Master of Science / Department of Diagnostic Medicine/Pathobiology / Raymond R. R. Rowland / Pestiviruses such as classical swine fever virus (CSFV) and bovine viral diarrhea virus (BVDV) are some of the most economically important livestock diseases in the world. The antigenic similarities between members of the pestivirus genus allow for both BVDV and CSFV to infect swine. Infections with heterologous pestiviruses in swine can interfere with diagnostic tests for CSFV. The identification of cross-reactive and cross-neutralizing epitopes between CSFV and BVDV for the development of improved diagnostics and vaccines that allow for the differentiation of infected animals from vaccinated animals (DIVAs) are necessary to accurately detect and control CSFV. The overall goal of this research was to identify epitope regions recognized by antibodies that can differentiate between CSFV and BVDV. The approach was to use serum neutralization assays to confirm the presence of neutralizing antibodies to BVDV in swine serum collected from animals immunized with one of three separate Alphavirus vaccine constructs: BVDV-1b, CSFV E2, and CSFV E[superscript]rns. Results showed that animals immunized with the Alphavirus BVDV-1b construct had high neutralizing titers against BVDV-1a and animals immunized with Alphavirus CSFV E2 and E[superscript]rns constructs had low, but detectable, neutralizing activity. Polypeptide fragments of CSFV and BVDV E2 were then expressed in E. coli and purified using affinity chromatography. Serum from a pig immunized with the CSFV E2 Alphavirus construct was tested against two fragments of CSFV E2, 2/4 and 4/4, and four fragments BVDV E2, 1/4, 2/4, 3/4, and 4/4, using western blot analysis. Reactivity to fragments CSFV E2 2/4 and 4/4 and BVDV E2 1/4 and 4/4 was observed. The results of this study identified CSFV amino acid positions 774 through 857 and BVDV amino acid positions 783 through 872 as the regions that contain the epitopes recognized by cross-reactive antibodies between BVDV and CSFV E2. These results provide more specific sequence regions to improve CSFV diagnostic assays and DIVA vaccines.

Doctor of Philosophy / Department of Diagnostic Medicine/Pathobiology / Raymond R. R. Rowland / Classical swine fever virus (CSFV) is an enveloped, positive strand RNA virus, and member of the genus Pestivirus. It is a highly infectious and transmissible swine pathogen that threatens the global swine industry. The United States has been free of CSFV since 1977, however, monitoring the millions of domestic and feral pigs present in the US puts a significant strain on national surveillance efforts. There are no validated diagnostic techniques that can simultaneously sample multiple pigs (i.e. all pigs in a pen or barn). Similarly, there are no validated serological assays that can quickly test for CSFV without cross-reacting with other pestiviruses. The purpose of the first study was to establish a moderate CSFV-infectious model and determine how a single oral fluid sample from a pen of pigs can function as a diagnostic sample for detecting CSFV. Oral fluid (OF) and serum samples were collected from 10 pigs experimentally infected with CSFV Paderborn strain. Using RT-PCR, CSFV was detected in OF on 8 days post infection (dpi), and in the serum of one pig on 6 dpi. A single OF sample can, therefore, take the place of 10 serum samples to detect CSFV in a population. In a second study, monoclonal antibodies reactive to CSFV glycoproteins were generated in mice immunized with recombinant E2 and Erns antigens. Five E2-specific clones and two Erns-specific clones showed reactivity to CSFV-infected. Epitope mapping of the E2 clones showed that all reacted with the N-terminal portion of E2; a region highly variable among pestiviruses. Together with OF sampling, monoclonal antibodies can be used to develop new tools for improving CSF surveillance in large swine populations.