The sialic acids of Horse serum with special reference to their virus inhibitory properties

Abstract

1. 1.Horse serum, which contains a substance capable of inhiting Asian influenza virus, has been investigated to determine whether or not sialic acids are important in this reaction, and if so, what types of sialic acid are present. 2. 2.Hydrolysis of horse serum and sub-fractions by dilute acid, alkali and Vibrio cholerae and influenza virus neuraminidases (EC 3.2.1.8) indicated that the sialic acids present are a mixture of N-acetyl- and N-glycolylneuraminic acids together with the 4- O-acetylated derivatives of these acids. 3. 3.The biological activity which horse serum exhibits specifically towards the 4. A2 strain of influenza virus appears to be determined by a 4- O-acetyl-N-acetylneuraminic acid substituted α 2-macroglobulin. 5. 4.The fraction of horse serum sialic acids (60%) which are resistant to V. cholerae neuraminidase but hydrolysed by A2 virus neuraminidase are the 4- O- acetylated neuraminic acids. 6. 5.It is suggested that a conjugate relationship exits between the type of sialic acid in an inhibitor, the virus strain which inhibits and the types of sialic acid which a given viral neuraminidase will hydrolyse. This relationship may be teh basis of a sensitive test for identifying different types of sialic acids.