J. Healer et al., Phagocytosis does not play a major role in naturally acquired transmission-blocking immunity to Plasmodium falciparum malaria, INFEC IMMUN, 67(5), 1999, pp. 2334-2339
Phagocytosis of Plasmodium falciparum sexual stages in vitro and within the
mosquito midgut was assayed in order to assess its role in transmission bl
ocking immunity to malaria. Both monocytes/macrophages (MM) and polymorphon
uclear neutrophils (PMN) phagocytosed malarial gametes in vitro, but levels
of phagocytosis were low. Intraerythrocytic gametocytes were not susceptib
le to phagocytosis, In vitro phagocytosis was positively correlated with le
vels of antibodies against the gamete surface proteins Pfs230 and Pfs48/45.
Immunoglobulin G (IgG) subclass analysis revealed that phagocytosis was co
rrelated with levels of antigamete IgG1, In vivo membrane-feeding experimen
ts were performed in the presence of both pooled and individual malaria imm
une sera. The phagocytic process proceeded less efficiently in vivo than in
vitro, which may be related to the lower ambient temperature (26 degrees C
, compared with 37 degrees C), Finally, although we found a correlation bet
ween the ability of a serum to promote phagocytosis in vitro and the presen
ce of antibodies against transmission-blocking target antigens, we were una
ble to demonstrate a role for MM- or PMN-mediated phagocytosis in reduction
of infectivity of the malarial parasite to mosquitoes.