Extended phylogeny of the equine arteritis virus sequences including South American sequences.

The research article discusses the genetic analysis of the ORF5 region of the Equine Arteritis Virus (EAV), focusing on the sequences found in Argentina, to gain insights into the virus’s evolution and origin.

Methods

• The researchers used a total of 76 sequences for their analysis.
• The sequences were studied using three analytical algorithms: Neighbor Joining (NJ), Maximum Parsimony, and Maximum Likelihood.
• The team used Tajima’s test to analyze the selective pressures acting on these sequences.

Results

• The trees generated from the three analytical methods displayed similar topologies.
• Two main clades (groups) were identified:
  1. The first clade was predominantly formed by strains isolated from a donkey.
  2. The second clade was made up of four large groups from different geographic regions, with these sequences exclusively found in Equus Caballus (horse).
• Within this second clade, a subgroup was found consisting of South African, South American, and European sequences. Specifically, within this subgroup, there was a monophyletic group formed by seven Argentinean sequences.
• In the NJ tree, a group formed by six Argentinean sequences was identified.
• The Tajima’s test revealed a D value of 1.73663, which suggests neutral evolution in the sequences analyzed.

Conclusions

• The researchers concluded that the Argentinean sequences have a paraphyletic origin, which means they do not include all descendants of a common ancestor.
• The team found evidence that point mutation fixation might follow a neutral model evolution, suggesting that changes in the virus’s DNA do not lead to evolutionarily advantageous or disadvantageous traits.
• However, the researchers also saw signs of purifying pressures that may have had a role in differentiating the EAV sequences, indicating some mutations might have been harmful and therefore selected against.