Virion-Targeted Viral Inactivation of Human Immunodeficiency Virus Type 1 by Using Vpr Fusion Proteins

Inactivation of progeny virions with chimeric virion-associated proteins represents a novel therapeutic approach against human immunodeficiency virus (HIV) replication. The HIV type 1 (HIV-1) Vpr gene product, which is packaged into virions, is an attractive candidate for such a strategy. In this study, we developed Vpr-based fusion proteins that could be specifically targeted into mature HIV-1 virions to affect their structural organization and/or functional integrity. Two Vpr fusion proteins were constructed by fusing to the first 88 amino acids of HIV-1 Vpr the chloramphenicol acetyltransferase enzyme (VprCAT) or the last 18 C-terminal amino acids of the HIV-1 Vpu protein (VprIE). These Vpr fusion proteins were initially designed to quantify their efficiency of incorporation into HIV-1 virions when produced in cis from the provirus. Subsequently, CD4⁺ Jurkat T-cell lines constitutively expressing the VprCAT or the VprIE fusion protein were generated with retroviral vectors. Expression of the VprCAT or the VprIE fusion protein in CD4⁺ Jurkat T cells did not interfere with cellular viability or growth but conferred substantial resistance to HIV replication. The resistance to HIV replication was more pronounced in Jurkat-VprIE cells than in Jurkat-VprCAT cells. Moreover, the antiviral effect mediated by VprIE was dependent on an intact p6^gag domain, indicating that the impairment of HIV-1 replication required the specific incorporation of Vpr fusion protein into virions. Gene expression, assembly, or release was not affected upon expression of these Vpr fusion proteins. Indeed, the VprIE and VprCAT fusion proteins were shown to affect the infectivity of progeny virus, since HIV virions containing the VprCAT or the VprIE fusion proteins were, respectively, 2 to 3 times and 10 to 30 times less infectious than the wild-type virus. Overall, this study demonstrated the successful transfer of resistance to HIV replication in tissue cultures by use of Vpr-based antiviral genes.