Immunohistochemical detection of an immediate early antigen of human cytomegalovirus in normal tissues.

As a member of the herpesvirus family, human cytomegalovirus (HCMV) induces a life-long latent infection in most individuals infected with it. This latent infection is subject to periodic reactivations that serve as an important source of disease and death in patients with defective immunologic responses. The specific types of cells that harbor latent HCMV have not yet been identified. To detect latent HCMV and identify the host cells carrying it, tissue sections from nine HCMV-seropositive normal individuals were examined using a murine monoclonal antibody specific for one of the immediate early (IE) antigens of HCMV. Cells expressing the IE antigen were detected in several different tissues from six of the subjects. Tissues found to contain positively stained cells included brain, kidney, spleen, lung, and liver. No positively stained cells were found in any tissue from seven HCMV-seronegative individuals studied by the same procedures. Cells undergoing productive infection with HCMV could not be detected in any of the tissues containing IE antigen-positive cells. It is proposed that these IE antigen-expressing cells represent at least some of the sites of HCMV latency in normal seropositive individuals.