ICTV Virus Taxonomy Profile: Poxviridae 2023.

Poxviridae is a family of enveloped, brick-shaped or ovoid viruses. The genome is a linear molecule of dsDNA (128-375 kbp) with covalently closed ends. The family includes the sub-families Entomopoxvirinae, whose members have been found in four orders of insects, and Chordopoxvirinae, whose members are found in mammals, birds, reptiles and fish. Poxviruses are important pathogens in various animals, including humans, and typically result in the formation of lesions, skin nodules, or disseminated rash. Infections can be fatal. This is a summary of the International Committee on Taxonomy of Viruses (ICTV) Report on the family Poxviridae, which is available at ictv.global/report/poxviridae.

Phylogenetic Analysis of South African Bovine Leukaemia Virus (BLV) Isolates.

Bovine leukaemia virus (BLV) causes chronic lymphoproliferative disorder and fatal lymphosarcoma in cattle, leading to significant economic losses in the beef and dairy industries. BLV is endemic globally and eleven genotypes have been identified. To date, only Zambian isolates have been genotyped from Africa. Although high BLV prevalence has been reported in South Africa, there has been no molecular characterisation of South African BLV isolates. To characterise BLV isolates in South Africa for the first time, we investigated the phylogenetic relationships and compared the genetic variability of eight South African BLV isolates with BLV isolates representing the eleven known genotypes from different geographical regions worldwide. Phylogenetic analyses based on full-length and partial env sequences as well as full-length gag sequences revealed that at least two genotypes, genotypes 1 (G1) and 4 (G4), are present in cattle in South Africa, which is consistent with studies from Zambia. However, our analysis revealed that the G1 South African isolate is more similar to other G1 isolates than the G1 Zambian isolates whereas, the G4 South African isolates are more divergent from other G4 isolates but closely related to the G4 Zambian isolate. Lastly, amino acid sequence alignment identified genotype-specific as well as novel amino acid substitutions in the South African isolates. The detection of two genotypes (G1 and G4) in southern Africa highlights the urgent need for disease management and the development of an efficacious vaccine against local strains.

Influence of the lumpy skin disease virus (LSDV) superoxide dismutase homologue on host transcriptional activity, apoptosis and histopathology.

Lumpy skin disease virus (LSDV), a Capripoxvirus, is of economic importance in the cattle industry and is controlled by vaccination. A comparison was made of the host response to the two LSDV vaccines Neethling and Herbivac LS, with reference to the well-studied Orthopoxvirus, modified vaccinia Ankara (MVA), in a mouse model. Because the vaccines differ at the superoxide dismutase homologue (SOD) gene locus, recombinant SOD knock-out and knock-in nLSDV vaccines were constructed and all four vaccines were tested for the induction and inhibition of apoptosis. The SOD homologue was associated both with induction of apoptosis as well as inhibition of camptothecin-induced apoptosis. Histological analysis of chorioallantoic membranes of fertilized hens' eggs infected with the four different vaccines indicated marked mesodermal proliferation associated with vaccines containing the full-length SOD homologue as well as increased immune cell infiltration. Our findings suggest that the SOD homologue may influence vaccine immunogenicity.

South African bovine ephemeral fever virus glycoprotein sequences are phylogenetically distinct from those from the rest of the world.

Bovine ephemeral fever virus (BEFV) is an economically important arbovirus affecting cattle and water buffalo. Currently, isolates can be separated into three phylogenetic groups, differentiated by the place of isolation, namely, East Asia, Australia, and the Middle East. BEFV surface glycoprotein (G) genes from 14 South African field strains collected between 1968 and 1999 were sequenced and compared to 154 published sequences. The BEFV isolates from South Africa were found to be phylogenetically distinct from those from other parts of the world.

Comparative analysis of avian poxvirus genomes, including a novel poxvirus from lesser flamingos (Phoenicopterus minor), highlights the lack of conservation of the central region.

