Feline panleukopenia virus (FPV), a globally pervasive and highly pathogenic pathogen, has garnered significant attention recently due to the cross-species transmission of its variants. Despite the vast body of research conducted on FPV, studies exploring its evolutionary history, dynamics, and the factors driving its evolution remain scarce. The pathogenicity of strains with the prevalent mutations (A91S and I101T) in the VP2 protein has also not been fully elucidated. This study conducted a comparative analysis of FPV VP2 sequences sourced from Xinjiang province in China, other provinces in China, and other countries. It was confirmed that the evolutionary rate of FPV approached that of RNA viruses, at approximately 1.13 × 10⁻⁴ substitutions/site/year. The study reconstructed molecular models of the VP2 protein with the A91S and I101T mutations and used viral strains carrying these mutations to perform the animal regression experiment. It was confirmed that isolates with the A91S and I101T mutations could cause typical leukopenia and acute enteritis symptoms, suggesting that the mutant strains still possess certain pathogenicity. This is the first study to report on the evolutionary dynamics of FPV in Xinjiang, China, and it emphasized the importance of continuously monitoring FPV evolutionary dynamics.

Li H, et al. J Vet Sci. 2019 Oct;21:e88. https://doi.org/10.4142/jvs.2020.21.e88

Listeria monocytogenes (L. monocytogenes) is a foodborne pathogen that causes listeriosis in humans and other animals. Surface proteins with the LPXTG motif have important roles in the virulence of L. monocytogenes. Lmo0159 is one such protein, but little is known about its role in L. monocytogenes virulence, motility, and biofilm formation. Here, we constructed and characterized a deletion mutant of lmo0159 (∆lmo0159). We analyzed not only the capacity of biofilm formation, motility, attachment, and intracellular growth in different cell types but also LD₅₀; bacterial load in mice’s liver, spleen, and brain; expression of virulence genes; and survival time of mice after challenge. The results showed that the cross-linking density of the biofilm of ∆lmo0159 strain was lower than that of WT by microscopic examination. The expression of biofilm-formation and virulence genes also decreased in the biofilm state. Subsequently, the growth and motility of ∆lmo0159 in the culture medium were enhanced. Conversely, the growth and motility of L. monocytogenes were attenuated by ∆lmo0159 at both the cellular and mouse levels. At the cellular level, ∆lmo0159 reduced plaque size; accelerated scratch healing; and attenuated the efficiency of adhesion, invasion, and intracellular proliferation in swine intestinal epithelial cells (SIEC), RAW264.7, mouse-brain microvascular endothelial cells (mBMEC), and human-brain microvascular endothelial cells (hCMEC/D3). The expression of virulence genes was also inhibited. At the mouse level, the LD₅₀ of the ∆lmo0159 strain was 10^0.97 times higher than that of the WT strain. The bacterial load of the ∆lmo0159 strain in the liver and spleen was lower than that of the WT strain. In a mouse model of intraperitoneal infection, the deletion of the lmo0159 gene significantly prolonged the survival time of the mice, suggesting that the lmo0159 deletion mutant also exhibited reduced virulence. Thus, our study identified lmo0159 as a novel virulence factor among L. monocytogenes LPXTG proteins.

Porcine epidemic diarrhea virus (PEDV) and transmissible gastroenteritis virus (TGEV) are responsible for significant economic losses in the swine industry. The S1 proteins of these viruses serve as key targets for vaccine development. In this study, prokaryotic expression vectors for pCZN1-PEDV S1, pCZN1-TGEV S1, and pCZN1-PEDV S1-TGEV S1 were constructed. The corresponding proteins were expressed, purified, and used to prepare monovalent, bivalent, and mixed (PEDV S1 + TGEV S1) vaccines. Kunming (KM) mice were immunized with subunit vaccines, with PBS as the negative control (NC) and a commercial inactivated vaccine as the positive control (PC). Immune responses, including specific antibody (IgG, IgG1, IgG2a) levels, virus neutralization, and IFN-γ production, were evaluated. All vaccines induced high levels of specific IgG, IgG1, and IgG2a antibodies. At weeks 2 and 8, the PEDV S1 + TGEV S1 vaccine induced significantly higher levels of specific IgG and IgG1 compared to the PC (p < 0.001). The PEDV S1 vaccine also induced significantly higher specific IgG2a levels than the PC at week 4 (p < 0.0001). Virus neutralization assays demonstrated that the subunit vaccines induced neutralizing antibody levels comparable to or exceeding those of the PC. Furthermore, IFN-γ levels were significantly elevated in all vaccinated groups compared to the NC (p < 0.0001), indicating a robust immune response. These results suggest that the subunit vaccines are promising candidates for the safe and effective control of both PEDV and TGEV infections.

The porcine reproductive and respiratory syndrome virus (PRRSV) possesses an inherent ability to adapt to environmental transformations and undergo evolutionary changes, which has imposed significant economic pressure on the global pig industry. Given the potential for recombination among PRRSV genomes and variations in pathogenicity, newly emerging PRRSV isolates are of considerable clinical importance. In this study, we successfully isolated a novel strain named XJ-Z5 from PRRSV-positive samples collected in Xinjiang province in 2022. Through comprehensive genomic sequencing, phylogenetic analysis, and recombination analysis, we confirmed that this strain belongs to the NADC30-like recombinant PRRSV. During pathogenicity tests in piglets, this strain exhibited moderate virulence, causing symptoms such as reduced appetite, persistent fever, and weight loss; however, no mortality cases were observed. Tests conducted at various time points detected the presence of PRRSV nucleic acid in nasal swabs, rectal swabs, tissue samples, and blood, with the highest viral loads found in lung tissue and blood. Serum biochemical tests indicated significant impairment of liver and kidney function. PRRSV antibodies began to appear gradually after 10 days post infection. Hematoxylin and eosin staining revealed substantial pathological changes in lung tissue and lymph nodes. This study enhances our understanding of the epidemiology of PRRSV and underscores the importance of ongoing monitoring and research in light of the challenges posed by the continuous evolution of viral strains. Furthermore, the research emphasizes the urgency of the rapid genomic analysis of emerging viral strains. Through these comprehensive research and monitoring strategies, we aimed to curb the spread of PRRSV more effectively and thus reduce the huge economic losses it caused to the pig industry.

Porcine reproductive and respiratory syndrome virus (PRRSV) infection inflicts enormous economic losses on the global swine industry and imposes significant pressure on agricultural production. However, there are currently no clinically approved effective therapeutics specifically targeting PRRSV. Accordingly, the development of novel antiviral agents against PRRSV is urgently needed. Notably, the structural glycoprotein 4 (GP4) of PRRSV—which plays a crucial role in viral entry into host cells—represents a promising target for antiviral development. Nanobodies, characterized by their small size, structural stability, high affinity, and excellent solubility, have emerged as attractive candidates for next-generation therapeutic development. Yet, to date, no specific nanobodies targeting PRRSV GP4 have been reported. In this study, we isolated GP4-specific nanobodies using phage display technology and investigated their mechanisms underlying viral suppression through a series of in vitro functional assays. Our results demonstrate that Nb6, Nb31, and Nb85 significantly inhibit PRRSV infection by disrupting both viral attachment to host cells and subsequent internalization processes. Collectively, these findings indicate that Nb6, Nb31, and Nb85 hold substantial potential for development as antiviral agents against PRRSV infection.