DETECTION AND CONTROL OF PORCINE REPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS AND EMERGING VIRAL DISEASES OF SWINE

<b>Project Methods</b><br> Objective 1. Control of PRRSV:1.1. PRRSV immunology/vaccinology: Significant impediments to achieving the PRRSV reduction goal include the frequent re-breaks of clinical disease in PRRSV Stable Farms and the need for safer and more efficacious vaccines providing broader protection. Reduction in disease incidence will be dependent in part on highly sensitive diagnostic assays/methods. The SDSU Station will focus on development of additional highly specific monoclonal antibody-based reagents and assays required for support of PRRSV immunology and vaccinology studies led by collaborating NC-229 institutions. Expressed proteins representing key antigenic epitopes of selected pathogens will be produced and additional monoclonal antibodies for the detection and differentiation of specific antigen targets as required for immunology and vaccinology studies will be developed using routine methods in our laboratory.1.2. PRRSV epidemiology: Developing an understanding of the epidemiology of contemporary viral strains circulating in the field is critical to reduce between-herd transmission and minimize the average time-to-stability of herds following outbreaks. The SDSU Diagnostic Laboratory conducts extensive PCR testing and sequencing of PRRSV cases and will contribute sequence data to databases coordinated by NC-229 partners, USDA-ARS and swine industry partners to contribute to PRRSV epidemiology studies. SDSU is contributing to a user-friendly informatics tool to summarize and report routine pathogen detection from samples submitted to participating veterinary diagnostic laboratories over time. Standardized submission data and results of tests performed on porcine samples are retrieved from four participating laboratories (ISU, UMN, SDSU, and KSU).1.3. PRRS Surveillance and Diagnostics: The development of effective testing and surveillance strategies supports the goal of reducing the impact of PRRSV as well as supporting future programs for the elimination of the virus. New tools and strategies are needed to effectively reach this goal. Novel cost effective ways to monitor populations will be considered in terms of sample types, procedures and target populations. The SDSU Station will focus on development of improved diagnostic strategies, reagents and assays to support this objective. Ongoing sequence analysis of currently circulating PRRSV strains will be utilized to update current PCR platforms as needed. Approaches to serological and antigen detection assay development will vary based on specific antigen and antibody targets and desired assay sensitivity and specificity. General methods for the development, optimization and validation of these assays have been thoroughly described in our previous publications. Archived samples of known status and control materials available in our laboratory will be used for optimization and validation of each individual assay. Assay specificity, sensitivity and cut-off points will be determined using receiver-operator characteristic (ROC) analysis.Objective 2. Developing effective and efficient approaches for detection, prevention and control of pressing viral diseases of swine of recent emergence. The SDSU station will focus primarily on sub-objective 2.2 (Swine Influenza Virus), sub-objective 2.5 (Senecavirus A) and sub-objective 2.8 (Foreign animal disease import risk through feed ingredients) in support of the overall NC-229 objectives.2.2. Swine Influenza Virus: In this objective, factors influencing influenza virus transmission within and between swine farms will be determined to reduce economic losses caused by this disease. Identifying the mechanisms by which these pathogens enter, circulate and persist in swine herds is a critical step to devising methods that effectively prevent, control and/or eliminate this virus. The relationships between virus diversity and evolution with the ecology, epidemiology, and virulence properties of influenza A (IAV) virus in swine will be investigated, including viruses from under-sampled pig populations in North America. Epidemiologic and ecologic factors such as production system type, population immunity, age of susceptibility, seasonality, and polymicrobial interactions will be assessed to determine how influenza viruses are introduced and persist on farms and how are they moved within and between production systems and globally. The genetic or genomic bases for viral fitness or virulence will be investigated. The effectiveness of current and novel practices for preventing IAV infection will be evaluated, identifying immune parameters that are correlates of heterologous protection with traditional and/or new vaccine platforms or evaluating new vaccine strategies. The extent that genetic diversity impacts antigenic diversity and suboptimal immunity contributes to evolution of influenza viruses in swine will be evaluated. Population studies in different age groups will be conducted to explain the transmission and control of swine influenza virus under the hypothesis that the piglet plays a central role in this transmission (UMN), because weaned piglets are the source of strain diversity reservoirs of influenza at a subclinical level. The goal in this study should derive a combination of practices that increase the resistance of pigs and practices that decrease risk of exposure to SIV, which is an essential part of influenza control prior to weaning. The SDSU Diagnostic Laboratory will conduct extensive PCR testing and sequencing of swine influenza cases and will contribute data in support of this sub-objective as described for sub-objective 1.2.2.5. Senecavirus A: Comprehensive studies to characterize the pathogenesis and immunity to SVA infection will be conducted. ISU is investigating Senecavirus immunopathogenesis, specifically the upregulation of pro-inflammatory cytokines in cell culture and in vivo. The SDSU station will assist with further studies to evaluate SVA pathogenesis and immunity led by Dr. Diego Diel (Cornell). The SDSU Station will focus on development of improved research reagents and assays to support these projects and will assist with animal studies. We will also develop and validate new reagents and assays to serve diagnostic laboratories and the swine industry. Approaches to serological and antigen detection assay development will vary based on specific antigen and antibody targets and desired assay sensitivity and specificity. Reagents required for immunohistochemistry and fluorescent antibody staining will be developed as described under sub-objective 1.3. Serological assays will include indirect and competitive ELISA formats, multiplex fluorescent microsphere-based assays and rapid virus neutralization assays.2.8. Foreign animal disease import risk through feed ingredients: Collaborative studies led by Dr. Scott Dee, Pipestone Applied Research, with investigators at SDSU, KSU, ISU and industry partners have evaluated the risk of importing FAD through contaminated feed ingredients. Further study is required to fully evaluate risks and develop appropriate mitigation strategies. The SDSU station will contribute to collaborative efforts by providing virus stocks, conducting specialized diagnostic testing and virus titrations and participating in pathogen mitigation studies. Studies to assess the risks for transmission of emerging and transboundary viral diseases through animal feed and individual feed ingredients will be conducted as previously described by our group. Selection of additional pathogens to be targeted will be based on risk assessment priorities established by the Swine Health Information Center. Appropriate surrogate viruses will be used for the evaluation key transboundary diseases not currently circulating in the U.S. Mitigation studies will focus on both novel and commercially available compounds that can be added to feed to reduce the risk of virus transmission.