A Comprehensive Analysis of H5N1 Evolution: Phylogenetic Insights and Emerging Mutations in Turkey's Avian Influenza Landscape

Abstract

Abstract Avian influenza (AI) H5N1 viruses, known for their high mortality in humans and poultry, pose a significant public health threat. This study examines seventeen H5N1 isolates from the 2006 outbreak in Turkey and one 2023 isolate for mutations in the hemagglutinin gene's receptor binding domain, which determines host specificity, and the evolutionary changes in the isolates. The hemagglutinin gene region of these isolates was partially amplified using RT-PCR, and critical mutations in the receptor binding domains were examined, alongside the phylogenetic relationships of the isolates in a time- and geography-dependent manner. Our findings showed that key mutations known for altering host selectivity (N224K, G225D, Q226L, S227N, G228S) were absent. However, additional mutations (D110N and S171N), potentially affecting receptor selectivity, were identified. Comprehensive phylogenetic analysis, conducted separately based on geographic regions and temporal distribution, encompassed H5N1 strains isolated from various locations and hosts from 2007 to 2023. This study highlights significant genetic divergence between the 2006 Turkish isolates and the 2023 isolate, highlighting notable evolutionary changes. Distinct clustering of the isolates was observed in both geographic and temporal phylogenetic frameworks, indicating substantial evolutionary shifts within the circulating H5N1 strains in Turkey. Given the global spread potential of H5N1 viruses via migratory birds and the risk of a new pandemic if human-to-human transmission is attained, monitoring H5N1's molecular traits and evolution is crucial for mitigating public health impacts.