Influence of HIV-1 on induced expression of granulopoietic factors: The role of HIV-1 vpr

Abstract

IL-1-induced expression of granulopoietic factors, including G-CSF, by human bone marrow stromal cells is suppressed by HIV-1 infection, a phenomenon that may account for the regenerative granulopoietic failure often seen in HIV-1 infected patients. Seeking to identify the HIV-1 gene products that account for stromal cell dysfunction, we used replication incompetent HIV-1 mutants to demonstrate that deletion of vpr abrogates the stromal cell defect. Bone marrow stromal cell cultures were established in primaria dishes containing VEGF and were allowed to grow to near confluence. HIV-1 pseudotyped with VSV-G envelope protein was produced by transient co-transfection of 293T cells with a VSV-G expression vector and HIV-1 proviral plasmids containing: (1) a deletion in the envelope gene (env-) or (2) deletions of both env and vpr. Expression of G-CSF, GM-CSF, and IL-6 by stromal cells expressing the env deleted mutant was reduced by more than 50%, but this inhibitory effect was largely relieved by mutants with deletions of both env and vpr. To confirm the vpr effect, we carried out gain-of-function studies using bone marrow stromal cells transduced with the Moloney based expression vector pSLX-CMV-vpr or vector control pSLX-CMVX. IL-6 and G-CSF expression was reduced in stromal cells expressing vpr. We conclude that blunted responses of HIV-1 infected hematopoietic stromal cells depends, at least in part, upon the expression of HIV-1 vpr and that, in the case of G-CSF and IL-6, vpr is sufficient to account for this effect.