The Genomic Characterization of Equid Alphaherpesviruses: Structure, Function, and Genetic Similarity

Abstract

Equine herpesvirus 1 (EHV-1), EHV-4, EHV-8, and EHV-9, are classified within the subfamily Alphaherpesvirinae and are recognized as causative agents of respiratory, urogenital, and neurological disorders in horses. These viruses, collectively referred to as αEHVs, exhibits both unique and shared characteristics in terms of host interaction, pathogenesis, epidemiology, and immune evasion, which arise from both the identities and discrepancies among respective genomic homologs. The genomic architecture of αEHVs is similar to other members of the same subfamily, such as well-known HSV-1, VZV, and PRV. However, research on the molecular mechanisms underlying αEHV infection and immune response remains significantly less advanced compared to studies on human, porcine, and bovine herpesviruses. This paper systematically describes the genomic structure, function, and genetic similarities of αEHVs and conducts a comparative analysis of selected αEHVs through pairwise sequence alignments of nucleotides and amino acids. This review offers an extensive synthesis of the current understanding related to the study of αEHVs, highlighting the challenges and potential solutions for future research endeavors.

Keywords: comparative analysis; equid alphaherpesvirus; function; future research; genomic structure.

Figure 1

The genomic map of EHV-8. The terminal direct repeat (TR) is shown in a thicker format than the unique region (U). ORFs predicted to encode functional proteins are indicated by arrows (see the key below), with the nomenclature without the ORF prefix given below. The poly(A) sites are indicated by vertical arrows above and below the genome for ORFs oriented toward the right and left, respectively. Reiterated sequences are shown as small filled rectangles, and candidate origins of DNA replication (open squares) are indicated above the genome.