Transmission blockade of Plasmodium falciparum: its variability with gametocyte numbers and concentration of antibody

Abstract
The transmission of Plasmodium falciparum through Anopheles stephensi was measured in the presence of anti-gamete (anti-45/48 kDa) and anti-zygote/ookinete (anti-25 kDa) antibodies. With lowering numbers of infectious gametocytes in the presence of the same concentration of antibodies, different results were obtained with the two types of antibodies. Transmission blocking appeared to weaken when using anti-45/48 kDa antibody, whilst, with the anti-25 kDa antibody, transmission inhibition was markedly strengthened with lower parasite numbers. Keeping the parasite numbers constant and progressively lowering the concentration of both types of antibodies resulted in a gradual loss of the latters' blocking ability. No enhancement of transmission occurred at low antibody concentrations.