Immunohistological detection of human herpes virus 6 in formalin‐fixed, paraffin‐embedded lung tissues

Abstract

Human herpes virus type 6 (HHV‐6) infection is widespread in healthy individuals. The only definite disease association is with exanthem subitum in infants though the virus has been linked with a variety of other diseases including interstitial pneumonitis in bone marrow allograft recipients. In order to investigate the role of HHV‐6 in the latter disease we have developed an optimised staining method for the demonstration of specific antigen in routinely processed post‐mortem tissues. Formalin‐fixed, paraffin‐embedded lung tissue from 8 immunocompromised patients who died from interstitial pneumonitis was subjected to immunoperoxidase staining with monoclonal antibodies against HHV‐6, cytomegalovirus (CMV), and adenovirus, using a modified avidin‐biotin complex (ABC) method. Staining for HHV‐6 was obtained in 6 of the 8 patients studied and was present in pneumocytes and macrophages. CMV and adenovirus antigens were identified in 4 and 6 patients, respectively. Whilst the lung tissue of 6 patients contained more than one virus, there was no evidence of cross‐reactivity between the monoclonal antibodies. We demonstrated that accurate localisation of HHV‐6 using monoclonal antibodies is possible in post‐mortem lung tissue and conclude that either HHV‐6 alone or in combination with other viruses may play a role in the development of interstitial pneumonitis following bone marrow transplantation or chemotherapy.