ON-1 and BA-IX Are the Dominant Sub-Genotypes of Human Orthopneumovirus A&B in Riyadh, Saudi Arabia

Human orthopneumovirus (HOPV) is the major viral pathogen responsible for lower respiratory
tract infections (LRTIs) in infants and young children in Riyadh, Saudi Arabia. Yet, predominant
HOPV subtypes circulating in this region and their molecular and epidemiological characteristics
are not fully ascertained. A total of 300 clinical samples involving nasopharyngeal aspirates (NPAs),
throat swabs, and sputum were collected during winter seasons of 2019/2020 and 2021/2022 for
HOPV subtyping and genotyping. Of the 300 samples, HOPV was identified in 55 samples (18.3%)
with a distinct predominance of type A viruses (81.8%) compared to type B viruses (18.2%). Importantly,
the ON1 strain of HOPV-A and BA-IX strain of HOPV-B groups were found to be responsible
for all the infections. Sequence analysis revealed a duplication region within 2nd HVR of G protein
gene of ON1 and BA-IX strains. This nucleotide duplication exerted a profound effect on protein
length and affinity towards cell receptors. Further, these modifications may aid the HOPV in immune
evasion and recurrent infections. Data from this study showed that ON-1 genotype of HOPV-A
and BA-IX genotype of HOPV-B were dominant in Riyadh, Saudi Arabia. Further, a duplication of
sequence within 2nd HVR of G protein gene was found.