Equine infectious anemia virus in China Equine infectious anemia virus in China

Porcine reproductive and respiratory syndrome virus (PRRSV), the causative agent of PRRS, has two distinct and highly diverse genotypes (genotype 1 and genotype 2) in the field. Accurate diagnosis and differentiation of the two genotypes of PRRSV are critical to the effective prevention and control of PRRS. The non-structural protein 10 (Nsp10) plays a vital role in viral replication and is one of the most conserved proteins of PRRSV, thus constituting a good candidate for PRRSV diagnosis. In this study, we generated a monoclonal antibody (mAb) 4D9 against Nsp10 by immunizing BALB/c mice with purified recombinant Nsp10 expressed by an Escherichia coli system. Through fine epitope mapping of mAb 4D9 using a panel of eukaryotic expressed polypeptides with GFP-tags, we identified the motif 286AIQPDYRDKL295 as the minimal unit of the linear B-cell epitope recognized by mAb 4D9. Protein sequence alignment indicated that 286AIQPDYRDKL295 was highly conserved in genotype 2 PRRSV strains, whereas genotype 1 PRRSV strains had variable amino acids in this motif. Furthermore, a mutant of the motif carrying two constant amino acids of genotype 1 PRRSV, Cys290 and Glu293, failed to react with mAb 4D9. More importantly, the mAb 4D9 could differentiate genotype 2 PRRSV strains from genotype 1 PRRSV strains using Western blotting and immunofluorescence analysis. Our findings suggest that Nsp10-specific mAb generated in this study could be a useful tool for basic research and may facilitate the establishment of diagnostic methods to discriminate between genotype 1 and genotype 2 PRRSV infection.

Since 2010,Porcine epidemic diarrhea virus(PEDV) has caused severe diarrhea disease in piglets in China, resulting in large economic losses. To understand the genetic characteristics of the PEDV strains that circulated in some provinces of China between 2015 and 2018, 375 samples of feces and small intestine were collected from pigs and tested. One hundred seventy-seven samples tested positive and the PEDV-positive rate was 47.20%. A phylogenetic tree analysis based on the entire S gene showed that these strains clustered into four subgroups, GI-a, GI-b, GII-a, and GII-b, and that the GII-b strains have become dominant in recent years. Compared with previous strains, these strains have multiple variations in the SP and S1-NTD domains and in the neutralizing epitopes of the S protein. We also successfully isolated and identified a new virulent GII-b strain, GDgh16, which is well-adapted to Vero cells and caused a high mortality rate in piglets in challenge experiments. Our study clarifies the genetic characteristics of the prevalent PEDV strains in parts of China, and suggests that the development of effective novel vaccines is both necessary and urgent.

Genetic variation analysis of Type 2 porcine reproductive and respiratory syndrome virus in Guangdong Province from 2016 to 2018

To understand the effect of Seneca valley virus (SVV) VP4 protein on innate immune factors, the VP4 gene was cloned into the pEGFP-C1 expression plasmid to construct the pEGFP-C1-VP4 recombinant plasmid. After the recombinant plasmid was transfected into 293 T cells, the cell fluid was collected 24 h after transfection for western blot assay to identify the correctness of VP4 protein expression. Cell culture medium was collected from un-transfected and transfected cells at three time points (12, 24, and 36 h). mRNA expression levels of cytokines (IL-1α, IL-1β, CCL-2, CCL-5, CXCL-10, and TNF-α) at three time points were detected by quantitative real-time PCR (qPCR) method, and relative quantitative analysis was performed by 2-ΔΔCt method. The results indicated that the expressed SVV VP4 protein exhibits good activity in vitro. Overexpression of the VP4 protein could significantly promote the transcription of IL-1α and IL-1β at 24 and 36 h. In addition, the transcription of CCL-2 and CCL-5 was also significantly promoted at 36 h, whereas the transcription of CCL-10 was significantly promoted only at 12 h. The TNF-α transcription was significantly inhibited at all the three time points. This study provides an important basis for the pathogenic mechanism of SVV and vaccine design in the future.