilution, and conversely a low effect upon invasion. These results suggest that sporozoites irradiated at doses that induce protection are able to prime T-cells which, upon challenge by non-irradiated sporozoites, provide help to B-lymphocytes to trigger the production of high titres of anti-LS antibodies that can inhibit LS development in vitro.
Chatterjee
S
S
Department of Parasitology, Institute of Tropical Medicine, Antwerp, Belgium. schatterjee@itg.be
Druilhe
P
P
Wery
M
M
D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D004307:Dose-Response Relationship, Radiation; D019084:Fluorescent Antibody Technique, Indirect; D007115:Immunization Schedule; D007074:Immunoglobulin G / Q000097:blood; D008099:Liver / Q000469:parasitology*; D008288:Malaria / Q000517:prevention & control; D017780:Malaria Vaccines / Q000008:administration & dosage / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010962:Plasmodium berghei / Q000254:growth & development* / Q000276:immunology / Q000528:radiation effects*; D015800:Protozoan Proteins / Q000276:immunology
D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D017780:Malaria Vaccines; D015800:Protozoan Proteins