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Tuberculosis Coinfection Increases Risk of Mother-to-Child HIV Transmission

HIV positive women coinfected with tuberculosis (TB) are more likely to transmit HIV to their babies during pregnancy, according to a study described in the February 1, 2011, Journal of Infectious Diseases. These findings underline the importance of TB treatment and use of antiretroviral therapy (ART) to prevent HIV transmission.

Amita Gupta and fellow investigators with the Six Week Extended-Dose Nevirapine (SWEN) India Study Team looked at risk factors for mother-to-child HIV transmission among nearly 800 HIV positive women.

Maternal HIV viral load, CD4 Tell count, breast-feeding, use of antiretroviral drugs, and coinfection with malaria are well-established factors associated with vertical HIV transmission, the study authors noted as background, but the impact of tuberculosis has not been well established.

The SWEN study was designed to compare extended nevirapine (Viramune) for 6 weeks versus single-dose nevirapine to reduce mother-to-child HIV transmission among breast-fed infants.

The present analysis included 783 HIV positive Indian women and their infants, who were randomly assigned to the 2 dosing schedules. The researchers assessed the impact of maternal TB occurring during pregnancy and the first year after delivery on vertical HIV transmission.

Results

• Among 783 mothers, 3 had existing TB at study entry and 30 developed new TB by 12 months after delivery.
• Among the 33 mothers with TB, 10 (30%) transmitted HIV to their infants, compared with 87 of 750 (12%) mothers without TB (odds ratio 3.31, or more than 3 times the risk).
• A majority of infants with HIV were identified at birth, indicating infection in the womb, rather than during delivery or through breast-feeding.
• In a multivariate analysis, maternal TB was associated with 2.51-fold increased risk of mother-to-child HIV transmission, after adjusting for other maternal factors (viral load, CD4 count, ART) and infant factors (breast-feeding duration, nevirapine use, gestational age, and birth weight) (P=?0.04).

"Maternal TB is associated with increased [mother-to-child transmission] of HIV," the study authors wrote. "Prevention of TB among HIV-infected mothers should be a high priority for communities with significant HIV/TB burden."

In an accompanying editorial, Ben Marais from Stellenbosch University in South Africa noted that TB is the most important infectious cause of disease and death among HIV positive women in areas with endemic TB such as sub-Saharan Africa and Asia.

Pregnant women may be more vulnerable to developing TB due to immune system changes (Th-1 down-regulation) during gestation, he suggested. "The strong Th-1 stimulus provided by TB may increase placental inflammation, explaining some of the adverse fetal outcomes observed and the increased risk of in utero HIV [mother-to-child transmission]."

Increased HIV viral load due to TB-related immune stimulation accounted for some of the increased risk, but excess risk remained after adjusting for viral load.

This study "demonstrates that prevention of TB among HIV-infected mothers should be considered as part of a well-functioning prevention of HIV [mother-to-child transmission] program," Marais recommended.

Investigator affiliations: Clinical Global Health Education, Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD; Johns Hopkins University-Byramji Jeejeebhoy Medical College HIV Clinical Trials Unit; Byramji Jeejeebhoy Medical College; National AIDS Research Institute, Pune, India.

2/1/11

References

A Gupta, R Bhosale, A Kinikar, and others (SWEN India Study Team). Maternal tuberculosis: a risk factor for mother-to-child transmission of human immunodeficiency virus. Journal of Infectious Diseases 203(3): 358-363 (free full text.) February 1, 2011.

BJ Marais. Impact of Tuberculosis on Maternal and Child Health. Journal of Infectious Diseases 203(3): 304-305 (free full text.) February 1, 2011.