Abstract. Serum samples from Ugandan residents of a malaria-hyperendemic region were tested by enzyme-linked immunosorbent assay for reactivity against recombinant constructs of the 47 (SE47Ј)-and 50 (SE50A)-kDa fragments of Plasmodium falciparum serine repeat antigen (SERA). Immunoglobulin (Ig) G3 and IgG1 were the predominant subclass responses to SE47Ј and SE50A, respectively. The geometric mean optical density (OD) for IgG3 anti-SE47Ј was significantly lower in children Ͻ 15 years compared with adults Ն 15 years (P Ͻ 0.0001). By contrast, the geometric mean IgG1 anti-SE50A was slightly higher in children compared with adults (P Ͻ 0.01). The proportion of high responders (ODs Ͼ 0.5) to SE47Ј was significantly lower in children compared with adults (P Ͻ 0.001), whereas the proportion of high responders to SE50A was comparable in children and adults (P ϭ 0.07). This first detailed study of SERA in a malaria-hyperendemic region suggests that natural human IgG3 anti-SE47Ј might be associated with immunity to malaria.

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Objective: To determine the natural human humoral immune responses to the 19 kilodalton carboxy terminal fragment of Plasmodium falciparum merozoite surface protein 1 (MSP1 19), a malaria candidate vaccine antigen and to determine the prevalence of MAD20 and K1 alleles of P. falciparum MSP1. Design: Community based cross-sectional study.

A cross-sectional study of pregnant women was conducted at Nsambya Hospital in Kampala, to investigate the prevalence and effect of Plasmodium falciparum infections during pregnancy, in a peri-urban/urban location. Overall, 544 pregnant women were recruited when they presented at the labour ward for delivery. After giving informed consent, each subject answered a questionnaire and underwent a physical examination, and peripheral-blood samples were obtained. After each uncomplicated delivery, samples of placental and cord blood were obtained from the placenta and infant, respectively, and infant birthweights were recorded. Smears were prepared from the blood samples and checked for parasites. Only 46 and 36 of the 537 women investigated were positive for P. falciparum infection in their peripheral and placental blood, respectively. Plasmodium falciparum was the only parasite encountered. The prevalences of low birthweight and maternal parasitaemia and the intensities of maternal infection were each greater in primigravidae than secundi- or multi-gravidae. Despite the low prevalence of parasitaemia in this population, P. falciparum infection in the primigravidae was a significant contributor to their ill health, leading to low birthweights in their infants.