Chimeric toxins targeted to the human immunodeficiency virus type 1 envelope glycoprotein augment the in vivo activity of combination antiretroviral therapy in thy/liv-SCID-Hu mice

Highly active antiretroviral therapy (HAART), which combines multiple inhib itors of essential human immunodeficiency virus type 1 (HIV-1) enzymes, ind uces dramatic and sustained viral load reductions in many people infected w ith HIV-1, However, reservoirs of infected cells capable of producing repli cation-competent virus persist even after years of HAART, preventing elimin ation of infection. CD4-PE40 and 3B3(Fv)-PE38, chimeric toxins designed to target the HIV envelope (Env), represent a complementary class of agents th at selectively kill productively infected cells. To investigate whether the se Env-targeted toxins might serve as adjuncts to HAART for the elimination of infected cells, we tested their ability to augment HAART efficacy in vi vo by using a thy/liv SCID-hu mouse model. CD4-PE40 and 3B3(Fv)-PE38 marked ly enhanced the capacity of HAART to suppress acute HIV-1 infection and imp roved HAART-mediated viral load reduction in mice with established HIV-1 in fection. These results represent the first demonstration of in vivo anti-HI V-1 efficacy for Env-targeted toxins and support their potential therapeuti c utility in combination with HAART.