Identification and pathogenicity of a variant porcine epidemic diarrhea virus field strain with reduced virulence
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Identification and pathogenicity of a variant porcine epidemic diarrhea virus field strain with reduced virulence Xiangbin Zhang1,3, Yongfei Pan2, Dongdong Wang2, Xiaoyan Tian2, Yanhua Song2* and Yongchang Cao1*
Abstract Background: Since 2010, a variant Porcine epidemic diarrhea virus (PEDV), which causes an acute, highly contagious, and devastating viral enteric disease with a high mortality rate in suckling pigs, broke out in China and spread rapidly to neighboring countries, even to the North America. This virus gradually became the main subtype of PEDV worldwide. However, there were no reports of mild pathogenicity of a variant porcine epidemic diarrhea virus in China. Findings: In 2013, a PEDV-positive sample from a sow with very mild clinical sign was used to inoculate in Vero cells to isolate the virus. This PEDV field strain, designated FL2013 strain, was successfully propagated and genetically characterized. The phylogenetic trees based upon either the complete genome or S gene showed that the FL2013 strain belongs to the genogroup G2b. The S gene of FL2013 has a 7-aa deletion (FEKVHVQ) in the C-terminus comparison with the other G2 PEDV sequences. Further comparative pathology study indicated that the FL2013 strain had reduced virulence to newborn piglets. Conclusions: A novel variant PEDV strain FL2013 with reduced virulence, as determined by the pathological study, was identified from east China. This strain is closely related to the genogroup- 2 PEDV strains prevalent in the U.S. and China currently, but had a short deletion at the 3′- end of the spike gene. Keywords: Porcine epidemic diarrhea virus, Variant, Reduced virulence
Findings Porcine epidemic diarrhea virus (PEDV) is an enveloped, single-stranded, positive-sense RNA virus in the genus Alphacoronavirinae of the family Coronaviridae. PED, which is caused by PEDV, is characterized by severe diarrhea, dehydration, and high mortality rates in the affected swine [1]. PEDV variants belonging to genogroup 2 (G2) have been emerging in China in a large-scale outbreak characterized by approximately 80–100 % morbidity rates and high mortality rates among suckling piglets since late 2010 [2]. Highly virulent PEDV strains, phylogenetically related to the G2 Chinese PEDV variants (shared ≥99.5 % nt identity), suddenly * Correspondence: [email protected]; [email protected] 2 Guangdong Wen’s Group Academy, Guangdong Wen’s Foodstuffs Group Co., Ltd., Xinxing, Guangdong, China 1 State Key Laboratory of Biocontrol, School of Life Sciences, Sun Yat-sen University, 510006 Guangzhou, P R China Full list of author information is available at the end of the article
emerged in the United States in May 2013 and rapidly spread throughout the country, causing severe economic losses [3, 4]. The second PEDV variant in the US, designated S INDEL PEDV, with insertions and deletions in the N terminal region (S1 subunit) of the spike (S) protein same as the G1 PEDV, was identified subsequently [5]. The S INDEL strains caused reportedly mi
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