Neuraminidase activity of blue eye disease porcine rubulavirus: Specificity, affinity and inhibition studies

Porcine rubulavirus (PorPV), also known as La Piedad Michoacan Virus (LPMV) causes encephalitis and reproductive failure in newborn and adult pigs, respectively. The hemagglutinin-neuraminidase (HN) glycoprotein is the most exposed and antigenic of the virus proteins. HN plays central roles in PorPV infection; i.e., it recognizes sialic acid-containing cell receptors that mediate virus attachment and penetration; in addition, its neuraminidase (sialic acid releasing) activity has been proposed as a virulence factor. This work describes the purification and characterization of PorPV HN protein (isolate PAC1). The specificity of neuraminidase is restricted to sialyl(alpha 2,3)lactose (3SL). HN showed typical Michaelis-Menten kinetics with fetuin as substrate (km = 0.029 mu M, Vmax = 522.8 nmol min(-1) mg(-1)). When 3SL was used as substrate, typical cooperative kinetics were found (S-50 = 0.15 mu M, Vmax = 154.3 nmol min(-1) mg(-1)). The influenza inhibitor zanamivir inhibited the PorPV neuraminidase with IC50 of 0.24 mu M. PorPV neuraminidase was activated by Ca2+ and inhibited by nucleoside triphosphates with the level of inhibition depending on phosphorylation level. The present results open possibilities to study the role of neuraminidase in the pathogenicity of PorPV infection and its potential inhibitors.