Human herpesvirus 6: An emerging pathogen. (1/35)

Infections with human herpesvirus 6 (HHV-6), a beta-herpesvirus of which two variant groups (A and B) are recognized, is very common, approaching 100% in seroprevalence. Primary infection with HHV-6B causes roseola infantum or exanthem subitum, a common childhood disease that resolves spontaneously. After primary infection, the virus replicates in the salivary glands and is shed in saliva, the recognized route of transmission for variant B strains; it remains latent in lymphocytes and monocytes and persists at low levels in cells and tissues. Not usually associated with disease in the immunocompetent, HHV-6 infection is a major cause of opportunistic viral infections in the immunosuppressed, typically AIDS patients and transplant recipients, in whom HHV-6 infection/reactivation may culminate in rejection of transplanted organs and death. Other opportunistic viruses, human cytomegalovirus and HHV-7, also infect or reactivate in persons at risk. Another disease whose pathogenesis may be correlated with HHV-6 is multiple sclerosis. Data in favor of and against the correlation are discussed.  (+info)

Isolation and identification of human herpesvirus 7 from an infant with exanthem subitum. (2/35)

Exanthem subitum (ES) is a common childhood exanthematous disease. In a recent study of ES due to human herpesvirus 6 (HHV 6), we isolated human herpesvirus 7 (HHV 7) from the peripheral blood mononuclear cells (PBMC) of a seven month-old infant with typical symptoms of ES. The identity of the virus was confirmed by indirect immunofluorescence using HHV 7 specific monoclonal antibody and by amplification of the HHV 7 specific genomic sequences using the polymerase chain reaction (PCR). Paired serum samples from the infant showed serological conversion to the isolated virus. The clinical manifestations of ES in this infant appeared to be milder than the classical ES due to HHV 6.  (+info)

Uvulo-palatoglossal junctional ulcers--an early clinical sign of exanthem subitum due to human herpesvirus 6. (3/35)

A provisional clinical diagnosis of exanthem subitum was made in six febrile infants seen in the Paediatric Unit of Assunta Hospital, Petaling Jaya, Malaysia with uvulo-palatoglossal junctional ulcers prior to the eruption of maculopapular rash. On follow-up, all six infants developed maculopapular rash with the subsidence of fever at the end of the fourth febrile day. Human herpesvirus 6 was isolated from the peripheral blood mononuclear cells during the acute phase of the illness and HHV 6 specific genome was also detected in these cells by nested polymerase chain reaction. All the six infants showed seroconversion for both specific IgG and IgM to the isolated virus. This study suggests that the presence of uvulo-palatoglossal junctional ulcers could be a useful early clinical sign of exanthem subitum due to human herpesvirus 6.  (+info)

The association of uvulo-palatoglossal junctional ulcers with exanthem subitum: a 10-year paediatric outpatient study. (4/35)

A 10-year follow-up of children having exanthem subitum (ES) seen in an outpatient paediatric clinic, Kuala Lumpur, Malaysia shows that uvulo-palatoglossal junctional (UPJ) ulcer is a reliable early clinical sign of ES. During this period, 1,977 children (1,086 males, 891 females) had adequate follow-up from the age of 3 months to 24 months old. 897 children (478 males, 419 females) were noted to have UPJ ulcers. Of these 897 children, 855 (459 males, 396 females) presented with the classical clinical features of ES of maculopapular rash following 3 to 4 days of fever. The positive predictive value and the negative predictive value of UPJ ulcers in the clinical diagnosis of ES are 95.3% and 100% respectively. Among the 855 children with clinical features of ES, a provisional diagnosis of ES could be made in 781 children during the pre-eruptive phase by the presence of the UPJ ulcers. The other 74 children already had the rash at the time of consultation at the clinic. The peak age of occurrence of ES was 6 months old with 98.2% of the total cases of ES seen between the age of 4 and 12 months. There was no significant gender difference in the incidence of ES nor any seasonal variation. Mild to moderate diarrhoea was the other commonly associated clinical feature which usually presented from the third febrile day onwards.  (+info)

Outbreaks of human-herpes virus 6 (HHV-6) infection in day-care centers in Belem, Para, Brazil. (5/35)

