Paired comparisons of the results of pig sera reactivities against PToV-HE52.7 and PToV-HE52.11 determined by HI and ELISA. Graphic representation of the mean HI (A) and ELISA (B) titers of sera grouped by pig ages against both PToV-HE52.7 (black bars) and PToV-HE52.11 (grey bars). Means ± standard error for each sample are shown. Asterisks indicate statistically significant differences of sera reactivity against the two proteins (**p < 0.05, *p < 0.1; Student’s t test). The dotted lines indicate the respective cut off values determined for each assay.