Simian Immunodeficiency Virus Infection of CD4+CD8+T Cells in a Macaque with an Unusually High Peripheral CD4+CD8+T Lymphocyte Count

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Abstract
We assessed the possible role in vivo CD4+ CD8+ T cells as a viral reservoir for simian immunodeficiency virus (SIV), in a macaque with 50% CD4+ CD8+ T cells in peripheral blood. During primary infection (day 14) of this rhesus macaque with the pathogenic SIVmac251 strain, proviruses were detected at similar frequencies in CD4+ CD8+ T cells (1/10) and CD4+ T cells (1/10) and at a lower frequency in CD8+ T cells (1/800). On day 235, no viral DNA was detected in CD8+ cells, despite the persistent high viral load, indicating that CD8+ cells do not constitute a reservoir during the chronic phase of SIV infection. Infection induced early lymphopenia of CD4+, CD4+ CD8+, and CD8+ cells; only the CD8+ cell population returned to initial levels and expanded further. We found that CD4+ CD8+ T cells expressed the costimulatory CD28 molecule less and were more prone to die in vitro after phytohemagglutinin/interleukin 2 stimulation than were CD4+ T cells. Taken together, massive death of CD4+ CD8+ T cells during acute stages of SIV infection may explain why CD8+ T cells did not represent a major reservoir for SIV at the onset of infection.