High molecular weight constituents of cranberry interfere with influenza virus neuraminidase activity in vitro.

Cranberry juice contains high molecular weight non-dialyzable material (NDM) which was found to inhibit hemagglutination induced by the influenza virus (IV) as well as to neutralize the cytotoxicity of IV in cell cultures. Because influenza virus surface glycoproteins hemagglutinin (HA) and neuraminidase (NA) are involved in viral replication and in the infectious process, we sought in the present study to examine the effect of NDM on neuraminidases which are the target of most anti-influenza drugs today. NDM inhibited the NA enzymatic activity of influenza A and B strains as well as that of Streptococcus pneumoniae.