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Irradiated sporozoites prime mice to produce high antibody titres upon viable Plasmodium berghei sporozoite challenge, which act upon liver-stage development
Published online by Cambridge University Press: 01 March 1999
Abstract
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.
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- 1999 Cambridge University Press
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