Genetic Divergence of H1N1pdm09 in Saudi Arabia: Unveiling a Novel N-Glycosylation Site and Its Role in Vaccine Mismatch

مقال فى مجلة

2025

Background/Objectives: Influenza A virus undergoes continuous antigenic drift, necessitating

annual vaccine reformulation. Saudi Arabia faces unique epidemiological challenges

owing to mass gatherings during religious pilgrimages and the dynamic movement of

foreign workers. This study aimed to characterize the genetic diversity of hemagglutinin

(HA) and neuraminidase (NA) genes of influenza A viruses circulating in Riyadh and to

assess their match with vaccine strains during the 2024–2025 period. Methods: Nasopharyngeal

samples (n = 363) were collected from patients presenting with influenza-like

illness. RT-PCR was used for detection and subtyping. Sequence and phylogenetic analysis

of the complete HA and NA gene sequences from A/H1N1pdm09 strains (n = 7) were

then performed. Results: Of the 363 samples, 110 (30.3%) were positive for influenza A;

among these, 68 (61.8%) were A/H1N1pdm09, and 42 (38.2%) were H3N2. Phylogenetic

analysis revealed that all A/H1N1pdm09 strains belonged to clade 5a.1, distinct from

vaccine strains. In comparison with the vaccine strain A/Wisconsin/67/2022, seven amino

acid substitutions in the HA gene and eight in the NA gene were recorded in Saudi circulating

strains. The significant genetic divergence between circulating A/H1N1pdm09

strains and current vaccine strains indicates potential vaccine mismatch. Conclusions:

The significant genetic divergence between circulating A/H1N1pdm09 strains and current

vaccine strains suggests potential vaccine mismatch. Continuous surveillance programs

along with vaccination plans are necessary to tackle the changing influenza A virus strains

in the special epidemiological context of Saudi Arabia.