Viral Pathology of Human Herpesvirus 6 Infection

Abstract

Since the first isolation of a new human herpesvirus (1), now referred to as human herpesvirus 6 (HHV-6) at the suggestion of Lusso et al. (2), several groups have been able independently to isolate the virus from patients with lymphoproliferative disorder and human immunodeficiency virus (HIV) infection and from normal adults (3–5). Recently, Yamanishi et al. (6) discovered that HHV-6 is a causal agent of exanthem subitum. Almost all children show seroconversion to HHV-6 from 5 mo by the time they are 2 yr old (7). Molecular characterization indicates antigenic distinction between HHV-6 and other human herpesviruses, human cytomegalovirus (CMV), herpes simplex types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), and Epstein-Barr virus (EBV) (1, 5). Tropism analysis using cord-blood lymphocytes has suggested that HHV-6, in addition to being the causal agent of exanthem subitum, causes a predominant CD4 mature T-lymphocyte tropism, but that has not been clarified yet (table 1). In this article we describe HHV-6-related pathological findings obtained by immunohistochemical methods.