Variant specific anti-VSA immune responses are thought to play an important role in the development of naturally acquired immunity to malaria. These antigens mediate adhesive parasite-host interactions thought to be essential for evading innate immune clearance mechanisms in the spleen. Ī major target for protective antibodies against malaria are the variant surface antigens (VSA) that are anchored in the cell membrane of infected erythrocytes. One novel way to explore this transition further is through observation of recrudescences, which can occur when drug treatment fails to eliminate a blood stage infection. The role of antibodies is demonstrated through studies in which purified IgG from immune adults was used to bring about rapid reduction in parasitaemia and symptoms of malaria. The staggered age distribution of severe malaria, mild malaria and asymptomatic infection suggests distinctive immunological mechanisms that (i) confer protection against pathogenic features of infection (ii) limit parasite replication leading to control of parasite burden. The transition from malaria to asymptomatic infection is still poorly understood. Thus, many individuals in malarious areas carry asymptomatic infections. This immunity takes several years to build up, even in hyperendemic areas, and probably never confers sterile immunity. This pilot study validates the utility of recurrent natural malaria infections as a functional readout for examining the incremental acquisition of immunity to malaria.Ĭhildren who grow up in malaria endemic areas develop naturally acquired immunity to severe forms of the disease. This is consistent with the prediction that anti-VSA IgG responses may play a role in promoting chronic asymptomatic infections. Additionally, compared to patients with reinfections by parasites of new merozoite surface protein 2 (MSP2) genotypes, baseline sera sampled from patients with persistent infections (recrudescence) tended to have higher recognition of heterologous parasites. ResultsĬonsistent with previous studies on anti-VSA responses, sera from each child taken at the time of recovery from their respective primary infection tended to recognize their own secondary parasites poorly. Immunofluorescence was used to explore the dynamics of anti-VSA IgG responses generated by children to (i) primary malaria episodes and (ii) recurrent P. Piecemeal acquisition of variant specific antibody responses to these antigens as a result of exposure to multiple re-infections has been proposed to play a role in acquisition of naturally acquired immunity.

During intra-erythrocytic replication Plasmodium falciparum escapes the human host immune system by switching expression of variant surface antigens (VSA).

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