Sialidase Activity in Rimantadine-Resistant and -Sensitive Influenza A Viruses

Abstract

Rimantadine-resistant and -sensitive influenza A variants were assayed for their sialidase (neuraminidase, EC 3.2.1.18) activity. The kinetic parameters determined (pH optimum, stability against different pH values, thermal stability, activity on methylumbelliferyl- α-D-N-acetylneuraminic acid, N-acetylneuraminyl-lactose, fetuin and bovine submandibular gland mucin as substrates, K(m) with the former substrate, inhibition by two competitive inhibitors, and behavior towards amantadine) revealed the same results for both variants of the virus. Thus, it can be deduced that resistance to rimantadine does not influence the sialidase activity of influenza A virus.

Reduced levels of neuraminidase of influenza A viruses correlate with attenuated phenotypes in mice

“…Neuraminidase reaction assays were carried out using 10 μl of dialysed viruses in 100 μl reaction mixtures containing 200 mM potassium phosphate buffer pH 6·0, 1 mM CaCl 2 , 2·8 mg/ml fetuin (Sigma) and different concentrations of sera from immunized mice. Reactions were carried out at 37 °C for 12 h, and the amount of neuraminic acids released from the fetuin was determined as previously described (García-Sastre et al ., 1990 ). The NI titres represent the serum dilution that resulted in 50% inhibition of the neuraminidase activity.…”