Tuberculosis (TB) is considered as a global burden. It is the most common opportunistic infection affecting HIV-positive people. Having HIV increases one’s risk to develop TB by up to 50 times. Out of 9.27 million cases of TB in 2007, it is estimated that 1.37 million were HIV positive. A study published in the Journal of Leukocyte Biology explains why HIV patients are susceptible to TB.

A team of Harvard scientists has made a significant discovery which may help in the development of new treatments to help HIV patients to combat tuberculosis. The investigators found out how HIV interrupts with the lungs’ cellular and molecular mechanisms that fight TB infection. The research was lead by Naimish Patel, M.D. of Beth Israel Deaconess Medical Center and Harvard Medical School. Patel’s team extracted immune cells known as alveolar macrophages from the lungs of asymptomatic HIV-positive patients as well as from a group who did not have HIV. In patient’s with HIV, the macrophages show a decreased response to the TB bacterium when compared to health controls. The scientists further examined lung specimens from the HIV-positive group and found increased levels of IL-10 molecule. High levels of IL-10 increased the amount of a protein called “BCL-3″ in alveolar macrophages and this results to HIV-patients’ weakened ability to counter tuberculosis.

The rise in HIV infections and the neglect of TB control programs have caused a resurgence of tuberculosis. In countries with a high number of HIV-positive patients, incidence rate of tuberculosis continue to increase. The heightened susceptibility of HIV patients to TB perplexed the medical world for decades. It is but logical to conclude that if the mechanism involving any disease process is unclear, the likelihood of coming up with appropriate therapies may not be very promising. The discovery of Dr. Patel and his team, is remarkable because it gives hope for millions of HIV-infected individuals. Solving the mystery behind HIV patients’ vulnerability to tuberculosis paves way for future research and possibly better drugs to cure and prevent TB in millions of people infected with HIV.

References:
http://data.unaids.org/pub/factsheet/2006/tb_hiv_qa.pdf

Patel et al. Impaired M. tuberculosis-mediated apoptosis in alveolar macrophages from HIV persons: potential role of IL-10 and BCL-3. Journal of Leukocyte Biology, 2009; 86 (1): 53 DOI: 10.1189/JLB.0908574

Photo credit: Mic Agbayani

Tags: AIDS, HIV, sexually-transmitted disease, STD, TB, Tuberculosis