Detection of equine arteritis virus by two chromogenic RNA in situ hybridization assays (conventional and RNAscope(®)) and assessment of their performance in tissues from aborted equine fetuses.

This article outlines the development of two tests for detecting the equine arteritis virus (EAV) in tissues from aborted horse fetuses, and compares their performance against widely-used techniques. The researchers found that one of the new tests had comparable sensitivity to the existing methods, and will be invaluable in investigating how EAV causes disease.

Development of RNA in situ hybridization Assays

• The research focused on the creation of two different RNA in situ hybridization (ISH) assays. These assays are designed to spot the presence of equine arteritis virus (EAV) RNA in formalin-fixed paraffin-embedded (FFPE) tissues.
• The EAV is responsible for equine viral arteritis which causes respiratory and reproductive disorders in equids. It can trigger abortion in pregnant mares and induce fulminant bronchointerstitial pneumonia in foals.

Comparison with Existing Techniques

• The team compared the performance of the newly designed ISH assays with virus isolation (VI) techniques, which are considered as the gold standard.
• The team also compared the tests with a technique known as nucleocapsid-specific immunohistochemistry (IHC). This method detects the presence of virus proteins in a tissue sample.
• Testing was performed on 80 FFPE tissue samples collected from 16 aborted fetuses infected with the EAV.

Assessment of the RNA in situ hybridization Assays

• The team found that the performance of the conventional RNA ISH assay was significantly less sensitive compared to the newly developed RNAscope® ISH and the traditional IHC assay.
• On the other hand, the RNAscope® assay’s sensitivity was comparable to that of the IHC assay.
• This indicates that the RNAscope® ISH assay is a highly sensitive technique for detecting the presence of EAV RNA in FFPE tissues.

Implications of the Study

• The study demonstrates that the use of oligonucleotide probes along with a signal amplification system (in this case, RNAscope®) can dramatically enhance the detection of EAV RNA in FFPE tissues.
• Notably, it shows that the sensitivity of such a system is similar to that of IHC techniques.
• The availability of these assays offers the potential for better understanding the mechanisms of EAV pathogenesis, thus providing valuable tools for EAV disease research.