Monoclonal and Polyclonal Antibodies Both Block and Enhance Transmission of Human Plasmodium Vivax Malaria

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  • * Department of Microbiology, Faculty of Medicine, University of Peradeniya, Sri Lanka
  • | Department of Parasitology, Faculty of Medicine, University of Colombo, Kynsey Road, Colombo 8, Sri Lanka
  • | Department of Animal Genetics, University of Edinburgh, West Mains Road, Edinburgh EH9 3JN, Scotland
  • | § Unite d'Immunoparasitologie, Institute Pasteur, 25 Rue du Dr Roux, Paris 75724, France

Antibodies against gametes of the malarial parasite inhibit the development of the parasite in the mosquito and curtail the transmission of malaria. We now report that a monoclonal antibody against gametes of the human malaria pathogen Plasmodium vivax and antibodies induced during natural infections of P. vivax in humans which suppress infectivity of the parasites to the vector at high concentrations can, at lower concentrations, have the opposite effect and enhance the level of malaria infection in the mosquitoes. Infectivity enhancing effects of up to 12-fold were demonstrated when a transmission blocking monoclonal antibody and immune human sera were diluted, in some undiluted immune human sera, and in the sera of vivax malaria patients during convalescence after drug cure.