Human herpesviruses 6 and 7: identification of newly recognized viral pathogens and their association with human disease

The Not-So-Soft Spot: Pathophysiology of the Bulging Fontanelle in Association With Roseola

Roseola infantum is a clinical syndrome characterized by high fever followed by the emergence of a rash. Case reports have documented an association between bulging fontanelles and roseola. We propose a novel mechanism for the development of intracranial hypertension caused by human herpesvirus 6-induced cytokine elevation leading to increased cerebrospinal fluid production.

Validation of Multiplex Serology detecting human herpesviruses 1-5

Human herpesviruses (HHV) cause a variety of clinically relevant conditions upon primary infection of typically young and immunocompetent hosts. Both primary infection and reactivation after latency can lead to more severe disease, such as encephalitis, congenital defects and cancer. Infections with HHV are also associated with cardiovascular and neurodegenerative disease. However, most of the associations are based on retrospective case-control analyses and well-powered prospective cohort studies are needed for assessing temporality and causality. To enable comprehensive investigations of HHV-related disease etiology in large prospective population-based cohort studies, we developed HHV Multiplex Serology. This methodology represents a low-cost, high-throughput technology that allows simultaneous measurement of specific antibodies against five HHV species: Herpes simplex viruses 1 and 2, Varicella zoster virus, Epstein-Barr virus, and Cytomegalovirus. The newly developed HHV species-specific ('Monoplex') assays were validated against established gold-standard reference assays. The specificity and sensitivity of the HHV species-specific Monoplex Serology assays ranged from 92.3% to 100.0% (median 97.4%) and 91.8% to 98.7% (median 96.6%), respectively. Concordance with reference assays was very high with kappa values ranging from 0.86 to 0.96 (median kappa 0.93). Multiplexing the Monoplex Serology assays resulted in no loss of performance and allows simultaneous detection of antibodies against the 5 HHV species in a high-throughput manner.

Fundamentals of Viruses and Their Proteases

Viruses are major pathogenic agents that can cause a variety of diseases, such as AIDS, hepatitis, respiratory diseases, and many more, in humans, plants, and animals. The most prominent of them have been adenoviruses, alphaviruses, flaviviruses, hepatitis C virus, herpesviruses, human immunodeficiency virus of type 1, and picornaviruses. This chapter presents an introductory remark on such viruses, mechanisms of their invasion, and diseases related to them. The inhibition of these viruses is of great concern to human beings. Each of these viruses encodes one or more proteases that play crucial roles in their replication, and thus they are important targets for the design and development of potent antiviral agents. The chapter, therefore, also introduces the readers to such proteases and their structures and functions. This chapter is thus a prelude to the remaining chapters in the book, which present in detail about the different viruses and their proteases.

Distribution patterns of beta- and gamma-herpesviruses within Waldeyer's ring organs

The Waldeyer's ring designates a functional unit of lymphoid tissue within the pharynx including the adenoids and tonsils. To gain insight into distribution patterns of beta- and gamma-human herpesviruses (HHVs) and their potential mutual influences at their natural portal of entry, quantitative polymerase chain reaction (qPCR) assays were applied to adenoids and tonsils obtained from 30 children. DNA of Epstein-Barr virus (EBV), cytomegalovirus (CMV), HHV-6, HHV-7, and HHV-8 was detected in adenoids, tonsils, or both of 24 (80%), 19 (63%), 23 (77%), 23 (77%), and 0 (0%) children, respectively. EBV, CMV, HHV-6, and -7 localized in both adenoids and tonsils from 92%, 37%, 52%, and 70% of children, respectively, with the virus detectable by qPCR. The amount of EBV was 2-10-fold higher than of other HHVs and correlated in autologous organs (P = 0.01) as did the amount of HHV-7 (P = 0.002). The amount of CMV correlated with the HHV-6 amount in adenoids (P = 0.028) and tonsils (P = 0.007), and with the amount of HHV-7 in adenoids (P < 0.01). Levels of HHV-6 DNA were lower in adenoids with detectable CMV DNA than in adenoids without detectable CMV DNA (P = 0.0062). Inversely, CMV and HHV-7 levels were higher in adenoids with than in adenoids without detectable EBV DNA (P = 0.019 and P = 0.039, respectively).Thus, beta- and gamma-HHV exhibit distinct distribution behaviors in Waldeyer's ring organs and seem to interact. This may be of medical importance in immunocompromised hosts who are likely to reactivate HHVs causing severe morbidity and death.

