Clinicopathologic, Immunohistochemical, and Ultrastructural Findings of a Fatal Case of Middle East Respiratory Syndrome Coronavirus Infection in the United Arab Emirates, April 2014

Abstract

Middle East respiratory syndrome coronavirus (MERS-CoV) infection causes an acute respiratory illness and is associated with a high case fatality rate; however, the pathogenesis of severe and fatal MERS-CoV infection is unknown. We describe the histopathologic, immunohistochemical, and ultrastructural findings from the first autopsy performed on a fatal case of MERS-CoV in the world, which was related to a hospital outbreak in the United Arab Emirates in April 2014. The main histopathologic finding in the lungs was diffuse alveolar damage. Evidence of chronic disease, including severe peripheral vascular disease, patchy cardiac fibrosis, and hepatic steatosis, was noted in the other organs. Double staining immunoassays that used anti-MERS-CoV antibodies paired with immunohistochemistry for cytokeratin and surfactant identified pneumocytes and epithelial syncytial cells as important targets of MERS-CoV antigen; double immunostaining with dipeptidyl peptidase 4 showed colocalization in scattered pneumocytes and syncytial cells. No evidence of extrapulmonary MERS-CoV antigens were detected, including the kidney. These results provide critical insights into the pathogenesis of MERS-CoV in humans.

Figure 1

CXR images. A: CXR at initial ED visit shows small left-sided opacity. B: CXR at second ED visit, with increase of left-sided opacity. C: Portable CXR 1 day after admission with substantial progression of the opacity. CXR, chest X-ray; ED, emergency department.

Figure 2

Histopathology of lung from MERS-CoV patient. A: Pulmonary edema. B: Diffuse alveolar damage, including prominent hyaline membrane formation (arrow). C: Alveolar fibrin deposits, type 2 pneumocyte hyperplasia, and thickened alveolar septa involved by edema and a mixed inflammatory infiltrate. D–F: Immunostaining of MERS-CoV antigen in pneumocytes (Ab 1511; D, arrow), a multinucleated syncytial cell (Ab 1511; E, arrow), and a binucleated cell (Ab 1514; F, arrow). G: Moderate lymphocytic inflammation of the submucosal glands. H: Magnified from the boxed area in G. Submucosal glands with focal areas of necrosis (arrow). I: Immunostaining of MERS-CoV antigen in necrotic foci of submucosal glands (arrow; Ab 1512). Original magnification: ×5 (A); ×20 (B–D); ×75 (E); ×100 (F); ×10 (G); ×40 (H); ×63 (I). Ab, antibody; MERS-CoV, Middle East respiratory syndrome coronavirus.

Figure 3

Immunohistochemical and ultrastructural localization of MERS-CoV and associated histologic findings. A: MERS-CoV and cytokeratin antigens in pneumocytes (arrow); red stain, MERS-CoV; brown stain, cytokeratin. B: MERS-CoV antigens in pneumocytes (arrowhead) and CD68 antigens in macrophages (arrow); red stain, CD68; brown stain, MERS-CoV. C: MERS-CoV and surfactant antigens in type 2 pneumocytes (arrow); red stain, surfactant; brown stain, MERS-CoV. D: MERS-CoV and DPP4 in pneumocytes (arrow); red stain, DPP4; brown stain, MERS-CoV. E: Fragmented pneumocyte infected with MERS-CoV, hyaline membrane (arrowhead) present. F: Magnified from the boxed area in E. MERS-CoV virions dispersed as single particles (arrow) or in clusters within membrane-bound vesicles (arrowhead). Spherical and pleomorphic particles ranged in size from 50 to 150 nm diameter. Scale bars: 2 μm (E); 500 nm (F). Original magnification: ×100 (A and C); ×63 (B); ×75 (D). DPP4, dipeptidyl peptidase 4; MERS-CoV, Middle East respiratory syndrome coronavirus.