#09-244

Complete

Date Full Report Received

03/27/2012

Date Abstract Report Received

03/27/2012

Investigation

Institution: , ,
Primary Investigator:

PRRS causes major economic losses to the US pig industry, as reflected in debilitating respiratory syndromes, major reproductive losses and unthrifty piglets; economic losses were calculated to be $642 million per year in 2011. Worldwide, PRRS affects pigs at all stages of growth and is easily spread. The studies supported by this NPB grant established the best practices for using a new multiplex Fluorescent Microbead ImmunoAssay (FMIA) to quantitate levels of swine immune proteins (cytokines, chemokines). These proteins help to predict the intensity and speed of the immune response and thus indicate which pigs will resist, or be more susceptible to, PRRSV infection or be protected as a result of PRRS vaccination. The FMIA measures immune proteins involved in 1) early, innate immunity [interleukin-1 (IL-1, IL-8, interferon- (IFN, and tumor necrosis factor (TNF)], 2) the late, adaptive anti-viral responses associated with T helper 1 (Th1) immunity (IL-12, IFN, 3) the alternative Th2 immunity (IL-4), 4) regulatory immunity (IL-10) and cell migration (CCL2). The interplay between levels and timing of expression of these immune proteins helps to predict overall immunity.

Our goal was to refine and improve our FMIA test developed with NPB grant #08-189 (Lawson et al. 2010). The test refinements developed through this grant provide for uniform, simultaneous identification and quantification of 8 important immune cytokines and 1 chemokine within a single serum or oral fluid sample. By careful studies the limit of assay detection was established and the minimum dilutions of serum and oral fluids determined. The refined cytokine multiplex test was then used to evaluate cytokine expression in oral fluid samples collected during NPB supported (#10-056) PRRS Host Genetics Consortium (PHGC). Analyses of the cytokine and chemokine data affirmed that PRRSV infection during PHGC trial 6 clearly stimulated innate cytokine (IL-1, IL-8) expression but not IFN and IL-12 expression. This appeared to stimulate only a low and slow production of protective IFN, and thus likely allowed high viral replication. This oral fluid data will be compared to data that is now being collected on individual pig sera from PHGC trials. That data will enable us to identify the most vigorously responding pigs and identify exactly which cytokines are the best predictors of pigs which will resist PRRSV infection better (have lower viral loads) in a herd.

In addition to our PHGC efforts these FMIAs will provide critical, rapid information on pig immune responses and thus help identify what viral proteins or vaccine constructs stimulate a timely and robust immune response to PRRSV in vitro or in vivo. In fact the refined FMIA will be useful for evaluation of immune responses to various swine infections and serve as an important new tool for comparison of alternate vaccination approaches. Once known, these results should help identify which cytokines to target as positive and negative indicators of efficacy of PRRSV vaccines. Indeed, the importance of this effort has been recognized by the commercial animal health industry. Three different companies are actively involved in establishing FMIAs for swine immune proteins (with advice from this team), thus opening up opportunities to explore swine disease, immune and vaccine responses in more depth in the future.
Contact information: Joan K. Lunney, Ph.D., USDA, ARS, BARC, APDL, Bldg. 1040, Beltsville, MD 20705
PH: 301-504-9368; FAX: 301-504-5306; email: Joan.Lunney@ars.usda.gov