The Genomic Sequence Analysis of the Left and Right Species-Specific Terminal Region of a Cowpox Virus Strain Reveals Unique Sequences and a Cluster of Intact ORFs for Immunomodulatory and Host Range Proteins

Abstract

Sequencing and computer analysis of the left (52,283 bp) and right (49,649 bp) variable DNA regions of the cowpox virus strain GRI-90 (CPV-GRI) has revealed 51 and 37 potential open reading frames (ORFs), respectively. Comparison of the structure-function organization of these DNA regions of CPV-GRI with those previously published for corresponding regions of genomes of vaccinia virus, strains Copenhagen (VAC-COP) and Western Reserve (VAC-WR); and variola major virus, strains India-1967 (VAR-IND), Bangladesh-1975 (VAR-BSH); and alastrim variola minor virus, strain Garcia-1966 (VAR-GAR), was performed. Within the left terminal region under study, an extended DNA sequence (14,171 bp), unique to CPV, has been found. Within the right region of the CPV-GRI genome two segments, which are unique to CPV DNA (1579 and 3585 bp) have been found. Numerous differences have been revealed in the genetic structure of CPV-GRI DNA regions, homologous to fragments of the genomes of the above-mentioned orthopoxvirus strains. A cluster of ORFs with structural similarity ot immunomodulatory and host range function of other poxviruses have also been detected. A comparison of the sequences of ORF B, crmA, crmB, crmC, IMP, and CHO hr genes of CPV Brighton strain (CPV-BRI) with the corresponding genes in strain GRI-90 have revealed an identity at the amino acid level ranging from 82 to 96% between the two strains. The findings are significant in light of the recent demonstration of CPV as an important poxvirus model system to probe the precise in vivo role(s) of the unique virally encoded immunomodulatory proteins. Also, the presence of a complete and intact repertoire of immunomodulatory proteins, ring canal proteins family, and host range genes indicates that CPV may have been the most ancient of all studied orthopoxviruses.

Vaccinia virus strains Lister, USSR and Evans express soluble and cell-surface tumour necrosis factor receptors.

“…and others 1998). On the other hand, CPV GRI-90 has four different TNFR-like genes (Shchelkunov et al, 1998), three of which express a vTNFR (Hu et al, 1994 ;Smith et al, 1996 ;Loparev et al, 1998). A soluble vTNFR has been predicted from sequence similarity in lymphocystis disease virus (Tidona & Darai, 1997), a large DNA iridovirus that infects fish, consistent with the conservation of TNF throughout evolution (Beck & Habicht, 1991).…”

“…On the other hand, the ability of CrmD and the putative VV vTNFR to bind LTα differ, and our studies found no cell-surface vTNFR expressed by this strain of CPV. Another possibility is that the fourth ORF with sequence similarity to TNFR superfamily members that was identified in CPV strain GRI-90 (K3R) (Shchelkunov et al, 1998) represents the novel VV vTNFR, although no TNFR activity has been demonstrated for K3R. However, neither CrmD nor K3R were reported to have membrane-anchoring domains (Loparev et al, 1998 ;Shchelkunov et al, 1998).…”

Cowpox Virus Evades CTL Recognition and Inhibits the Intracellular Transport of MHC Class I Molecules

“…Genomic comparisons suggest that CPV is an ancestor of other orthopoxviruses (3), including VAR, which is now considered a bioterrorist threat. This ancestral role of CPV is supported by the observation that CPV contains the most complete set of immune modulators, of which many are mutated and/or deleted in vaccinia virus (VV) (4). It is likely that these mutations and deletions contribute to its diminished virulence and success as an attenuated vaccine against smallpox (5) CPV is thus an excellent model for identifying immune modulators of orthopoxviruses and their relationship to viral virulence.…”

Molecular mimicry of the inflammation modulatory proteins (IMPs) of poxviruses: evasion of the inflammatory response to preserve viral habitat

“…CPV is a good model to study the viral modulation of the inflammatory response because it encodes several proteins that can influence the inflammatory response, e.g., the complement control protein termed inflammation modulatory protein (IMP), the interleukin-1 (IL-1) receptor-like protein termed CrmB, the IL-1␤-converting enzyme inhibitor (ICE/Caspase), termed CrmA, the tumor necrosis factor (TNF) receptor-like protein CrmC, and the macrophage inflammatory protein-1␣ (MIP-1␣) receptor-like protein. Our studies have also shown that of all the orthopoxviruses (a group that includes vaccinia and variola viruses), CPV seems to be the most ancient and has the most complete and intact repertoire of open reading frames (ORFs) for immunomodulatory proteins [2]. Because rodents are the primary reservoir hosts for cowpox virus, a number of different knockout mice can be employed to characterize the contribution and relative importance of an individual host defense molecule in response to viral infection as well as to evaluate the role of an individual viral protein in its interaction with the immune system.…”