Immunohistochemical detection of respiratory syncytial virus at autopsy

Background: Respiratory syncytial virus (RSV) infection can be fatal in infants <1 year after birth. Morphological findings associated with infant death, however, are insufficient, and screening procedures are problematic. The aim of the present study was to establish a postmortem diagnosis of RSV pathogenicity. Methods: Serial forensic autopsies of 55 infants who suddenly died ≤1 year after birth due to viral pneumonia (n = 18), bacterial pneumonia (n = 12), or other diseases and trauma (n = 25) were assessed. Causes of viral pneumonia determined on immunochemical screening and histological staining of airway effusions consisted of RSV (n = 8) and other viruses (n = 10). Results: Bronchial epithelial and inflammatory cells in the interstitium around bronchioles and alveoli were immunopositive for RSV. Bronchial epithelium was more frequently positive for RSV (5/8, 62.5%) than for bacterial pneumonia and other causes of death (7/47, 14.9%); and intra-alveolar sites were also more frequently positive for RSV pneumonia (3/8, 37.5%) than for bacterial pneumonia and other causes of death (4/47, 8.5%). Screening immunoassays and immunohistochemical staining for RSV can serve as an index of RSV infection when serum antibody titers, viral identification and polymerase chain reaction (PCR) are not informative. Peribronchiolar interstitial RSV positivity was similar between RSV pneumonia (7/8, 87.5%) and other causes of death (34/47, 72.3%). Conclusions: RSV was the cause of death in only eight infants because RSV infection was difficult to diagnose. Therefore, more deaths associated with RSV need to be investigated. Bronchial epithelium and intra-alveolar cells that are RSV immunopositive might augment RSV pathogenicity in viral pneumonia.