Localisation cutanée et épidurale d’une histiocytose de Rosai-Dorfman

BACKGROUND

Rosai-Dorfman disease, or sinus histiocytosis with massive lymphadenopathy, is a rare benign histiocytic proliferative lymph node disorder. Whereas the association of nodal and extranodal involvement is common, purely extranodal diseases are rare.

CASE-REPORT

We report the case of a thirty-year-old man with papulonodular skin lesions of the face and the legs initially followed by onset of hyposensitivity of the lower extremities. Histologic examination of a facial lesion showed a dermal polymorphous infiltrate, chiefly composed of large histiocytes, some of which contained intracytoplasmic lymphocytes and neutrophils, a process referred to as emperipolesis. Immunohistochemistry revealed positive staining of the histiocytes with anti-S100 protein and anti-CD68 antibodies and negative staining with anti-CD1a antibody. Magnetic resonance showed spinal cord compression linked to epidural involvement. We concluded on cutaneous and epidural Rosai-Dorfman disease. Neurological symptoms rapidly and partially resolved after intravenous corticosteroid therapy, which was followed by oral corticosteroid therapy and etoposide chemotherapy leading to the regression of the cutaneous lesions.

DISCUSSION

This case report of cutaneous and epidural Rosai-Dorfman disease is interesting because of the lack of lymph node involvement associated with the cutaneous lesions and because of the presence of an epidural site, rarely described in this disease.

Autoimmune neutropenia of infancy with multiple brain abscesses during the course of human herpesvirus-6 infection

Autoimmune neutropenia of infancy is characterized by recurrent infections such as pneumonia, otitis media, impetigo, purulent skin regions, gastritis, and upper respiratory infection. However, severe bacterial infection is uncommon. This report documents a 9-month-old boy presenting with autoimmune neutropenia in association with multiple brain abscesses during the course of human herpesvirus (HHV)-6 infection. HHV-6 has a tendency of neurovirulence, which can destroy the blood-brain barrier and facilitate the easy invasion of agents inside the brain. Although autoimmune neutropenia of infancy is benign and self limiting, it must be emphasized that severe bacterial infection will be induced by concurrent viral infection in this specific disorder.

Hypertransaminasemia in childhood as a marker of genetic liver disorders

BACKGROUND

The widespread use of routine biochemical assays has led to increased incidental findings of hypertransaminasemia. We aimed to evaluate the prevalence of different causes of raised aminotransferase levels in children referred to a university department of pediatrics.

METHODS

We investigated 425 consecutive children (age range, 1-18 years) with isolated hypertransaminasemia. All patients had raised aminotransferase levels on at least two occasions in the last month before observation. Cases due to major hepatotropic viruses were excluded.

RESULTS

During the first 6 months of observation, 259 children showed normalized liver enzymes. Among the remaining 166 patients with hypertransaminasemia lasting for more than 6 months, 75 had obesity-related liver disease; 51, genetic disorders; 7, autoimmune hepatitis; 5, cholelithiasis; 3, choledochal cyst; and 3, celiac disease. Among the 51 children with genetic disorders, 18 had Wilson disease; 14, muscular dystrophy; 4, alpha-1-antitrypsin deficiency; 4, Alagille syndrome; 4, hereditary fructose intolerance; 3, glycogen storage disease (glycogenosis IX); 2, ornithine transcarbamylase deficiency; and 2, Shwachman's syndrome. In 22 children, the hypertransaminasemia persisted for more than 6 months in the absence of a known cause.

CONCLUSIONS

Genetic disease accounted for 12% of cases of isolated hypertransaminasemia observed in a tertiary pediatric department. A high level of suspicion is desirable for an early diagnosis of these disorders, which may present with isolated hypertransaminasemia and absence of typical clinical signs.

Human herpesviruses 6 and 7 and central nervous system infection in children

Human herpesviruses 6 and 7 were infrequently found in cerebrospinal fluid of children with central nervous system infection.

