Enhanced induction of inflammatory cytokines in human lung cells infected with highly pathogenic recent H5N1/2024 avian influenza virus.

Highly pathogenic (HP) H5N1 avian influenza viruses are zoonotic pathogens and are endemic in wild birds and poultry around the world. Pro-inflammatory cytokines are supposed to contribute to the severe clinical symptoms in infected animals and humans. In this study, we determined the infectivity and cytokine induction in primary human lung cells infected with HP H5N1 avian influenza viruses and seasonal H3N2 influenza viruses. MDCK cells were used to measure viral titers in the supernatants of infected human lung cells by log10TCID50/ml. Quantitative real-time PCR was used to detect the induction of cytokine genes using mRNA from the infected primary human lung cells. HP H5N1 avian influenza viruses induced higher viral titers than seasonal H3N2 influenza viruses in supernatants of primary human lung cells. In addition, HP H5N1avian influenza viruses induced the genes of pro-inflammatory cytokines such as IL-23, IL-1α, IL-1β, IL-6, and IL-8 at significantly higher levels than seasonal H3N2 influenza viruses in primary human lung cells. Our data suggest that the high viral replication and the high induction of pro-inflammatory cytokines in the human lung cells infected with HP H5N1 avian influenza viruses may enhance pathogenicity in the infected humans as compared to seasonal H3N2 influenza viruses.