CategorySwine Health - General Disease
Date Full Report Received04/25/2019
Date Abstract Report Received04/25/2019
InvestigationInstitution: Iowa State University
Primary Investigator: Pablo Pineyro
Co-Investigators: Luis Gimenez-Lirola
Funded ByPork Checkoff
Senecavirus A, also known as Seneca Valley Virus, has been identified in the U.S. swine population since the late 1980s and has most commonly been associated with “Swine Vesicular Disease.” In 2015, a reemergence of clinical cases associated with SVA was first reported in the US and Brazil. Since its reemergence, outbreaks of SVA have been reported in multiple swine-producing countries, with cases appearing in new locations each year. Thus, SVA appears to be on the path to becoming a virus with global prevalence. One of the most concerning problems for practitioners besides the presence of transient vesicular lesions that can impair final production goals is arriving at an accurate clinical diagnosis. Lesions induced by SVA cannot be clinically differentiated from other vesicular diseases such as foot-and-mouth disease (FMD), swine vesicular disease (SVD), swine vesicular exanthema (SVE) and vesicular stomatitis virus (VSV). Today, SVA diagnosis is mostly based on direct pathogen detection. However, lesions and viremia are transient, which might preclude etiological diagnosis. Thus, detection of antibodies against SVA should be considered an important tool for making the diagnosis of virus contact/circulation in the farm.
The objective of this study was to evaluate potential epitopes that can be used to improve the current serological assay and develop a new antibody assay that allows determination of specific antibodies on oral fluids.
Multiple overlapping epitopes from two structural proteins were synthetically constructed. The immune reactivity of each epitope was evaluated against monoclonal antibodies and clinical samples collected during an outbreak of Senecavirus swine vesicular disease. In addition, in order to evaluate the presence of specific antibodies in oral fluids, a total of 30 pigs were randomly housed in three different rooms and allocated in pens containing two pigs per pen. One group (n=10) was inoculated with SVV historical strain, one group with a contemporary SVA strain (n=10) and one control (n=10) with cell culture media. Oral fluids and serum were collected at 0, 3, 7, 10, 14, 21, 28, 35, 42, 49, 54, 60 and 67 dpi. The presence of different antibodies isotypes was evaluated in serum and oral fluids by a recombinant protein ELISA.
Results of this study showed that the humoral response could be detected using a small set of epitopes targeting small regions of two main structural proteins. This small set of epitopes used as a target antigen in the indirect ELISA format were capable of discriminating not only positive samples generated experimentally, but also clinical samples collected during an outbreak of vesicular disease. Although further studies are necessary to identify if these specific regions of the structural proteins play a major role in the induction of immune response, these linear epitopes will provide the basis to improve and develop more specific immunological tests.
In this study, specific antibodies against two different strains of Seneca virus were detected in serum one week post-infection by a recombinant protein ELISA. The same immunological test was adapted for oral fluids and demonstrated that specific SVA antibodies can also be detected after seven days post-infection. Interestingly, this test was also capable of identifying antibodies generated by two different SVA strains. Thus, oral fluid has the potential to replace individual pig serum samples for SVA routine and emergency disease surveillance. This is a faster and less expensive method to evaluate pathogen circulation in a farm, which can accurately reflect the prevalence of SVA in the population.