Sequence analysis of ORFs 5, 6 and 7 of equine arteritis virus during persistent infection of the stallion–a 7-year study.

This study follows a persistent infection of equine arteritis virus (EAV) in a stallion over 7 years, analyzing the changes in specific virus genes (ORFs 5, 6, and 7) in blood and semen samples collected during this period.

Research Methodology

• The research team studied the nucleotide and amino acid sequences ORFs (Open Reading Frames) 5, 6, and 7 of EAV in a stallion representing the Malopolska breed.
• Over seven years, from 2004 to 2011, a total of 11 blood and semen samples were taken from the stallion for this study.
• They maintained a follow-up on the level of specific EAV antibodies in the stallion, noting it as consistently high at an approximate ratio of 1:128.

Results

• Upon analyzing the sequence of ORF5, they observed 16 variable sites, of which 12 demonstrated synonymous substitutions and 4 showed non-synonymous substitutions.
• The nucleotide sequence similarities among the studied strains ranged from 98.92% to 100%, whereas the amino acid similarities ranged from 98.06% to 100%.
• For ORF6, ten substitutions were identified, with 7 of them showing synonymous changes and 3 non-synonymous mutations.
• In this case, the similarity among strains ranged from 94.55% to 100% at the nucleotide level and from 98.41% to 100% at the amino acid sequence level.
• In ORF7, they found only one point mutation at position 255 (99.6% identity).

Conclusion

• The phylogenetic analysis showed that all strains found in the semen samples of this stallion formed a separate cluster of “quasi-species” within the second European subgroup of Equine Arteritis Virus.
• This grouping implies a potential genetic variation within the same species, reflecting the virus’s adaptive mechanisms during an ongoing infection.