HIV-1 specific T-Cell responses in chronic HIV infected children during continuous treatment and structured treatment interruptions (STI).
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BACKGROUND Sub-Saharan Africa has the highest number of HIV-infected individuals and limited treatment programs. The use of Highly Active Antiretroviral Therapy (HAART) has resulted in a considerable decrease in morbidity and mortality among HIV-infected individuals. Long-term use of HAART has several limitations relating to cost, drug toxicity and adherence. Structured Treatment Interruption (STI) has been proposed as a therapeutic approach which limits the exposure to continuous HAART, but retains the benefits thereof. The role of HIV-specific Tcell responses in the control of viraemia has not been well studied in children and it is not clear when these responses become detectable or whether they are associated with improved viral control. Furthermore, antiretroviral drug resistance is well documented in adults infected with HIV-1 clade B virus but comparable information is lacking for chronic paediatric clade C virus infection. This pilot study focused on a chronic HIV-infected paediatric cohort from Durban, South Africa, to assess the immunologic and virologic responses in perinatal HIVinfected children undergoing STI. METHODS Thirty chronic HIV-infected treatment naïve children were enrolled and randomised into either the treatment interruption or continuous treatment group. Longitudinal measurements of viral loads and CD4 percentages were done at scheduled intervals. Peripheral blood mononuclear cells (PBMCs) were screened for cytotoxic T-lymphocyte (CTL) gamma interferon (IFN-?) enzyme-linked immunospot (ELISpot) assay responses using 410 peptides which spanned the entire HIV-1 clade C proteome. Intracellular cytokine staining (ICS) was done to distinguish between IFN-? Gag-specific T-helper and cytotoxic T cell responses. Pre-HAART drug resistance mutations testing and HLA typing were done for all children. RESULTS There was a significant increase in the median CD4 percentage after HAART was introduced. Six children randomized to the STI arm did not undergo treatment interruption because their viral loads remained detectable at the time of scheduled interruption. Most HIV proteins were targeted in this paediatric cohort. Gag was the most frequently targeted HIV-1 protein (93.1%). In both treatment groups, there were broadening of T-cell responses, however, the magnitude of T-cell responses decreased over time on HAART. Drug-resistant mutations were detectable in 4/29 children before initiation of HAART. CONCLUSION In this pilot study, the HIV-1-specific CD8+ and CD4+ T-cell responses were detected before and during HAART. Although the treatment interruption period was short, there were no adverse outcomes in either the continuous or treatment interruption groups in terms of death or other clinical outcomes. This study suggests that it is important to continue to explore alternative treatment strategies in order to reduce cost and toxicity as well as to enhance adherence.