BACKGROUND: Avian poxviruses are important pathogens of both wild and domestic birds. To date, seven isolates from subclades A and B and one from proposed subclade E, have had their genomes completely sequenced. The genomes of these isolates have been shown to exhibit typical poxvirus genome characteristics with conserved central regions and more variable terminal regions. Infection with avian poxviruses (APVs) has been reported in three species of captive flamingo, as well as a free-living, lesser flamingo at Kamfers dam, near Kimberley, South Africa. This study was undertaken to further characterise this virus which may have long term effects on this important and vulnerable, breeding population. RESULTS: Gene content and synteny as well as percentage identities between conserved orthologues was compared between Flamingopox virus (FGPV) and the other sequenced APV genomes. Dotplot comparisons revealed major differences in central regions that have been thought to be conserved. Further analysis revealed five regions of difference, of differing lengths, spread across the central, conserved regions of the various genomes. Although individual gene identities at the nucleotide level did not vary greatly, gene content and synteny between isolates/species at these identified regions were more divergent than expected. CONCLUSION: Basic comparative genomics revealed the expected similarities in genome architecture but an in depth, comparative, analysis showed all avian poxvirus genomes to differ from other poxvirus genomes in fundamental and unexpected ways. The reasons for these large genomic rearrangements in regions of the genome that were thought to be relatively conserved are yet to be elucidated. Sequencing and analysis of further avian poxvirus genomes will help characterise this complex genus of poxviruses.

Six host-range restricted poxviruses from three genera induce distinct gene expression profiles in an in vivo mouse model.

BACKGROUND: Host-range restricted poxviruses make promising vaccine vectors due to their safety profile and immunogenicity. An understanding of the host innate immune responses produced by different poxvirus vectors would aid in the assessment, selection and rational design of improved vaccines for human and veterinary applications. Novel avipoxviruses are being assessed to determine if they are different from other poxvirus vectors. Analysis of the transcriptome induced in a mouse model would aid in determining if there were significant differences between different poxvirus vectors which may reflect different adjuvant potential as well as establish if they should be further evaluated as vaccine vectors. RESULTS: We compared host transcript abundance in the spleens of BALB/c mice twenty four hours after intravenous infection (10(5) pfu/mouse) with six host-restricted poxvirus species from three genera, namely Lumpy Skin Disease virus (LSDV), Canarypox virus (CNPV), Fowlpox virus (FWPV), modified vaccinia Ankara (MVA) and two novel South African avipoxviruses, Feral Pigeonpox virus (FeP2) and Penguinpox virus (PEPV). These six viruses produced qualitatively and quantitatively distinct host responses with LSDV, followed by MVA, inducing the greatest interferon (IFN) response. FeP2 and PEPV caused very little change to host transcript abundance compared to the other 4 viruses tested. CNPV and FWPV induced the up regulation of two immunoglobulin genes (Ighg and Ighg3 (IgG3)) with CNPV inducing a third, Ighm (IgM). HIV-1-specific IgG3 antibodies have been correlated with decreased risk of HIV-1 infection in the RV144 trial, which included a CNPV-based vector (Yates et al. (Sci Transl Med, 6(228) p228, 2014). Up regulation of IgG3 by CNPV and FWPV but not the other poxviruses tested in vivo, implies that these two avipoxvirus-vector backbones may be involved in stimulation of the clinically important IgG3 antibody subclass. Differential transcript abundance associated with the different poxviruses is further discussed with particular emphasis on responses related to immune responses. CONCLUSION: Six, genetically diverse host-restricted poxviruses produce different responses in a mouse model early after infection. These differences may affect the immune response induced to vaccine antigen in vectors based on these viruses. The two novel avipoxviruses were clearly distinguishable from the other viruses.

The complete genome sequences of poxviruses isolated from a penguin and a pigeon in South Africa and comparison to other sequenced avipoxviruses.

