Human herpesviruses-6 and -7 infections

Asymptomatic viruses detectable in saliva in the first year of life: a narrative review

Viral infections are common in children. Many can be asymptomatic or have delayed health consequences. In view of increasing availability of point-of-care viral detection technologies, with possible application in newborn screening, this review aimed to (1) identify potentially asymptomatic viruses detectable in infants under one year old, via saliva/nasopharyngeal swab, and (2) describe associations between viruses and long-term health conditions. We systematically searched Embase(Ovid), Medline(Ovid) and PubMed, then further searched the literature in a tiered approach. From the 143 articles included, 28 potentially asymptomatic viruses were identified. Our second search revealed associations with a range of delayed health conditions, with most related to the severity of initial symptoms. Many respiratory viruses were linked with development of recurrent wheeze or asthma. Of note, some potentially asymptomatic viruses are linked with later non-communicable diseases: adenovirus serotype 36 and obesity, Enterovirus-A71 associated Hand, Foot, Mouth Disease and Attention-Deficit Hyperactivity Disorder, Ebstein Barr Virus (EBV) and malignancy, EBV and multiple sclerosis, HHV-6 and epilepsy, HBoV-1 and lung fibrosis and Norovirus and functional gastrointestinal disorders. Our review identified many potentially asymptomatic viruses, detectable in early life with potential delayed health consequences, that could be important to screen for in the future using rapid point-of-care viral detection methods. IMPACT: Novel point-of-care viral detection technologies enable rapid detection of viruses, both old and emerging. In view of increasing capability to screen for viruses, this is the first review to explore which potentially asymptomatic viruses, that are detectable using saliva and/or nasopharyngeal swabs in infants less than one year of age, are associated with delayed adverse health conditions. Further research into detecting such viruses in early life and their delayed health outcomes may pave new ways to prevent non-communicable diseases in the future.

Pregnancy and viral infections: Mechanisms of fetal damage, diagnosis and prevention of neonatal adverse outcomes from cytomegalovirus to SARS-CoV-2 and Zika virus

Some maternal infections, contracted before or during pregnancy, can be transmitted to the fetus, during gestation (congenital infection), during labor and childbirth (perinatal infection) and through breastfeeding (postnatal infection). The agents responsible for these infections can be viruses, bacteria, protozoa, fungi. Among the viruses most frequently responsible for congenital infections are Cytomegalovirus (CMV), Herpes simplex 1–2, Herpes virus 6, Varicella zoster. Moreover Hepatitis B and C virus, HIV, Parvovirus B19 and non-polio Enteroviruses when contracted during pregnancy may involve the fetus or newborn at birth. Recently, new viruses have emerged, SARS-Cov-2 and Zika virus, of which we do not yet fully know the characteristics and pathogenic power when contracted during pregnancy.

Viral infections in pregnancy can damage the fetus (spontaneous abortion, fetal death, intrauterine growth retardation) or the newborn (congenital anomalies, organ diseases with sequelae of different severity). Some risk factors specifically influence the incidence of transmission to the fetus: the timing of the infection in pregnancy, the order of the infection, primary or reinfection or chronic, the duration of membrane rupture, type of delivery, socio-economic conditions and breastfeeding. Frequently infected neonates, symptomatic at birth, have worse outcomes than asymptomatic. Many asymptomatic babies develop long term neurosensory outcomes.

The way in which the virus interacts with the maternal immune system, the maternal-fetal interface and the placenta explain these results and also the differences that are observed from time to time in the fetal‑neonatal outcomes of maternal infections. The maternal immune system undergoes functional adaptation during pregnancy, once thought as physiological immunosuppression. This adaptation, crucial for generating a balance between maternal immunity and fetus, is necessary to promote and support the pregnancy itself and the growth of the fetus. When this adaptation is upset by the viral infection, the balance is broken, and the infection can spread and lead to the adverse outcomes previously described. In this review we will describe the main viral harmful infections in pregnancy and the potential mechanisms of the damages on the fetus and newborn.

