Preservation of functional virus-specific memory CD8+ T lymphocytes in vaccinated, simian human immunodeficiency virus-infected rhesus monkeys

Functional impairment of virus-specific memory CD8⁺ T lymphocytes has been associated with clinical disease progression following HIV, SIV, and simian human immunodeficiency virus infection. These lymphocytes have a reduced capacity to produce antiviral cytokines and mediators involved in the lysis of virally infected cells. In the present study, we used polychromatic flow cytometry to assess the frequency and functional capacity of central memory (CD28⁺CD95⁺) and effector memory (CD28 ^-CD95⁺) subpopulations of Gag-specific CD8⁺ T cells in SIV/simian human immunodeficiency virus-infected rhesus monkeys. The aim of this study was to determine whether Ag-specific, memory CD8⁺ T cell function could be preserved in infected monkeys that had been immunized before infection with a vaccine regimen consisting of a plasmid DNA prime followed by a recombinant viral vector boost. We observed that vaccination was associated with the preservation of Gag-specific central memory CD8⁺ T cells that were functionally capable of producing IFN-γ, and effector memory CD8⁺ T cells that were capable of producing granzyme B following viral Ag exposure.