Vpx is required for dissemination and pathogenesis of SIVSM PBj: Evidence of macrophage-dependent viral amplification

Abstract

The viral accessory protein Vpx is required for productive in vitro infection of macrophages by simian immunodeficiency virus from sooty mangabey monkeys (SIV(SM)). To evaluate the roles of Vpx and macrophage infection in vivo, we inoculated pigtailed macaques intravenously or intrarectally with the molecularly cloned, macrophage tropic, acutely pathogenic virus SIV(SM) PBj 6.6, or accessory gene deletion mutants (deltaVpr or deltaVpx) of this virus. Both wild-type and SIV(SM) PBj deltaVpx viruses were readily transmitted across the rectal mucosa. A subsequent 'stepwise' process of local amplification of infection and dissemination was observed for wild-type virus, but not for SIV(SM) PBj deltaVpx, which also showed considerable impairment of the overall kinetics and extent of its replication. In animals co-inoculated with equivalent amounts of wild-type and SIV(SM) Pbj deltaVpx intravenously or intrarectally, the deltaVpx mutant was at a strong competitive disadvantage. Vpx-dependent viral amplification at local sites of initial infection, perhaps through a macrophage-dependent mechanism, may be a prerequisite for efficient dissemination of infection and pathogenic consequences after exposure through either mucosal or intravenous routes.

Macrophages and HIV-1: dangerous liaisons

“…In these viruses, Vpx performs the functions of HIV-1 Vpr associated with replication in macrophages and nuclear targeting (Fletcher et al, 1996). It is noteworthy that a Vpx mutant SIV that was unable to replicate in macrophages did not disseminate in infected macaques and did not cause disease (Hirsch et al, 1998).…”

Evidence for a cytopathogenicity determinant in HIV-1 Vpr

“…Vpr genes were directly amplified from plasma viral RNA as described (21). To analyze the frequency of truncated Vpr alleles in plasma virions, recombinant PCR-script clones containing amplified Vpr alleles were analyzed by oligonucleotide probe-specific hybridization (21).…”

“…Vpr genes were directly amplified from plasma viral RNA as described (21). To analyze the frequency of truncated Vpr alleles in plasma virions, recombinant PCR-script clones containing amplified Vpr alleles were analyzed by oligonucleotide probe-specific hybridization (21). Briefly, XL-1 Blue MRF-Kan cells were transformed with recombinant PCR clones and transferred to nylon membranes (Magna Lift; Micron Separations, Westboro, MA) and disrupted after successive treatments with 10% SDS (3 min), 0.5 M NaOH͞1.5 M NaCl (5 min), 0.5 M Tris⅐HCl, pH 8.0͞1.5 M NaCl (5 min), and 2ϫ SSPE [standard saline phosphate͞EDTA (0.18 M NaCl͞10 mM phosphate, pH 7.4͞1 mM EDTA)] for 5 min.…”

The Engagement of Activating FcγRs Inhibits Primate Lentivirus Replication in Human Macrophages

“…HIV and SIV infection of monocytes and differentiated tissue-resident macrophages may play a major role in viral transmission, dissemination, and persistence (1)(2)(3)(4). The capacity of monocytes and macrophages to migrate in tissues makes them potential conveyors of HIV and SIV infections.…”