Severe herpes virus 6 interstitial pneumonia in an infant with three variants in genes predisposing to lung disease

Infections due to human herpesvirus 6 (HHV-6) are frequent during early childhood. Usually, they have a favorable clinical course. Conversely, HHV-6 congenital infections occur in about 1% of neonates and may present with more severe clinical pictures. HHV-6 can be found in lung tissues and bronchoalveolar lavage (BAL) samples from patients with pneumonia and in immunocompromised patients can cause mild to severe pneumonia. In neonates, the role of HHV-6 in the genesis of severe pneumonia is poorly defined still now. We describe a healthy infant with a late-onset (15 days of life) severe interstitial pneumonia and heavy HHV-6 genome load, persistently detected in its BAL fluid. The baby underwent high-frequency oscillatory ventilation, hydroxychloroquine, steroids, and ganciclovir for 6 weeks and at 9 months she died. Next-generation sequencing of genes known to cause neonatal respiratory insufficiency revealed the presence of a "probably pathogenetic" heterozygous variant in the autosomal recessive DRC1 gene, a heterozygous variant of unknown significance (VUS) in the autosomal recessive RSPH9 gene, and a heterozygous VUS in the autosomal recessive MUC5B gene. HHV-6 infection should be considered in the differential diagnosis of late-onset severe respiratory distress in neonates and the co-occurrence of genetic predisposing factors or modifiers should be tested by specific molecular techniques. The intensity of HHV-6 genome load in BAL fluid could be an indicator of the response to antiviral therapy.

Transcriptome sequencing of neurologic diseases associated genes in HHV-6A infected human astrocyte

Human Herpesvirus 6 (HHV-6) has been involved in the development of several central nervous system (CNS) diseases, such as Alzheimer's disease, multiple sclerosis and glioma. In order to identify the pathogenic mechanism of HHV-6A infection, we carried out mRNA-seq study of human astrocyte HA1800 cell with HHV-6A GS infection. Using mRNA-seq analysis of HA1800-control cells with HA1800-HHV-6A GS cells, we identified 249 differentially expressed genes. After investigating these candidate genes, we found seven genes associated with two or more CNS diseases: CTSS, PTX3, CHI3L1, Mx1, CXCL16, BIRC3, and BST2. This is the first transcriptome sequencing study which showed the significant association of these genes between HHV-6A infection and neurologic diseases. We believe that our findings can provide a new perspective to understand the pathogenic mechanism of HHV-6A infection and neurologic diseases.

Limbic Encephalitis Associated with Human Herpesvirus-7 (HHV-7) in an Immunocompetent Adult: The First Reported Case in Japan

A 35-year-old male who had not previously suffered any major illnesses was admitted to our hospital because of general fatigue, fever, headache, vomiting, consciousness disturbance, and seizures. A neurological examination showed that he was in a semi-comatose state and exhibited neck stiffness. Brain magnetic resonance imaging detected high-intensity areas in the bilateral hippocampi and periventricular white matter. A cerebrospinal fluid examination revealed mononuclear pleocytosis, an elevated protein level, and positivity for human herpesvirus-7 (HHV-7) DNA. The patient's condition improved after the administration of methylprednisolone, intravenous immunoglobulins, and acyclovir. This is the first known case of limbic encephalitis associated with HHV-7 in an immunocompetent Japanese adult.

Piracy on the molecular level: human herpesviruses manipulate cellular chemotaxis

Cellular chemotaxis is important to tissue homeostasis and proper development. Human herpesvirus species influence cellular chemotaxis by regulating cellular chemokines and chemokine receptors. Herpesviruses also express various viral chemokines and chemokine receptors during infection. These changes to chemokine concentrations and receptor availability assist in the pathogenesis of herpesviruses and contribute to a variety of diseases and malignancies. By interfering with the positioning of host cells during herpesvirus infection, viral spread is assisted, latency can be established and the immune system is prevented from eradicating viral infection.

A child with acute encephalopathy associated with quadruple viral infection

Pediatric acute encephalopathy (AE) was sometimes attributed to virus infection. However, viral infection does not always result in AE. The risk factors for developing infantile AE upon virus infection remain to be determined. Here, we report an infant with AE co-infected with human herpesvirus-6 (HHV-6) and three picornaviruses, including coxsackievirus A6 (CVA6), Enterovirus D68 (EV-D68), and human parechovirus (HPeV). EV-D68 was vertically transmitted to the infant from his mother. CVA6 and HPeV were likely transmitted to the infant at the nursery school. HHV-6 might be re-activated in the patient. It remained undetermined, which pathogen played the central role in the AE pathogenesis. However, active, simultaneous infection of four viruses should have evoked the cytokine storm, leading to the pathogenesis of AE.

CONCLUSION

an infant case with active quadruple infection of potentially AE-causing viruses was seldom reported partly because systematic nucleic acid-based laboratory tests on picornaviruses were not common. We propose that simultaneous viral infection may serve as a risk factor for the development of AE.