The role and frequency of human herpesviruses (HHV)-6 and -7 in central nervous system (CNS) diseases of children are unclear. Cerebrospinal fluid samples from 245 pediatric patients (median age 43 days), submitted for evaluations of possible sepsis or of neurologic symptoms, were tested for HHV-6 and HHV-7 DNA by polymerase chain reaction. HHV-6 DNA was found in 3 of 245 samples, and HHV-7 was found in 0 of 245 samples. The three patients with HHV-6 DNA were <2 months of age. HHV-6 was likely pathogenic in two patients with meningitis who lacked evidence of another microbiologic cause. HHV-6 and HHV-7 are uncommon causes of CNS infection in children. HHV-6 may occasionally cause meningitis in young infants.

Evidence of active herpesvirus 6 (variant-A) infection in patients with lymphadenopathy in Belém, Pará, Brazil

A total of 323 patients with lymphadenopathy were selected in Belém, Brazil, between January 1996 and December 2001, and screened for the presence of human herpesvirus-6 (HHV-6) IgM- and--IgG antibodies by enzyme-linked immunosorbent assay (ELISA). When seroprevalence is analyzed by gender, similar rates are found for female (60.6%) and male (55.7%) individuals. Seventy-seven (23.8%) patients were HHV-6-IgM-and--IgG-positive (IgM+ subgroup), with positivity rates of 29.7% and 17.7% (p = 0.0007) for female- and male individuals, respectively. Sera from a subgroup (n = 120) of these subjects, with high HHV-6 antibody levels (either IgM+ or IgG+ reactivities), were subsequently processed for the presence of HHV-6 DNA by polymerase chain reaction (PCR)/nested PCR. Active infections (IgM+ and/or IgG+ high levels specific antibodies plus detection of viral DNA) were diagnosed in 20/77 (20.0%) and 8/43 (18.6%); subgroup of the 120 individuals suspected of having HHV-6 suggestive recent infection. All (n = 28) cases of active infection were found to be associated with HHV-6 variant-A (HHV-6A), as detectable by PCR/nested PCR, using variant-specific primer that amplify regions of 195 base pairs (bp) (HHV-6A) and 423 bp (HHV-6B). Rates of HHV-6 DNA detection between female and male patients were similar (p > 0.05) in the IgM+ and IgG+ groups: 20.4% versus 35.7% and 25.0% versus 13.0%, respectively. HHV-6 DNA was detected across < or = 5 through 41-50-year age-groups for patients whose serum samples were IgM+, with rates ranging from 7.7% (female subjects aged < or = 5 years) to 80.0% (male, 11-20 years). Among patients whose serological status was IgG+, HHV-6 DNA was detected in < or = 5, 6-10, 21-30 and > 50 age-groups at rates that ranged from 15.4% (male, < or = years of age) to 100.0% (female aged 11-20 years). Swelling cervical lymph nodes were the most common sign, accounting for 9 (32.0%) cases in each gender group. Among patients (n = 28) with active infection by HHV-6A variant, duration of symptoms lasted 1-5 days in 35.7% of subjects, whereas in 64.3% of them the disease lasted 6-20 days. Our data suggest that it is worth seeking for HHV-6 infection whenever a patient (infant or adult) presents with lymphadenopathy as a prominent symptom in the course of an acute febrile illness.

Determination of antiviral efficacy against lymphotropic herpesviruses utilizing flow cytometry

Epstein-Barr virus (EBV), human herpesvirus type 6 (HHV-6), and human herpesvirus type 8 (HHV-8) comprise a group of lymphotropic herpesviruses which are responsible for a wide range of diseases, including lymphoproliferative disorders and tumors. We have developed several flow cytometric assay (FACS) systems to evaluate antiviral efficacy against EBV, HHV-6 and HHV-8. Assays using either EBV or HHV-8, members of the gammaherpesvirus subfamily, have shown that while EBV responds well to acyclovir (ACV), HHV-8 was most sensitive to cidofovir (CDV). Since HHV-6 strains are divided into two sub-groups, A and B, we evaluated antiviral efficacy for strains from each group. The group A strain, HHV-6(GS), was inhibited by foscarnet (PFA), CDV and ganciclovir (GCV) in both Sup-T1 and HSB-2 cell lines. HHV-6(Z-29), a representative group B virus, was inhibited by GCV and CDV but not by PFA. Our findings indicate that flow cytometry can be utilized to efficiently evaluate new antiviral agents against lymphotropic herpesviruses and that the results are comparable to those obtained by other methods such as immunofluorescence.

