An 85-aa segment of the GB virus type C NS5A phosphoprotein inhibits HIV-1 replication in CD4 + Jurkat T cells

The nonpathogenic human GB virus C (GBV-C), a member of the Flaviviridae, is highly prevalent in individuals with HIV-1 infections or with parenteral and sexual risk factors. Long-term GBV-C viremia has been associated with better survival or improved diagnosis in several epidemiological studies. In a previous study we reported that the E2 glycoprotein of GBV-C interferes with HIV-1 entry in vitro. To address the question what region of the E2 protein is involved in suppression of HIV-1 replication, we performed an E2-derived peptide scanning and determined the HIV-inhibitory activity of each peptide in HIV replication assays. We demonstrate here that peptides representing the N-terminal part of the E2 protein from amino acids (aa) 29 to 72 are able to inhibit efficiently HIV-1 replication in vitro. In particular, the peptides P6-2 (representing the E2-region from aa 45 to 64) and P4762 (aa 37 to 64) showed the highest potency in HIV replication assays performed on TZM-bl cells with 50% inhibitory concentrations between 0.1 and 2 M. However, primary HIV-1 isolates representing clades A to H showed a high variability in their sensitivity to E2 peptides. Pseudovirus inhibition assays revealed that the sensitivity is determined by the gp120/gp41 envelope proteins. Using HIV-1 BlaM-Vpr-based fusion assays, we demonstrate that the E2-derived peptides prevent HIV-1 binding or fusion, presumably via interaction with the HIV-1 particle. Together, these findings reveal a new mechanism of viral interference, suggesting that the envelope protein E2 of GBV-C target directly HIV-1 particles to avoid entry of these virions.

Section: Discussionsupporting

confidence: 69%

Section: Gb Virus C (Gbv-c) a Positive-strand Rna Virus Of The Flavimentioning

confidence: 99%

Peptides Derived from a Distinct Region of GB Virus C Glycoprotein E2 Mediate Strain-Specific HIV-1 Entry Inhibition

Koedel

Eissmann

Wend

et al. 2011

“…Plasmid pTRE2/A3G was created by PCR amplification of an ϳ1.2-kb DNA fragment from pHA-A3G, followed by insertion of the fragment into the pTRE2-Hyg-GFP expression vector. This plasmid was modified from the original pTRE2-Hyg vector by insertion of the encephalomyocarditis virus internal ribosomal entry site element to direct translation of green fluorescent protein (GFP) (30). WT and mutant viruses were obtained by transfecting 293T cells with infectious plasmids using calcium phosphate precipitation as previously described (2).…”

Section: Methodsmentioning

confidence: 99%

Regulation of vif mRNA Splicing by Human Immunodeficiency Virus Type 1 Requires 5′ Splice Site D2 and an Exonic Splicing Enhancer To Counteract Cellular Restriction Factor APOBEC3G

Mandal

Exline

Feng

et al. 2009

The human immunodeficiency virus type 1 (HIV-1) accessory protein Vif is encoded by an incompletely spliced mRNA resulting from splicing of the major splice donor in the HIV-1 genome, 5 splice site (5ss) D1, to the first splice acceptor, 3ss A1. We have shown previously that splicing of HIV-1 vif mRNA is tightly regulated by suboptimal 5ss D2, which is 50 nucleotides downstream of 3ss A1; a GGGG silencer motif proximal to 5ss D2; and an SRp75-dependent exonic splicing enhancer (ESEVif). In agreement with the exon definition hypothesis, mutations within 5ss D2 that are predicted to increase or decrease U1 snRNP binding affinity increase or decrease the usage of 3ss A1 (D2-up and D2-down mutants, respectively). In this report, the importance of 5ss D2 and ESEVif for avoiding restriction of HIV-1 by APOBEC3G (A3G) was determined by testing the infectivities of a panel of mutant viruses expressing different levels of Vif. The replication of D2-down and ESEVif mutants in permissive CEM-SS cells was not significantly different from that of wild-type HIV-1. Mutants that expressed Vif in 293T cells at levels greater than 10% of that of the wild type replicated similarly to the wild type in H9 cells, and Vif levels as low as 4% were affected only modestly in H9 cells. This is in contrast to Vif-deleted HIV-1, whose replication in H9 cells was completely inhibited. To test whether elevated levels of A3G inhibit replication of D2-down and ESEVif mutants relative to wild-type virus replication, a Tet-off Jurkat T-cell line that expressed approximately 15-fold-higher levels of A3G than control Tet-off cells was generated. Under these conditions, the fitness of all D2-down mutant viruses was reduced relative to that of wild-type HIV-1, and the extent of inhibition was correlated with the level of Vif expression. The replication of an ESEVif mutant was also inhibited only at higher levels of A3G. Thus, wild-type 5ss D2 and ESEVif are required for production of sufficient Vif to allow efficient HIV-1 replication in cells expressing relatively high levels of A3G.

“…Latent herpesvirus infection may make HIV susceptible to acyclovir, which fails to exhibit anti-HIV effect in cells singly infected with HIV (53). Other viruses, both DNA- and RNA-containing viruses, may also interfere with HIV reproduction (33,84,90). Nonapparent persistent infection with a virus (e.g., SV5) may modulate the innate immune system of host cells, altering thereby reproduction of another virus in these cells (93).…”

Section: Discussionmentioning

confidence: 99%

Interactions between Viral and Prokaryotic Pathogens in a Mixed Infection with Cardiovirus and Mycoplasma

Lidsky

Romanova

Kolesnikova

et al. 2009

In the natural environment, animal and plant viruses often share ecological niches with microorganisms, but the interactions between these pathogens, although potentially having important implications, are poorly investigated. The present report demonstrates, in a model system, profound mutual effects of mycoplasma and cardioviruses in animal cell cultures. In contrast to mycoplasma-free cells, cultures contaminated with Mycoplasma hyorhinis responded to infection with encephalomyocarditis virus (EMCV), a picornavirus, but not with poliovirus (also a picornavirus), with a strong activation of a DNase(s), as evidenced by the TUNEL (terminal deoxynucleotidyltransferase-mediated dUTP-biotin nick end labeling) immunofluorescence assay and electrophoretic analysis of host DNA. This degradation was reminiscent of that observed upon apoptosis but was caspase independent, judging by the failure of the specific pan-caspase inhibitor Q-VD-OPh to prevent it. The electrophoretic mobility of the enzyme responsible for DNA degradation and dependence of its activity on ionic conditions strongly suggested that it was represented by a DNase(s) of mycoplasma origin. In cells not infected with EMCV, the relevant DNase was dormant. The possibility is discussed that activation of the mycoplasma DNase might be linked to a relatively early increase in permeability of plasma membrane of the infected cells caused by EMCV. This type of unanticipated virus-mycoplasma "cooperation" may exemplify the complexity of pathogen-host interactions under conditions when viruses and microorganisms are infecting the same host. In the course of the present study, it was also demonstrated that pan-caspase inhibitor zVAD(OMe).fmk strongly suppressed cardiovirus polyprotein processing, illustrating an additional pitfall in investigations of viral effects on the apoptotic system of host cells.