Roseola infantum and its causal human herpesviruses

Roseola infantum, also known as exanthem subitum or sixth disease, is a generally benign febrile exanthem of infancy. It has a characteristic clinical course of high fever followed by the appearance of an exanthem upon defervescence. Febrile seizures are a frequent complication. Roseola is caused by infection with human herpesviruses 6 or 7 (HHV-6/7), which are acquired at a young age. Diagnosis is made by serology or by virus detection in body fluids and tissues. Treatment of roseola is supportive; recovery is usually complete with no significant sequelae. However, HHV-6/7 can reactivate in immunocompetent as well as immunocompromised individuals with severe systemic consequence.

Acute hepatitis with periportal confluent necrosis associated with human herpesvirus 6 infection in liver transplant patients

OBJECTIVES

To correlate human herpesvirus 6 (HHV-6) viral load with pathologic features in graft acute hepatitis of unknown origin.

METHODS

Liver frozen samples from 26 patients with graft hepatitis of unknown origin were available for HHV-6 DNA quantification.

RESULTS

In 10 (38.5%) of 26 liver samples, HHV-6 DNA was detectable, with a median viral load of 3.84 log10 copies/10⁶ cells. Confluent periportal necrosis was observed in 4 of 10 patients and associated with high viral load. These 4 patients responded to antiviral therapy. Mild unspecific hepatitis was observed in 4 patients with low intragraft viral load and in 2 patients with high viral load in a context of deep immunosuppression. Patients with HHV-6-negative graft hepatitis disclosed lobular necrotico-inflammatory activity without periportal necrosis.

CONCLUSIONS

Our study provides data supporting the pathogenic role of HHV-6 for liver allografts. The presence of confluent periportal necrosis could be a clue for prompt diagnosis of HHV-6-induced graft hepatitis.

Detection of human herpesvirus 7 DNA from the CSF in association with neurosarcoidosis

This study reports a previously healthy, immunocompetent adult male in whom human herpesvirus 7 (HHV-7) DNA was detected continuously from the cerebrospinal fluid (CSF). This patient developed definite sarcoidosis with primary symptomatic manifestations in the central nervous system (CNS). The initial presentation was with loss of visual acuity and papilledema. Brain MR imaging at presentation confirmed papilledema, but otherwise there were no focal abnormalities or signs of hydrocephalus. CSF investigation revealed pleocytosis and elevated protein levels. HHV-7 DNA was detected repeatedly from CSF but not from blood over 1 year follow-up. High resolution computed tomography of lungs was normal. Positron emission tomography showed several metabolically active lymph nodes in the mediastinum, and the histopathological investigation revealed granulomatous inflammation consistent with sarcoidosis. The finding of HHV-7 DNA in the CSF in the context of neurosarcoidosis has not been reported previously. The detection of HHV-7 DNA may result from the selective activation of CD4+ T-lymphocytes in the CSF caused by neurosarcoidosis. Further studies are needed to establish whether the detection of HHV-7 DNA in the CSF in association with neurosarcoidosis represents a clinically significant HHV-7 CNS infection.

Herpesviruses and the microbiome

The focus of this article will be to examine the role of common herpesviruses as a component of the microbiome of atopic patients and to review clinical observations suggesting that atopic patients might be predisposed to more severe and atypical herpes-related illness because their immune response is biased toward a TH2 cytokine profile. Human populations are infected with 8 herpesviruses, including herpes simplex virus HSV1 and HSV2 (also termed HHV1 and HHV2), varicella zoster virus (VZV or HHV3), EBV (HHV4), cytomegalovirus (HHV5), HHV6, HHV7, and Kaposi sarcoma-associated herpesvirus (termed KSV or HHV8). Herpesviruses are highly adapted to lifelong infection of their human hosts and thus can be considered a component of the human "microbiome" in addition to their role in illness triggered by primary infection. HSV1 and HSV2 infection and reactivation can present with more severe cutaneous symptoms termed eczema herpeticum in the atopic population, similar to the more severe eczema vaccinatum, and drug reaction with eosinophilia and systemic symptoms syndrome (DRESS) is associated with reactivation of HSV6 and possibly other herpesviruses in both atopic and nonatopic patients. In this review evidence is reviewed that primary infection with herpesviruses may have an atypical presentation in the atopic patient and conversely that childhood infection might alter the atopic phenotype. Reactivation of latent herpesviruses can directly alter host cytokine profiles through viral expression of cytokine-like proteins, such as IL-10 (EBV) or IL-6 (cytomegalovirus and HHV8), viral encoded and secreted siRNA and microRNAs, and modulation of expression of host transcription pathways, such as nuclear factor κB. Physicians caring for allergic and atopic populations should be aware of common and uncommon presentations of herpes-related disease in atopic patients to provide accurate diagnosis and avoid unnecessary laboratory testing or incorrect diagnosis of other conditions, such as drug allergy or autoimmune disease. Antiviral therapy and vaccines should be administered promptly when indicated clinically.

