Comprehensive Analysis of Equid Herpesvirus Recombination: An Insight Into the Repeat Regions.
Authors: Tau Rocío Lucía, Ferreccio Carola, Bachir Natalia, Torales Fatima, Romera Sonia Alejandra, Maidana Silvina Soledad
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Equid Herpesvirus Recombination in the Repeat Regions Genetic recombination between herpesvirus species increases viral diversity and can alter virulence and transmissibility—a significant concern given that equid herpesvirus 1 (EHV-1) and EHV-4 cause substantial economic losses in the equine industry. Researchers analysed whole genome sequences of six equid alphaherpesviruses (EHV-1, EHV-3, EHV-4, EHV-6, EHV-8, and EHV-9) using comparative sequence analysis tools (RDP4 and Simplot) to identify recombination events across species boundaries. Fourteen recombination events were detected, predominantly involving EHV-1, EHV-4, EHV-8, and EHV-9, with ten of these occurring within ORF64—a repeat region gene encoding infected cell protein 4 (ICP4). Notably, recombination breakpoints in ICP4 matched previously documented field isolates and implicated zebra-adapted EHV-1 genotypes in cross-species mixing, establishing ICP4 as a recombination hotspot. These findings underscore the evolutionary plasticity of equid alphaherpesviruses and suggest that clinicians and researchers should monitor for novel recombinant strains, particularly those arising from wildlife-equine virus interfaces, as such variants may carry unpredictable pathogenic or epidemiological properties.
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Practical Takeaways
- •EHV recombination events create genetic diversity that may complicate vaccine efficacy and clinical disease manifestation; veterinarians should monitor for atypical EHV presentations in mixed-species or wild equid populations
- •The identification of recombination hotspots in ICP4 and repeat regions provides potential targets for developing more stable diagnostic markers and rationally designed vaccines against recombinant EHV strains
- •Field practitioners should be aware that EHV-1 strains affecting zebras and other wild equids may recombine with domestic horse EHV strains, potentially introducing novel pathogens to managed horse populations
Key Findings
- •14 recombination events were identified between equid alphaherpesviruses using RDP4 and Simplot analysis across EHV-1, EHV-3, EHV-4, EHV-6, EHV-8, and EHV-9 genomes
- •10 of 14 recombination events (71%) involved ORF64, a double-copy gene in repeat regions encoding infected cell protein 4 (ICP4)
- •ICP4 is identified as a recombination hotspot with events detected between EHV-1×EHV-9, EHV-8×EHV-9, and EHV-1×EHV-4 pairs
- •Recombination events involving zebra-borne EHV-1 genotypes and field isolate breakpoints suggest active recombination in natural equid herpesvirus populations