Cell Fusion and Syncytium Formation in Betaherpesvirus Infection.

Cell-cell fusion is a fundamental and complex process that occurs during reproduction, organ and tissue growth, cancer metastasis, immune response, and infection. All enveloped viruses express one or more proteins that drive the fusion of the viral envelope with cellular membranes. The same proteins can mediate the fusion of the plasma membranes of adjacent cells, leading to the formation of multinucleated syncytia. While cell-cell fusion triggered by alpha- and gammaherpesviruses is well-studied, much less is known about the fusogenic potential of betaherpesviruses such as human cytomegalovirus (HCMV) and human herpesviruses 6 and 7 (HHV-6 and HHV-7). These are slow-growing viruses that are highly prevalent in the human population and associated with several diseases, particularly in individuals with an immature or impaired immune system such as fetuses and transplant recipients. While HHV-6 and HHV-7 are strictly lymphotropic, HCMV infects a very broad range of cell types including epithelial, endothelial, mesenchymal, and myeloid cells. Syncytia have been observed occasionally for all three betaherpesviruses, both during in vitro and in vivo infection. Since cell-cell fusion may allow efficient spread to neighboring cells without exposure to neutralizing antibodies and other host immune factors, viral-induced syncytia may be important for viral dissemination, long-term persistence, and pathogenicity. In this review, we provide an overview of the viral and cellular factors and mechanisms identified so far in the process of cell-cell fusion induced by betaherpesviruses and discuss the possible consequences for cellular dysfunction and pathogenesis.

Development of an enzyme-linked immunosorbent assay for diagnosis of human herpesvirus-7 infection.

INTRODUCTION: Human herpesvirus (HHV)-7 establishes a latent infection during the lifetime of the host and can reactivate after the primary infection, leading to lytic replication in immunosuppressed patients. METHODS: This study aimed to develop an enzyme-linked immunosorbent assay (ELISA) to identify HHV-7 serum antibodies and compare its performance with that of an indirect immunofluorescence assay (IFA). RESULTS: Serum samples (n=102) were tested by IgG-IFA and by ELISA. IFA and ELISA showed IgG-positive results in 77 and 73 samples, respectively. Qualitative concordance of 96% was demonstrated between the two techniques. CONCLUSIONS: ELISA may be useful to diagnose HHV-7 infection.

Development of an enzyme-linked immunosorbent assay for diagnosis of human herpesvirus-7 infection

Abstract INTRODUCTION: Human herpesvirus (HHV)-7 establishes a latent infection during the lifetime of the host and can reactivate after the primary infection, leading to lytic replication in immunosuppressed patients. METHODS: This study aimed to develop an enzyme-linked immunosorbent assay (ELISA) to identify HHV-7 serum antibodies and compare its performance with that of an indirect immunofluorescence assay (IFA). RESULTS: Serum samples (n=102) were tested by IgG-IFA and by ELISA. IFA and ELISA showed IgG-positive results in 77 and 73 samples, respectively. Qualitative concordance of 96% was demonstrated between the two techniques. CONCLUSIONS: ELISA may be useful to diagnose HHV-7 infection.

Summary of the 9th international conference on human herpesviruses 6 and 7 (HHV-6A, HHV-6B, and HHV-7).

The 9th International Conference on Human herpesviruses 6 and 7 (HHV-6A, HHV-6B, and HHV-7) was held at Harvard Medical School in Boston, Massachusetts from November 9 to 11, 2015. Important new information was presented regarding: the biology of these viruses, particularly HHV-6A and HHV-6B; the biology and epidemiology of inherited chromosomally integrated HHV-6A/B; improved diagnostic tests; animal models for studying HHV-6 and HHV-7, and animal viruses with similarities to HHV-6 and HHV-7; established and possible disease associations; and new approaches to treatment. Here, we summarize work of particular interest. J. Med. Virol. 88:2038-2043, 2016. © 2016 Wiley Periodicals, Inc.

Cerebral Vasculitis in X-linked Lymphoproliferative Disease Cured by Matched Unrelated Cord Blood Transplant.

