Production of a novel Affimer based biosensor for the detection of porcine reproductive and respiratory syndrome virus nucleocapsid protein.

Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically important infection with no current point of care (POC) diagnostic available. PRRSV causes reproductive and respiratory illness in swine with the recent emergence of highly pathogenic strains. This highlights the need for measures to control the spread of this infection to be taken more seriously in order to reduce the economic impact of this virus. Current diagnostics for PRRSV are laboratory based and inherently these tests are expensive and are not rapid enough for the adequate management of outbreaks of the virus and implementation of biosecurity measures. This study presents a novel lateral flow device (LFD), using Affimer binding proteins to detect the nucleocapsid protein of PRRSV within a clinical sample to provide a cheap, rapid and reliable diagnostic for this infection in clinical samples. Affimer reagents were raised against the nucleocapsid proteins from two strains of PRRSV, a high pathogenic and a low pathogenic strain. Affimers that were able to distinguish between the two were taken forward for assessment in lateral flow. The Affimers were able to bind to the nitrocellulose membrane component of the device and were stable once dehydrated. The Affimers were able to migrate through the membrane via capillary action when rehydrated and can detect the viral protein at a test line within a clinical sample, swine serum. This study provides the basis for further investigations in to the applications of Affimer reagents in lateral flow devices able to detect other viral infections as well as medically important diseases such as cancer. In addition to their use in diagnostics, this study proposes the use of Affimers raised against the nucleocapsid protein of PRRSV as molecular tools for the further investigation into the role of this protein in the viral lifecycle as well as their potential as anti-viral therapeutics to address the lack of these medicines against this virus.