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How effectively does HAART restore immune responses to Mycobacterium tuberculosis? Implications for tuberculosis control.
Lawn SD, Bekker LG, Wood R.
AIDS
2005 Jul 22;19(11):1113-1124.
Abstract
Use of highly active antiretroviral treatment (HAART) has had a major impact on HIV-associated morbidity and mortality in industrialized countries. Access to HAART is now expanding in low-income countries where tuberculosis (TB) is the most important opportunistic disease. The incidence of TB has been fuelled by the HIV epidemic and in many countries with high HIV prevalence current TB control measures are failing. HAART reduces the incidence of TB in treated cohorts by approximately 80% and therefore potentially has an important role in TB control in such countries. However, despite the huge beneficial effect of HAART, rates of TB among treated patients nevertheless remain persistently higher than among HIV-negative individuals. This observation raises the important question as to whether immune responses to Mycobacterium tuberculosis (MTB) are completely or only partially restored during HAART. Current data suggest that full restoration of circulating CD4 cell numbers occurs only among a minority of patients and that, even among these, phenotypic abnormalities and functional defects in lymphocyte subsets often persist. Suboptimal restoration of MTB-specific immune responses may greatly reduce the extent to which HAART is able to contribute to TB control at the community level because patients receiving HAART live much longer and yet would maintain a chronically heightened risk of TB.
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Reviewed by
Susa Coffey, MD
Comment
Tuberculosis (TB) is one of the most common causes of death in HIV-infected people worldwide. The risk of TB increases with advancing immune suppression, but TB, unlike most opportunistic infections, also occurs more frequently in HIV-infected people than HIV-uninfected people even at high CD4 cell counts, and its risk remains higher after reconstitution of CD4 numbers on antiretroviral therapy (ART). Indeed, a new study of the incidence of TB in patients with recent HIV seroconversion indicates that the risk of TB doubles in the first year after HIV infection, at a time when CD4 counts could be expected to be relatively well preserved.(1)
Tuberculosis (TB) is one of the most common causes of death in HIV-infected people worldwide. The risk of TB increases with advancing immune suppression, as does the liklihood of death from TB. However, unlike most opportunistic infections, TB also occurs more frequently in HIV-infected people with high CD4 cell counts, as compared to HIV-uninfected people, and its risk remains higher even after reconstitution of CD4 numbers on antiretroviral therapy (ART). Indeed, a new study of the incidence of TB in patients with recent HIV seroconversion indicates that the risk of TB doubles in the first year after HIV infection, at a time when CD4 counts could be expected to be relatively well preserved.(1)
This excellent review examines current knowledge on the complex interactions of HIV, immune system function, and tuberculosis. It summarizes issues such as immune system dysregulation early in HIV infection, immune recovery with ART, and the impact of ART on TB, and offers a perspective on the possible role of ART in TB control.
See also
Sonnenberg, Glynn, Fielding
References
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