Malaria vaccine

Abstract

A fusion protein, derived fromGlutamate-rich protein (GLURP) genetically coupled toMerozoite surface protein 3 (MSP3) was produced inas a secreted recombinant GLURP-MSP3 hybrid protein and experiments showed that the GLURP-part of the hybrid increased the overall antibody response. Immunizations with the hybrid protein consistently generated a stronger antibody response against the individual GLURP and MSP3 domains than a mixture of the two recombinant molecules injected at one site or the individual recombinant molecules injected simultaneously at two different sites. The difference was most pronounced for the MSP3-specific antibody response suggesting that T cell epitopes located in the GLURP RO-region provide help for B-cell epitopes in the MSP3 region. Moreover, when the animals were injected with a mixture of GLURP and MSP3, individual mice tended to mount a predominant antibody response against either molecule: in some animals GLURP was immunodominant whereas in other animals MSP3 was the dominant immunogen. Additionally, the hybrid was also more antigenic than the individual recombinant proteins since the ELISA-titer of naturally occurring IgG antibodies, in clinically immune African adults, against the hybrid protein was higher than the titers against the individual recombinant proteins. The hybrid protein was also demonstrated to be a potential protective antigen as mouse anti-GLURP-MSP3 IgG antibodies were able to inhibit parasite-growth in vitro in a monocyte-dependent manner.