A LONGITUDINAL-STUDY OF SEROREACTIVITIES TO PLASMODIUM-FALCIPARUM ANTIGENS IN NIGERIAN INFANTS DURING THEIR FIRST YEAR OF LIFE

The kinetics of passively transferred maternal antibodies to antigens of Plasmodium falciparum and the dynamics of acquisition of these anti bodies during the first year of life was investigated in infants born in a malaria endemic area of south-western Nigeria. Blood samples were collected from the infants at bi-monthly follow-up visits for the ana lysis of total serum immunoglobulin G, IgM, IgA and antibodies to the antigen Pf155/RESA and against synthetic peptides representing antigen ic sequences of the blood stage antigen Pf155/RESA and Ag332 or the ci rcumsporozoite protein (CSP). IgG levels fell from birth till 4 months and a steady rise was observed thereafter till ten months of life. On the contrary mean IgM and IgA levels increased throughout the first y ear of life. Generally the number of infants positive for antibodies t o the antigens under investigation fell from birth and between 4-6 mon ths of age was either low or absent. None of the infants were positive for antibodies to the peptide representing Ag332 during the first yea r of life. The earliest seroconversion was detected at 6 months of age involving the Pf155/RESA and (NANP)(6) antigens. The results indicate a high level of exposure in this study area to malaria infection earl y in life. The finding of an active antibody response to malarial anti gens in infancy encourages the hope that a malaria Vaccine administere d early in life may accelerate the development of naturally acquired i mmunity and thus protect the population most at risk.