ERVW-1 and infection: In agreement with the lack of in vivo expansion following SIVsmE660 infection, SERV-K Env-specific CD4+ T cells failed to recognize SIV-infected macrophage targets (Fig. 4A) and SERV-K Env-specific CD8+ T cells failed to recognize SIV-infected CD4+ T cell targets (Fig. 4B) as measured by cytokine secretion.