Myocarditis in two pigs infected with FMDV A24 Cruzeiro (case 1; A-B) or FMDV O1 Campos (case 2; C-D). Both cases have infiltrates of distinct populations of CD8+ and CD163+ cells which are in close proximity to FMDV infected cardiomyocytes but which do not co-localize with FMDV capsid (red) or actin (blue). On serial sections, there was no detection of CD3 and CD21, indicating a CD8+/CD3-/CD21 –phenotype, consistent with NK-cells. FMDV VP1 capsid protein (red), actin (blue), CD163 (turquoise), CD8 (green). Multichannel immunofluorescence, A&C: scale bars =25 μm. B&D: scale bars = 10 μm.