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.
Sample Population—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.
Procedure—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 and Clinical Relevance—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. (Am J Vet Res 2003;64:779–784)