Background: A study of respiratory syncytial virus-A (RSV A) genotype ON1 genetic variability and clinical severity in infants hospitalized with bronchiolitis over 6 epidemic seasons (2012-2013 to 2017-2018) was carried out.
Methods: From prospectively enrolled term infants hospitalized for bronchiolitis, samples positive for RSV A ON1 (N = 139) were sequenced in the second half of the G gene. Patients' clinical data were obtained from medical files and each infant was assigned a clinical severity score. ANOVA comparison and adjusted multinomial logistic regression were used to evaluate clinical severity score and clinical parameters.
Results: The phylogenetic analysis of 54 strains showed 3 distinct clades; sequences in the last 2 seasons differed from previous seasons. The most divergent and numerous cluster of 2017-2018 strains was characterized by a novel pattern of amino acid changes, some in antigenic sites. Several amino acid changes altered predicted glycosylation sites, with acquisition of around 10 new O-glycosylation sites. Clinical severity of bronchiolitis increased in 2016-2017 and 2017-2018 and changed according to the epidemic seasons only.
Conclusions: Amino acid changes in the hypervariable part of G protein may have altered functions and/or changed its immunogenicity, leading to an impact on disease severity.
Keywords: bronchiolitis; clinical severity; genetic variability; genotypes; respiratory syncytial virus.
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