Peripheral Plasmodium Falciparum Infection and Antibody Levels among Pregnant Women on Intermittent Preventive Treatment In Ghana: Implications For Malaria and Transfer of Immunity to Babies

Abstract

The effect of pregnancy associated malaria (PAM) differs according to the level of malaria endemicity and the level of immunity to infection acquired by pregnant woman. Generally, the incidence as well as severity of PAM is parity-linked. Immunologically naive primigravid women are at greater risk compared to multigravida who have some level of immunity against the specific malaria parasites which colonize the placenta. The adverse consequences of PAM which include maternal anaemia, complications at delivery and infants with low birth weight (LBW) are preventable by intermittent preventive treatment (JPT p), however, the IPTp may interfere with the acquisition of protective immunity against PAM as well as passive transfer of antibodies to infants in utero. In a longitudinal study, 320 pregnant women at an urban antenatal clinic in Madina, a suburb of Accra, Ghana were studied. Malaria infection, maternal anaemia, IPTp and other antimalarial practices, and the acquisition and transfer of antimalarial antibody immunity to infants were documented. Venous blood samples were collected at first ANC registration and four weeks post-TPTp administration and at delivery. Infants were followed monthly for six months. Anti-IgG and IgM antibodies against a crude antigen preparation as well as the Glutamate Rich Protein (GLlJRP) of P. falciparum were quantified by the enzyme linked immunosorbent assay (ELISA). The prevalence of peripheral blood infection with P. falciparum among the pregnant women was very low, 5.0% mean haemoglobin level at registration was normal, 11.4gdL. The mean gestation at registration was 18.5 weeks. The first dose of IPTp was administered at a mean gestation age of 24.4weeks, above the recommended 16 weeks Knowledge of bednets and experience in bednet usage were relatively high, 97.3% and 60.5% respectively but ITN possession and use were only 31.6% and 17.5% respectively. Both IgG and IgM antibodies against crude antigen and GLURP were high at first ANC visit, peaking at 4 weeks after the first dose of IPTp and dropping gradually up to delivery. Rise in IgM antibodies post-IPTpl confirmed new infections and a possible increase in susceptibility despite IPTp. Levels of antibodies in cord blood and placenta were well correlated and IPTp did not interfere with transfer of antibodies to infants in utero. There were 4 infants with LBW out of 121 who were delivered at the clinic. None of the children had fever, throughout the first six months of life. IPTp reduces the amount of malaria acquired antibody immunity among pregnant women during pregnancy. However, the study was not able to conclude that the levels of maternal and cord blood antibodies at delivery had adverse implications on malaria among the children at six months. A significant positive correlation was found between the number of IPTp doses taken in pregnancy and the weight of the baby at delivery.