The wild type influenza strain A/Aichi/2/68 (H3N2), when disrupted with SDS and electrophoresed on cellulose acetate paper, yielded two separate neuraminidases, NA(H+) and NA(H-). These enzymes after extraction were biologically active and possessed different specific activities. Enzyme NA(H+) possessed neuraminidase as well as hemagglutinin activities whereas enzyme NA(H-) demonstrated only neuraminidase activity. Similar results were obtained when the Aichi strain was treated with Tween-ether and the two enzymes were separated by affinity chromatography. Techniques used failed to separate the hemagglutinin activity from neuraminidase NA(H+). These results suggest that the dual activity present in enzyme NA(H+) may be characteristic of this protein. Both enzymes are antigenically different and are apparently present as distinct entities in the Aichi strain. Experiments showed that only enzyme NA(H-) of the Aichi strain was incorporated into the hybrid X-32 virus during genetic recombination.

The neuraminidase located on the influenza virus recombinant A/Eq (Heq1) x A/PR8 (N1) was relatively a poor antigen (NI titre less than 10) as compared with the enzyme present on the parent virus A/PR8/34 (H0N1) (NI titre 160). This difference in the antigenic behavior of the neuraminidase of A/PR8/34 (H0N1) virus was explored. Results obtained showed that rabbit anti-A/PR8/34 (H0N1) serum contained two distinct types of antineuraminidase antibody and only one type of antineuraminidase antibody was precipitable by the neuraminidase located on the recombinant virus. Evidence suggests that the parent enzyme(s) is not detectable in its entirety on its recombinant virus.

A ribonuclease activity associated with influenza virus has been purified to homogeneity. This preparation is free of DNAase, phosphodiesterase, and phosphatase activities. The purified enzyme has a pH optima of 7.0 at 37 degrees C, and moves as a single band on sodium dodecyl sulfate - polyacrylamide gel with an estimated molecular weight of 84 000.