UNLABELLED: Vasculitis occurs rarely in association with X-linked lymphoproliferative disease (XLP). There are four published cases of non-EBV XLP-associated cerebral vasculitis reported, none of whom have survived without major cognitive impairment. CASE: A 9-year old boy initially presented aged 5 years with a restrictive joint disease. He subsequently developed dysgammaglobulinemia, episodic severe pneumonitis, aplastic anaemia, gastritis and cerebral vasculitis. A diagnosis of XLP was made, based on flow cytometric analysis and the identification of a novel mutation in SH2D1A, c.96G>C. No peripheral blood lymphocyte clonal proliferation was identified and he was EBV negative, although human herpes virus-7 (HHV7) was detected repeatedly in his cerebrospinal fluid. He underwent a reduced intensity unrelated umbilical cord blood transplant, but failed to engraft. A second 5/6 matched cord gave 100 % donor engraftment. Complications included BK virus-associated haemorrhagic cystitis, a possible NK-cell mediated immune reconstitution syndrome and post-transplant anti-glomerular basement membrane disease, the latter treated with cyclophosphamide and rituximab. At +450 days post-transplant he is in remission from his vasculitis and anti-glomerular basement membrane disease, and HHV-7 has remained undetectable. CONCLUSION: This is the second published description of joint disease in XLP, and only the fourth case of non-EBV associated cerebral vasculitis in XLP, as well as being the first to be successfully treated for this manifestation. This case raises specific questions about vasculitis in XLP, in particular the potential relevance of HHV-7 to the pathogenesis.

Pityriasis Rosea in Children: Clinical Features and Laboratory Investigations.

Pityriasis rosea (PR) is a common, self-limiting exanthematous disease associated with a systemic reactivation of human herpesvirus 6 (HHV-6) and/or HHV-7. It usually occurs in the second or third decade of life whereas it is uncommon in patients younger than 10 years. We studied the clinical features and virological parameters of 31 children with PR, comparing them with those in adults. Our findings indicate that PR presents different characteristics between children and adults, mainly consisting of time lapse between herald patch and generalized eruption, duration of the exanthem, oropharyngeal involvement and persistence of HHV-6 and HHV-7 plasma viremia. Overall, these results suggest that, following HHV-6 and/or HHV-7 systemic active infection, the pathogenetic mechanisms involved in PR may at least partly be different in children and adults.

Persistent pityriasis rosea: an unusual form of pityriasis rosea with persistent active HHV-6 and HHV-7 infection.

Pityriasis rosea (PR) is an acute, self-limiting exanthematous disease, associated with the reactivation of the human herpesvirus 6 (HHV-6) and/or human herpesvirus 7 (HHV-7) that usually lasts 6-8 weeks. We studied, from a clinical and virological point of view, 12 patients in whom the features of PR lasted longer than 12 weeks, defining this form of the disease as persistent PR (PPR). As in typical PR, in most of the PPR patients the disease begins with a herald patch, but compared to typical PR, systemic symptoms and oral lesions are more common. Moreover, in PPR we found a persistent reactivation of HHV-6 and/or HHV-7 with higher viral loads than in typical PR, accounting for the unusual persistence of the illness, the more frequent and severer systemic symptoms and the oral lesions. In conclusion, we describe an unusual persistent form of PR, whose prevalence has probably been underestimated so far and which should be added to the other variants of PR.

Detección y respuesta inmune de virus herpes humano 6 (VHH-6) y virus herpes humano 7 (VHH-7) en población sana / Detection and immune response of human herpes virus 6 (HHV-6) and human herpesvirus 7 (HHV-7) in healthy population

El Herpesvirus Humano 6 (VHH-6) y el Herpesvirus humano 7 (VHH-7) pertenecen a la familia Herpesviridae con una amplia distribución en la población humana. La infección primaria ocurre a muy temprana edad, antes de los 2 años de vida, y el virus establece, en el hospedero susceptible, un modelo persistente de infección. La latencia del virus se produce en las células linfoides y en las glándulas salivales. La reactivación puede suceder en reiteradas ocasiones a lo largo de la vida de un infectado, ya sea éste inmunocompetente o inmunocomprometido, pudiendo el virus ser detectado en saliva y /o plasma. En individuos sanos, inmunocompetentes, la historia natural de la infección es poco conocida. El objetivo de este trabajo es contribuir a la comprensión de los modelos de persistencia viral de HHV-6 y de HHV-7 y de la respuesta inmune que la actividad viral desencadena en el hospedero sano, la cual se pone en evidencia por el perfil de isotipos específco de Inmunoglobulina G (IgG) específicos.(AU)