A total of 730 children aged less than 7 years, attending 8 day-care centers (DCCs) in Belem, Brazil were followed-up from January to December 1997 to investigate the occurrence of human-herpes virus 6 (HHV-6) infection in these institutional settings. Between October and December 1997 there have been outbreaks of a febrile- and -exanthematous disease, affecting at least 15-20% of children in each of the DCCs. Both serum- and- plasma samples were obtained from 401 (55%) of the 730 participating children for the detection of HHV-6 antibodies by enzyme-linked immunosorbent assay (ELISA), and viral DNA amplification through the nested-PCR. Recent HHV-6 infection was diagnosed in 63.8% (256/401) of them, as defined by the presence of both IgM and IgG-specific antibodies (IgM+/IgG+); of these, 114 (44.5%) were symptomatic and 142 (55.5%) had no symptoms (p = 0.03). A subgroup of 123 (30.7%) children were found to be IgM-/IgG+, whereas the remaining 22 (5.5%) children had neither IgM nor IgG HHV-6- antibodies (IgM-/IgG-). Of the 118 children reacting strongly IgM-positive (> or = 30 PANBIO units), 26 (22.0%) were found to harbour the HHV-6 DNA, as demonstrated by nested-PCR. Taken the ELISA-IgM- and- nested PCR-positive results together, HHV-6 infection was shown to have occurred in 5 of the 8 DCCs under follow-up. Serological evidence of recent infections by Epstein-Barr virus (EBV) and parvovirus B19 were identified in 2.0% (8/401) and 1. 5% (6/401) of the children, respectively. Our data provide strong evidence that HHV-6 is a common cause of outbreaks of febrile/exanthematous diseases among children attending DCCs in the Belem area.  (+info)

Fatal acute myocarditis in an infant with human herpesvirus 6 infection. (6/35)

A 5 month old girl had typical clinical features of acute myocarditis just after the febrile period of exanthem subitum and died immediately. She had been healthy, with normal development, and there was no family history of particular note. Myocardial postmortem findings were compatible with acute myocarditis. Although the isolation of human herpesvirus 6 (HHV-6) was not attempted, positive IgM antibody to HHV-6 was detected in the patient's serum. Moreover, HHV-6 variant B DNA was detected in several tissues, including myocardium, by the polymerase chain reaction (PCR). In contrast, antibody responses to human herpesvirus 7, another causal agent of exanthem subitum, were not found, and enteroviral RNA was not detected in myocardial tissues by reverse transcription PCR. Apoptotic changes were seen in infiltrating cells within the myocardial tissues by means of the TUNEL method. HHV-6 antigen was not detected in several tissues (including myocardium) by immunohistochemical analysis. In conclusion, HHV-6 may have been the causative agent of fatal acute myocarditis in this infant.  (+info)

Selection of the same mutation in the U69 protein kinase gene of human herpesvirus-6 after prolonged exposure to ganciclovir in vitro and in vivo. (7/35)

After serial passage in the presence of increasing concentrations of ganciclovir (GCV) in vitro, a human herpesvirus-6 (HHV-6) mutant exhibiting a decreased sensitivity to the drug was isolated. Analysis of drug susceptibility showed that the IC(50) of this mutant was 24-, 52- and 3-fold higher than that of the wild-type (wt) IC(50) in the case of GCV, cidofovir and foscarnet, respectively. Genotypic analysis showed two single nucleotide changes as compared to the wild-type: an A-->G substitution of the U69 protein kinase (PK) gene resulted in an M(318)V amino acid substitution and the other change, located in the C-terminal part of the U38 gene, resulted in an A(961)V amino acid substitution within the DNA polymerase. The M(318)V change was located within the consensus sequence DISPMN of the putative catalytic domain VI of the PK. This change was homologous to the M(460)V and M(460)I changes that had been reported previously within the consensus sequence DITPMN of the human cytomegalovirus (HCMV) UL97 PK and associated with the resistance of HCMV to GCV. The M(318)V change was also detected by PCR in HHV-6-infected PBMCs from an AIDS patient who had been treated with GCV for a long period of time and exhibited a clinically GCV-resistant HCMV infection. These findings provide strong circumstantial evidence that the M(318)V change of the PK gene is associated with resistance to GCV and raise the question of cross resistance to this drug among different betaherpesviruses.  (+info)

Prevalence and cellular reservoir of latent human herpesvirus 6 in tonsillar lymphoid tissue. (8/35)

There are few studies that examine prevalence, quantity, and cellular proclivity of latent human herpesvirus 6 (HHV-6) in healthy populations. We examined 69 tonsils with paired blood specimens from children without evidence of acute infection. By polymerase chain reaction (PCR), HHV-6 was detected at low levels in 100% of tonsils and 39% of blood samples (n = 27), suggesting that prevalence of latent HHV-6 infection is high in children and may be underestimated by PCR analysis of blood. Although HHV-6A and HHV-6B were detected, HHV-6B predominated, being found in 97% of samples (n = 67). Tonsil sections from 7 cases were examined by in situ hybridization using 2 HHV-6 probes and immunohistochemical analysis. Using both in situ hybridization and immunohistochemical analysis, all tissues revealed marked HHV-6-specific staining in the squamous epithelium of the tonsillar crypts and rare positive lymphocytes. We conclude that HHV-6 is present universally in tonsils of children, and tonsillar epithelium may be an important viral reservoir in latent infection.  (+info)