Reproductive disorders caused by porcine reproductive and respiratory syndrome virus-1
are not yet fully characterized. We report QuPath-based digital image analysis to
count inflammatory cells in 141 routinely, and 35 CD163 immunohistochemically stained
endometrial slides of vaccinated or unvaccinated pregnant gilts inoculated with a
high or low virulent PRRSV-1 strain. To illustrate the superior statistical feasibility
of the numerical data determined by digital cell counting, we defined the association
between the number of these cells and endometrial, placental, and fetal features.
There was strong concordance between the two manual scorers. Distributions of total
cell counts and endometrial and placental qPCR results differed significantly between
examiner1’s endometritis grades. Total counts’ distribution differed significantly
between groups, except for the two unvaccinated. Higher vasculitis scores were associated
with higher endometritis scores, and higher total cell counts were expected with high
vasculitis/endometritis scores. Cell number thresholds of endometritis grades were
determined. A significant correlation between fetal weights and total counts was shown
in unvaccinated groups, and a significant positive correlation was found between these
counts and endometrial qPCR results. We revealed significant negative correlations
between CD163+ counts and qPCR results of the unvaccinated group infected with the
highly virulent strain. Digital image analysis was efficiently applied to assess endometrial
inflammation objectively.