ABSTRACT: Human herpesvirus 6 (HHV-6) and Human herpesvirus 7 (HHV-7) belong to the Herpesviridae family and are widely distributed among the human population. The human primary infection occurs early, before the two years of age, and the virus establishes a persistent model of infection in the susceptible host. The virus remains latent mainly in lymph cells and salivary glands. Reactivation may occur several times throughout the life of infected individual, whether immune competent or immune compromised, with the virus being detected in saliva and/or plasma. In healthy immune competent individuals, the natural history of the infection is little known. The aim of this research was to contribute to the understanding of the models of viral persistence of HHV-6 and HHV-7 and the immune response that viral activity triggers in the healthy host, manifested by the profile of specific IgG isotypes (IgG1, IgG2, IgG3 and IgG4).(AU)

Roseoloviruses and their modulation of host defenses.

Human cytomegalovirus (HCMV), the prototypical human ß-herpesvirus, encodes approximately 40 known gene products that function to subvert our host defense mechanisms. From HCMV, we have learned about interferon signaling, cytokine function, chemokine signaling, natural killer (NK) cells' cytotoxicity toward tumors and virus-infected cells, antigen processing and presentation, and protective initiation of the apoptotic signaling cascade. With each successive discovery of novel host evasion mechanism encoded by the cytomegaloviruses, we illuminate what these herpesviruses have learned over the course of their 100 MYr-long evolution with their hosts. As much as we have learned from HCMV, the other members of the human ß-herpesvirus family, HHV-6 and HHV-7, are closely-related and yet largely unexplored. These viruses likely have much yet to teach us.

Anti-N-methyl-D-aspartate receptor encephalitis with positive serum antithyroid antibodies, IgM antibodies against mycoplasma pneumoniae and human herpesvirus 7 PCR in the CSF.

We report the case of a boy with an encephalopathy associated with extrapyramidal and psychiatric symptoms and anti-N-methyl-D-aspartate receptor antibodies. He had positive serum antithyroid antibodies, IgM antibodies against Mycoplasma pneumoniae and human herpesvirus 7 polymerase chain reaction in the cerebrospinal fluid. He was successfully treated with rituximab, after steroids, intravenous immunoglobulin and plasma exchange. The pathophysiology of this disorder may be post-infectious and autoimmune.

N-glycosylation of asparagine 8 regulates surface expression of major histocompatibility complex class I chain-related protein A (MICA) alleles dependent on threonine 24.

NKG2D is an activating receptor expressed on several types of human lymphocytes. NKG2D ligands can be induced upon cell stress and are frequently targeted post-translationally in infected or transformed cells to avoid immune recognition. Virus infection and inflammation alter protein N-glycosylation, and we have previously shown that changes in cellular N-glycosylation are involved in regulation of NKG2D ligand surface expression. The specific mode of regulation through N-glycosylation is, however, unknown. Here we investigated whether direct N-glycosylation of the NKG2D ligand MICA itself is critical for cell surface expression and sought to identify the essential residues. We found that a single N-glycosylation site (Asn(8)) was important for MICA018 surface expression. The frequently expressed MICA allele 008, with an altered transmembrane and intracellular domain, was not affected by mutation of this N-glycosylation site. Mutational analysis revealed that a single amino acid (Thr(24)) in the extracellular domain of MICA018 was essential for the N-glycosylation dependence, whereas the intracellular domain was not involved. The HHV7 immunoevasin, U21, was found to inhibit MICA018 surface expression by affecting N-glycosylation, and the retention was rescued by T24A substitution. Our study reveals N-glycosylation as an allele-specific regulatory mechanism important for regulation of surface expression of MICA018, and we pinpoint the residues essential for this N-glycosylation dependence. In addition, we show that this regulatory mechanism of MICA surface expression is likely targeted during different pathological conditions.

Herpesvirus infections and allergic sensitization in children of families with anthroposophic and non-anthroposophic lifestyle - the ALADDIN birth cohort.

