RELATIONSHIP BETWEEN MATERNALLY DERIVED ANTI-PLASMODIUM FALCIPARUM ANTIBODIES AND RISK OF INFECTION AND DISEASE IN INFANTS LIVING IN AN AREA OF LIBERIA, WEST-AFRICA, IN WHICH MALARIA IS HIGHLY ENDEMIC

In areas where Plasmodium falciparum is endemic, immunoglobulin G is a cquired by the fetus in utero, mainly during the third trimester of pr egnancy. The potential protective effect of transferred anti-P. falcip arum maternal antibodies was examined in a longitudinal study of 100 i nfants from birth to 1 year of age. The probability of acquiring a P. falciparum infection and developing an episode of clinical malaria was determined in relation to the P. falciparum-specific antibody level o f the infant at birth against P. falciparum schizont antigen or recomb inant merozoite surface protein MSP1(19) antigen. The risk of acquirin g an episode of clinical malaria increased from birth to 6 months of a ge, after which it decreased. The overall prevalence of P. falciparum parasitemia was highest (48.9%) in the 6-month-old infants. The age-sp ecific hematocrit value showed the lowest mean value (30.2) from 6 to 9 months, and the spleen rate was the highest (69.8%) at the same age. There was a lower risk of developing an episode of clinical malaria d uring the first gear of life in the infants with high levels of anti-M SP1(19) antibodies at birth. The level of maternally derived overall a nti-schizont antigen antibodies did not seem to play a role in the rel ative risk of developing malaria infection or disease during the first year of life, though the level of specific anti-MSP1(19) antibodies m ay be associated with protection.