Phylogenetic Analysis of the Main Neutralization and Hemagglutination Determinants of All Human Adenovirus Prototypes as a Basis for Molecular Classification and Taxonomy

Abstract

ABSTRACT Human adenoviruses (HAdV) are responsible for a wide spectrum of diseases. The neutralization ε determinant (loops 1 and 2) and the hemagglutination γ determinant are relevant for the taxonomy of HAdV. Precise type identification of HAdV prototypes is crucial for detection of infection chains and epidemiology. ε and γ determinant sequences of all 51 HAdV were generated to propose molecular classification criteria. Phylogenetic analysis of ε determinant sequences demonstrated sufficient genetic divergence for molecular classification, with the exception of HAdV-15 and HAdV-29, which also cannot be differentiated by classical cross-neutralization. Precise sequence divergence criteria for typing (<2.5% from loop 2 prototype sequence and <2.4% from loop 1 sequence) were deduced from phylogenetic analysis. These criteria may also facilitate identification of new HAdV prototypes. Fiber knob (γ determinant) phylogeny indicated a two-step model of species evolution and multiple intraspecies recombination events in the origin of HAdV prototypes. HAdV-29 was identified as a recombination variant of HAdV-15 (ε determinant) and a speculative, not-yet-isolated HAdV prototype (γ determinant). Subanalysis of molecular evolution in hypervariable regions 1 to 6 of the ε determinant indicated different selective pressures in subclusters of species HAdV-D. Additionally, γ determinant phylogenetic analysis demonstrated that HAdV-8 did not cluster with -19 and -37 in spite of their having the same tissue tropism. The phylogeny of HAdV-E4 suggested origination by interspecies recombination between HAdV-B (hexon) and HAdV-C (fiber), as in simian adenovirus 25, indicating additional zoonotic transfer. In conclusion, molecular classification by systematic sequence analysis of immunogenic determinants yields new insights into HAdV phylogeny and evolution.