Two Distinct Genotypes of Porcine Epidemic Diarrhoea Virus in Vaccinated Pig Flocks in Shandong Province of China, 2012-2015

Isolation and characterization of porcine epidemic diarrhea virus with mutations in the spike gene in China

Porcine epidemic diarrhea (PED) caused by porcine epidemic diarrhea virus (PEDV) has caused enormous economic losses to the global swine industry. Due to frequent mutations in the spike (S) gene of PEDV, commercial vaccines used today are gradually losing their protective efficacy against variants. It's significant to monitor the S gene of PEDV variants and understand its evolutionary trend. In this study, we report four novel PEDV strains isolated from Sichuan, Guangdong and Shanxi Provinces and determined their S gene sequences. Phylogenetic analysis showed that they all belong to GII genotype. Amino acid alignment revealed a unique mutation pattern. We also predicted their three-dimensional structures and continuous B-cell epitopes and compared them to those of the vaccine strain. Our study provides references for understanding the evolution of S gene and antigenic change of S protein, which are of great significance for formulating the prevention and control of PEDV.

The S protein of a novel recombinant PEDV strain promotes the infectivity and pathogenicity of PEDV in mid-west China

Porcine epidemic diarrhoea virus (PEDV) is an emerging and re-emerging swine enterovirus that causes highly contagious diarrhoea and mortality in piglets. To better understand the current prevalence of PEDV in mid-west China, and to find out the reason for the re-emergence of PEDV from the viral genomic characteristics. Herein, we firstly investigated epidemiology of PEDV in mid-west China from 2019 to 2020. A total of 62.23% (257/413) of diarrhoea samples were positive for PEDV, and the PEDV-positive cases were mainly detected in winter. Then, we selected the SXSL strain as a representative strain to study the genetic and pathogenic characterization of PEDV pandemic strains in mid-west China. The recombination analysis showed that SXSL strain was a recombinant strain, and the major and minor parent strains of the recombination are CH/SCZJ/2018 strain and GDS48 strain, respectively. Complete genome sequencing and homology analysis showed that the S protein of SXSL strain contained multiple amino acid indels and mutations compared to the PEDV representative strains. Furthermore, we evaluated the effect of S protein on the infectivity and pathogenicity of PEDV by the PEDV reverse genetics system, and results showed that SXSL S protein increased the infectivity and pathogenicity of chimeric virus. Overall, our findings provided important information for understanding the roles of S protein in the prevalence of PEDV in mid-west China and developing vaccines based on PEDV pandemic strains.

Molecular characterization of porcine epidemic diarrhea virus associated with outbreaks in southwest China during 2014-2018

Porcine epidemic diarrhea virus (PEDV), which re-emerged in China since 2010, has swept across the whole country leading to tremendous economic losses. In this study, a total of 645 diarrhea samples collected from 156 pig farms in Sichuan and Guizhou province during 2014-2018 were tested for PEDV. We found that samples from 47.66% (84/156) of the farms were positive for PEDV with an overall detection rate of 35.81% (231/645). Fifty-two strains were selected for full-length S gene analyses, and these strains were classified into three subgroups, an S-INDEL subgroup (G1c), and two non-S-INDEL subgroups (G2b, AJ1102-like and G2c), accounting for 15.38% (8/52), 23.08% (12/52) and 59.62% (31/52) of the total analysed strains, respectively. We found these three subgroups of PEDV coexisted in Sichuan province, and the S-INDEL strain was detected in Guizhou. Further antigenic variation analysis of the neutralizing epitopes (S10, COE, SS2, SS6 and 2C10) on the spike protein revealed that the S-INDEL and non-S-INDEL strains shared similar variation features in COE and SS6, but exhibited distinct variation patterns in the S10 domain. Unique variation patterns on N-glycosylation sites in the S protein were also observed for the S-INDEL and non-S-INDEL strains. Moreover, nine strains (three from each subgroup) were subjected to full-genome characterization. Complete genome phylogeny showed an inconsistent tree topology for genotyping, with two G2c strains grouped into the GII-b (AH2012-like) genogroup and the remaining seven strains including three S-INDEL strains grouped into the GII-c genogroup. Further recombination analyses indicated that six of the GII-c strains probably originated from intra-genogroup recombinations. Notably, three newly emerged S-INDEL strains with novel recombination patterns were first identified. Together, our data revealed a new status of PEDV in southwest China, which can increase understanding of the prevalence, genetic characteristics and evolutionary profiles of circulating PEDV strains in China.

Recombinant Lactobacillus acidophilus expressing S1 and S2 domains of porcine epidemic diarrhea virus could improve the humoral and mucosal immune levels in mice and sows inoculated orally

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The recombinant L. acidophilus expressing S₁ and S₂ domains of PEDV were generated.

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The oral vaccines for PED were based on a swine-origin L. acidophilus.

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The oral L. acidophilus vaccines induced humoral and mucosal immunity in mice.

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The L. acidophilus-S₁ vaccine induced humoral and mucosal immunity in sows.

Porcine epidemic diarrhea (PED) is a highly contagious intestinal infectious disease caused by porcine epidemic diarrhea virus (PEDV), which is characterized by a high mortality rate in piglets. Since 2012, a remarkable growth in PED outbreaks occurred in many pig farms in China, landing a heavy blow on the pig industry. In order to develop a new effective vaccine for the current PEDV, oral vaccines were generated by transferring eukaryotic expression recombinant plasmids carrying the S₁ and S₂ (antigenic sites of the S protein) epitopes of PEDV into a swine-origin Lactobacillus acidophilus (L. acidophilus). After oral immunization of the BALB/c mice, higher levels of anti-PEDV specific IgG and SIgA antibodies and cellular immune responses were detected in mice orally administered with the recombinant L. acidophilus-S₁ compared to the L. acidophilus-S₂. Furthermore, L. acidophilus-S₁ was used to inoculate the pregnant sows orally and the results showed that the recombinant L. acidophilus-S₁ could elicit a specific systemic and mucosal immune response. In summary, our study demonstrated that oral immunization with L. acidophilus-S₁ could improve the humoral and mucosal immune levels in sows and would be a promising candidate vaccine against PEDV infection in piglets.

A G3P[13] porcine group A rotavirus emerging in China is a reassortant and a natural recombinant in the VP4 gene

Group A rotaviruses (RVAs) are a major cause of serious intestinal disease in piglets. In this study, a novel pig strain was identified in a stool sample from China. The strain was designated RVA/Pig/China/LNCY/2016/G3P[13] and had a G3-P[13]-I5-R1-C1-M1-A8-N1-T1-E1-H1 genome. The viral protein 7 (VP7) and non-structural protein 4 (NSP4) genes of RVA/Pig/China/LNCY/2016/G3P[13] were closely related to cogent genes of human RVAs, suggesting that a reassortment between pig and human strains had occurred. Recombination analysis showed that RVA/Pig/China/LNCY/2016/G3P[13] is a natural recombinant strain between the P[23] and P[7] RVA strains, and crossover points for recombination were found at nucleotides (nt) 456 and 804 of the VP4 gene. Elucidating the biological characteristics of porcine rotavirus (PoRV) will be helpful for further analyses of the epidemic characteristics of this virus. The results of this study provide valuable information for RVA recombination and evolution and will facilitate future investigations into the molecular pathogenesis of RVAs.