Differentiation and genomic and antigenic variation among fetal, respiratory, and neurological isolates from EHV1 and EHV4 infections in The Netherlands.

The researchers used ten monoclonal antibodies to classify 282 isolates of equine herpes virus and found that a majority of those from fetal or neonatal cases were EHV1, while those from respiratory cases were mostly EHV4. Unexpectedly, some isolates from neurological cases were also EHV4. There was significant uniformity amongst these isolates, although some differences were noted in specific fragments.

Development and Usage of Monoclonal Antibodies

• The researchers produced ten monoclonal antibodies against Equine Herpes Virus type 1 (EHV1). Among these, two appeared to be type-specific to EHV1 while the others were effective against both EHV1 and EHV4.
• Two of these antibodies were found to act against the glycoprotein gp2 and their functionality was confirmed via a technique called Western blotting.

Typing and Classification of Viral Isolates

• These antibodies were then used to type a total of 282 field isolates in a procedure called an immunoperoxidase monolayer assay (IPMA).
• Out of 254 isolates from fetal or neonatal cases, 244 (96%) were identified as EHV1, while 14 out of 15 (93%) respiratory tract isolates were identified as EHV4.
• Surprisingly, 3 out of 13 isolates (23%) from horses presenting neurological disease were typed as EHV4. This finding is unexpected because EHV4 infections are generally less severe than EHV1.

Consistency Across Techniques and Observations of Uniformity

• No significant antigenic variation was found among 75 randomly selected EHV1 isolates when tested against the panel of ten antibodies, as well as six additional antibodies directed against specific glycoproteins.
• Isolate typing by restriction endonuclease analysis with an enzyme called BamHI completely matched with the results from monoclonal antibody analysis, demonstrating consistency across methodologies.
• A remarkable uniformity was found in the BamHI restriction patterns, with 90% of the EHV1 isolates belonging to one specific subtype, the 1P electropherotype. This indicates a high degree of genomic similarity among these virus isolates.

Findings from EHV1 Electropherotype analysis

• Upon examination of 30 randomly selected EHV1 isolates, the researchers could not detect the EHV1.1B electropherotype. The non-detection was notable as this subtype has been dominant in Kentucky since 1982.
• Some differences were observed in fragments originating from the repeat regions, but these were not caused by heterologous cell passage as all viruses were processed in equine cell systems.