Abstract: A method of inhibiting expression of HIV antigens in human blood cells infected with HIV. The infected cells are exposed to a plant protein or glycoprotein, such as trichosanthin or momorcharin, at a concentration sufficient to (a) produce a substantial reduction in the level of HIV antigen, and (b) effect a selective reduction in the number of HIV-infected cells, with respect to uninfected cells of the same type. The method is used to treat HIV infection in humans. In another aspect, the invention includes a method of screening drug agents effective in treating HIV infection in humans.