Risk Assessment for Highly Pathogenic Avian Influenza A(H5N6/H5N8) Clade 2.3.4.4 Viruses

• Main Authors: Christine H.T. Bui, Denise I.T. Kuok, Hin Wo Yeung, Ka-Chun Ng, Daniel K.W. Chu, Richard J. Webby, John M. Nicholls, J.S. Malik Peiris, Kenrie P.Y. Hui, Michael C.W. Chan
• Format: Article
• Language: English
• Published: Centers for Disease Control and Prevention 2021-10-01
• Series: Emerging Infectious Diseases
• Subjects: influenza; human airway organoids; risk assessment; tropism; innate host responses; HPAI H5Nx
• Online Access: https://wwwnc.cdc.gov/eid/article/27/10/21-0297_article
• ISSN: 1080-6040; 1080-6059

The numerous global outbreaks and continuous reassortments of highly pathogenic avian influenza (HPAI) A(H5N6/H5N8) clade 2.3.4.4 viruses in birds pose a major risk to the public health. We investigated the tropism and innate host responses of 5 recent HPAI A(H5N6/H5N8) avian isolates of clades 2.3.4.4b, e, and h in human airway organoids and primary human alveolar epithelial cells. The HPAI A(H5N6/H5N8) avian isolates replicated productively but with lower competence than the influenza A(H1N1)pdm09, HPAI A(H5N1), and HPAI A(H5N6) isolates from humans in both or either models. They showed differential cellular tropism in human airway organoids; some infected all 4 major epithelial cell types: ciliated cells, club cells, goblet cells, and basal cells. Our results suggest zoonotic potential but low transmissibility of the HPAI A(H5N6/H5N8) avian isolates among humans. These viruses induced low levels of proinflammatory cytokines/chemokines, which are unlikely to contribute to the pathogenesis of severe disease.