Sialic acid is cleaved from glycoconjugates at the cell surface when influenza virus neuraminidases are expressed from recombinant vaccinia viruses.

Three different influenza virus neuraminidase (NA) genes have been subcloned into the vector pSC11 and expressed from the recombinant vaccinia viruses. These genes are from influenza viruses A/Tokyo/3/67 (N2); A/tern/Australia/G70c/75 (N9); and B/Hong Kong (HG)(NA of B/Lee/40). Cells infected with recombinants containing the NA gene express enzymatically active NA on the cell surface. The expressed protein results in the infected cells beings stripped of sialic acid, the receptor for influenza virus. This is not due to cleavage by NA from detached cells since at low multiplicity of infection only cells present at plaques are devoid of sialic acid. Thus NA is able to cleave sialic acid from neighboring glycoconjugates on the same membrane.