Immunolocalization and Distribution of Rubella Antigen in Fatal Congenital Rubella Syndrome

Abstract

Background: An estimated 100,000 cases of congenital rubella syndrome (CRS) occur worldwide each year. The reported mortality rate for infants with CRS is up to 33%. The cellular mechanisms responsible for the multiple congenital defects in CRS are presently unknown. Here we identify cell types positive for rubella virus (RV) in CRS infants.

Methods: Cells and organs involved in RV replication were identified in paraffin-embedded autopsy tissues from three fatal case-patients by histopathologic examination and immunohistochemical (IHC) staining using a rabbit polyclonal RV antibody. Normal rabbit antisera and RV antisera preabsorbed with highly purified RV served as negative controls.

Results: RV antigen was found in interstitial fibroblasts in the heart, adventitial fibroblasts of large blood vessels, alveolar macrophages, progenitor cells of the outer granular layer of the brain, and in capillary endothelium and basal plate in the placenta. The antibody specificity was verified by IHC staining of multiple tissue sections from other infectious disease cases. RV infection of each cell type is consistent with abnormalities which have been identified in patients with CRS, in the heart, large blood vessels, and brain. Antigen distribution was consistent with inflammatory response to vascular injury and systemic spread of RV.

Conclusions: The identification of RV positive cell types in CRS is important to better understand the pathology and pathogenesis of CRS.

Keywords: Autopsy; CRS pathology; Congenital rubella syndrome (CRS); Fatal cases; Immunohistochemistry.

Fig. 1

Pulmonary histopathologic and immunohistochemical features in a fatal CRS case (Case 1). Low-power image of lung (a) shows congestion, edema, mild interstitial inflammation and hyaline membrane formation. Diffuse alveolar damage and interstitial pneumonitis (b). High-power image (c) shows intra-alveolar macrophages. Rubella virus antigens in intra-alveolar macrophages (d). Note immunostaining of globular inclusions.

Fig. 2

Cardiac histopathologic and immunohistochemical features in fatal cases of CRS. Higher-power magnification of the heart (a) showing reactive myocytes with plump nuclei and focal inflammatory cells, but no clinically significant inflammation (H&E staining). Abundant immunostaining of interstitial fibroblasts (b).

Fig. 3

Aortic histopathologic and immunohistochemical features in a fatal case of CRS (Case 1). Low-power magnification of the aorta (a) shows the lack of pathologic changes (H&E staining). Immunostaining of mesenchymal cells (between myocytes) and numerous fibroblasts in a section of the aorta (b).

Fig. 4

Central nervous system histopathologic and immunohistochemical features in a fatal case of CRS (Case 1). Low-power (a) and high-power (b) images of the cerebellum show meninges with no evidence of inflammation. Immunostaining of neuronal cells (c and d) in external granular cell layer of the cerebellum.

Fig. 5

Immunohistopathologic features in the placenta of Case 2. Low-power (a) and high-power (b) images of sections of chorionic villi show immunostaining of endothelial cells. (c) Section of the placenta (maternal plate) shows extracellular immunostaining throughout the basal plate.