TB R&D Weekly Update: Study of Mother-to-Child Transmission of HIV Shows TB to be Risk Factor

Gupta A, Bhosale R, Kinikar A, Gupte N, Bharadwaj R, Kagal A, Joshi S, Khandekar M, Karmarkar A, Kulkarni V, Sastry J, Mave V, Suryavanshi N, Thakar M, Kulkarni S, Tripathy S, Sambarey P, Patil S, Paranjape R, Bollinger RC, Jamkar A; Six Week Extended-Dose Nevirapine (SWEN) India Study Team. Maternal tuberculosis: a risk factor for mother-to-child transmission of human immunodeficiency virus. J Infect Dis. 2011 Feb 1;203(3):358-63.

Gupta, et al, conducted a study of HIV-infected mothers in an urban teaching hospital in Pune, India. In their Six Week Extended-Dose Nevirapine (SWEN) study they compared the effect of single dose nevirapine, with extended treatment, on the rate of mother-to-child transmission (MTCT) of HIV in breast feeding mothers. Analyzing the data, they found that TB-infected mothers were more likely to pass HIV to their children even when controlling for factors such as: increased viral load as a result of TB infection, CD4 count, breast-feeding duration, and ARV use. Since the study was designed to measure nevirapine administration it faced some design limitations in analyzing the role of TB as a risk factor for MTCT of HIV due to sample size (of 783 total mothers in the study, 33 mothers had TB and of 10 of those mothers passed on HIV to their children).

While acknowledging these limitations, the authors present three possible reasons for why TB might be associated with MTCT of HIV:

  1. TB may make the mothers more infectious
    1. Due to a “transient increase in viral load” that was not accounted for in their measurements
    2. “Mediated by immune activation and inflammation due to maternal TB”
  2. Maternal TB may lead to some “immune activation” where “the infant’s CD4-expressing immune cells become more susceptible to infection.”
  3. There may be reason that was not sufficiently controlled for in their study

Given the limitations of the study design and sample size, there is need for further research to verify the authors’ findings. If, however, TB is shown as a risk factor for MTCT of HIV it would mark yet another deadly symbiosis between these two diseases, and would have important bearing on HIV infection control efforts.

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