Morphologic study of inclusions in tissues from pigs inoculated with cytomegalovirus.

Six 5-day-old gnotobiotic pigs inoculated intranasally with the J-1 strain of porcine cytomegalovirus (PCMV) were euthanatized within 9 to 18 days after inoculation. All pigs developed a subclinical form of PCMV infection and had characteristic intranuclear inclusions in all tissues. Morphologically, 2 types of inclusions were observed. One was a small herpetic intranuclear inclusion in reticuloendothelial cells, which contained a few nucleocapsids in the nucleus. The other was a typical cytomegalic intranuclear inclusion in macrophages in the lungs and in tubuloalveolar gland cells in the nasal mucosa. Inclusions contained many nucleocapsides in the nucleus and a large number of enveloped viral particles in the cytoplasm. The distribution of the specific immunofluorescent antigen of PCMV was coincident with the presence of herpetic and cytomegalic inclusions.