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
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
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.
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.
783 mothers, 3 had existing TB at study entry and 30 developed
new TB by 12 months after delivery.
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).
majority of infants with HIV were identified at birth,
indicating infection in the womb, rather than during delivery
or through breast-feeding.
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).
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,"
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,
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.
Marais. Impact of Tuberculosis on Maternal and Child Health.
Journal of Infectious Diseases 203(3): 304-305 (free
full text.) February 1, 2011.