BACKGROUND: Two novel avipoxviruses from South Africa have been sequenced, one from a Feral Pigeon (Columba livia) (FeP2) and the other from an African penguin (Spheniscus demersus) (PEPV). We present a purpose-designed bioinformatics pipeline for analysis of next generation sequence data of avian poxviruses and compare the different avipoxviruses sequenced to date with specific emphasis on their evolution and gene content. RESULTS: The FeP2 (282 kbp) and PEPV (306 kbp) genomes encode 271 and 284 open reading frames respectively and are more closely related to one another (94.4%) than to either fowlpox virus (FWPV) (85.3% and 84.0% respectively) or Canarypox virus (CNPV) (62.0% and 63.4% respectively). Overall, FeP2, PEPV and FWPV have syntenic gene arrangements; however, major differences exist throughout their genomes. The most striking difference between FeP2 and the FWPV-like avipoxviruses is a large deletion of ~16 kbp from the central region of the genome of FeP2 deleting a cc-chemokine-like gene, two Variola virus B22R orthologues, an N1R/p28-like gene and a V-type Ig domain family gene. FeP2 and PEPV both encode orthologues of vaccinia virus C7L and Interleukin 10. PEPV contains a 77 amino acid long orthologue of Ubiquitin sharing 97% amino acid identity to human ubiquitin. CONCLUSIONS: The genome sequences of FeP2 and PEPV have greatly added to the limited repository of genomic information available for the Avipoxvirus genus. In the comparison of FeP2 and PEPV to existing sequences, FWPV and CNPV, we have established insights into African avipoxvirus evolution. Our data supports the independent evolution of these South African avipoxviruses from a common ancestral virus to FWPV and CNPV.

Phylogenetic and histological variation in avipoxviruses isolated in South Africa.

Thirteen novel avipoxviruses were isolated from birds from different regions of South Africa. These viruses could be divided into six groups, according to gross pathology and pock appearance on chick chorioallantoic membranes (CAMs). Histopathology revealed distinct differences in epidermal and mesodermal cell proliferation, as well as immune cell infiltration, caused by the different avipoxviruses, even within groups of viruses causing similar CAM gross pathology. In order to determine the genetic relationships among the viruses, several conserved poxvirus genetic regions, corresponding to vaccinia virus (VACV) A3L (fpv167 locus, VACV P4b), G8R (fpv126 locus, VLTF-1), H3L (fpv140 locus, VACV H3L) and A11R-A12L (fpv175-176 locus) were analysed phylogenetically. The South African avipoxvirus isolates in this study all grouped in clade A, in either subclade A2 or A3 of the genus Avipoxvirus and differ from the commercial fowlpox vaccines (subclade A1) in use in the South African poultry industry. Analysis of different loci resulted in different branching patterns. There was no correlation between gross morphology, histopathology, pock morphology and phylogenetic grouping. There was also no correlation between geographical distribution and virus phenotype or genotype.

Avian poxvirus epizootic in a breeding population of Lesser Flamingos (Phoenicopterus minor) at Kamfers Dam, Kimberley, South Africa.

Avian pox has a worldwide distribution, but prior to this investigation has not been reported in free-ranging flamingo populations. During observations of the first successful breeding of Lesser Flamingos on a purpose-built island, at Kamfers Dam near Kimberley, South Africa, multiple small, raised, crusted plaques on the legs and facial area were noticed on 30% of the fledgling flamingos. A diagnosis of avipoxvirus infection was made on the basis of the macroscopic, histologic, and electron microscopic features, and was further confirmed by DNA sequence analysis. The avipoxvirus detected was very similar to that previously detected in albatross and falcons.

Phylogenetic analysis of three genes of Penguinpox virus corresponding to Vaccinia virus G8R (VLTF-1), A3L (P4b) and H3L reveals that it is most closely related to Turkeypox virus, Ostrichpox virus and Pigeonpox virus.

Phylogenetic analysis of three genes of Penguinpox virus, a novel Avipoxvirus isolated from African penguins, reveals its relationship to other poxviruses. The genes corresponding to Vaccinia virus G8R (VLTF-1), A3L (P4b) and H3L were sequenced and phylogenetic trees (Neighbour-Joining and UPGMA) constructed from MUSCLE nucleotide and amino acid alignments of the equivalent sequences from several different poxviruses. Based on this analysis, PEPV was confirmed to belong to the genus Avipoxvirus, specifically, clade A, subclade A2 and to be most closely related to Turkeypox virus (TKPV), Ostrichpox virus (OSPV)and Pigeonpox virus (PGPV).