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Swinepox virus (SPV) has several advantages as a potential clinical vector for a live vector vaccine. In this study, to obtain a safer and more efficient SPV vector, three SPV mutants, Δ003, Δ010, and ΔTK were successfully constructed. A virus replication experiment showed that these SPV mutants had lower replication abilities compared to wtSPV in 10 different host-derived cell lines. Animal experiments with mouse and rabbit models demonstrate that these three mutants and wtSPV did not cause any clinical signs of dermatitis. No fatalities were observed during a peritoneal challenge assay with these mutants and wtSPV in a mouse model. Additionally, the three mutants and wtSPV were not infectious at 60 h after vaccination in rabbit models. Furthermore, we evaluated biosafety, immunogenicity and effectiveness of the three mutants in 65 1-month-old piglets. The results show that there were no clinical signs of dermatitis in the Δ003 and ΔTK vaccination groups. However, mild signs were observed in the Δ010 vaccination groups when virus titres were high, and apparent clinical signs were observed at the sites of inoculation. Samples from all experimental pig groups were assessed by qPCR, and no SPV genomic DNA was found in five organs, faeces or blood. This suggests that the infectious abilities of wtSPV and the SPV mutants were poor and limited. In summary, this study indicates that two mutants of SPV, Δ003 and ΔTK, may be promising candidates for an attenuated viral vector in veterinary medicine.

Background: Porcine epidemic diarrhea virus (PEDV) is the main causative agent of porcine epidemic diarrhea (PED). Since December 2010, a large-scale outbreak of diarrhea has been observed in swine farms in China. Accumulated evidence indicates that this large-scale outbreak of diarrhea were caused by highly virulent PEDV variants., Methods: A PEDV strain, YC2014, was isolated from intestinal samples of suckling piglets with acute diarrhea in 2014. The complete genomic sequence of YC2014 and the nucleotide sequence of S gene were aligned with sequences of published isolates using MEGA 5.1 software. The immune protective efficiency of YC2014 were determined by testing PEDV neutralizing antibodies in sera, the colostrum and the milk on 7th day after farrowing of the immunized sows. The diarrhea symptoms of piglets after challenge were also observed., Results: Phylogenetic analysis of the complete genomic sequence of YC2014 and the nucleotide sequence of S gene demonstrated that the YC2014 PEDV strain was clustered with the PEDV epidemic strains, with >99 % nucleotide identity to these PEDV strains. The S gene sequence of YC2014 shared only 93.9 % ~ 94.4 % identities with classical CV777, DR13 and JS2008 strains, with 15 nucleotide insertion in three sites and three nucleotide deletion in one site. The amino acid (AA) sequence of S gene of YC2014 shared only 92.8 % ~ 93.4 % identities with classical CV777, DR13 and JS2008 strains, with 5 AA insertion in two sites and 1 AA deletion in one site. In the immune protective efficiency tests, the neutralizing antibody titers in sera, the colostrum and the milk on 7th day after farrowing of the inactivated YC2014 PEDV strain immunized group were significantly higher than the inactivated CV777 immunized group and the inactivated DR13 immunized group (P < 0.05). The traditional inactivated PEDV vaccines made from CV777 or DR13 could not protect piglets from YC2014 challenge, while inactivated YC2014 could provide piglets with 100 % protection against YC2014 challenge., Conclusions: The results showed that, great antigenicity variation had occurred to this YC2014 PEDV strain. The YC2014 PEDV strain could provide piglets against homologous challenge. It is critical for future pathogenic and antigenic studies, as well as for the development of effective preventive and control vaccines against PEDV.