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Pseudorabies virus is a major pathogen in the pig industry, causing substantial economic losses. The emergence of pseudorabies virus variant strains in China has led to extensive spread, raising concerns about their potential impact. However, the differences in pathogenicity between the classical strains and the variant strains of genotype II are not well understood. In this study, we isolated three pseudorabies virus strains to evaluate their replication characteristics and to examine the differences in virulence genes among various subgenotypes strains. Additionally, a piglet infection model was utilized to investigate the clinical features of infection, tissue tropism, and the inflammatory responses induced by these strains. Our results showed that the genotype II variant strains (MS, XJ, LS, and CZ) had significantly larger plaque sizes and higher replication capacities than the genotype II classical strain Fa. The animal experiments revealed significant differences in pathogenicity among the pseudorabies virus subgenotype strains, with the variant strains showing higher mortality rates, more severe clinical symptoms, increased nasal virus shedding, and a more robust inflammatory response compared to the genotype II classical strain. There were also notable differences in tissue tropism among the strains. In terms of tissue viral loads, the genotype II variant strains did not exhibit a significant advantage over the genotype I classical strain. Furthermore, our findings indicate that antibodies against the genotype II classical strains have a reduced neutralizing capacity against the genotype II variant strains. On the other hand, antibodies against the genotype II variant strains displayed similar neutralizing abilities against both classical and variant strains. Overall, these findings offer important insights into the distinctions among pseudorabies virus subgenotypes and their implications for the clinical control of pseudorabies virus infections in pig farming.

IntroductionSenecavirus A (SVA) belongs to the genus Senecavirus in the family Picornaviridae. PIWI-interacting RNAs (piRNAs) are a class of small Ribonucleic Acids (RNAs) that have been found in mammalian cells in recent years. However, the expression profile of piRNAs in the host during SVA infection and their roles are poorly understood.MethodsHere, we found the significant differential expression of 173 piRNAs in SVA-infected porcine kidney (PK-15) cells using RNA-seq and 10 significant differentially expressed (DE) piRNAs were further verified by qRT-PCR.ResultsGO annotation analysis showed that metabolism, proliferation, and differentiation were significantly activated after SVA infection. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that significant DE piRNAs were mainly enriched in AMPK pathway, Rap1 pathway, circadian rhythm and VEGF pathway. It was suggested that piRNAs may regulated antiviral immunity, intracellular homeostasis, and tumor activities during SVA infection. In addition, we found that the expression levels of the major piRNA-generating genes BMAL1 and CRY1 were significantly downregulated after SVA infection.DiscussionThis suggests that SVA may affect circadian rhythm and promote apoptosis by inhibiting the major piRNA-generating genes BMAL1 and CRY1. The piRNA transcriptome in PK-15 cells has never been reported before, and this study will further the understanding of the piRNA regulatory mechanisms underlying SVA infections.

IntroductionSurveillance of the Seneca Valley virus (SVV) shows a disproportionately higher incidence on Chinese pig farms. Currently, there are no vaccines or drugs to treat SVV infection effectively and effective treatment options are urgently needed.MethodsIn this study, we evaluated the antiviral activity of the following medium-chain fatty acids (MCFAs) or triglycerides (MCTs) against SVV: caprylic acid, caprylic monoglyceride, capric monoglyceride, and monolaurin.ResultsIn vitro experiments showed that monolaurin inhibited viral replication by up to 80%, while in vivo studies showed that monolaurin reduced clinical manifestations, viral load, and organ damage in SVV-infected piglets. Monolaurin significantly reduced the release of inflammatory cytokines and promoted the release of interferon-γ, which enhanced the viral clearance activity of this type of MCFA.DiscussionTherefore, monolaurin is a potentially effective candidate for the treatment of SVV infection in pigs.

