Diagnosis of human herpesvirus-6 infection in two patients with central nervous system complications

HHV-6-Associated Neurological Disease in Children: Epidemiologic, Clinical, Diagnostic, and Treatment Considerations

Human herpesviruses 6A and 6B, often referred to collectively as human herpesvirus 6, are a pair of beta-herpesviruses known to cause a variety of clinical syndromes in both immunocompetent and immunocompromised individuals. Most humans are infected with human herpesvirus 6B, and many with human herpesvirus 6A. Primary infection typically occurs in early childhood, although large-scale reviews on the topic are limited. Herein, the authors explore the clinical manifestations of human herpesvirus 6-associated disease in both immunocompetent and immunocompromised pediatric patients, the risk factors for development of human herpesvirus 6-associated neurological disease, the risk of autoimmunity associated with development of active or latent infection, the relevance of human herpesvirus 6-specific diagnostic tests, and the medications used to treat human herpesvirus 6. The goal of this review is to improve the current understanding of human herpesvirus 6 in pediatric populations and to examine the most effective diagnostic and therapeutic interventions in this disease state.

Remission associated with human herpesvirus infection in west syndrome

Generally, West syndrome is an intractable epileptic syndrome in infancy, although spontaneous remission has been reported in some cases. An immunologic response to infection might be one of the factors involved in the remission of West syndrome, but the mechanisms remain unknown. On the other hand, exanthema subitum is a common disease occurring in infancy with the characteristics of fever and rash. Two kinds of human herpesvirus, 6 and 7, have been isolated as causal agents of exanthema subitum. We experienced one symptomatic case and three cryptogenic cases of West syndrome that showed spontaneous remission. In the symptomatic case, the subject showed a temporary remission; however, in the other cases, the remissions were long term. In the present study, we report the patients' improvement and electroencephalographic (EEG) findings. In all of our cases, hypsarrythmia disappeared on the EEG findings, the human herpesvirus 6 IgG antibodies increased in all four cases, and the herpesvirus 7 IgG antibodies increased in two cases. We postulate that the remission of the four cases proceeded from infection by exanthema subitum. The changes in serum antibody values suggest that the spontaneous remission of West syndrome was related to human herpesvirus 6 and 7 infections.

Evaluation of a commercial enzyme-linked immunosorbent assay for detection of serum immunoglobulin G response to human herpesvirus 6

A rapid (60-min) commercially available enzyme-linked immunosorbent assay (ELISA) for the detection of immunoglobulin G (IgG) class antibodies to human herpesvirus 6 (HHV-6) was evaluated. The specificity of the ELISA for HHV-6 was confirmed by absorption studies, with the reactivities of HHV-6-positive sera being unaffected by other herpesviruses (cytomegalovirus, herpes simplex virus, and varicella-zoster virus) or the HSB2 cell line used to culture HHV-6. HHV-6 IgG antibody levels in a panel of 502 serum samples were determined by ELISA and an indirect immunofluorescence assay (IFA). Results obtained by the two methods were in close agreement, suggesting that the ELISA provides a suitable test method for the determination of HHV-6 IgG antibodies in a routine clinical laboratory. Both tests were positive in 398 cases (79%), and both were negative in 71 cases (14%), with a different result obtained by IFA and ELISA in only 33 cases (7%). Furthermore, absorption of sera with HHV-6 prior to assay revealed that the majority of these results were false positive (n = 8) or false negative (n = 23) in the IFA (true positives or negatives in the ELISA). Subsequently, the ELISA showed a sensitivity of 99.76% and a specificity of 98.75%. HHV-6-specific IgG levels were also determined in paired serum samples collected from 49 donors--14 with exanthem subitum (ES), 15 with ES which was complicated with central nervous system involvement, and 20 undergoing bone marrow transplantation--in whom HHV-6 infection had been demonstrated by virus isolation and/or PCR. All patients with ES or central nervous system complications showed an increase in HHV-6-specific IgG, indicating that this ELISA may be a useful aid in the diagnosis of these conditions. Furthermore, 14 of 20 patients undergoing bone marrow transplantation showed an increase in HHV-6-specific IgG levels, possibly reflecting a reactivation of HHV-6 in these patients.