- Bovine respiratory syncytial virus lacking the virokinin or with a mutation in furin cleavage site RA(R/K)R109 induces less pulmonary inflammation without impeding the induction of protective immunity in calves. Valarcher, J.F., Furze, J., Wyld, S.G., Cook, R., Zimmer, G., Herrler, G., Taylor, G. J. Gen. Virol. (2006)