Sequence analysis of equine adenovirus 2 hexon and 23K proteinase genes indicates a phylogenetic origin distinct from equine adenovirus 1.

This research article presents the complete nucleotide sequence data on equine adenovirus 2 (EAdV2), highlighting its molecular uniqueness compared to equine adenovirus 1 (EAdV1) through a detailed analysis of its hexon and 23K proteinase genes.

Research Background and Objective

• This study aims to examine and compare the genetic composition of two strains of equine adenovirus, EAdV2 and EAdV1. The objective was to confirm that EAdV2 is distinct from EAdV1, using the sequence data of its hexon and 23K proteinase genes.

Methodology

• The hexon gene of EAdV2 was identified through sequence homology with EAdV1. The hexon and eight other viral genes encapsulated within HindIII restriction fragments were cloned into the plasmid pUC19.
• The nucleotide sequence of the hexon and the 23K proteinase genes of EAdV2 was completely determined.
• Amino acid (aa) comparison was carried out to identify the genes for the E1B/19K, IVa2, DNA polymerase, terminal protein, pVI, DNA binding and 100K proteins in the EAdV2. The similarities were mostly found with human AdV proteins.

Key Findings

• The authors reported that the nine EAdV2 genes were in the same relative order as homologous genes of other adenoviruses. They found that the EAdV2 hexon is encoded between the minor capsid precursor protein pVI upstream and the 23K proteinase gene downstream and comprises 2712 nucleotides that translate into 903 aa residues.
• The EAdV2 hexon gene was found to be more closely related to the human AdV48 hexon, with 71.6% identical and 82.7% functionally similar aa than the EAdV1 hexon gene.
• The deduced aa sequence of the EAdV2 23K proteinase gene comprised 201 residues and shared 59.7% identical and 75% similar aa residues with the bovine AdV3 23K proteinase, which marked it as the closest relative.
• The researchers found a significant difference in the phylogenetic relationship of EAdV2 as compared to EAdV1 and other adenoviruses based on the hexon and 23K proteinase genes. This suggests that EAdV2 does not share an immediate common ancestor with EAdV1 and other adenoviruses, confirming its molecular uniqueness.