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ARS Home » Research » Research Project #437239

Research Project: Heterologous Flavivirus Infections of Swine and Cattle

Location: Operations

Project Number: 3022-32000-013-002-S
Project Type: Non-Assistance Cooperative Agreement

Start Date: Sep 1, 2019
End Date: Aug 31, 2024

This research is particularly relevant to the research programs of the ARS and specifically relevant to predictive biology investigations directed towards questions of emergence and re-emergence of viral diseases, trans-species transmission of viruses and creation of ecological reservoirs of infection. These questions are important for all the Flaviviridae that infect swine (such as Classic Swine Fever Virus and Japanese Encephalitis Virus) with transmission potential to other mammalian and arthropod species. Thus, these studies establish a framework of research to investigate these questions in multiple mammalian species across multiple zoonotic viruses. Specific Objectives: A. Continue relevant training through graduate courses and clinical case work that will allow Scientist to complete the requirements for board-certification by the American College of Veterinary Internal Medicine and the Auburn University Graduate School for a doctoral degree in Biomedical Sciences. B. Investigate the implications of heterologous BVDV infection on the viral genome following congenital infections in pigs, infectivity of BVDV for cattle, and antigenic changes for immune recognition in vaccinated cattle. 1. Investigate whether viral genetic change allows clearance of BVDV in some congenitally infected piglets. 2. Determine whether persistently or chronically infected (PI or CI) heterologous hosts can cause spill-back infections to cattle. 3. Evaluate antigenic changes of BVDV propagated in heterologous hosts during immune recognition in vaccinated cattle. 4. Determine the prevalence of BVDV and BVDV antibody in white-tailed deer and feral swine in Alabama.

Objective 1 4 pregnant gilts will be inoculated with BVDV 1b of porcine origin. Following delivery, piglets will be assessed for viremia by virus isolation and seroconversion by virus neutralization at birth and every two weeks until 6 months of age. Upon seroconversion, BVDV from CI pigs will be compared by whole-genome sequencing with previously isolated BVDV and BVDV from age-matched PI piglets to determine if clearance of BVDV is associated with significant viral genomic change. Objective 2 In two separate experiments, BVDV transmission from PI piglets to seronegative calves will be evaluated using indirect (feed and water troughs) and direct (cohabitation in a pasture) transmission routes. Exposed calves will be evaluated for viremia and seroconversion following exposure. Objective 3 To assess the impact on antigenicity in vaccinated cattle, BVDV-naïve steers will be vaccinated with a commercial BVDV 1 and BVDV 2 vaccine. Sera will be collected on day 28 and used for comparative virus neutralization assays in bovine and porcine kidney (MDBK and PK15) cells using 100 CCID50 of BVDV AU526 from the original PI cow or a swine-adapted isolate. On day 56 post vaccination, the steers will be randomly assigned to one of two groups, and will be inoculated with either the original BVDV isolate or the isolate from the last gilt. Comparative virus neutralization assays will be performed in MDBK cells to determine the anamnestic response to vaccination. The scope of immunological studies will be increased in the later phases of the research project and these data will enhance Objective 4, below. Objective 4 Samples (sera, meat juice, and/or ear notch) from white-tailed deer and feral swine will be obtained from ongoing CWD surveillance efforts and feral swine research, respectively and evaluated for presence of BVDV, BVDV antigen, and BVDV antibodies by virus isolation/RT-PCR, antigen capture ELISA, and/or virus neutralization, respectively.