Emergence and characterization of a putative novel human adenovirus recombinant HAdV-C104 causing pneumonia in Southern China

In 2017, a survey of the molecular epidemiology of human adenovirus (HAdV) infections in Southern China based on hexon and fiber genotype demonstrated that the most prevalent genotypes of HAdV were HAdV-3 (n = 62), HAdV-2 (n = 21), and HAdV-7 (n = 16). In addition, two patients were co-infected with two genotypes of HAdV. Interestingly, a novel human adenovirus C recombinant genotype strain was isolated from one of the pneumonia patients in this survey. Phylogenetic, recombination, and proteotyping analysis showed that this novel pathogen originated from the recombination of parental viruses harboring the HAdV-1 penton and hexon gene, and the HAdV-2 fiber gene. It was named ‘P1H1F2’ and was assigned as HAdV-C104 based on the nomenclature protocol of using three major capsid proteins for characterization. Subsequent in vitro experiments demonstrated that HAdV-C104 had comparable proliferation capacity to HAdV-1, HAdV-2, and another recombination genotype P1H2F2. In addition, the HAdV-C104 infected patient was diagnosed with pneumonia and recovered after antiviral therapy. This report strengthens the hypothesis of recombination as a major pathway for the molecular evolution of HAdV-C species.