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London School of Hygiene & Tropical Medicine Malaria Centre

Malaria research in immunology and vaccination

Human immune responses that reduce the transmission of Plasmodium falciparum in African populations.

LSHTM investigators:
Teun Bousema, Colin Sutherland, Eleanor Riley, Geoffrey Targett & Chris Drakeley.
External collaborators:
Thomas Churcher (Imperial College London, UK); Bert Mulder (Microbiology Laboratory Twente, The Netherlands); Louis Gouagna (L’Institut de recherche pour le développement, France).
Funding body:
Wellcome Trust and European Union

Malaria-infected individuals can develop antibodies which reduce the infectiousness of Plasmodium gametocytes to biting Anopheles mosquitoes.

When ingested in a bloodmeal together with gametocytes, these antibodies reduce or prevent subsequent parasite maturation in the insect host. This transmission blocking immunity is usually measured in human sera by testing its effect on the infectivity of

gametocytes grown in vitro. Here we evaluate evidence of transmission-blocking immunity in eight studies conducted in three African countries. Plasmodium falciparum gametocytes isolated from each individual were fed to mosquitoes in both autologous plasma collected with the parasites, and permissive serum from non-exposed donors. Evidence of transmission reducing effects of autologous plasma was

found in all countries. Experiments involving 116 Gambian children (aged 0.5–15 years) were combined to determine which factors were associated with transmission reducing immune responses. The chances of infecting at least one mosquito and the average proportion of infected mosquitoes were negatively associated with recent exposure to gametocytes and sampling late in the season. These results suggest

that effective malaria transmission-reducing antibodies do not commonly circulate in African children, and that recent gametocyte carriage is required to initiate and/or boost such responses.