[Show abstract][Hide abstract] ABSTRACT: Infections with monkeypox, cowpox and weaponized variola virus remain a threat to the increasingly unvaccinated human population, but little is known about their mechanisms of virulence and immune evasion. We now demonstrate that B22 proteins, encoded by the largest genes of these viruses, render human T cells unresponsive to stimulation of the T cell receptor by MHC-dependent antigen presentation or by MHC-independent stimulation. In contrast, stimuli that bypass TCR-signaling are not inhibited. In a non-human primate model of monkeypox, virus lacking the B22R homologue (MPXVΔ197) caused only mild disease with lower viremia and cutaneous pox lesions compared to wild type MPXV which caused high viremia, morbidity and mortality. Since MPXVΔ197-infected animals displayed accelerated T cell responses and less T cell dysregulation than MPXV US2003, we conclude that B22 family proteins cause viral virulence by suppressing T cell control of viral dissemination.
[Show abstract][Hide abstract] ABSTRACT: Cowpox virus, a zoonotic poxvirus endemic to Eurasia, infects a large number of host species which makes its eradication impossible. The elimination of world-wide smallpox vaccination programs renders the human population increasingly susceptible to infection by orthopoxviruses resulting in a growing number of zoonotic infections including CPXV transmitted from domestic animals to humans. The ability of CPXV to infect a wide range of mammalian host is likely due to the fact that, among the orthopoxviruses, CPXV encodes the most complete set of open reading frames expected to encode immunomodulatory proteins. This renders CPXV particularly interesting for studying poxviral strategies to evade and counteract the host immune responses.
Microbes and Infection 11/2010; 12(12-13):900-9. · 2.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Cowpox virus encodes an extensive array of putative immunomodulatory proteins, likely contributing to its wide host range, which includes zoonotic infections in humans. Unlike Vaccinia virus, cowpox virus prevents stimulation of CD8(+) T cells, a block that correlated with retention of MHC class I in the endoplasmic reticulum by the cowpox virus protein CPXV203. However, deletion of CPXV203 did not restore MHC class I transport or T cell stimulation. Here, we demonstrate the contribution of an additional viral protein, CPXV12, which interferes with MHC class I/peptide complex formation by inhibiting peptide translocation by the transporter associated with antigen processing (TAP). Importantly, human and mouse MHC class I transport and T cell stimulation was restored upon deletion of both CPXV12 and CPXV203, suggesting that these unrelated proteins independently mediate T cell evasion in multiple hosts. CPXV12 is a truncated version of a putative NK cell ligand, indicating that poxviral gene fragments can encode new, unexpected functions.
[Show abstract][Hide abstract] ABSTRACT: Acquisition of the membrane and genome encapsidation is an important step in the replication of enveloped viruses. The biogenesis of the poxviral primary membrane and the core as well as the mechanisms of their maturation are poorly understood. Using RNA interference approach, we demonstrate that a cellular trans-Golgi network membrane protein, golgin-97, is essential for virus replication. Analysis of the virion morphology in the cells depleted of golgin-97 shows that the protein is required for the virus morphogenesis and, in particular, for the formation of the first infectious virus form, mature virus, but not its precursor, immature virus. This suggests that golgin-97 may be involved in the maturation of the virus core and, potentially, the virus membrane.
[Show abstract][Hide abstract] ABSTRACT: Poxviruses are the only DNA viruses known to replicate and assemble in the cytoplasm of infected cells. Poxvirus morphogenesis is a complicated process in which four distinct infectious forms of the virus are produced: intracellular mature virus, intracellular enveloped virus, cell-associated enveloped virus, and extracellular enveloped virus. The source of primary membrane wrapping the intracellular mature virus, the first infectious form, is still unknown. Although the membrane was suggested to originate from the endoplasmic reticulum-Golgi intermediate compartment, none of the marker proteins from this or any other cell compartments has been found in the intracellular mature virus. Thus, it was hypothesized that the membrane is either extensively modified by the virus or synthesized de novo. In the work described here, we demonstrate that a host cell protein residing in the trans-Golgi network membrane, golgin-97, is transported to the sites of virus replication and assembly and becomes incorporated into the virions during poxvirus infection. Inside the virion, golgin-97 is associated with the insoluble core protein fraction. Being able to adopt a long rod-like structure, the protein apparently extends through the virion envelope and protrudes from its surface. Here we discuss the potential role and functions of golgin-97 in poxvirus replication and propose two working models.
Journal of Virology 01/2007; 80(23):11520-7. · 5.08 Impact Factor