Herpesviruses: emerging nosocomial pathogens?

BACKGROUND

Herpesviruses are ubiquitous pathogens that are known to cause infection in humans and animals. It is likely that more than 90% of adults have been infected by one or more herpesviruses. As hospitalized patients become increasingly immunosuppressed by virtue of illness or therapies, it is increasingly likely that human herpesvirus infection will become manifest in the hospital. Whether these manifestations represent manifestations of reactivated latent disease or true nosocomial infections is an open question.

METHODS

Review of the pertinent English-language literature.

RESULTS

There are eight known herpesviruses that cause disease in humans. Herpesviruses are double-stranded DNA viruses. The prototypical structure consists of an inner DNA core that is encased within a nucleocapsid that is icosahedral in configuration and consists of capsomere subunits. Herpesvirus infection generally occurs when virus is transmitted in oral secretions from an infected to a naive host. Clinical reactivation syndromes can occur in transplant patients, cancer chemotherapy patients, and patients with acquired immunodeficiency syndrome. Life-threatening infections are most closely associated with human herpesvirus-5 (cytomegalovirus), whereas the relationships between human herpesvirus-7 and clinical disease are largely undefined.

CONCLUSION

Clinical expressions of herpesvirus in surgical patients are not nosocomial infections, but are in the vast majority of cases the reactivation of latent infection. Reactivation disease can be lethal to the immunosuppressed host.

Absence of associations between influenza-associated encephalopathy and human herpesvirus 6 or human herpesvirus 7

BACKGROUND

Influenza-associated encephalopathy is a severe complication of influenza virus infection, but its pathogenesis is unknown. It was recently suggested that the neurologic complications of influenza, including encephalopathy, are associated with human herpesvirus 6 (HHV-6) and human herpesvirus 7 (HHV-7). AIM To confirm or refute the association between influenza-associated encephalopathy and HHV-6 or HHV-7.

METHODS

Cerebrospinal fluid and serum from 25 patients with central nervous system complications of influenza (18 patients with encephalopathy and 7 patients with febrile convulsions) were investigated. The specimens were examined by real time polymerase chain reaction (PCR) and nested PCR for HHV-6 and HHV-7 DNA.

RESULTS

In the cerebrospinal fluid samples neither HHV-6 DNA nor HHV-7 DNA was detected by real time PCR or nested PCR. HHV-6 DNA was detected in a single serum sample from a patient with febrile convulsions.

CONCLUSION

In our study there was no association with HHV-6 or HHV-7 in most patients with central nervous system complications of influenza.

The impact of human herpesvirus-6 and -7 infection on the outcome of liver transplantation

Human herpesvirus (HHV)-6 and -7 are novel members of the beta-herpesvirus family that maintain latency in the human host after primary infection. Reactivation from latency and/or increased degree of viral replication occurs during periods of immune dysfunction. The clinical effect of HHV-6 and HHV-7 reactivation in recipients of liver transplants is now being recognized. Clinical illnesses such as fever, rash, pneumonitis, encephalitis, hepatitis, and myelosuppression have been described in a number of anecdotal reports. Moreover, a growing body of evidence suggests that the more important effect of HHV-6 and HHV-7 reactivation on the outcomes of liver transplantation may be mediated indirectly by their interactions with the other beta-herpesvirus-cytomegalovirus (CMV). Coinfection among these three beta-herpesviruses in clinical syndromes that were classically ascribed to be solely caused by CMV has been shown and has raised substantial interest in the potential role of HHV-6 and HHV-7 as copathogens in the direct and indirect illnesses caused by CMV. This article reviews the current scientific data on the role and the magnitude of impact of HHV-6 and HHV-7 infection on the outcomes of liver transplantation.

Human herpesviruses 6 and 7

Human herpesviruses 6 and 7 are newly discovered viruses that belong to the genus Roseolavirus within the subfamily Betaherpesvirinae. These ubiquitous viruses may cause primary or chronic persistent infection or remain in a state of latency for many years, until a decrease in the immunologic state of the host leads to reactivation of infection. Several diseases have been linked with HHV-6 and HHV-7. In the dermatologic arena, a definite association has been proven only for HHV-6 and exanthema subitum (roseola infantum), whereas the role of HHV-7 in the pathogenesis of pityriasis rosea remains a matter of debate.

