Mathematical modelling of in vitro replication dynamics for multiple highly pathogenic avian influenza clade 2.3.4.4 viruses in chicken and duck cells.

Abstract

The introduction, spread, and subsequent detection of highly pathogenic avian influenza viruses (HPAIV) in poultry are influenced by the virus replication fitness, transmission fitness, and virulence. Quantifying these fitness parameters is important for implementing surveillance and control measures for poultry. This study employs an avian in vitro model using primary chicken (CEF) and duck (DEF) embryo fibroblasts, to identify cellular correlates of fitness for a reference panel of eight dominant HPAI clade 2.3.4.4 virus genotypes (H5N1, H5N8, and H5N6) isolated between 2014 and 2024. Because HPAI viruses are pantropic in poultry, the use of primary fibroblasts could provide a robust systemic model to assess virus fitness in different poultry species. By integrating longitudinal infectious virus titres and cytopathogenicity data with a mathematical model, which delineates cell populations into susceptible, latent, infectious, and dead compartments, we disentangled (traditional) virological parameters such as peak virus titre and time to 50% cell death, from mechanistic parameters, including the infecting time (t_inf), generation time (t_gen) and basic reproduction number (R0). Our results confirm host-specific fitness characteristics consistent with in vivo observations. This study underscores the potential of integrating avian in vitro models with mathematical modeling to provide high resolution characterization of genetically similar viruses building towards rapid risk assessments of novel HPAI viruses.