The identification of a porcine pneumovirus from an immunological perspective

International audienceThe presence of pneumoviruses in pigs is extremely poorly documented. To inquire about these viruses in French pig farms, we used the published sequence of the nucleoprotein (N) of the recently identified Swine Orthopneumovirus (SOV) to express and purify SOV N as a recombinant protein in Escherichia coli. Then, SOV N was purified as nanorings and used to set up an enzyme-linked immunosorbent assay (ELISA). Using that ELISA we analysed the presence of anti-SOV N Immunoglobulins G (IgG) in various swine sera to inquire about the circulation of the virus in France. Since the virus has never been isolated, real positive controls were unavailable and negative controls challenging to obtain. Sera collected from specific pathogen free new born piglets before colostrum uptake were used as negative controls. These sera were negative for anti-SOV N IgG while most of the other sera collected in older animals from different pig farms in Brittany (France) were positive at various levels. To further confirm the validity of our ELISA assay cross-reactivity with bovine sera, human respiratory syncytial virus (hRSV) N, and whole inactivated bovine RSV (bRSV) particles were tested. Bovine sera were negative for IgG anti-SOV N and porcine sera did not react with inactivated bRSV. Interestingly, in two pig farms presenting respiratory clinical signs and negative or under control for common respiratory pathogens such as influenza virus and Mycoplasma spp, pigs were detected positive for anti-SOV N IgG. Several field and laboratory studies will be required to further characterize the circulation of the virus amongst pigs, to isolate the circulating virus, and to determine its potential pathogenicity and interactions with the porcine immune system. SOV may prove to be an overlooked actor of the porcine respiratory complex, important on its own or in association with other viral and bacterial micro-organisms