Antibody responses to Plasmodium falciparum: Evolution according to the severity of a prior clinical episode and association with subsequent reinfection

We measured sporozoite- and total parasite antigen-specific IgG and IgM ant ibodies before and after treatment in matched groups of Gabonese children w ho presented with either mild or severe Plasmodium falciparum malaria. We i nvestigated the influence of Various parameters on these antibody responses , including clinical presentation, age, and post-treatment reinfection prof iles. IgG but not IgM responses were strongly influenced by both clinical a nd parasitological status. IgG responses to the repeat region of the circum sporozoite protein, which were low at admission, particularly so in those w ith severe anemia, increased after treatment but showed no association with either age or reinfection profiles. Total parasite antigen-specific IgG re sponses were strongly influenced by parasitological status, and also differ ed significantly when segregated according to clinical status at admission, age, and reinfection histories. Most notably, anti-parasite IgG responses measured when children were parasite-free were higher and a good indicator of recent reinfections in those who presented with mild rather than with se vere malaria. The profile of responses in the latter group suggests some im mune system dysfunction, which may reflect the induction of tolerance to pa rasite antigens.