LACK OF ASSOCIATION BETWEEN LEVELS OF TRANSPLACENTALLY ACQUIRED PLASMODIUM FALCIPARUM-SPECIFIC ANTIBODIES AND AGE-OF-ONSET OF CLINICAL MALARIA IN INFANTS IN A MALARIA ENDEMIC AREA OF NIGERIA

A cohort of 117 newborns was followed longitudinally for 12 months to determine the age of onset of clinical malaria and the subsequent epis odes of malaria, and to investigate the possible existence of a correl ation between level of transplacentally acquired Plasmodium falciparum -specific antibodies and age of onset of malaria in the infant. The me an age of onset of malaria in 49 infants was 4.48+/-1.54 months. Mean (+/-S.D.) age of onset of clinical malaria in haemoglobin AA infants ( 4.38+/-1.14) was significantly (P<0.05) lower compared with haemoglobi n AS (5.58+/-2.43) infants. No correlation was obtained between the ag e of onset of malaria and the level of cord serum total IgG, IgM and a ntibodies to P. falciparum antigens. Cord blood seropositivity for ant ibodies to the blood stage antigen Pfl55/RESA and its C-terminal repea t sequence (EENV)(6) or to the (NANP)(6) peptide representing repeats of the circumsporozoite protein (CSP) did not influence the age of ons et of clinical malaria. However, infants with haemoglobin AS whose cor d blood was seropositive for antibodies to the (EENV)(6) or (NANP)(6) peptide showed delayed onset (P<0.001) of malaria compared with AA ser opositive infants. Although our results indicate that transplacentally acquired antibodies to the studied antigens alone offer no significan t protection against malaria during the first few months of life, anti bodies in concert with other factors such as haemoglobin genotype may contribute to the protection of the newborn.