Residue 752 in DNA polymerase of equine herpesvirus type 1 is non-essential for virus growth in vitro.

This research explores the role of a single amino acid in the DNA polymerase of equine herpesvirus type 1 (EHV-1) and its impact on the virus’s drug-sensitivity and growth characteristics. The findings demonstrate that the specific amino acid, residue 752, is not necessary for the virus’s growth and that only a specific variant of it, N752, makes the virus susceptible to a certain drug.

Objective and Approach

• The study aimed to understand whether residue 752 in the DNA polymerase (Pol) of EHV-1 is essential for the virus’s growth. This residue is notable as a variation at this location – either D752 or N752 – is known to determine the neuropathogenic potential of the virus.
• To pursue this, researchers created a version of EHV-1 where residue 752 was deleted. They then reconstituted it to encode either D752 or N752.

Testing and Results

• The variant of the virus which lacked residue 752 (Delta752) showed replication kinetics that matched both D752 and N752 viruses, indicating that residue 752 is not necessary for the growth of the virus.
• The research also showed that the deletion variant resisted aphidicolin (a drug that targets Pol) more than the N752 variant but about as much as the D752 variant. Aphidicolin resistance suggests that only the N752 mutation influences the virus’s drug-sensitive phenotype.
• In tests involving equine peripheral blood mononuclear cells, no significant difference was found in cellular tropism or virus replication among the variants.

Conclusions

• In conclusion, the research demonstrates that residue 752 in EHV-1 Pol is not required for the growth of the virus. Additionally, it highlighted that it’s the presence of the specific amino acid variant N752 that makes the virus susceptible to aphidicolin, a drug that targets Pol.