Molecular phylogeny of human adenovirus type 41 lineages.

Type 41 of human adenovirus species F (HAdV-F41) is a frequent aetiology of gastroenteritis in children, and nosocomial as well as kindergarten outbreaks have been frequently described. In contrast to other HAdV types, HAdV-F41 was not associated with a life-threatening disseminated disease in allogeneic haematopoietic stem cell transplant (HSCT) recipients or any severe organ infections so far. Due to the limited clinical significance, the evolution of HAdV-F41 has not been studied in detail. Recently, HAdV-F41 has been associated with severe hepatitis in young children, and interest in HAdV-F41 has skyrocketed, although the aetiology of hepatitis has not been resolved. Complete genomic HAdV-F41 sequences from thirty-two diagnostic specimens of the past 11 years (2011-22) were generated, all originating from gastroenteritis patients. Additionally, thirty-three complete HAdV-F41 genomes from GenBank were added to our phylogenetic analysis. Phylogenetic analysis of sixty-five genomes indicated that HAdV-F41 evolved with three lineages co-circulating. Lineage 1 included the prototype 'Tak' from 1973 and six isolates from 2007 to 2017 with an average nucleotide identity of 99.3 per cent. Lineage 2 included 53 isolates from 2000 to 2022, had an average nucleotide identity of 99.8 per cent, and split into two sublineages. Lineage 3, probably described for the first time in 2009, had a 45-nucleotide deletion in the long fibre gene and had evolved significantly in the short fibre and E3 region. Moreover, a recent Lineage 3 isolate from 2022 had a recombinant phylogeny of the short fibre gene. Fibres interact with cellular receptors and determine cellular tropism, whereas E3 gene products interfere with the immune recognition of HAdV-infected cells. This in-depth study on the phylogeny of HAdV-F41 discovered significant evolution of recently described Lineage 3 of HAdV-F41, possibly resulting in altered cellular tropism, virulence, and pathophysiology.