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Higher risk of perinatal HIV transmission in TB mothers
By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor, Stanford University School of Medicine. Dr. Winslow is a speaker for Cubist Pharmaceuticals and GSK, and is a consultant for Siemens Diagnostic.
Synopsis: In this study, 783 HIV-infected mother-infant pairs were evaluated as part of a randomized, controlled trial of nevirapine (NVP) given for 6 weeks vs. single-dose NVP to reduce mother-to-child transmission (MTCT) of HIV. Thirty percent of mothers with TB vs. 12% of mothers without TB transmitted HIV to their infants.
Source: Gupta A, et al. Maternal tuberculosis: a risk factor for mother-to-child transmission of human immunodeficiency virus. J Infect Dis 2011; 203:358-363.
In this study, 783 HIV-infected Indian mother-infant pairs participated in a randomized clinical trial comparing NVP given for 6 weeks vs. single-dose NVP to prevent MTCT of HIV among breast-fed infants. As a secondary study endpoint, multivariate logistic regression analysis was used to assess the impact of maternal TB occurring during pregnancy through 12 months post-partum. Of the 783 mothers, three had prevalent TB and 30 had incident TB by 12 months post-partum. Of the 33 mothers with TB, 10 (30%) transmitted HIV to their infants vs. 87 of 750 (12%) mothers without TB who transmitted HIV to their infants. In multivariate analysis, maternal TB was associated with 2.51-fold increased odds of HIV transmission, adjusting for maternal factors (HIV RNA, CD4+ count, and antiretroviral therapy) and infant factors (breast-feeding duration, infant NVP administration, gestational age, and birth weight).
This is an interesting study done in an area of the world with a high prevalence of TB, and emphasizes the inter-relatedness of TB and HIV in the developing world. While there were no differences at the time of enrollment into the trial in plasma HIV RNA between mothers diagnosed with TB vs. those without TB, the most likely explanation for the increased risk of HIV transmission in mothers with TB would be immune activation and, likely, increased mean HIV RNA levels in the TB-infected mothers, resulting in both increased transplacental, intrapartum, and post-partum transmission. Unfortunately, the design of the study precluded confirming this hypothesis, since post-enrollment maternal HIV RNA levels were not systematically collected. Other potential mechanisms (including maternal immune activation increasing levels of HIV RNA in breast milk and immune activation in the infants leading to increased susceptibility to MTCT) were postulated by the authors, but the design of the study precluded being able to examine these hypotheses.
TB in HIV-infected mothers has been shown to be associated with higher maternal and infant mortality.1,2 Clearly, it is critical that efforts continue to focus on control of both of these scourges to human health, with particular emphasis on prevention and prompt treatment of maternal TB in HIV-infected women.