Research published this week in PLoS Medicine synthesizes information from many different studies that attempt to link specific antibody responses to Plasmodium falciparum with protection from clinical malaria and comes to important conclusions about which antigens might be worth advancing as vaccine candidates.
Malaria is a major global health problem. P. falciparum is the major cause and kills about one million people every year, mainly young children. However, immune responses to malaria are poorly understood, which has hindered the development of a vaccine against malaria. Antibody responses to proteins (antigens) produced by the merozoite life stage of malaria might protect against subsequent malaria infection. Therefore studying these antibody responses could be useful for identifying antigens to incorporate into vaccines against malaria.
Numerous studies have been performed on human antibody responses to P. falciparum merozoite antigens, but they have given conflicting results. Freya Fowkes and colleagues have completed a systematic review with meta-analysis for the first time of immune responses to P. falciparum. This study confirms that merozoite antigens are important targets of protective immunity in people and identifies specific antigens that could be prioritized for vaccine development. Specifically, in people with antibodies to the merozoite proteins MSP-3 and MSP-119, the risk of developing P. falciparum malaria was reduced by 54% and 18%, respectively, compared to people without antibodies to these antigens. Antibodies to other antigens, such as AMA1 were also linked with substantial protection from malaria.
The authors recommend that new prospective cohort studies are urgently needed to guide vaccine development. These studies must include a larger number of lead antigens and populations outside Africa.
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