A secreted high-affinity inhibitor of human TNF from Tanapox virus

Abstract

A class of secreted poxvirus tumor necrosis factor (TNF)-binding proteins has been isolated from Tanapox-infected cell supernatants. The inhibitor bound to a TNF-affinity column and was identified as the product of the 2L gene. Sequence analysis of 2L family members from other yatapoxviruses and swinepox virus yielded no sequence homology to any known cellular gene. The expressed Tanapox virus 2L protein bound to human TNF with high affinity (Kd ‫؍‬ 43 pM) and exhibits an unusually slow off-rate. However, 2L is unable to bind to a wide range of human TNF family members. The 2L protein can inhibit human TNF from binding to TNF receptors I and II as well as block TNF-induced cytolysis. Thus, Tanapox virus 2L represents an inhibitor of human TNF and offers a unique strategy with which to modulate TNF activity.T he tumor necrosis factor (TNF) superfamily of ligands plays critical roles in both adaptive and innate immunity. These ligands form a trimeric structure and bind to members of the TNF receptor (TNFR) superfamily that mediate the signaling events that regulate diverse responses, particularly inflammation and apoptosis (1). During a viral infection, TNF, the prototypic ligand for the family, is induced as an early response of the immune system to an invading pathogen (2). TNF is expressed by activated macrophages as a membrane-associated ligand, which subsequently is cleaved and secreted as a trimer. The proinflammatory effects of TNF are mediated through the cell surface TNFRI and, to a lesser extent, TNFRII (3). Binding of the TNF trimer causes conformational reorganization of the receptors and subsequent recruitment of signaling proteins such as TNFR-associated factor 2 (TRAF2) and Fas-associated death domain (FADD) (3). The TNF͞TNFR signal transduction pathway is such an important aspect of the antiviral response that a number of viruses have evolved targeted strategies to specifically disrupt it.Poxviruses employ a wide range of strategies to modulate, avoid, or diminish the various antiviral immune responses, including the secretion of cytokine-and chemokine-binding proteins and the production of cytokine and growth factor homologs (4-7). The best characterized of these strategies are the secreted homologs of the TNFRs that most likely were derived by the acquisition of an ancestral host TNFR cDNA and subsequent deletion of the transmembrane domain and cytoplasmic tail (8). The first characterized viral homolog of TNFR was the secreted T2 protein from Shope fibroma virus, which binds both TNF and lymphotoxin-␣ (LT-␣) just as its cellular counterpart (9, 10). Deletion of the related T2 gene from myxoma virus greatly attenuated the virus in vivo (11).Other poxvirus-secreted TNFRs were described for monkeypox virus, variola virus, vaccinia virus, ectromelia virus, and cowpox virus (4,8,12). Cowpox virus is atypical among poxviruses because it encodes multiple, unique, soluble TNFRs designated as cytokine response modifier (Crm)B (13), CrmC (14), CrmD (15), and CrmE (16). Each of these cowpox virus TNFRs has...

Genome of Deerpox Virus

“…DPV151 lacks amino-terminal signal peptide and carboxylterminal cytoplasmic domains homologous to cellular MHC-I, and the ␣ 1 domain is not well conserved (data not shown). DPV151 is less similar to the MHC-I homologue from molluscum contagiosum virus (16% identity over 201 amino acids to MC080R) and to homologues of the MHC-I-like TNFBP of Tanapox virus and its homologues in DPV (DPV008), Yabalike disease virus, and swinepox virus (21% identity over 254 amino acids to SPV003) (13). Notably, an MHC-I homologue encoded by murine cytomegalovirus (m144 gene) functions to protect against NK-mediated clearance of virus-infected cells (25).…”

Effects of Ebola Virus Glycoproteins on Endothelial Cell Activation and Barrier Function

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