Here we present the genomic sequence, with analysis, of a pathogenic fowlpox virus (FPV). The 288-kbp FPV genome consists of a central coding region bounded by identical 9.5-kbp inverted terminal repeats and contains 260 open reading frames, of which 101 exhibit similarity to genes of known function. Comparison of the FPV genome with those of other chordopoxviruses (ChPVs) revealed 65 conserved gene homologues, encoding proteins involved in transcription and mRNA biogenesis, nucleotide metabolism, DNA replication and repair, protein processing, and virion structure. Comparison of the FPV genome with those of other ChPVs revealed extensive genome colinearity which is interrupted in FPV by a translocation and a major inversion, the presence of multiple and in some cases large gene families, and novel cellular homologues. Large numbers of cellular homologues together with 10 multigene families largely account for the marked size difference between the FPV genome (260 to 309 kbp) and other known ChPV genomes (178 to 191 kbp). Predicted proteins with putative functions involving immune evasion included eight natural killer cell receptors, four CC chemokines, three G-protein-coupled receptors, two beta nerve growth factors, transforming growth factor beta, interleukin-18-binding protein, semaphorin, and five serine proteinase inhibitors (serpins). Other potential FPV host range proteins included homologues of those involved in apoptosis (e.g., Bcl-2 protein), cell growth (e.g., epidermal growth factor domain protein), tissue tropism (e.g., ankyrin repeat-containing gene family, N1R/p28 gene family, and a T10 homologue), and avian host range (e.g., a protein present in both fowl adenovirus and Marek's disease virus). The presence of homologues of genes encoding proteins involved in steroid biogenesis (e.g., hydroxysteroid dehydrogenase), antioxidant functions (e.g., glutathione peroxidase), vesicle trafficking (e.g., two alpha-type soluble NSF attachment proteins), and other, unknown conserved cellular processes (e.g., Hal3 domain protein and GSN1/SUR4) suggests that significant modification of host cell function occurs upon viral infection. The presence of a cyclobutane pyrimidine dimer photolyase homologue in FPV suggests the presence of a photoreactivation DNA repair pathway. This diverse complement of genes with likely host range functions in FPV suggests significant viral adaptation to the avian host. (+info)
Fowlpox virus encodes a novel DNA repair enzyme, CPD-photolyase, that restores infectivity of UV light-damaged virus.
Fowlpox virus (FPV), a pathogen of poultry, can persist in desiccated scabs shed from infected hosts. Although the mechanisms which ensure virus survival are unknown, it is likely that some type of remedial action against environmentally induced damage is required. In this regard, we have identified an open reading frame (ORF) coding for a putative class II cyclobutane pyrimidine dimer (CPD)-photolyase in the genome of FPV. This enzyme repairs the UV light-induced formation of CPDs in DNA by using blue light as an energy source and thus could enhance the viability of FPV during its exposure to sunlight. Based on transcriptional analyses, the photolyase gene was found to be expressed late during the FPV replicative cycle. That the resultant protein retained DNA repair activity was demonstrated by the ability of the corresponding FPV ORF to complement functionally a photolyase-deficient Escherichia coli strain. Interestingly, insertional inactivation of the FPV photolyase gene did not impair the replication of such a genetically altered virus in cultured cells. However, greater sensitivity of this mutant than of the parental virus to UV light irradiation was evident when both were subsequently photoreactivated in the absence of host participation. Therefore, FPV appears to incorporate its photolyase into mature virions where the enzyme can promote their survival in the environment. Although expression of a homologous protein has been predicted for some chordopoxviruses, this report is the first to demonstrate that a poxvirus can utilize light to repair damage to its genome. (+info)
Reticuloendotheliosis virus sequences within the genomes of field strains of fowlpox virus display variability.
Nine field strains of fowlpox virus (FPV) isolated during a 24-year span from geographically diverse outbreaks of fowlpox in the United States were screened for the presence of reticuloendotheliosis virus (REV) sequences in their genomes by PCR. Each isolate appeared to be heterogeneous in that either a nearly intact provirus or just a 248- or 508-nucleotide fusion of portions of the integrated REV 5' and 3' long terminal repeats (LTRs) was exclusively present at the same genomic site. In contrast, four fowlpox vaccines of FPV origin and three originating from pigeonpox virus were genetically homogeneous in having retained only the 248-bp LTR fusion, whereas two other FPV-based vaccines had only the larger one. These remnants of integrated REV presumably arose during homologous recombination at one of the two regions common to both LTRs or during retroviral excision from the FPV genome. Loss of the provirus appeared to be a natural event because the tripartite population could be detected in a field sample (tracheal lesion). Moreover, the provirus was also readily deleted during propagation of FPV in cultured cells, as evidenced by the detection of truncated LTRs after one passage of a plaque-purified FPV recombinant having a "genetically marked" provirus. However, the deletion mutants did not appear to have a substantial replicative advantage in vitro because even after 55 serial passages the original recombinant FPV was still prevalent. As to the in vivo environment, retention of the REV provirus may confer some benefit to FPV for infection of poultry previously vaccinated against fowlpox. (+info)
Postural and neurological deficits in broiler chicks after cervical vaccination with live vaccine.
A disease characterized by paresis and paralysis was seen in 7-9-day-old broiler chicks after vaccination in the neck area at day-of-age with a live virus vaccine containing viruses of Marek's disease, fowl pox, and infectious bursal disease. Affected birds presented with variable signs of ataxia, lateral recumbency, leg paralysis, and twisting or S-shaped flexure of the neck. Gross lesions noted at necropsy included swelling and edema of the subcutaneous tissues and muscles of the neck at the injection site area. A heavy mononuclear inflammatory cell infiltration was seen in the subcutaneous tissues, connective tissues, and muscles of the neck at the injection site. In some cases, the inflammatory process extended along fascial planes to involve the epidural spaces surrounding the spinal cord. Fatty changes with possible demyelination of nerve fibers were noted in some sections of the spinal cord adjacent to the inflammatory lesions. Clusters of poxviruses were found within some inflammatory lesions on transmission electron photomicrographs. (+info)
Phenotypic and kinetic analysis of effective simian-human immunodeficiency virus-specific T cell responses in DNA--and fowlpox virus-vaccinated macaques.
Although T cell immunity is important in the control of HIV-1 infection, the characteristics of effective HIV-specific T cell responses are unclear. We previously observed protection from virulent SHIV challenges in macaques administered priming with DNA vaccines and boosting with recombinant fowlpox viruses expressing shared SIV Gag antigens. We therefore performed a detailed kinetic and phenotypic study of the T cell immunity induced by these vaccines prior to and following SHIV challenge utilizing intracellular cytokine staining. Pigtail macaques vaccinated intramuscularly with DNA/recombinant fowlpox virus exhibited a coordinated induction of first Gag-specific CD4 T cell responses and then a week later Gag-specific CD8 T cell responses following the fowlpox virus boost. Overall, the magnitude and timing of the peak CD8 T cell responses following challenge was significantly associated with reductions in SHIV viremia following pathogenic challenge. After pathogenic lentiviral challenge, virus-specific effector memory T cells derived from animals controlling SHIV infection recognized a broad array of epitopes, expressed multiple effector cytokines and rapidly recognized virus-exposed cells ex vivo. These results shed light on some of the requirements for T cells in the control of pathogenic lentiviral infections. (+info)
Integration of the reticuloendotheliosis virus envelope gene into the poultry fowlpox virus genome is not universal.