Expression of Porcine Reproductive and Respiratory Syndrome Virus Nucleocapsid Protein in Nicotiana benthamiana for Diagnostic Applications

Porcine reproductive and respiratory syndrome virus (PRRSV), the causative agent of Porcine reproductive and respiratory syndrome (PRRS) in pigs, is an enveloped positive strand RNA virus belongs to the family Arteriviridae. PRRSV poses severe threat to swine industry worldwide. Routine surveillance, rapid timely diagnosis of PRRSV infection is crucial for effective monitoring and disease control. Serological tests based on highly conserved viral nucleocapsid (N) protein are widely used for the detection of antibodies to PRRSV. Here, we investigated the potential of plant system to produce PRRSV N-protein in order to use as a reagent for the diagnosis of PRRSV infection. In this regard, the codon-optimised PRRSV N-protein coding sequence was cloned in geminiviral vector and expressed in Nicotiana benthamiana. The transient expression conditions such as effective gene construct, leaf harvesting time and Agrobacterium cell density were optimized for maximal protein production. Further, by using western blot assay, with a plant-produced protein we sought to detect the antibodies against PRRSV in pig sera. Preliminary testing revealed that the recombinant protein was identified by antibodies present in pig sera. However sensitivity/specificity and correlation of results with other assays needs to be evaluated. This proof of concept study indicated that plant-produced N-protein can likely be used as diagnostic reagent and demonstrate the potential of plant expression system for the production of recombinant PRRSV antigens.