Equine Herpesvirus 1 Variant and New Marker for Epidemiologic Surveillance, Europe, 2021.

Equine herpesvirus 1 isolates from a 2021 outbreak of neurologic disease in Europe have a mutation, A713G, in open reading frame 11 not detected in 249 other sequences from equine herpesvirus 1 isolates. This single-nucleotide polymorphism could help identify horses infected with the virus strain linked to this outbreak.

Screening and evaluation of antiviral compounds against Equid alpha-herpesviruses using an impedance-based cellular assay.

Equid alpha-herpesviruses (EHV) are responsible for different diseases in equine population. EHV-1 causes respiratory diseases, abortions and nervous disorders, EHV-4 causes respiratory diseases and sporadic abortion, while EHV-3 is responsible of equine coital exanthema. In view of the lack of efficacy of vaccines against EHV-1 and EHV-4 and in the absence of vaccines against EHV-3, the use of antiviral treatment is of great interest. In this study, we documented the interest of the Real-Time Cell Analysis (RTCA) technology to monitor the cytopathic effects induced by these viruses on equine dermal cells, and established the efficacy of this method to evaluate the antiviral effect of aciclovir (ACV) and ganciclovir (GCV). In addition, the RTCA technology has also been found appropriate for the high-throughput screening of small molecules against EHV, allowing the identification of spironolactone as a novel antiviral against EHV.

Equine PBMC Cytokines Profile after In Vitro α- and γ-EHV Infection: Efficacy of a Parapoxvirus Ovis Based-Immunomodulator Treatment.

Equine herpesviruses (EHV) infect horses early during life and the persistence of these viruses through establishment of latency represents a real risk. A better understanding of the immune response to EHV infection is necessary to improve our methods of prevention and decrease the risk of transmission. The objectives of this study were to characterise the cytokine gene expression profile of peripheral blood mononuclear cells (PBMC) after in vitro EHV-1, EHV-4, and EHV-2 infection and to determine the efficacy of inactivated Parapoxvirus ovis (iPPVO) against these 3 viruses. PBMC were isolated from 3 horses and infected in vitro with EHV-1, EHV-4, or EHV-2 in the presence or absence of iPPVO. In vitro culture of PBMC with EHV-1, EHV-4, and iPPVO induced a significant increase of IFN-α, IFN-ß, and IFN-γ gene expression. EHV-4 also triggered a significant increase of IL-6 and TNF-α mRNA. EHV-2 triggered a significant increase of IFN-α, IFN-ß, IFN-γ, IL-1ß, IL-6, and TNF-α mRNA. The presence of iPPVO induced an earlier and stronger expression of IFN-α, IFN-ß, and IFN-γ mRNA during EHV infection and reduced the inflammatory response induced by EHV-2. In conclusion, this study suggests that the presence of iPPVO potentiates the development of the immune response to in vitro EHV infection.

Development and Validation of a Quantitative PCR Method for Equid Herpesvirus-2 Diagnostics in Respiratory Fluids.

The protocol describes a quantitative RT-PCR method for the detection and quantification of EHV-2 in equine respiratory fluids according to the NF U47-600 norm. After the development and first validation step, two distinct characterization steps were performed according to the AFNOR norm: (a) characterization of the qRT-PCR assay alone and (b) characterization of the whole analytical method. The validation of the whole analytical method included the portrayal of all steps between the extraction of nucleic acids and the final PCR analysis. Validation of the whole method is very important for virus detection by qRT-PCR in order to get an accurate determination of the viral genome load. Since the extraction step is the primary source of loss of biological material, it may be considered the main source of error of quantification between one protocol and another. For this reason, the AFNOR norm NF-U-47-600 recommends including the range of plasmid dilution before the extraction step. In addition, the limits of quantification depend on the source from which the virus is extracted. Viral genome load results, which are expressed in international units (IU), are easier to use in order to compare results between different laboratories. This new method of characterization of qRT-PCR should facilitate the harmonization of data presentation and interpretation between laboratories.

Detection and quantitation of equid gammaherpesviruses (EHV-2, EHV-5) in nasal swabs using an accredited standardised quantitative PCR method.

Equid gammaherpesviruses-2 and -5 are involved in respiratory problems, with potential clinical manifestations such as nasal discharge, pharyngitis and swollen lymph nodes. These viruses are sometimes associated with a poor-performance syndrome, which may result in a significant and negative economic impact for the horse industry. The aim of the present study was to develop and validate quantitative PCR methods for the detection and quantitation of EHV-2 and EHV-5 in equine respiratory fluids. Two distinct tests were characterised: (a) for the qPCR alone and (b) for the whole method (extraction and qPCR) according to the standard model AFNOR XP U47-600-2 (viz., specificity, quantifiable sensibility, linearity, accuracy, range of application, trueness, precision, repeatability and precision of reproducibility). EHV-2 and EHV-5 detection were performed on nasal swabs collected from 172 horses, all of which exhibited clinical signs of respiratory disease. The data revealed a high rate of EHV-2/EHV-5 co-detection that was correlated significantly with age. Viral load of EHV-2 was significantly higher in young horses whereas viral load of EHV-5 was not significantly different with age.