Fig. 4.

Subsequent PRCV infection promotes PRRSV replication in the lungs and induction of severe PRRSV-related apoptotic lesions at PRCV PIDs 4–10. (a, b) PRRSV replication in the lungs. Each data point represents the mean±sem. *P<0.05 (statistically significant differences between dual-infected pigs and pigs singly infected by either virus by the Kruskal–Wallis test. (c) Paraffin-embedded lung tissues were evaluated by an in situ TUNEL assay (black staining) for detection of apoptosis. Magnification: ×50. Cells were counterstained with methyl green. +, A few positive cells; ++, moderate numbers of positive cells; +++, many positive cells.