Fig. 2.

Enzymes secreted by oral bacteria can spread influenza infection.

In the life cycle of influenza viruses, adsorption to target cells by hemagglutinin (HA) and release from target cells by neuraminidase (NA) are the most important processes for viral replication and spread.

Gingipains secreted by the periodontal pathogen Porphyromonas gingivalis can facilitate viral infection by cleaving influenza virus HA into HA1 and HA2. In addition, NA secreted by oral streptococci may act as a substitute for viral NA, whose activity is inhibited by anti-NA drugs, resulting in a weakened effect of anti-NA drugs and accelerated viral release.