AUTHOR=Vidya Vijayan K. K. , Karthigeyan Krithika Priyadarshini , Tripathi Srikanth P. , Hanna Luke Elizabeth TITLE=Pathophysiology of CD4+ T-Cell Depletion in HIV-1 and HIV-2 Infections JOURNAL=Frontiers in Immunology VOLUME=Volume 8 - 2017 YEAR=2017 URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2017.00580 DOI=10.3389/fimmu.2017.00580 ISSN=1664-3224 ABSTRACT=The hall mark of HIV infection is gradual loss of CD4+ T cells and imbalance of CD4+ T cells homeostasis, with progressive impairment of immunity that leads ultimately to death. HIV infection in humans can be caused by two related yet distinct viruses: HIV-1 and HIV-2. HIV-2 is typically less virulent as compared to HIV-1 which may permit the host to mount more effective, sustained T-cell immunity. Although both the infections manifest the same clinical spectrum, the much lower rate of CD4+ T cell decline and slower progression of disease in HIV-2 infected individuals has grabbed the attention of several researchers. Here, we review the most recent findings on the differential rate of decline of CD4+T cell in HIV-1 and HIV-2 infection and provide plausible reasons for the observed differences between the two groups.