Expression and maturation of human foamy virus Gag precursor polypeptides.

In this report, we address the processing of the Gag polypeptides of human foamy virus previously reported to be atypical. In the cytoplasm or the nucleus of infected cells as well as in free virus particles, two Gag precursor polypeptides were identified at approximately 72 and 68 kDa, p72 giving rise to p68 by a maturation process. Efficient maturation of Gag precursors was observed only in two situations: (i) during the early steps of virus adsorption and (ii) under experimental conditions, including treatment with DNase I, known to dissociate actin polymers associated with high ionic strength and ionic detergents. Rather than being a defective viral protease function, an association of Gag precursors with a cytoskeleton network might be responsible for the low rate of Gag protein maturation through inhibition of their cleavage by the protease.

Transient immunosuppressive effect induced in rabbits and mice by the human spumaretrovirus prototype HFV (human foamy virus).

Spumaviruses (foamy viruses) constitute one of the three retroviral genera isolated from man. Although spumaviruses have not been clearly linked to a given pathology in humans and other infected species, it is well established that they lead in vivo to chronic infections without detectable viral expression. We thought it of interest to investigate certain aspects of the pathology induced in laboratory animals by human foamy virus (HFV). In this work, we demonstrate that HFV infection of rabbits and mice gives rise to a transient immunosuppressive effect, as evaluated in vitro by lymphocyte transformation tests. This phenomenon occurs shortly after viral inoculation, at around 4-5 days, and regresses within thirty days.

Human foamy virus polypeptides: identification of env and bel gene products.

Human foamy virus (HFV) proteins were identified in human cells cultured in vitro by immunoprecipitation and immunoblotting with specific antisera. Among several viral polypeptides, four glycoproteins of approximately 160, 130, 70, and 48 kDa were identified in HFV-infected cells. gp130 was shown to represent the intracellular env precursor, and gp70 and gp48 were shown to represent the external and transmembrane env proteins, respectively. The nature of gp160, which shares sequences with the env, bel1, and bel2 proteins, is not yet resolved. In addition, a p62 identified with bel1- and bel2-specific antisera likely corresponds to the bet gene product.

Molecular differences between two immunologically related spumaretroviruses: the human prototype HSRV and the chimpanzee isolate SFV6.

A comparative study at the genomic and protein level was performed between two immunologically related spumaretroviruses, the human HSRV and the simian SFV6. Cross immunoprecipitation analysis with specific polyclonal and monoclonal antisera indicates shared antigenic determinants. However, restriction analysis of the viral DNAs and thermal stability of the hybrids demonstrate that HSRV and SFV6 are two different isolates.

Effect of recombinant human alpha A interferon on Visna virus multiplication in acutely infected ovine cells.

We have studied the effects of recombinant human alpha A interferon (IFN) on the multiplication of Visna retrovirus in ovine cells. Pretreatment with IFN followed by continuous IFN treatment, drastically blocked the Visna virus induced cytopathogenic effect and the emergency of neoformed virions. Thus, virus yield and virus dependent reverse transcriptase activity were highly reduced in supernatant fluids. All these effects were accompanied by a strong inhibition of viral protein synthesis. In the light of these data, human IFN action on Visna retrovirus seems to be determined by a mechanism of action distinct from that described in the case of other Retroviridae.