Sequence variability of Hungarian RSV G and F proteins between 2017 and 2023: single-center study

Our study determined the prevalence, types of RSV, and sequence variability of the G and F genes in Hungary between 2017 and 2023. During the study, 1828 respiratory samples were collected from hospitalised pediatric patients. We confirmed the presence of RSV A in 12.74%, RSV B in 13.85%, and their simultaneous presence in 0.27%. The highest RSV positivity was observed in the 2018-2019 season, while the lowest was in the 2017-2018 season. Following the SARS-CoV-2 pandemic, the RSV season has an earlier onset and longer duration than it did previously; however, an earlier onset was already detected in 2018. All RSV A isolates are classified into the A.D., while RSV B into the B.D. clades. The entire ectodomain of G protein showed a high sequence diversity, higher than in the case of B.D. strains. Mutations at position 276, adjacent to the palivizumab binding site of the F protein, could be detected. At the same time, neither K272E/N nor any other mutation is present in the palivizumab binding region in our strains. Several mutations in the nirsevimab binding region could be detected in our strains; however, none of these mutations, which would affect nirsevimab activity, were found in our isolates. • We studied circulating RSV strains and their seasonality in Hungary from 2017 to 2023 in children under 18. • The SARS-CoV-2 pandemic's restrictions altered the seasonal patterns of respiratory infections. • Our isolates exhibit several sequence variations in the G and F proteins and can be classified into A.D. and B.D. clades. • RSV A strains belonging to the 2019–2020 clade exhibit a rare amino acid substitution pattern in the HRV1 and HRV2 region, like two German isolates in GenBank. • We found no N208D and I64M combined with K65R or any other mutations that reduce nirsevimab activity.