Induction of mucosal homing virus-specific CD8⁺ T lymphocytes by attenuated simian immunodeficiency virus

Induction of virus-specific T-cell responses in mucosal as well as systemic compartments of the immune system is likely to be a critical feature of an effective AIDS vaccine. We investigated whether virus-specific CD8⁺ lymphocytes induced in rhesus macaques by immunization with attenuated simian immunodeficiency virus (SIV), an approach that is highly effective in eliciting protection against mucosal challenge, express the mucosa-homing receptor α4β7 and traffic to the intestinal mucosa. SIV-specific CD8⁺ T cells expressing α4β7 were detected in peripheral blood and intestine of macaques infected with attenuated SIV. In contrast, virus-specific T cells in blood of animals immunized cutaneously by a combined DNA-modified vaccinia virus Ankara regimen did not express α4β7. These results demonstrate the selective induction of SIV-specific CD8⁺ T lymphocytes expressing α4β7 by a vaccine approach that replicates in mucosal tissue and suggest that induction of virus-specific lymphocytes that are able to home to mucosal sites may be an important characteristic of a successful AIDS vaccine.