Ultrastructural Changes and Virus‐Like Particles Localized in Liver Hepatocytes of Chimpanzees Infected With Non‐A, Non‐B Hepatitis

Abstract

Virus-like particles have been visualized by electron microscopy in the liver hepatocytes of two out of four chimpanzees inoculated with two different human non-A, non-B hepatitis-implicated plasmas. The first two chimpanzees, which were infected with the same inoculum (inoculum A), developed liver histological features characteristic of mild acute viral hepatitis as well as rises in their serum alanine aminotransferase levels. Clusters of intranuclear particles, 22 k 2 nm in diameter, were visualized in one of every fifth hepatocytes in one of these two chimpanzees. Intracytoplasmic circular membrane fusions, 100 t o 350 nm in diameter, were observed in the hepatocytes of the other chimpanzee receiving inoculum A.The second two animals were infected with a different human plasma containing infectious NANB material (inoculum B). Both animals developed mild increased serum enzyme levels that were variable but generally elevated throughout the course of this study (220 days); minor, equivocal histologic changes were also observed. Intranuclear and intracytoplasmic particles, 20 + 1 nm and 37 nm in diameter, respectively, were visualized in the liver of one of the two chimpanzees infected with inoculum B; intranuclear particles were observed in one of seventy-five hepatocytes and intracytoplasmic particles were observed less frequently. In this same animal, intracytoplasmic circular membrane fusions, similar, if not identical to those described above, were also noted. The intranuclear particles observed in animals receiving inocula A and B were essentially identical, as were the cytoplasmic membrane fusions. Thus, both inocula produced nuclear and cytoplasmic ultrastructural changes. The intracytoplasmic particle clusters (37 nm) were seen in only one animal and demonstrated a high degree of homogeneity, as evidenced by their presence in highly ordered crystalline arrays. All chimpanzees were screened for and found to be negative for evidence of hepatitis A and B, as well as for Epstein-Barr virus or cytomegalo- 2 Burketal virus-induced hepatitis. Previous studies have suggested that nuclear and cytoplasmic ultrastructural changes, similar to those described herein, result from two distinct NANB infectious agents. In contrast, our data suggest that both morphologic changes may be caused by a single agent.

Detection of non-A, non-B hepatitis antigen by immunocytochemical staining.

“…Several investigators (15)(16)(17) have confirmed the original observation that NANB virus-infected hepatocytes contain cytoplasmic membrane fusions and intranuclear aggregates of 20-to 27-nm particles (18). Direct demonstration of NANB-specified antigen(s) within the nucleii of hepatocytes associated with NANB hepatitis virus-infected liver tissue has also been reported (4,5).…”

“…Liver biopsy material was obtained from four chimpanzees (nos. 90, 92, 94, and 159) infected with human plasma containing infectious NANB hepatitis virus (16). Liver wedge biopsies were obtained from each of the animals at a time during which liver enzyme profiles were elevated and pathological indicators of viral hepatitis were noted (16).…”

“…90, 92, 94, and 159) infected with human plasma containing infectious NANB hepatitis virus (16). Liver wedge biopsies were obtained from each of the animals at a time during which liver enzyme profiles were elevated and pathological indicators of viral hepatitis were noted (16). Sera were collected from each of these four animals prior to experimental infection with NANB hepatitis virus and at weekly intervals after infection for documentation of liver enzyme changes and establishment of the acute disease phase.…”

“…In an effort to study the various aspects of this serious human disease, chimpanzees have been shown to be suitable experimental models that are susceptible to NANB hepatitis virus infection (2,3,16,17,24). The reagent materials (NANB antigen) obtained from experimental animals have been used in conjunction with presumed convalescent human antibody to NANB in attempts to demonstrate immunological reactions with specificity for NANB hepatitis antigen.…”

“…To date, neither specific antigen nor antibody has been identified. Similarly, a number of NANB hepatitis-associated ultrastructural changes and virus-like particles have been described (15)(16)(17)(18). However, the NANB hepatitis virus has not yet been definitively identified.…”