Antiviral pressure exerted by HIV-1-specific cytotoxic T lymphocytes (CTLs) during primary infection demonstrated by rapid selection of CTL escape virus. Por Borrow, P, Lewicki, H, Wei, X, Horwitz, MS, Peffer, N, Meyers, H, Nelson, J, Gairin, J, Hahn, B, Oldstone, M, Shaw, G