U937 cells overexpressing bcl-xl are resistant to human immunodeficiency virus-1-induced apoptosis and human immunodeficiency virus-1 replication

Many viruses, including human immunodeficiency virus type 1 (HIV-1), induce apoptosis and are affected by cellular expression of antiapoptotic genes. We sought to examine the effect of antiapoptotic gene expression on HIV rep lication by transfecting the promyelomonocytic cell line U937 with the bcl- xl gene to obtain clones of U937 cells that overexpressed bcl-xl (designate d U937bcl-xl), a negative control U937 clone transfected with vector alone (designated U937neo) and a clone overexpressing bcl-2 (designated U937bcl-2 ). After infection with HIV-1, U937neo cells underwent apoptosis four times as frequently as the U937bcl-xl cells. Furthermore, U937bcl-xl cells produ ced 5-fold less HIV-I protein than U937neo, whereas U937bcl-2 produced at l east 2-fold more p24 than the U937neo control. Transient coexpression of bc l-2 or bcl-xl decreased HIV production and transcription from the HIV LTR. To define the mechanism by which bcl-xl, but not bcl-2, inhibits HIV expres sion, we examined bcl-2 and bcl-xl expression after HIV infection and CD4 c ross-linking. Although HIV-I infection or cross-linking CD4 led to a decrea se in expression of bcl-2, it had no effect on bcl-xl expression. These res ults provide a mechanism for the resistance of U937bcl-xl transfectants, bu t not U937bcl-2 transfectants, to HIV-1 replication in monocytic cells in v itro. Therapies that up-regulate bcl-xl expression potentially provide a no vel means to decrease the destructiveness Of HIV-1. (C) 1999 Academic Press .