Differentiation of strains of equine arteritis virus of differing virulence to horses by growth in equine endothelial cells.
OBJECTIVE
To compare growth characteristics of strains of equine arteritis virus (EAV) of differing virulence to horses in rabbit kidney (RK)-13 cells and equine endothelial cells (EECs) cultured from the pulmonary artery of a foal.


METHODS
13 strains of EAV, including 11 field isolates of differing virulence to horses; the highly virulent, horse-adapted Bucyrus strain; and the modified-live virus (MLV) vaccine derived from it.


METHODS
The growth characteristics of the 13 strains were compared in EECs and RK-13 cells. Viral nucleoprotein expression, cytopathogenicity, and plaque size were compared to determine whether growth characteristics of the 13 strains were predictive of their virulence to horses.


RESULTS
Cytopathogenicity, viral nucleoprotein expression, and plaque size induced by all 13 viruses were similar in RK-13 cells, whereas virulent strains of EAV caused significantly larger plaques in EECs than did the avirulent strains of EAV. Paradoxically, the highly attenuated MLV vaccine and 1 field isolate of EAV caused plaques in EECs that were larger than those caused by any of the other viruses, and sequence analysis confirmed the field isolate of EAV to be indistinguishable from the MLV vaccine.


CONCLUSIONS
With the notable exception of the MLV vaccine, growth of the various strains of EAV in EECs was predictive of their individual virulence to horses. Thus, EECs provide a relevant and useful model to further characterize determinants of virulence and attenuation amongst strains of EAV.
Moore
Brian D
BD
Bernard and Gloria Salick Equine Viral Disease Laboratory, Department of Pathology, Microbiology, and Immunology, School of Veterinary Medicine, University of California, Davis, CA 95616, USA.
Balasuriya
Udeni B R
UB
Nurton
Jane P
JP
McCollum
William H
WH
Timoney
Peter J
PJ
Guthrie
Alan J
AJ
MacLachlan
N James
NJ
D000818:Animals; D016923:Cell Death; D002478:Cells, Cultured; D004727:Endothelium / Q000166:cytology* / Q000821:virology*; D007240:Equartevirus / Q000145:classification* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D006736:Horses / Q000821:virology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011651:Pulmonary Artery; D014774:Virulence