IntroductionPorcine circovirus type 2 (PCV2) is considered one of the viruses with substantial economic impact on swine industry in the word. Recently, porcine circovirus type 3 (PCV3) has been found to be associated with porcine dermatitis and nephropathy syndrome (PDNS)-like disease. And the two viruses were prone to co-infect clinically.MethodsTo further investigate the prevalence and genetic diversity of the two viruses, 257 pig samples from 23 different pig farms in southwest China with suspected PCVAD at different growth stages were analyzed by real-time PCR between 2020 and 2022 to determine the presence of PCV2 and PCV3.ResultsResults showed high prevalence of PCV2 and PCV3: 26.46% samples were PCV2 positive and 33.46% samples were PCV3 positive. The coinfection rate was doubled from 2020 (5.75%) to 2022 (10.45%). Subsequently, the whole genome sequences of 13 PCV2 and 18 PCV3 strains were obtained in this study. Of these, 1 strain was PCV2a, 5 strains were PCV2b and 7 strains were PCV2d, indicating that PCV2d was the predominant PCV2 genotype prevalent in the Southwest of China.DiscussionIn addition, the phylogenetic analysis of PCV3 showed high nucleotide homology (>98%) between the sequences obtained in this study and reference sequences. And 3 mutations (A24V, R27K and E128D) were found in PCV3 antibody recognition domains, which might be related to the mechanism of viral immune escape. Thus, this study will enhance our understanding of the molecular epidemiology and evolution of PCV2 and PCV3, which are conducive to the further study of the genotyping, immunogenicity and immune evasion of PCVs.

To investigate the effect of monoglyceryl laurate (GML) against PEDV in vivo, the clinical signs, pathological changes, tissue viral load and cytokine levels of piglets were compared in different GML treatment groups and PEDV infected group. The diets of experimental groups were supplemented with different doses of GML (5g for A1, 10g for A2, 20g for A3) on day 1, 2, and 3 after PEDV challenge, and the virus challenge group (group C) and blank group (group B) were set as control. The results showed that compared with group C, groups As could reduce the mortality rate of piglets, among which the protection rates of groups A2 and A3 could reach 100%. The trend of weight loss of piglets was effectively slowed down and growth performance recovered in GML treated groups. GML reduced the pathological damage of intestinal tract and the viral load in intestine and mesenteric lymph nodes. The levels of IL-8 and TNF-α in the blood of group As were inhibited by GML in a dose-dependent manner when compared with group C. Our study suggests that GML has potential anti-PEDV effects in vivo.

Porcine rotavirus type A (PoRVA) is the main cause of dehydration and diarrhea in piglets, which has a great impact on the development of the pig industry worldwide. A rapid, accurate and sensitive detection method is conducive to the monitoring, control, and removal of PoRVA. In this study, a PoRVA real-time fluorescent reverse transcription recombinase-aided amplification (RT-RAA) assay was developed. Based on the PoRVA VP6 gene, specific primers and probes were designed and synthesized. The sensitivity of RT-RAA and TaqMan probe-based RT-qPCR was 7 copies per reaction and 5 copies per reaction, respectively. The sensitivity of the RT-RAA method was close to TaqMan probe-based RT-qPCR. The detection results of RT-RAA and TaqMan probe-based quantitative real-time RT-PCR methods were completely consistent in 241 clinical samples. Therefore, we successfully established a rapid and specific RT-RAA diagnostic method for PoRVA.

Getah virus (GETV) is a zoonotic arbovirus that can cause infection in many animals. It can cause pyrexia and reproductive losses in animals. The objective of the study was to explore the effects of GETV on male reproductive ability. Male mice were injected with 100 × TCID50/0.1 ml in a volume of 100-μL GETV in their hindquarter muscle, resulting in decreased semen quality and testicular histopathological changes, and the virus was detected in the testes. At 0.5 dpi (day post-infection), male mice showed decreased sperm density, motility, and decreased serum testosterone concentration, an increased sperm malformation rate, vacuoles in spermatogonial cells/spermatocytes in spermatogenic tubules, and the highest virus copies in testis. At 2 dpi, the sperm density and motility reached the lowest value of 3.99 × 106/ml and 62.03%, and the malformation rate reached 43.67%. At 28 dpi, the sperm indexes of the experimental group gradually approached that of the control group, but there were still significant differences. Since then, histopathological changes have worsened, with the most severe histopathological changes at 7 dpi and gradual recovery. Up to 14 dpi, the virus was detected by qRT-PCR and immunohistochemistry, which showed that the virus was only present in the testicular interstitium. GETV infection can rapidly enter the testis of mice and reduce the semen quality of mice, which needs to be paid attention to in the prevention and control of GETV.