Increased prevalence of dhfr and dhps mutants at delivery in Malawian pregnant women receiving intermittent preventive treatment for malaria.

In the context of an Intermittent preventive treatment (IPTp) trial for pregnant women in Malawi, Plasmodium falciparum samples from 85 women at enrollment and 35 women at delivery were genotyped for mutations associated with sulfadoxine-pyrimethamine resistance. The prevalence of the highly resistant haplotype with mutations at codons 51 and 108 of dihydrofolate reductase (dhfr) and codons 437 and 540 of dihydropteroate synthase (dhps) increased from 81% at enrollment to 100% at delivery (P = 0.01). Pregnant women who were smear-positive at enrollment were more likely to have P. falciparum parasitemia at delivery. These results lend support to concerns that IPTp use may lead to increased drug resistance in pregnant women during pregnancy and emphasise the importance of screening pregnant women for malaria parasites in areas with prevalent SP resistance even when they are already on IPTp.

Antibody to P. falciparum in pregnancy varies with intermittent preventive treatment regime and bed net use.

BACKGROUND: Antibodies towards placental-binding P. falciparum are thought to protect against pregnancy malaria; however, environmental factors may affect antibody development. METHODS AND FINDINGS: Using plasma from pregnant Malawian women, we measured IgG against placental-binding P. falciparum parasites by flow cytometry, and related results to intermittent preventive treatment (IPTp) regime, and bed net use. Bed net use was associated with decreased antibody levels at mid-pregnancy but not at 1 month post partum (1 mpp). At 1 mpp a more intensive IPTp regime was associated with decreased antibody levels in primigravidae, but not multigravidae. CONCLUSIONS/SIGNIFICANCE: Results suggest bed nets and IPTp regime influence acquisition of pregnancy-specific P. falciparum immunity.

Effect of repeated treatment of pregnant women with sulfadoxine-pyrimethamine and azithromycin on preterm delivery in Malawi: a randomized controlled trial.

Preterm delivery, which is associated with infections during pregnancy, is common in sub-Saharan Africa. We enrolled 1,320 pregnant women into a randomized, controlled trial in Malawi to study whether preterm delivery and low birth weight (LBW) incidence can be reduced by intermittent preventive treatment of maternal malaria and reproductive tract infections. The participants received either sulfadoxine-pyrimethamine (SP) twice (controls), monthly SP, or monthly SP and two doses of azithromycin (AZI-SP). The incidence of preterm delivery was 17.9% in controls, 15.4% in the monthly SP group (P = 0.32), and 11.8% in AZI-SP group (risk ratio = 0.66, P = 0.01). Compared with controls, those in AZI-SP group had a risk ratio of 0.61 (P = 0.02) for LBW. Incidence of serious adverse events was low in all groups. In conclusion, the incidence of preterm delivery and LBW can in some conditions be reduced by treating pregnant women with monthly SP and two azithromycin doses.

Comparison of real-time PCR and microscopy for malaria parasite detection in Malawian pregnant women.

BACKGROUND: New diagnostic tools for malaria are required owing to the changing epidemiology of malaria, particularly among pregnant women in sub-Saharan Africa. Real-time PCR assays targeting Plasmodium falciparum lactate dehydrogenase (pfldh) gene may facilitate the identification of a high proportion of pregnant women with a P. falciparum parasitaemia below the threshold of microscopy. These molecular methods will enable further studies on the effects of these submicroscopic infections on maternal health and birth outcomes. METHODS: The pfldh real-time PCR assay and conventional microscopy were compared for the detection of P. falciparum from dried blood spots and blood smears collected from the peripheral blood of 475 Malawian women at delivery. A cycle threshold (Ct) of the real-time PCR was determined optimizing the sensitivity and specificity of the pfldh PCR assay compared to microscopy. A real-time PCR species-specific assay was applied to identify the contribution to malaria infections of three Plasmodium species (P. falciparum P. ovale and P. malariae) in 44 discordant smear and pfldh PCR assay results. RESULTS: Of the 475 women, P. falciparum was detected in 11 (2.3%) by microscopy and in 51 (10.7%) by real-time PCR; compared to microscopy, the sensitivity of real-time PCR was 90.9% and the specificity 91.2%. If a Ct value of 38 was used as a cut-off, specificity improved to 94.6% with no change in sensitivity. The real-time PCR species-specific assay detected P. falciparum alone in all but four samples: two samples were mixed infections with P. falciparum and P. malariae, one was a pure P. malariae infection and one was a pfldh PCR assay-positive/species-specific assay-negative sample. Of three P. malariae infections detected by microscopy, only one was confirmed by the species-specific assay. CONCLUSIONS: Although microscopy remains the most appropriate method for clinical malaria diagnosis in field settings, molecular diagnostics such as real-time PCR offer a more reliable means to detect malaria parasites, particularly at low levels. Determination of the possible contribution of these submicroscopic infections to poor birth outcomes and maternal health is critical. For future studies to investigate these effects, this pfldh real-time PCR assay offers a reliable detection method.

Antibodies to chondroitin sulfate A-binding infected erythrocytes: dynamics and protection during pregnancy in women receiving intermittent preventive treatment.

