REPLICATION OF INFLUENZA-B VIRUS IN CHICKEN EMBRYOS IS SUPPRESSED BY EXOGENOUS APROTININ

Chicken embryo proteinases, one of which is a blood clotting factor Xa -like proteinase, are known to effectively cleave the haemagglutinin ( HA) of Influenza B viruses to permit their replication in chicken embr yonated eggs. Here we show that injection of the serine proteinase inh ibitor, aprotinin, into the allantoic cavity of eggs infected with Inf luenza B/Hong Kong/73 and B/Lee/40 viruses suppresses the viral HA cle avage and reduces the virus proteolytic activation and replication. Ef fective inhibition dose was determined as similar to 10.0 mu g of apro tinin per embryo that corresponds to 0.1 mu M concentration. However, heparin, which is known to be a direct inhibitor of the Factor Xa, was not able to suppress Influenza B virus hemagglutinin cleavage and rep lication in chicken embryo system. These data shed light on the patter n of proteinases involved in the Influenza B virus proteolytic activat ion and indicate that aprotinin possesses antiviral potential against Influenza B viruses.