EFFECTIVE INHIBITORS OF HEMAGGLUTINATION BY INFLUENZA-VIRUS SYNTHESIZED FROM POLYMERS HAVING ACTIVE ESTER GROUPS - INSIGHT INTO MECHANISM OF INHIBITION

Highly effective sialic acid-containing inhibitors of influenza virus X-31 were synthesized using poly[N-(acryoyloxy)succinimide] (pNAS), a polymer preactivated by incorporation of active ester groups. Polymers containing two and three different components were prepared by sequen tial reaction of pNAS with two and three amines, respectively. This pr eparation of co- and terpolymers was synthetically more efficient than methods involving copolymerization of different monomers and gave pol ymers that were more easily compared than those generated by copolymer ization. Polymers in this study (prepared from a single batch of pNAS) had a constant degree of polymerization (DP approximate to 2000) and probably had a distribution of components that was more random than an alogous polymers prepared by copolymerization. Use of C-glycosides of sialic acid made it possible to investigate inhibition by different po lymers at temperatures ranging from 4 to 36 degrees C without artifact s due to the hydrolytic action of neuraminidase. The inhibitors were, in general, more effective at 36 degrees C than at 4 degrees C. The he magglutination (HAI) assay was used to measure the value of the inhibi tion constant K-i(HAI) each polymer. The value of K-i(HAI) for the two -component polymer containing 20% sialic acid on a polyacrylamide back bone at 4 degrees C was 4 nM (in terms of the sialic acid moieties pre sent in solution) and was approximately 50-fold more effective than th e best inhibitors previously described and 25-fold more effective than the best naturally occurring inhibitor. The most effective inhibitor synthesized in this work contained 10% benzyl amine and 20% sialic aci d on a polyacrylamide backbone, and its value of K-i(HAI) was 600 pM a t 36 degrees C. Approximately 100 polymers that differed in one or two components were assayed to distinguish between two limiting mechanism s for inhibition of the interaction between the surfaces of virus and erythrocytes: high-affinity binding through polyvalency, and steric st abilization. The results suggest that both mechanisms play an importan t role. The system comprising polyvalent inhibitors of agglutination o f erythrocytes by influenza provides a system that may be useful as a model for inhibitors of other pathogen-host interactions, a large numb er of which are themselves polyvalent.