Parvovirus particles in a fetal-heart with myocarditis: ultrastructural and immunohistochemical study.

We report on the occurrence of parvovirus particles and VP1 (84 kDa) and VP2 (58 kDa) viral antigens in the heart of a case of fatal myocarditis in a fetus of a 26 year old women. Numerous cells containing intranuclear inclusions were identified within the blood vessels of the heart in a close apposition to muscle fibers. These cells were characterized by plentiful mitochondria and were consistent with erythroblasts. Typically, inclusions consisted of electrondense marginated chromatin and granular and amorphous "cores". At higher magnification, parvovirus particles, approximately 23 nm in diameter, were visualized either as relatively small clusters or forming large paracrystalline arrays. Virus buds were never observed. In addition, unusual membrane proliferation was seen. These findings support a notion that parvovirus may invade the fetal heart.