Ganciclovir is effective for prophylaxis and treatment of human herpesvirus-6 in allogeneic stem cell transplantation

Human herpesvirus 6 (HHV-6) infection and disease are serious complications of allogeneic hematopoietic stem cell transplantation (allo-SCT). Ganciclovir (GCV) is effective against HHV-6 in vitro but the antiviral susceptibility of HHV-6 has not been well characterized in vivo. We retrospectively compared the HHV-6 reactivation rate in pediatric allo-SCT recipients with and without GCV prophylaxis. The HHV-6 reactivation rate at 3 weeks after allo-SCT in patients without prophylactic GCV administration was significantly higher than that in those receiving prophylactic GCV (11/28 vs 0/13, P < 0.01). Five of 36 patients without prophylactic GCV showed clinical manifestations including skin rash, interstitial pneumonitis, persistent thrombocytopenia, enterocolitis and thrombotic microangiopathy, respectively. HHV-6-associated symptoms were observed in one of the 13 patients receiving prophylactic GCV. This patient showed fever, diarrhea and graft rejection concomitantly with a sudden increase of HHV-6 DNA copy number. Patients who received GCV for treatment of HHV-6 infection showed an improvement in symptoms and/or decrease of HHV-6 copy number. Thus, GCV is effective for treating HHV-6 disease after allo-SCT in vivo.

Human herpesvirus 6 and cytomegalovirus infections in children with human immunodeficiency virus infection and cancer

AIM

Measure the prevalence of human herpesvirus 6 (HHV-6) and cytomegalovirus (CMV) infections in children and adolescents with HIV infection and malignancy.

METHODS

Semiquantitative polymerase chain reaction and serology were used to test for HHV-6 and CMV infections in 31 cases (HIV-infected children with cancer), 56 HIV controls (HIV-infected children without cancer) and 30 cancer controls (HIV-uninfected children with cancer).

RESULTS

In cases, HIV controls and cancer controls, HHV-6 DNA was detected in 29, 39 and 34%, respectively, and CMV DNA was detected in 13, 4 and 7%, respectively. Four cases (13%) and no HIV controls or cancer controls harbored HHV-6 subtype A (P = 0.014). In cases, HIV controls and cancer controls, the prevalence of HHV-6 antibodies was 58, 68 and 93%, respectively, and the prevalence of CMV antibodies was 71, 48 and 70%, respectively. HHV-6 seroprevalence was lower in cases than in cancer controls (P = 0.002), even with adjustments for age and CD4 concentrations; however, HHV-6 infection rates (presence of HHV-6 DNA and/or HHV-6 antibodies) were similar in all groups. Stratification showed that CMV infection was more common in younger patients (ages < 8 years) without severe immune suppression (CD4 concentration >200 cells/microl) than in HIV controls (odds ration, 10.343; 95% confidence interval, 1.65, 121.57). Geometric mean titers of serum anti-CMV antibodies, but not anti-HHV-6 antibodies, were higher in cases (1:71) than in HIV controls (1:33) (P = 0.005).

CONCLUSIONS

HHV-6 and CMV infections were common among children with HIV infection and cancer. CMV seropositivity also was associated with cancer in younger HIV-infected patients who did not have severe immune suppression. HHV-6A was detected only in HIV-infected children with cancer.

Emerging viral infections

The past decade has witnessed the emergence of several significant viral pathogens and the further evolution of additional viral pathogens. Transmitted by a variety of differing routes, these organisms have presented substantial intellectual challenges to medicine of the 20th and 21st centuries. As perhaps the benchmark pathogen of the past decade, HIV has provided medicine and society with a most formidable opponent, and one that has yet to be fully conquered. Nonetheless, a variety of additional viral pathogens have also perplexed medicine over the past 10-15 years.

Encephalitis caused by human herpesvirus-6 in transplant recipients: relevance of a novel neurotropic virus

BACKGROUND

Human herpesvirus-6 (HHV-6) is a neurotropic virus. Encephalitis is a significant clinical manifestation of HHV-6; however, sparse data on this entity exist in transplant recipients.

