The NPB Initiative recognizes that the most effective way to control PRRS is to eliminate the virus from domestic swine herds. Control and elimination strategies should include diagnostic tools that can identify all PRRSV isolates so infected animals can be culled from the herd. This report demonstrates that our newly developed and optimized bELISA provides a more sensitive assay to confirm the true positive animals versus false positive in herds or when transient positive/negative results arise. It could also be used to validate IDEXX ELISA results when PRRSV antibodies are just above or below the level of detection (low S/P ratios). By adding components such as a dual set of monoclonal antibodies AT-13 and SDOW-17 and recombinant nucleocapsid protein derived from both North American and European-like PRRS virus strains, we demonstrate an increased specificity and sensitivity which ultimately leads to the assay’s broadened detection capabilities.
The bELISA is a single assay taking just three and a half hours to perform and provides an accurate and convenient alternative method to assist with the evaluation of results obtained when using the IDEXX ELISA. Other candidate assays for a follow-up test have drawbacks. VI is sensitive within days of infection, but becomes less useful in the following weeks (Christopher-Hennings et al., 2001) Temperature of storage and shipping of serum samples also may decrease the likelihood of virus recovery. SVN detects neutralizing antibodies that appear 30 to 60 days post infection, so it is a poor test for early infection. PCR provides a quick and sensitive method for the detection of viral antigen; however, it is very expensive to perform on a routine screening basis. Although the IFA detection window is similar to that of the IDEXX ELISA, it requires techniques and equipment not available in all laboratories. It is also very subjective and has less repeatability between diagnostic laboratories. The bELISA shows specificity and sensitivity over a wide time frame, and shows good repeatability. Therefore, the blocking ELISA assay is a better candidate for a confirmatory assay. The addition of antibody and antigen components to detect Type 1 PRRSV will expand the detection capabilities of the assay. We have developed the components of this assay into a stable “kit” format that will retain its activity after storage, making it a good candidate for commercial applications. This bELISA could supplement the current IDEXX ELISA and would directly benefit producers by allowing them to detect any PRRSV strains present in their herd quickly and accurately.