Malaria cellular immune responses in neonates from Cameroon.

T cell responses to leucoagglutinin, PPD, and seven Plasmodium falciparum blood stages antigens were investigated in 164 cord blood samples from Cameroonian neonates. In vitro T cell responses were measured by lymphocyte proliferation, and IL-2, IFN-gamma, and IL-4 release in the presence of crude schizont extract, purified Pf155/RESA protein, and synthetic peptides from Pf155/ RESA. Following culture in presence of leucoagglutinin or PPD, proliferation and cytokine production were very low, as compared to adults from the same area. Interestingly, following stimulation of cord blood lymphocytes by malaria antigens, the percentage of responders and the mean level of positive responses were of the same order than those observed in adults for IL-2 production, while proliferative and IL-4 responses were only marginally decreased. Conversely, IFN-gamma production was highly reduced, as compared to adults. Our results demonstrate that prenatal immune priming to malarial antigens is common in this area and that the fetal immune system is able to respond to antigenic stimuli, as cells proliferate and generate cytokines. As cord blood lymphocytes may be induced to differentiate into effector cells producing predominantly Th1 or Th2 cytokines, malaria during pregnancy might direct the functional capacity of fetal T cells to respond to further infection.