Fig. 1
Clinical findings and virus detection after experimental infection with the EHV-1 strain Ab4 or its deletion mutant Ab4ΔORF2. Three groups of horses (n = 8/group) were either not infected (control), infected with the neuropathogenic EHV-1 strain Ab4 (Ab4) or infected with its ORF2 deletion mutant (Ab4ΔORF2) on day 0 (arrow). Clinical signs were monitored and virus detection was performed before (day − 1) and after infection (day 1 to 14). Body temperature (a); clinical score calculated as the sum of numerical scores for nasal discharge, ocular discharge, lymph node enlargement, ataxia, depression and reduced appetite ranging from 0 to 22 (b); viral shedding expressed as plaque forming units (PFU/ml) detected by virus isolation in nasopharyngeal secretions (c); viremia determined in 1 × 107 PBMC by real time PCR and shown as Ct values for the gB gene (d) were analyzed; Mean and standard errors are plotted for each group. Dotted horizontal lines represent a cutoff of fever at 101.5 °F (a) and EHV-1 detection at a Ct 38 (D). Significant differences between groups are marked: a = Ab4 vs. control, b = Ab4ΔORF2 vs. control, c = Ab4 vs. Ab4ΔORF2