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Research Project: Intervention Strategies to Control Endemic and New and Emerging Viral Diseases of Swine

Location: Virus and Prion Research

Title: Comparison of historical and contemporary isolates of Senecavirus A

Author
item Buckley, Alexandra
item Michael, David
item Faaberg, Kay
item GUO, BAOQING - Iowa State University
item YOON, KYOUNG-JIN - Iowa State University
item Lager, Kelly

Submitted to: Veterinary Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2020
Publication Date: 12/7/2020
Citation: Devries, A.C., Michael, D.D., Faaberg, K.S., Guo, B., Yoon, K., Lager, K.M. 2020. Comparison of historical and contemporary isolates of Senecavirus A. Veterinary Microbiology. 253. https://doi.org/10.1016/j.vetmic.2020.108946.
DOI: https://doi.org/10.1016/j.vetmic.2020.108946

Interpretive Summary: Senecavirus A (SVA) is a picornavirus that causes vesicular disease in swine. These vesicles are blister-like lesions that form along the coronary bands and snouts. SVA was first discovered as a cell culture contaminant in 2002, but subsequent analysis determined that the National Veterinary Services Laboratory had found similar isolates in swine samples since the late 1980s. Attempts to reproduce clinical disease experimentally in swine with historical isolates were unsuccessful. After outbreaks of vesicular disease in the United States in 2015, multiple research groups were able to reproduce vesicular disease in swine with contemporary isolates. Due to this discrepancy, it was hypothesized that historical isolates were less pathogenic than contemporary isolates. The objectives of this study were to compare the pathogenicity of historical and contemporary SVA isolates in growing pigs and compare the sequences of the virus especially areas that could be involved with receptor binding or antigenic sites. Three historical isolates (2002, 2011, 2012) and three contemporary isolates (2015) were used for challenge (n=8 pigs/isolate). Contrary to the hypothesis, all isolates produced similar clinical disease. In addition, all animals replicated virus, though shedding dynamics were different among the isolate. All animals developed cross-neutralizing titers against all viruses used in the study. Sequence analysis revealed that the 2002 isolate had more amino acid changes in areas that are suspected to be involved in receptor binding compared to the remaining isolates, which were more similar. Though there were differences found between isolates, this work demonstrates that both historical and contemporary SVA isolates can cause vesicular disease in swine.

Technical Abstract: Senecavirus A (SVA) was discovered as a cell culture contaminant in 2002, and multiple attempts to experimentally reproduce disease were unsuccessful. Field reports of porcine idiopathic vesicular disease (PIVD) cases testing PCR positive for SVA in addition to outbreaks of PIVD in Brazil and the United States in 2015 suggested SVA was a causative agent, which has now been consistently demonstrated experimentally. Ease of experimental reproduction of disease with contemporary strains of SVA raised questions concerning the difficulty of reproducing vesicular disease with historical isolates. The following study was conducted to compare the pathogenicity of SVA between historical and contemporary isolates in growing pigs. Six groups of pigs (n=8) were intranasally inoculated with the following SVA isolates: SVV001/2002, CAN/2011, HI/2012, IA/2015, NC/2015, SD/2015. All isolates induced vesicular disease in at least half of the inoculated pigs from each group. All pigs replicated virus as demonstrated by serum and/or swab samples positive for SVA by quantitative PCR. Pig sera tested by virus neutralization assay demonstrated cross-neutralizing antibodies against all viruses utilized in the study. Cross-neutralizing antibodies from pigs inoculated with historical isolates were lower than those pigs that were inoculated with contemporary isolates. Phylogenetic analysis revealed two clades with SVV001/2002 being in a separate clade compared to the other five isolates. Though this research showed there are differences the infection dynamics and sequences of these six isolates in swine, clinical presentation of vesicular disease was similar between both historical and contemporary isolates.