early loss of mycobacterium tuberculosis–specific helper t cell responses after HIV infection
HIV+ individuals have increased susceptibility to becoming infected with tuberculosis. In fact, a second epidemic of tuberculosis has arisen in the last decade due to the increasing number of people who are immunodeficient from HIV infection. In contrast to many opportunistic infections which occur in late-stage HIV infection (or AIDS), increased tuberculosis susceptibility occurs when HIV+ individuals are largely asymptomatic and not susceptible to many other infections. In the December 1 issue of Journal of Infectious Diseases, Geldmacher et al try to understand the mechanism for the early susceptibility of HIV+ people to tuberculosis. Below are some of the pertinent points from the abstract of that study:
The acid-fast bacillus Mycobacterium tuberculosis is often the first manifestation of acquired immunodeficiency syndrome (AIDS) in patients infected with human immunodeficiency virus (HIV). This study was conducted to better understand the mechanism underlying M. tuberculosis–specific pathogenicity early after onset of HIV infection. In tuberculosis (TB)–asymptomatic subjects (i.e., subjects with unknown TB status who did not show clinical signs suggestive of TB), chronic HIV infection was associated with a decreased percentage of subjects with detectable M. tuberculosis–specific Th1 cells, a decrease which was not observed among subjects with active TB. Acute HIV infection induced a rapid depletion of M. tuberculosis–specific Th1 cells in 4 subjects who remained TB asymptomatic, whereas the population of these cells remained stable in subjects who remained HIV negative. Taken together, these data suggest a mechanism of rapid M. tuberculosis–specific Th1 cell depletion that may contribute to the early onset of TB in individuals with latent M. tuberculosis infection who become HIV infected.
