Despite recent advances in anti-retroviral therapy (ART), human immunodeficiency virus (HIV) infections and the resulting acquired immunodeficiency syndrome (AIDS) remain an important cause of morbidity and mortality worldwide with 2.6 million new cases and 1.8 million deaths by the year 2009 . In Ethiopia, according to the 2007 single point HIV prevalence estimate, there were 1,216,908 adult people living with HIV (PLHIV), and of these 397,818 expected to take ART treatment by the year 2010 . On the other hand, tuberculosis (TB) caused by Mycobacterium tuberculosis, remains the leading causes of death from infectious diseases worldwide. In 2012, about 8.6 million incident TB and 1.3 million deaths due to TB were reported globally. The majority of TB cases occurred in Asian (58%) and African (27%) countries .
In developing countries, TB remains a major public health threat among HIV-infected individuals [3, 4]. HIV is the most potent risk factor for TB and TB is the leading cause of morbidity and mortality in HIV/AIDS patients [5, 6]. Tuberculosis enhances progression of HIV infection and HIV increases the risk of infection as well as reactivation of latent tuberculosis. It is estimated that 50 - 60% of PLHIV will develop TB disease in their lifetime in contrast with HIV negative persons, whose lifetime risk is only 10% [4, 7]. The proportion of TB cases co-infected with HIV is highest in African countries. In African countries, about 37% of TB cases were co-infected with HIV which accounted for 75% of TB cases among HIV positive people worldwide . In 2007, based on Federal HIV/AIDS Prevention and Control Office report in Ethiopia, the TB/HIV co-infection rate was 20 - 50% . According to WHO report, in 2012 the incidence of TB infection in Ethiopia was 247 per 100,000 people and 10.2% of them were estimated to have co-infection with HIV .
With the advent of ARV drugs, HIV/AIDS has become a treatable chronic disease. Effective anti-retroviral therapy (ARV) therapy is usually convoyed by an increase in the number of CD4+ T - cells and the functional restoration of patents’ immune response and decline in HIV viral load as well. However, the requirement of regular and lifelong medication of HIV patient is challenged with emergencies of treatment failure [8–10]. Impaired immunological recovery may indicate incomplete suppression of plasma HIV - RNA which results ARV drug resistance . HIV treatment failure can be defined as progression of disease after ART initiation. Anti-retroviral treatment failure can be assessed clinically, immunologically and virologically. However, on the basis of clinical criteria treatment failure can’t be concluded. Despite viral load testing is preferred approach for monitoring ART response, in resource limited settings, immunological failure criteria, trends in CD4+ T - cells counts over time, remains the strongest predictor of treatment failure .
The recovery of CD4+ T - cells count during ART in HIV/TB co-infected patients is less clear. However, studies assessing immune responses to ART have found poor CD4+ T - cells recovery to occur in patients who develop incident TB after initiating ART [11–16]. Moreover, in spite of HIV statuses sever CD4+ T -lymphocytopenia has been observed in TB patients . An in vitro study indicated that TB infection impairs cellular immune responses through M. tuberculosis-induced apoptosis of T - cells . Therefore, TB may act as a cofactor that accelerates the impairment of the immune function and shortens survival of HIV - infected individuals. Although TB/HIV co-infection is a major public health problem in Ethiopia, no studies have reported the effect of TB on immunological responses of HIV patients during ART. Hence, assessing the effect of TB on immunological responses of HIV patients will provide information for clinicians for appropriate management of TB/HIV co-infected patients. Moreover, policy makers and health professionals can use the findings to design ART related programs. Therefore, the aim of this study was to assess the effect of incident TB on immunological response of HIV/AIDS patients during ART at the University of Gondar Hospital.