METHODS

Cases of HHV-6 encephalitis reported in the literature (13 bone marrow transplant recipients and 1 liver transplant recipient) were reviewed. The diagnosis was established in all by viral isolation and/or detection of HHV-6 DNA in the cerebrospinal fluid by polymerase chain reaction or histopathologic method.

RESULTS

HHV-6 encephalitis occurred a median of 45 days (range 10 days to 15 months) after transplantation. Mental status changes, ranging from confusion to coma (92%), seizures (25%), and headache (25%) were the predominant clinical presentations. Focal neurologic findings occurred in only 17% of the patients. Twenty-five percent of the patients had fever; however, the height of fever (< or =40 degrees C) in febrile patients was striking. Cerebrospinal fluid pleocytosis was generally lacking. Abnormal neuroimaging findings, characterized by low-attenuation lesions in the posterior cerebral lobes, were present only in 17% of the patients. Overall mortality in patients with HHV-6 encephalitis was 58% (7 of 12); 42% (5 of 12) of the deaths were caused by HHV-6. Cure was documented in 7 of 8 patients who received ganciclovir or foscarnet for > or =7 days, compared with 0% (0 of 4) in those who did not receive these drugs or received them for < 7 days (P=.01).

CONCLUSIONS

HHV-6 may be associated with encephalitis after transplantation and warrants consideration in transplant recipients with encephalitis of unidentifiable etiology.

Human herpesvirus-6 in liver transplant recipients: role in pathogenesis of fungal infections, neurologic complications, and outcome

BACKGROUND

The clinical impact and relevance of human herpesvirus-6 (HHV-6) infection in liver transplant recipients, has not been fully discerned.

METHODS

A prospective study of 80 consecutive liver transplant recipients was performed using surveillance cultures for HHV-6 at weeks 2, 3, 4, and 6 after transplantation. Viral isolation was used for the detection of HHV-6.

RESULTS

HHV-6 infection occurred in 39% (31 of 80) of the patients. Patients with HHV-6 infection were more likely to have hepatocellular carcinoma as underlying liver disease (P=.09). Mental status changes of unidentifiable etiology were significantly more likely to occur in patients with HHV-6 compared with those without (26%, 9 of 31 vs. 6%, 3 of 49, P=.008). HHV-6 infection was an independent predictor of invasive fungal infections (odds ratio 8.3, 95% confidence interval, 1.2-58.0, P=.03). A significant association between HHV-6 infection and CMV infection after transplantation, CMV recipient and donor serostatus, rejection, or fever of unknown origin, could not be documented. Mortality at last follow-up in patients with HHV-6 infection (29%, 9 of 31) was significantly greater than those without HHV-6 (6%, 3 of 49, P=.008).

CONCLUSIONS

Central nervous system complications of unknown etiology after liver transplantation may be related to HHV-6 infection. HHV-6 viremia was an independently significant predictor of invasive fungal infections and was associated with late mortality in liver transplantation recipients.

Human herpes virus 6 fatal encephalitis in a bone marrow recipient

Human herpes virus 6 (HHV-6) has been implicated as a human pathogen in both normal and immunocompromised hosts. It has been associated with interstitial pneumonitis and bone marrow suppression after transplantation. We report here a case of fatal encephalitis in a bone marrow transplant recipient. This case illustrates the importance of considering HHV6 as an emerging pathogen in immunocompromised hosts.

Meningoencephalitis caused by human herpesvirus-6 in an immunocompetent adult patient: case report and review of the literature

Human herpesvirus-6 (HHV-6) is the etiologic agent of roseola infantum, and has been implicated as a possible cause of encephalitis in pediatric and adult patients. A case of meningoencephalitis in an otherwise healthy, immunocompetent 59-year-old woman is described. The diagnosis of HHV-6 meningoencephalitis was confirmed by detecting viral DNA in cerebrospinal fluid collected in the acute stage of the disease by polymerase chain reaction. The patient was treated with acyclovir and recovered without any sequelae. The current knowledge of the pathophysiology, clinical course and outcome of HHV-6 meningoencephalitis in immunocompetent adult patients is also reviewed.