BACKGROUND: Growing up in families with an anthroposophic lifestyle has been associated with reduced risk of allergic disease in children. The aim of this report was to assess whether children with this lifestyle are infected earlier with Epstein-Barr virus (EBV), which has been associated with reduced risk of allergic disease, and three other herpesviruses potentially involved in allergy development, namely Human herpesvirus 6 (HHV6), Human herpesvirus 7 (HHV7) and cytomegalovirus (CMV). METHODS: Within the ALADDIN (Assessment of Lifestyle and Allergic Disease During Infancy), birth cohort study 157 children were categorized according to lifestyle into anthroposophic and non-anthroposophic. IgG-levels for EBV, HHV6, HHV7 and CMV were determined in plasma samples collected at ages 12 and 24 months and from parents. IgE levels against seven common allergens were analyzed at 24 months. RESULTS: No significant differences in seroprevalence of EBV, HHV7 or CMV were detected at any age between the two lifestyle groups. The seroprevalence of HHV6 was significantly lower in the anthroposophic group at 24 months of age (74.6% vs. 87.5%, p-value 0.048). Further, no significant associations between allergic sensitization and seropositivity to any of the viruses were detected; however, an interaction effect of lifestyle could not be ruled out. CONCLUSIONS: Our results indicate that there is no strong influence of exposure to the anthroposophic lifestyle on the time for infection with EBV, HHV6, HHV7 or CMV. These infections can therefore not be assumed to be important factors in the allergy-protective effect of this lifestyle.

Correlation of cytomegalovirus and human herpesvirus 7 with CD3+ and CD3+ CD4+ cells in chronic periodontitis patients.

BACKGROUND AND OBJECTIVE: Human chronic periodontitis is an inflammatory process characterized by dense accumulation of immune cells in the periodontal tissue. The periodontitis can lead to loss of teeth in the patient and the pathogenesis of this disease is not completely known. This study tested the hypothesis that chronic periodontitis-affected sites can harbor betaherpesviruses and that viruses are linked to a profile of the inflammatory infiltrate. MATERIAL AND METHODS: Biopsies of periodontal tissue were taken from periodontitis-affected patients and from healthy subjects. Immunohistochemistry was performed to count CD19(+) B cells, CD3(+) total T cells, T-CD4(+) and T-CD8(+) cell subsets, and PCR was performed to detect cytomegalovirus and human herpesvirus 6 and 7 in the samples. One slide of each sample was stained with Giemsa for histopathological examination and to evaluate the quality of the cellular infiltrate. RESULTS: As expected, tissues collected from healthy subjects presented no significant level of inflammatory infiltration and were therefore excluded from immunostaining procedures. Results showed that CD19(+) B cells were in higher number than CD3(+) T cells in the periodontitis-affected tissue, but this was not statistically significant. The T-CD4(+) lymphocyte subset was significantly higher than the T-CD8(+) lymphocyte subset (p = 0.004) in the samples. Cytomegalovirus and human herpesvirus 7 were found at periodontitis-affected sites, but not in tissue collected from healthy subjects (p = 0.04 and p = 0.04, respectively). Human herpesvirus 6 was rarely detected. We found a correlation between cytomegalovirus and lower CD19(+) /CD3(+) ratios (ratio < 0.9, p = 0.003) and between human herpesvirus 7 and lower CD19(+) /CD3(+) ratios (ratio < 0.9, p = 0.003) and higher CD4(+) /CD8(+) ratios (ratio > 1.1, p = 0.002). CONCLUSION: This study shows that cytomegalovirus and human herpesvirus 7 can be present at periodontitis-affected sites but are uncommon at healthy periodontal sites. Moreover, our data suggest that cytomegalovirus can be related to an inflammatory infiltrate with predominance of CD3(+) T cells, whereas human herpesvirus 7 can be associated with an infiltrate with predominance of T-CD4(+) cells. However, further studies are necessary to support this hypothesis. Herpesviruses could play a role in human chronic periodontitis by modulation of the T cell response.

The human herpesvirus-7 (HHV-7) U21 immunoevasin subverts NK-mediated cytoxicity through modulation of MICA and MICB.

Herpesviruses have evolved numerous immune evasion strategies to facilitate establishment of lifelong persistent infections. Many herpesviruses encode gene products devoted to preventing viral antigen presentation as a means of escaping detection by cytotoxic T lymphocytes. The human herpesvirus-7 (HHV-7) U21 gene product, for example, is an immunoevasin that binds to class I major histocompatibility complex molecules and redirects them to the lysosomal compartment. Virus infection can also induce the upregulation of surface ligands that activate NK cells. Accordingly, the herpesviruses have evolved a diverse array of mechanisms to prevent NK cell engagement of NK-activating ligands on virus-infected cells. Here we demonstrate that the HHV-7 U21 gene product interferes with NK recognition. U21 can bind to the NK activating ligand ULBP1 and reroute it to the lysosomal compartment. In addition, U21 downregulates the surface expression of the NK activating ligands MICA and MICB, resulting in a reduction in NK-mediated cytotoxicity. These results suggest that this single viral protein may interfere both with CTL-mediated recognition through the downregulation of class I MHC molecules as well as NK-mediated recognition through downregulation of NK activating ligands.

