Porcine epidemic diarrhea virus in the United States: Cell culture isolation, genetic phylogeny, pathogenesis, and immunity

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2016-01-01
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Chen, Qi
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Jianqiang Zhang
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Veterinary Microbiology and Preventive Medicine
Our faculty promote the understanding of causes of infectious disease in animals and the mechanisms by which diseases develop at the organismal, cellular and molecular levels. Veterinary microbiology also includes research on the interaction of pathogenic and symbiotic microbes with their hosts and the host response to infection.
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Porcine epidemic diarrhea virus (PEDV) was first identified in 1971 in England, and it then spread to Asian countries. It did not cause severe outbreaks until the 1990s in Asia. There was no PEDV reported in American countries prior to the first United States (U.S.) outbreak that started in April, 2013.

The goals of this dissertation are to better characterize the features of U.S. PEDVs, particularly cell culture isolation methods, genetic phylogeny, pathogenesis, and immunity, to aid the PEDV diagnosis and control. Genetic analyses showed that two major PEDV strains are currently circulating in the U.S, designated as U.S. prototype strain and U.S. S-INDEL-variant strain. Initially, multiple U.S. PEDV prototype isolates and one U.S. PEDV S-INDEL-variant isolate were successfully isolated in Vero (ATCC CCL-81), which provided sustainable pure viral materials for various applications. Subsequently, two-way cross-reactivity and cross-neutralization between the two U.S. PEDV strains were evaluated in vitro. It was found that PEDV serological assays including indirect fluorescent antibody (IFA) assay, enzyme-linked immunosorbent assays (ELISA) and virus neutralization assay (VN) with either virus strain as indicator virus were able to detect antibodies against both U.S. PEDV strains. Pathogenesis difference was then compared amongst different U.S. PEDV strains and clades in 5-day-old neonatal pigs, 3-week-old and 7-week-old weaned pigs. The results revealed that U.S. prototype PEDV strain was more virulent than U.S, S-INDEL-variant PEDV strain in 5-day-old and 3-week-old pigs, but U.S. S-INDEL-variant was more virulent than U.S, prototype PEDV strains in 7-week-old weaned pigs. In vivo cross-protection efficacy evaluation in weaned pig models indicated that immunization with U.S. PEDV prototype strain provided similar protection against challenge with U.S. prototype strain or U.S. PEDV S-INDEL-variant strain. Immunization with U.S. PEDV S-INDEL-variant strain provided efficient protection against challenge with U.S. PEDV S-INDEL-variant strain and provided at least partial cross-protection against U.S. prototype PEDV challenge. In summary, in this dissertation, isolation of circulating U.S. PEDVs in cell cultures was successfully obtained and pathogenicity and cross-protective immunity of U.S. PEDVs were characterized.

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Fri Jan 01 00:00:00 UTC 2016