Whole-Genome Phylogenetic Characterization of Human Parainfluenza Virus Type 4 Circulating in St. Petersburg, Russia

Human parainfluenza virus type 4 (hPIV4) remains poorly characterized compared with other hPIV serotypes and information on its genomic diversity is particularly limited for Russia and Eastern Europe. In this study, we report the first complete genome sequences of hPIV4 isolates from Russia and place them in the context of global hPIV4 genetic diversity. Eight hPIV4 viruses were isolated in cell culture from respiratory samples collected from hospitalized children in Saint Petersburg between 2017/2018 and 2023/2024. Complete viral genomes were recovered using a metagenomic whole-genome amplification approach based on SMART-9N technology. Phylogenetic analysis of 178 complete hPIV4 genomes showed clear separation into hPIV4a (n = 132) and hPIV4b (n = 46) subtypes. Based on genetic distance approach, hPIV4a formed two major clusters, with the dominant cluster B subdivided into four subclusters (B1-B4); and subcluster B4 further resolved into four genetic lineages. All Russian isolates belonged to the subcluster B4 and were distributed among multiple co-circulating lineages. In contrast, hPIV4b genomes segregated into three distinct clusters, reflecting structured genetic diversity within the subtype. Collectively, this study provides, to the best of our knowledge, the first p-distance-based framework for hPIV4 whole-genome classification and contributes new complete genome sequences for an underrepresented region.