BACKGROUND: Plasmodium falciparum parasites that cause malaria in pregnancy express unique variant surface antigens (VSAs). Levels of immunoglobulin G (IgG) antibody to pregnancy-associated VSAs measured at delivery are gravidity dependent, and they have been associated with protection from disease. It is not known how these IgG responses develop in pregnant women receiving intermittent preventive treatment during pregnancy (IPTp) or whether IgG levels in early pregnancy predict pregnancy outcomes. METHODS: We performed longitudinal measurements of IgG antibody to VSAs by flow cytometric analysis of serum samples obtained from 549 Malawian women receiving IPTp. We examined fluctuations in IgG levels over time and associated the IgG levels noted at study enrollment with clinical outcomes. RESULTS: Levels of IgG antibody to pregnancy-associated VSAs were gravidity dependent. Overall, levels decreased while women were receiving IPTp, but the levels of the individuals were highly dynamic. Primigravidae developed low levels of pregnancy-specific IgG, which were often boosted during second pregnancies. The prevalence of parasites was low (8.4% at enrollment and 2.4% in late pregnancy). Antibody levels at enrollment did not predict birth weight, duration of gestation at delivery, or the maternal hemoglobin level in late pregnancy. CONCLUSION: Levels of IgG antibody to pregnancy-specific VSAs decrease during receipt of IPTp. Antibody levels in early pregnancy did not predict clinical outcome. IPTp and decreasing malaria prevalence pose challenges for the evaluation of novel interventions for malaria during pregnancy.

International epidemiology of human pre-existing adenovirus (Ad) type-5, type-6, type-26 and type-36 neutralizing antibodies: correlates of high Ad5 titers and implications for potential HIV vaccine trials.

Replication-defective adenoviruses have been utilized as candidate HIV vaccine vectors. Few studies have described the international epidemiology of pre-existing immunity to adenoviruses. We enrolled 1904 participants in a cross-sectional serological survey at seven sites in Africa, Brazil, and Thailand to assess neutralizing antibodies (NA) for adenovirus types Ad5, Ad6, Ad26 and Ad36. Clinical trial samples were used to assess NA titers from the US and Europe. The proportions of participants that were negative were 14.8% (Ad5), 31.5% (Ad6); 41.2% (Ad26) and 53.6% (Ad36). Adenovirus NA titers varied by geographic location and were higher in non-US and non-European settings, especially Thailand. In multivariate logistic regression analysis, geographic setting (non-US and non-European settings) was statistically significantly associated with having higher Ad5 titers; participants from Thailand had the highest odds of having high Ad5 titers (adjusted OR=3.53, 95% CI: 2.24, 5.57). Regardless of location, titers of Ad5NA were the highest and Ad36 NA were the lowest. Coincident Ad5/6 titers were lower than either Ad5 or Ad6 titers alone. Understanding pre-existing immunity to candidate vaccine vectors may contribute to the evaluation of vaccines in international populations.

Cross-clade reactivity of HIV-1-specific T-cell responses in HIV-1-infected individuals from Botswana and Cameroon.

An effective HIV type 1 (HIV-1) vaccine will likely require elicitation of broadly reactive cell-mediated immune (CMI) responses against divergent HIV-1 clades. We compared anti-HIV-1 T-cell immune responses among 363 unvaccinated adults infected with diverse HIV-1 clades. Response rates to clade B Gag and/or clade B Nef in Botswana (95%) and Cameroon (98%) were similar when compared with those in countries previously studied, including Brazil (92%), Thailand (96%), South Africa (96%), Malawi (100%), and the United States (100%). Substantial cross-clade cell-mediated immune responses in Botswana and Cameroon confirm previous findings in a larger, more genetically diverse collection of HIV-1 samples.

Cross-reactivity of anti-HIV-1 T cell immune responses among the major HIV-1 clades in HIV-1-positive individuals from 4 continents.

BACKGROUND: The genetic diversity of human immunodeficiency virus type 1 (HIV-1) raises the question of whether vaccines that include a component to elicit antiviral T cell immunity based on a single viral genetic clade could provide cellular immune protection against divergent HIV-1 clades. Therefore, we quantified the cross-clade reactivity, among unvaccinated individuals, of anti-HIV-1 T cell responses to the infecting HIV-1 clade relative to other major circulating clades. METHODS: Cellular immune responses to HIV-1 clades A, B, and C were compared by standardized interferon- gamma enzyme-linked immunospot assays among 250 unvaccinated individuals, infected with diverse HIV-1 clades, from Brazil, Malawi, South Africa, Thailand, and the United States. Cross-clade reactivity was evaluated by use of the ratio of responses to heterologous versus homologous (infecting) clades of HIV-1. RESULTS: Cellular immune responses were predominantly focused on viral Gag and Nef proteins. Cross-clade reactivity of cellular immune responses to HIV-1 clade A, B, and C proteins was substantial for Nef proteins (ratio, 0.97 [95% confidence interval, 0.89-1.05]) and lower for Gag proteins (ratio, 0.67 [95% confidence interval, 0.62-0.73]). The difference in cross-clade reactivity to Nef and Gag proteins was significant (P<.0001). CONCLUSIONS: Cross-clade reactivity of cellular immune responses can be substantial but varies by viral protein.