Genetic studies of terminal regions of vaccine and field isolates of capripoxviruses

Generation and application of immortalized sertoli cell line from sheep testis

Primary sheep testicular Sertoli cells (STSCs) are ideal for investigating the molecular and pathogenic processes of capripoxvirus. However, the high cost of isolation and culture of primary STSCs, time-consuming operation, and short lifespan greatly limit their real-world application. In our study, the primary STSCs were isolated and immortalized by transfection of a lentiviral recombinant plasmid containing simian virus 40 (SV40) large T antigen. Androgen-binding protein (ABP) and vimentin (VIM) protein expression, SV40 large T antigen activity, proliferation assays, and apoptosis analysis results showed that immortalized large T antigen STSCs (TSTSCs) still had the same physiological characteristics and biological functions as primary STSCs. Moreover, immortalized TSTSCs had strong anti-apoptosis ability, extended lifespan, and enhanced proliferative activity compared to primary STSCs, which had not transformed in vitro and showed any signs of malignancy phenotype in nude mice. Besides, immortalized TSTSCs were susceptible to goatpox virus (GTPV), lumpy skin disease virus (LSDV), and Orf virus (ORFV). In conclusion, immortalized TSTSCs are useful in vitro models to study GTPV, LSDV, and ORFV in a wide range of ways, suggesting that it can be safely used in virus isolation, vaccine and drug screening studies in future.

The complete genome sequence of Indian sheeppox vaccine virus and comparative analysis with other capripoxviruses

Sheeppox virus (SPPV) is responsible for a significant economic loss to sheep husbandry in enzootic regions of Africa, the Middle East, and Asia including the Indian subcontinent. In this study, we present the complete genome sequence of SPPV vaccine strain SPPV-Srin38/00 from India determined by next-generation sequencing (NGS) using Illumina technology. The attenuated Srinagar vaccine strain of SPPV (SPPV-Srin38/00) was developed by serial passaging the virus initially in lamb testes (LT) cells followed by Vero cell line. The SPPV-Srin38/00 virus has a genome size of 150, 103 bp, which encodes for 147 functional putative genes and consists of a central coding region flanked by two identical 2353 bp inverted terminal repeats (ITRs). Comparative phylogenetic analysis based on complete genome sequences of Capripoxviruses formed three distinct groups each for SPPV, GTPV, and LSDV with clustering of SPPV-Srin38/00 strain with SPPV-A strain. Nine ORFs of SPPV-Srin38/00 namely SPPV-Srin_002/SPPV-Srin_155, SPPV-Srin_004/SPPV-Srin_153, SPPV-Srin_009, SPPV-Srin_013, SPPV-Srin_026, SPPV-Srin_132, and SPPV-Srin_136 were found to be fragmented as compared to LSDV, whereas only one ORF (such as SPPV-Srin_136) was found to be fragmented as compared to GTPV. SPPV genomes, including the SPPV-Srin38/00 strain, shared 99.78-99.98% intraspecies nucleotide identity, indicating that SPPV strains have extremely low genetic diversity. The strain shared 96.80-97.08% and 97.11-97.61% nt identity with GTPV and LSDV strains, respectively. Its ORFs 016, 021, 022, 130 and 138 are the least identical ORFs among three species of the genus Capripoxvirus with 72.5-93% aa identity to GTPV and LSDV strains and may be potentially used for differentiation of CaPV species. This study may contribute to a better understanding of the epidemiology and evolution of capripoxviruses as well as the development of specific detection methods, better expression vectors, and vaccines with improved safety and efficacy.

Comparative analysis of ankyrin (ANK) genes of five capripoxviruses isolate strains from Xinjiang province in China

Background

Sheeppox and goatpox are both economically important animal diseases in which pathogens are goatpox virus (GTPV) and sheeppox virus (SPPV). They can’t cause cross-species infection between sheep and goats in general. But in recent decades, the infection of sheep by goatpox or goats by sheeppox has been reported. The literature has indicated that the occurrence of these cases has a significant and direct relationship with mutations of ankyrin genes families (ANK genes 010,138,140,141.2,145) located in two-terminal regions of capripoxvirus genomes. So it is very important to decipher these nucleotides and their coding amino acid sequences of the five genes regarded as host range and virulence factors for effective prevention and control of capripoxvirus diseases.

Methods

In this study, all the ankyrin genes of three goatpox virus, two sheeppox virus, and one GTPV vaccine strains from Nanjiang areas of Xinjiang province of China during 2010–2011 were collected, amplified, cloned and sequenced. The sequence of every ankyrin genes has been compared with not only sequences from six viruses but also all sequences from three species of capripoxvirus genus from Gene bank, and every ANK gene’s mutated nucleotides and amino acids have been screened, and the relationship of genetic evolution among different virus strains has been analyzed, as well as the domain architecture of these genes was forecasted and analyzed.

Results

The six capripoxvirus strains can be well-distinguished GTPV and SPPV based on five ANK genes’ sequence identicalness except for GTPV-SS strain, which showed higher identicalness with SPPV. The ANK gene sequence of the GTPV-SS strain was 100% identical with SPPV-M1 (ANK138,140,145) and SPPV-M2 (ANK138,145), respectively. Phylogenetically, these six capripoxvirus strains were also grouped into the same cluster of India reference strains in lineages and showed extreme identical conservative or variable regions with India capripoxvirus isolates by sequence alignment. Moreover, for the functional domains, these ANK genes of capripoxvirus except for ANK gene 145, are identical in size, and ANK genes 145 of SPPV are usually 100 bp (approximately 30 aa) longer than those of GTPV and eventually form a PRANC domain at C-terminus.

Conclusions

The isolated strain of GTPV-SS may be a cross-species infection or the collected material was contaminated, and the inferred Capripox outbreak in Xinjiang in 2010 can be introduced from India. ANK genes 138,140,141.2 and 145 of capripoxvirus can be used as the target genes to identify GTPV and SPPV. Moreover, the four ANK genes determining the host range are more significant than the ANK gene 010. These ANK genes play combining roles for their function.