The Pathology of Experimental Aerosolized Monkeypox Virus Infection in Cynomolgus Monkeys (Macaca fascicularis)

Abstract

SUMMARY:Cynomolgus monkeys (Macaca fascicularis) were exposed by fine-particle aerosol to lethal doses of monkeypox virus, Zaire strain. Death, attributable to fibrinonecrotic bronchopneumonia, occurred 9 to 17 days postexposure. Lower airway epithelium served as the principal target for primary infection. The relative degree of involvement among lymphoid tissues suggested that tonsil, mediastinal, and mandibular lymph nodes were also infected early in the course of the disease, and may have served as additional, although subordinate, sites of primary replication. The distribution of lesions was consistent with lymphatogenous spread to the mediastinal lymph nodes and systemic dissemination of the virus through a monocytic cell-associated viremia. This resulted in lesions affecting other lymph nodes, the thymus, spleen, skin, oral mucosa, gastrointestinal tract, and reproductive system. The mononuclear phagocyte/dendritic cell system was the principal target within lymphoid tissues and may also have provided the means of entry into other systemic sites. Hepatic involvement was uncommon. Lesions at all affected sites were characterized morphologically as necrotizing. Terminal deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining of select lesions suggested that cell death within lymphoid and epithelial tissues was due in large part to apoptosis. Skin and mucosal surfaces of the respiratory and gastrointestinal tracts also exhibited variable proliferation of epithelial cells and subjacent fibroblasts. Epithelial intracytoplasmic inclusion bodies, consistent with Guarnieri bodies, were usually inconspicuous by light microscopy, but when present, were most readily apparent in the stratified squamous epithelium of the oral mucosa and epidermis. Multinucleated syncytial cells were also occasionally observed in the stratified squamous epithelium of the tongue, tonsil, and skin, and in the intestinal mucosa. Monkeypox virus antigen was readily demonstrated by immunohistochemistry using anti-vaccinia mouse polyclonal antibodies as well as anti-monkeypox rabbit polyclonal antibodies. Detectable poxviral antigen was limited to sites exhibiting obvious morphologic involvement and was most prominent within epithelial cells, macrophages, dendritic cells, and fibroblasts of affected tissues. The presence of poxviral antigen, as determined by immunohistochemistry, correlated with ultrastructural identification of replicating virus. Concurrent bacterial septicemia, present in one monkey, was associated with increased dissemination of the virus to the liver, spleen, and bone marrow and resulted in a more rapidly fatal clinical course. (Lab Invest 2001, 81:1581-1600.

Vaccinia virus: shedding and horizontal transmission in a murine model

“…On day 10 p.e., mice were euthanized and blood samples were collected to be tested by NT to check for the presence of antibodies against OPV. Intestine samples were also collected for titration assays (Campos & Kroon, 1993) and histological analyses (Crouch et al, 1995;Zaucha et al, 2001).…”

Monkeypox virus detection in rodents using real-time 3′-minor groove binder TaqMan® assays on the Roche LightCycler

“…Smallpox infections in monkeys are an important surrogate model for human smallpox infections. 27 Likewise, the two MPXVspecific assays reported here could be used to monitor, in real time, the progression of monkeypox in nonhuman primates as has been done in smallpox animal models (unpublished data).…”

Characterization of Macaque Pulmonary Fluid Proteome during Monkeypox Infection

“…Although both pathogenic MPXV and nonpathogenic VV infections produced increased levels of proteins indicative of inflammation, only MPXV infection produced a dramatic decrease of structural and metabolic proteins. It is generally believed that inflammation is the primary cause of mortality, contributing to fibrinonecrotic bronchopneumonia (19,57). In this study, the increased levels of inflammatory proteins occurred simultaneously with specific loss of structural and metabolic proteins, which suggests that inflammation may not be the direct or sole contributor to disease progression.…”

“…to skin, oral mucosa, lymphoid tissue, gastrointestinal tract, liver, and reproductive system). The lungs are highly affected, and the MPXV antigen has been observed in multiple pulmonary cell types during infection (19).…”