The chemical reactions of the haemagglutinins and neuraminidases of different strains of influenza viruses: II. Effects of reagents modifying the higher order structure of the protein molecule

Abstract

The results of treatment of influenza virus strains with chemical reagents acting on the higher-order structure of protein molecules shows that both the haemagglutinating and enzymic activities are susceptible to these agents but there are considerable differences between the different strains and the neuraminidase activity is more sensitive than the haemagglutinating activity.The neuraminidase activity of A and A₁strains is destroyed by urea, guanidine, urea+dithiothreitol and mercuric chloride. The haemagglutinin of the PR 8 and SWINE strains is resistant to urea and mercuric chloride but destroyed by guanidine and by urea+dithiothreitol. The haemagglutinin of the DSP strain of virus A and the A₁strains is resistant to urea, guanidine and mercuric chloride but is destroyed by urea+dithiothreitol.The neuraminidase activity of the A₂strains is more resistant than that of the A and A₁strains. It is resistant to mercuric chloride and partially resistant to urea but is destroyed by guanidine and by urea+dithiothreitol. The A₂haemagglutinin is resistant to urea, urea+dithiothreitol, and mercuric chloride but is destroyed by guanidine.The LEE virus neuraminidase is resistant to urea and partially resistant to guanidine but is destroyed by urea+dithiothreitol and mercuric chloride. The LEE haemagglutinin is resistant to urea, guanidine and mercuric chloride but is destroyed by urea+dithiothreitol.It is suggested that the surface projections of the virus particle are protein polymers each made up of three or four monomers which are the components of the V antigen complex. Antigenic activity is a function of the primary or secondary structure of the monomers, haemagglutinin activity is a function of the tertiary structure of the monomers, while neuraminidase activity is a function of the quaternary structure of the polymer.From studies of the chemical reactions of their haemagglutinins and neuraminidases strains of influenza virus A can be classified into groups. These groups are very similar to but not precisely identical with groupings made by serological methods.