Background: The high-burden regions of Sub-Saharan Africa, which accounted for greater than 70% of the HIV epidemic, are disproportionately affected by the high rates of TB coinfection. This might be explained by, the low immune tolerance of the population due to malnutrition and chronic infections aggravating immune suppression. In this review, we discuss the immunopathogenesis of this common co-infection that causes significant morbidity and mortality in people living with HIV globally.
Methods: We used published studies using a two-step search strategy. Initial search of Pub Med Central and Google Scholar was undertaken followed by an analysis of the keywords. A second search using all the reference list of all identified reports and articles was searched for additional studies. Literature published as of January 1, 1981, that meets the inclusion criteria were considered. Qualitative data was extracted from papers included in the review.
Result: Mortality occurs at both ends of the immunological spectrum of TB at one end HIV uninfected patient dies from asphyxiation from acute massive hemoptysis due to cavitary TB; at the other end, and far more frequently HIV-infected patient with disseminated TB dies from overwhelming infection with less evidence of focal pathology. There is no clear sign that the HIV-TB epidemic is slowing, especially considering the emergence of increasingly drug-resistant strains of MTB. A major challenge for the future is to discover immune correlates of TB protection and TB disease risk. Failure to define this conclusively has hindered TB prevention strategies, including the design of new TB vaccines to replace BCG, which provides only shortlived efficacy, prevents severe forms of the extra-pulmonary disease and is contraindicated in PLHIV.
Conclusion: Understanding TB and HIV infection through immunological advances needs to be combined to describe the complex interactions between TB and HIV and the effects of ART. The complex interactions between the individual components of innate and acquired immune responses to TB and HIV infection is also likely to be the next step forward.
Keywords: HIV-infection; co-infections; immune tolerance; tuberculosis.