Anti-inflammatory Drugs Will Decrease Endothelial Cell Infection with Equine Herpesvirus-1 in vitro

Central nervous system (CNS) endothelial cell (EC) infection with EHV-1 is commonly thought to be the initiating cause of EHV-1 Myelo-encephalopathy (EHM). Cell-associated viremia in peripheral blood mononuclear cells (PBMC) transports virus to the CNS EC, and EC infection likely requires contact between EC and PBMC for a viral transfer. Intercellular contact may be facilitated by inducible adhesion molecules. We hypothesize that anti-inflammatory drugs will decrease the interaction between PBMC and EC, and, therefore, will decrease EC infection.

EC monolayers were exposed in vitro to either EHV-1 infected PBMC or to an EHV-1 suspension (control). For this, infected PBMC were incubated (24 hrs) with media alone (NTx), or with equine therapeutic plasma concentrations (1xTx) or 10x concentrations (10xTx) of one of the following drugs: flunixin meglumine, firocoxib or dexamethasone. Virus suspension or NTx/Tx PBMC in media were added to monolayers for 4 hours. Then, monolayers were washed 3x times, and media NTx, 1xTx or 10xTx -various drugs- were re-applied. All media contained an EHV-1 neutralizing antibody titer of 1:200. After 48 hrs of incubation monolayers were stained with crystal violet solution to allow a plaque count. Generalized linear and latent mixed models were used to evaluate differences in plaque counts. Statistical significance was assumed with a p-value of <0.05.  

In the cell contact model all drugs significantly decreased the plaque count at 1xTx and at 10xTx (p<0.001); however, there was no statistical difference between the effects of 1xTx and 10xTx (p=0.163) on plaque reduction. There was no statistical difference between NTx/Tx when virus-in-suspension inoculation was used.

These results provide a rationale for the use of anti-inflammatory drugs during early phases of EHV-1 infection. Moreover, the use of anti-inflammatory drugs during viremia may aid in preventing EC infection in vivo.