THE EFFECT OF SOME PATHOGENIC BACTERIAL PROTEASES ON AVIAN INFLUENZA VIRUSES H5N1 AND H9N2

Noha Awwad, Emad Eldin Elgendy, Nabil Mohamed and Madiha Salah Ibrahim*

ABSTRACT

Microbial proteases are responsible for proteolytic cleavage activation of Influenza A Virus (H5N1 and H9N2) hemagglutinin (HA). We examined the proteolytic activities of some pathogenic bacterial isolates such as Staphylococcus aureus, Pseudomonas aeruginosa and Mycoplasma gallisepticum. The contribution of endogenous and microbial proteases (exogenous proteases) in the avian influenza pathogenicity were studied by inoculation of three groups of embryonated chicken eggs (SPF). The first group was inoculated simultaneously with either viruses; H5 and H9, with different concentrations of bacterial proteases. The second group was inoculated with pre-incubated viruses with different concentrations of the bacterial proteases. The third group was control (virus only, protease only and PBS). An increase in viruses’ titer was observed in eggs inoculated with virus treated with microbial proteases incomparable to that inoculated with untreated viruses. These results confirmed the synergism between influenza virus and pathogenic bacteria based on proteolytic activation of the hemagglutinin by bacterial proteases. Further, H9N2 virus titer was significantly increased as compared to H5N1 virus titer in eggs with prominent increase of H9N2 virulence that was noted in the death time of the eggs reaching that of H5N1. M. gallisepticum showed an increase in virus titer but lower than that caused by Staphylococcus aureus and Pseudomonas aeruginosa revealing the difference between serine and cysteine proteases in cleavage activation of influenza virus HA.

Keywords: S. Aureus, P. Aeruginosa, M. Gallisepticum, Proteases, AIV.