Diversity of Plasmodium falciparum antibodies in pregnancy

Impact of a double dose of sulphadoxine-pyrimethamine to reduce prevalence of pregnancy malaria in southern Mozambique

Malarial infection during pregnancy increases the risks of severe sequelae for the pregnant woman and the risk of delivering a low birthweight baby. The aim of this intervention study was to reduce significantly the prevalence of malaria parasitaemia in adolescent parturients in Matola and Boane in Mozambique. The study was focused upon the most malaria-vulnerable group, adolescent nulliparous and primiparous women. After completing the usual antenatal clinic and giving informed consent, 600 pregnant women were randomly chosen in a double blind manner to one of two regimens comparing the prevailing routine (placebo) for malaria prevention with a two dose regimen of sulphadoxine-pyrimethamine (SP). The first dose was given at enrollment with a second dose at the beginning of the third trimester. At delivery maternal and placental malaria parasitaemia as well as birthweight and gestational duration were analysed. At booking the prevalence of malaria parasitaemia was 35.3% in the placebo group and 30.6% in the SP group. At the second dose, the prevalence of malaria parasitaemia in the placebo group and SP group was 19.7% and 8.7%, respectively. This implies a relative risk (RR) of 2.24 with 95% CI (1.34, 3.75). The corresponding figures at delivery were 13.6% and 6.3% with an RR of 2.22 (1.07, 4.60) and in placenta 13.3% and 2.4% with an RR of 4.87 (1.58, 15.0). Newborns with malaria within 7 days were significantly more frequent in the placebo group, 6.4% and 0.7% respectively, with an RR of 6.55 (1.20, 35.7). Almost all (approximately 98%) of the women studied had Plasmodium falciparum, the remainder had P. malariae and P. ovale. The mean birthweight in the SP group was 3077 g and in the placebo group 2926 g. The estimated mean difference between the two groups was 151 g with 95% CI (51, 252). The mean placental weight in the placebo group was 596 and 645 g in the SP group, implying a difference of 49 g with a 95% CI (11, 88). The mean gestational duration was 6.1 days longer in the SP group, 95% CI (1.5, 10.6). In the placebo group there were two cases of urticaria and one case of nausea; in the SP group there was one case of vomiting. No newborn showed any sign of serious SP side-effect. Two doses of SP were enough to significantly reduce the prevalence of peripheral and placental malaria parasitaemia among young nulliparous and primiparous pregnant women in Matola and Boane.

Increased prevalence of malaria in HIV-infected pregnant women and its implications for malaria control

OBJECTIVES

To examine in pregnant women the relationship between HIV infection and malaria prevalence and to determine, in relation to HIV infection, the effectiveness of sulphadoxine-pyrimethamine in clearing P. falciparum infection.

METHOD

Descriptive cross-sectional analysis of P. falciparum prevalence in pregnant women at first antenatal visit and of women at delivery who had received two sulphadoxine-pyrimethamine treatments for malaria. HIV status was assessed in 621 women who attended for antenatal care and for delivery at two rural hospitals in southern Malawi in 1993-94. Information was collected on maternal age, parity and gestational age. Prevalence of P. falciparum was measured at first antenatal visit and delivery. Women were given two routine treatment doses of sulphadoxine-pyrimethamine (SP), at first antenatal visit and between 28 and 34 weeks gestation, conforming to Malawi government policy on antimalarial control during pregnancy.

RESULTS

Prevalence of HIV infection was 25.6% and all infections were HIV type-1. In primigravidae malaria prevalence at recruitment was 56.3% in HIV-infected and 36.5% in HIV-uninfected women (P=0.04). The corresponding figures for multigravidae were 23.8% and 11.0%, respectively (P<0.01). HIV-infected primigravidae had increased malaria prevalence at all gestational ages. Peak parasite prevalence occurred earlier in gestation in HIV-infected primigravidae (16-19 weeks if HIV-infected; 20-23 weeks if HIV-uninfected). The relative risk for parasitaemia in HIV-infected compared to HIV-uninfected women was significantly increased in three of five parity groups, including the two highest ones (parity>3), indicating parity-specific immunity to malaria was impaired. Malaria prevalence at delivery remained high in HIV-infected women despite prior routine treatment with sulphadoxine-pyrimethamine in pregnancy There was no significant difference in parasite prevalence at delivery between women who did or did not use sulphadoxine-pyrimethamine.

CONCLUSIONS

HIV infection is associated with a significant increase in malaria prevalence in pregnant women of all parities with the effect apparent from early in gestation. Two treatment doses of sulphadoxine-pyrimethamine were inadequate to clear parasitaemia in many women by the time of delivery and this occurred independently of HIV status and despite high sensitivity to SP in this area. There is a need to undertake longitudinal studies to determine the incidence of P. falciparum infection in HIV-infected and uninfected pregnant women and to reassess the frequency and timing of sulphadoxine-pyrimethamine treatment doses in these women. Late pregnancy re-infections with P. falciparum probably explain the high parasite prevalence at delivery following sulphadoxine-pyrimethamine treatment at 28-34 weeks gestation.

Serological reactivity to the ring-infected erythrocyte surface antigen and circumsporozoite protein in gravid and nulligravid women infected with Plasmodium falciparum

To investigate potential mechanisms for pregnancy-associated alterations in the immune response to malaria, we tested plasma samples from Plasmodium falciparum-infected nulligravida (42), primigravida (23) and multigravida (38) Kenyan women for reactivity to the ring-infected erythrocyte surface antigen (RESA) by a modified indirect fluorescent antibody assay and to synthetic peptides derived from amino acid sequences of RESA and the circumsporozoite (CS) protein of P. falciparum by an enzyme-linked immunosorbent assay. Reactivity to RESA showed the lowest titres in primigravid women, intermediate titres in nulligravid women and the highest titres in multigravid women (loge mean antibody = 3.28, 4.64, and 5.28, respectively, P less than 0.03), but was not associated with initial parasite density or response to chloroquine treatment. No relationship in antibody reactivity to the 3 synthetic peptides of the RESA molecule was observed by gravidity (0, 1, or greater than or equal to 2), age, initial parasite density or response to treatment. Levels of antibody to the synthetic peptides of the CS protein increased with age and were higher in gravid than in nulligravid women in the 15-19 year age group. The increased malaria prevalence and parasite density and the decreased response to antimalarial treatment in pregnant women is not explained by lower levels of antibody to RESA or CS protein during pregnancy.