Full expression of transfected nonproducer interfering HIV-1 proviral DNA abrogates susceptibility of human He-La CD4+ cells to HIV.

An Hut-78 cell clone (F12) harboring a nonproducer human immunodeficiency virus-1 (HIV) variant, and showing a complete resistance to HIV-1 or HIV-2 superinfection, was previously characterized. We demonstrated that the replication of the superinfecting HIVs is blocked at the retrotranscription step, despite the CD4 down-regulation, since HIVs are able to cross the Hut-78/F12 cell membrane. In order to establish if the expression of the HIV-1 variant (F12/HIV) could be per se sufficient to induce the homologous viral interference shown in the F12 cells, the whole F12/HIV provirus was cloned and transfected in He-La CD4+ cells. In F12/HIV expressing He-La CD4+ clones, both the viral proteins expressed and the HIV nonproducer phenotype remain unmodified compared to F12 cells. Furthermore, despite the full expression of CD4 HIV receptors, the life cycle of the superinfecting HIV could be either strongly inhibited or totally abolished, depending on the cell clone considered. The inhibition of the superinfecting HIV was also reproduced when an HIV infectious molecular clone was transfected in F12/HIV He-La CD4+ clones, thus indicating that a post-cDNA synthesis block may operate against the superinfecting HIV. These data demonstrate that HIV susceptibility could be abrogated in cells expressing the F12/HIV genome, even in absence of any CD4 down-regulation.