The chemical reactions of the haemagglutinins and neuraminidases of different strains of influenza viruses. 3. Effects of proteolytic enzymes.

The action of trypsin and pronase on the haemagglutinins and neuraminidases of eight strains of influenza virus has been examined.The haemagglutinins of all the strains were highly susceptible to digestion by pronase but there were great variations in resistance to trypsin.The neuraminidases of the eight strains were of three types. The neuraminidases of the A 1 strains and the DSP strain of virus A were highly susceptible to destruction by both enzymes. The neuraminidases of the PR 8 and Swine strains showed partial resistance especially to trypsin, while the A 2 strains and the LEE strains of virus B possessed neuraminidases that were completely resistant to both trypsin and pronase.Proteolytic enzymes released free neuraminidases from the A 2 and LEE viruses the morphology of which was different from that of neuraminidases released by detergent treatment.