Organ distribution of severe acute respiratory syndrome (SARS) associated coronavirus (SARS-CoV) in SARS patients: implications for pathogenesis and virus transmission pathways

Abstract

We previously identified the major pathological changes in the respiratory and immune systems of patients who died of severe acute respiratory syndrome (SARS) but gained little information on the organ distribution of SARS-associated coronavirus (SARS-CoV). In the present study, we used a murine monoclonal antibody specific for SARS-CoV nucleoprotein, and probes specific for a SARS-CoV RNA polymerase gene fragment, for immunohistochemistry and in situ hybridization, respectively, to detect SARS-CoV systematically in tissues from patients who died of SARS. SARS-CoV was found in lung, trachea/bronchus, stomach, small intestine, distal convoluted renal tubule, sweat gland, parathyroid, pituitary, pancreas, adrenal gland, liver and cerebrum, but was not detected in oesophagus, spleen, lymph node, bone marrow, heart, aorta, cerebellum, thyroid, testis, ovary, uterus or muscle. These results suggest that, in addition to the respiratory system, the gastrointestinal tract and other organs with detectable SARS-CoV may also be targets of SARS-CoV infection. The pathological changes in these organs may be caused directly by the cytopathic effect mediated by local replication of the SARS-CoV; or indirectly as a result of systemic responses to respiratory failure or the harmful immune response induced by viral infection. In addition to viral spread through a respiratory route, SARS-CoV in the intestinal tract, kidney and sweat glands may be excreted via faeces, urine and sweat, thereby leading to virus transmission. This study provides important information for understanding the pathogenesis of SARS-CoV infection and sheds light on possible virus transmission pathways. This data will be useful for designing new strategies for prevention and treatment of SARS.

Figure 1

Detection of SARS‐CoV N protein by immunofluorescence. (A) Vero E6 cells infected by SARS‐CoV (×200). (B) Uninfected Vero E6 (×200); (C) 293 cells infected with adenovirus type 5 (×400). (D) MA104 cells infected by Group A rotavirus (×200). The green colour represents the positive signal for SARS‐CoV N protein, while the negative cells without SARS‐CoV infection display a red colour

Figure 2

Detection of SARS‐CoV in lung tissues from patients who died of SARS (A–F) and from a patient who died through rupture of a thoracic aortic aneurysm (G and H). (A) Viral inclusion body in a pneumocyte (arrow; H&E, ×400). (B) Viral inclusion body in a pneumocyte (arrow; Macchiavello's stain, ×400). (C) Clusters of corona‐like viral particles in the endoplasmic reticulum of a type II alveolar epithelial cell (transmission electron microscopy; bar = 200 nm); (D) SARS‐CoV M protein gene (a, 667bp) and RNA polymerase gene fragment (b, 190bp) detected in lung tissues from three SARS cases (1–3), but not in the negative control (N), who died through rupture of a thoracic aortic aneurysm (RT‐PCR). M = marker. (E) SARS‐CoV N protein expression in pneumocytes (IHC, ×400). (F) SARS‐CoV RNA polymerase gene expression in pneumocytes (ISH, ×400); the positive cells (brown‐yellow) are indicated by arrows. (G) SARS‐CoV N protein expression (IHC, ×200). (H) SARS‐CoV RNA polymerase gene expression (ISH, ×200) is not detectable in lung tissue from the individual who died through rupture of a thoracic aortic aneurysm

Figure 3

Detection of SARS‐CoV N protein by IHC (A and C) and of SARS‐CoV RNA polymerase gene fragments by ISH (B and D) in the following samples from SARS patients (A and B; DAB; figures 3, 7A, 8A, 10, 13 ×200; figures 1, 2, 4–6, 8B, 9, 11, 12 ×400; 7B ×480) and from control patients (C and D; DAB; figures 1–11 × 400). (1) Bronchial serous gland epithelium; (2) gastric parietal cells; (3) small intestinal epithelium; (4) acidophilic cells of parathyroid; (5) pancreatic acinar cells; (6) acidophilic cells of pituitary; (7) adrenal cortical cells; (8) sweat gland cells; (9) cerebral neurones; (10) epithelial cells of distal convoluted renal tubule; (11) hepatocytes near the central vein; (12) myocardium; (13) seminiferous tubules of testis. The brownish‐yellow colour in cells represents positive signal for SARS‐CoV N protein in IHC, and for SARS‐CoV RNA polymerase gene fragments in ISH