Viral Inclusions

Abstract

Viruses account for a large number of acute infections and occur as a consequence of hereditary or acquired forms of immunodeficiency. Because of their small size (20–300 nm), single virus particles can only be detected by electron microscopy. Some viruses may form aggregates in the nucleus and/or cytoplasm of the infected cells. Such viral inclusion bodies may be visible by light microscopy and definitely by electron microscopy. Polyoma viruses are ubiquitous in nature. Infections can be often observed in kidney tubular cells of renal transplants. Panels Band C show viral inclusion bodies due to Polyoma viruses in a renal biopsy of a kidney transplant patient. The spherical virus particles have a diameter of 30–45 nm and are arranged in characteristic paracrystalline arrays, which occupy most of the nucleoplasm (B) and parts of the cytoplasm (C). The paracrystalline arrays formed by the viruses can be well appreciated at higher magnification (inset in B). The nuclear viral inclusions can be unequivocally distinguished from the nucleolus (Nu in B).