ABSTRACT
The fact that wild felines are carriers of pernicious infectious viruses should be a major concern due to the potential cross-species transmission between the felines and human or domestic animals. However, studies on the virus in the captive wild felines, especially in tigers, are thin on the ground. In this study, we screened four infectious viruses, namely, feline parvovirus (FPV), feline coronavirus (FCoV), canine distemper virus (CDV), and influenza A virus (IAV), in the blood samples of 285 captive Siberian tigers (Panthera tigris altaica) and in the spleen samples of two deceased lions (Panthera leo), which were collected from 2019 to 2021 in three Siberian Tiger Parks from the northeast of China. Nucleic acids isolated from the blood samples collected from tigers and the spleen samples collected from two deceased lions were positive for FPV by PCR, and the positive rate was 4.6% (13/285) in tigers. Furthermore, the VP2 gene of FPV was amplified by nested PCR, and the sequences of the VP2 gene from these six FPV positive strains shared 98.3-99.9% homology with the reference. The key amino acid sites of VP2 protein were consistent with that of FPV reference strains. Phylogenetic analysis based on the VP2 gene showed that in this study, FPV-positive strains were grouped within the FPV clade and closely related to the Asian strains clade. The results of this study showed that FPV circulated in the captive Siberian tigers and lions in northeastern China and provided valuable information for the study of FPV epidemiology in wild felines. Therefore, we suggest that regular antibody monitoring and booster immunization for tigers should be performed.
ABSTRACT
Canine parvovirus type 2 (CPV2) is a highly contagious cause of serious and often fatal disease in young dogs. Despite the widespread availability of attenuated vaccines, safer, more stable, and more effective CPV2 vaccine candidates are still under exploration. Vaccinia virus (VV) has already been proved to be a safe, stable, and effective vaccine vector. In this study, we generated a VV-based CPV2 vaccine candidate (VV-CPV-VP2) and then evaluated its immunogenicity in mice and dogs. The exogenous vp2 gene of CPV2, which replaced the major virulence gene hemagglutinin (ha) of VV, expressed efficiently and stably in vitro. Subsequently, intramuscular immunization of mice induced robust and lasting systemic immune responses, including neutralizing antibody against both CPV2a and CPV2b, and CPV2-VP2-specific interferon gamma (IFN-γ) secreting T cell. In addition, administration with a high-dose of VV-CPV-VP2 did not cause significant side effects for mice, thus indicating marked safety of this vaccine candidate. Most importantly, a single-dose vaccination of VV-CPV2-VP2 elicited substantial antibody responses and provided comparable protection for dogs with attenuated CPV2 vaccine. Collectively, this study demonstrated that VV-CPV2-VP2 could be used as a promising vaccine candidate preventing CPV2 from infection for dogs.