Cytomegalovirus, human herpesvirus-6, and human herpesvirus-7 in adult liver transplant recipients: diagnosis based on antigenemia.

Human herpesvirus (HHV)-6, HHV-7, and cytomegalovirus (CMV) that remain latent after primary infection can be reactivated during immunosuppression following organ transplantation in liver transplant recipients. The aim of this study was to monitor active infections for HHV-6, HHV-7, and CMV among adult liver transplantation recipients using antigenemia detected by an immunoperoxidase staining. Twenty-eight adult liver transplant patients were monitored using antigenemia in blood samples obtained at the time of transplantation, as well as weekly in the first month and once a month for 6 months. Of these patients, 28.5% showed positive CMV antigenemia; 39.2%, HHV-6 antigenemia; and 14.2%, HHV-7 antigenemia. The detection of the three viruses was considered to be independent of one another (P>.05). The results described above showed that few patients remain free of beta herpesviruses after liver transplantation. Most patients were infected sequentially and not concurrently. Antigenemia has been considered useful to detect active HHV-6 and HHV-7 infections. Antigenemia can be more efficiently interpreted when compared with polymerase chain reaction results, although other studies are necessary to establish the reference of HHV-6 and HHV-7 antigenemia.

IgG subclasses and DNA detection of HHV-6 and HHV-7 in healthy individuals.

Human herpesvirus 6 (HHV-6) and 7 (HHV-7) are common opportunistic agents in immunocompromised hosts, although infection with HHV-6 and HHV-7 can also be observed in immunocompetent hosts. Despite similar biology and epidemiology, this study evaluated differences in the IgG subclass distribution associated with HHV-6 and HHV-7 in seropositive, healthy persons. The identified subclasses were also compared with the detection of HHV-6 and HHV-7 DNA. For these assays, sera, plasma, and saliva samples were obtained from 40 healthy blood donors in Argentina who were seropositive for both HHV-6 and HHV-7. HHV-6 and HHV-7 DNA were detected in saliva and plasma samples using nested PCR, and specific IgG subclasses were determined using immunofluorescent assays of sera samples. HHV-7 DNA was detected in 90% of all plasma samples and in 100% of saliva samples. In contrast, HHV-6 DNA was not detected in any of the plasma samples, and it was detected in only 6 of 40 saliva samples. Determination of IgG subclass distributions showed that HHV-6 was restricted to IgG1, whereas HHV-7 IgG subclasses included two groups, one restricted only to IgG1 and the other to IgG1 and IgG3. These results demonstrate the differences between HHV-6 and HHV-7 DNA range detection in saliva and plasma samples, as well as the IgG subclass patterns for each virus type, in healthy persons in Argentina.

Detection of ß-herpesviruses in Polish adult cord blood stem cell recipients by real-time PCR: single centre study.

Umbilical cord blood transplantation (UCBT) is known to be associated with increased risk of infections, compared to bone marrow or peripheral blood stem cell transplantation. In viral diseases for which specific treatment is available, real-time PCR assays are reliable diagnostic tools for timely initiation of appropriate therapy and for rapid assessment of the efficacy of antiviral treatment strategies. A retrospective review of samples from a group of seven adult cord blood stem cell recipients was made. Serum samples taken up to 180 days after transplantation were examined with quantitative real-time PCR for measurement of viral load (CMV, HHV-6, and HHV-7). Cytomegalovirus (CMV) DNA was detected in samples taken from four patients (57%) in the period of 20-80 days after transplantation. Products of amplification of human herpesvirus 6 (HHV-6) DNA were found in samples taken between days 25 and 37 following UCBT from only one patient (14%). On the other hand, the majority of patients (n = 6, 86%) had HHV-7 DNA detected in the period 15-58 days after transplantation. Co-infection with HHV-7 was demonstrated at onset of all episodes of microbiologically confirmed CMV or HHV-6 infection. Our observations indicate that real-time PCR is not only useful for monitoring herpesviral infections in transplant recipients, but is also a powerful method for clarifying the relationships between the viral load and clinical symptoms. Further investigation with a much larger group of patients will be needed to confirm these observations and translate them into a clinical approach.