The microarray technology: facts and controversies

Molecular diagnostic techniques for viral testing have undergone rapid development in recent years. They are becoming more widely used than the classical virological assays in the majority of clinical virology laboratories, and now represent a new method for the diagnosis of human viral infections. Recently, new techniques based on multiplex RT‐PCR amplification followed by microarray analysis have been developed and evaluated. On the basis of amplification of viral genome‐specific fragments by multiplex RT‐PCR and their subsequent detection via hybridization with microorganism‐specific binding probes on solid surfaces, they allow simultaneous detection and identification of multiple viruses in a single clinical sample. The management of viral central nervous system and respiratory tract infections currently represents the two main applications of the microarrays in routine virological practice. Microarrays have shown reliable results in comparison with those of referenced (RT)‐PCR assays, and appear to be of major interest for the detection of a broad range of respiratory and neurotropic viruses, assessment of the pathogenicity of newly discovered or neglected viruses, and identification of multiple viral infections in clinical samples. Despite several limitations observed during the different studies performed, this new technology might improve the clinical management of patients by enlarging the range of the viruses detected, in particular in cases of severe infections leading to patient hospitalization in the intensive‐care unit. They might also help in the prevention of nosocomial transmission in hospital departments by contributing to the development of new epidemiological surveillance systems for viral infections.

Rapid virological diagnosis of central nervous system infections by use of a multiplex reverse transcription-PCR DNA microarray

Viruses are the main etiological cause of central nervous system (CNS) infections. A rapid molecular diagnosis is recommended to improve the therapeutic management of patients. The aim of this study was to evaluate the performances of a DNA microarray, the Clart Entherpex kit (Genomica, Coslada, Spain), allowing the rapid and simultaneous detection of 9 DNA and RNA neurotropic viruses: herpes simplex virus 1 (HSV-1), HSV-2, varicella-zoster virus (VZV), cytomegalovirus (CMV), Epstein-Barr virus (EBV), human herpesvirus 6 (HHV-6), HHV-7, HHV-8, and the human enteroviruses (HEVs). This evaluation was performed with 28 samples from the European proficiency panels (Quality Control for Molecular Diagnostics [QCMD]; Glasgow, Scotland) and then with 78 cerebrospinal fluid (CSF) specimens. The majority of the QCMD results obtained by the DNA microarray were similar to those recorded by the overall QCMD participants. The main discrepant results were observed for low concentrations of HSV-2 and HEVs. From the clinical samples, the kit detected 27 of the 28 herpesvirus CNS infections and all of the 30 HEV-positive CSF samples. No false-positive result was observed among the 20 virus-negative CSF samples. The clinical sensitivity, specificity, and negative and positive predictive values of the assay were 98.3, 100, 95.2, and 100%, respectively, when the results were compared to those of commercially available PCR assays. Interestingly, HHV-7 was detected in 11 (37%) of the 30 HEV-positive CSF samples from children suffering from aseptic meningitis causing significantly longer lengths of stay at the hospital than infection with HEVs alone (2.4 versus 1.4 days; P = 0.038). In conclusion, this preliminary study showed that this DNA microarray could be a valuable molecular diagnostic tool for single and mixed DNA and RNA virus infections of the CNS.

Herpes viruses in transplant recipients: HSV, VZV, human herpes viruses, and EBV

The herpes viruses are responsible for a wide range of diseases in patients following transplant, resulting from direct viral effects and indirect effects, including tumor promotion. Effective treatments and prophylaxis exist for the neurotropic herpes viruses HSV-1, HSV-2, varicella zoster virus, and possibly HHV-6. Antivirals seem to be less effective at prevention of the tumor-promoting effects of Epstein-Barr virus and HHV-8. Reduction in immunosuppression is the cornerstone to treatment of many diseases associated with herpes virus infections.

Human herpesvirus-6 as an inducer of porphyria cutanea tarda: implications from a case

Here we describe a case that might deliver a link between sporadic porphyria cutanea tarda (PCT) and human-herpesvirus-6 (HHV6) hepatitis. Sporadic PCT is a rare disease of the heme synthesis pathway. The pathogenesis has not been fully determined but iron overload and viral infections - e.g., hepatitis C virus - are thought to play an important role. We present the case of a patient suffering from myelo-monocytic leukemia. He developed symptomatic sporadic PCT concomitant with HHV6-associated subclinical hepatitis after allogeneic stem cell transplantation (SCT). Although HHV6 often reactivates after SCT and HHV6-induced hepatitis can occur in immunocompromised patients, it has not been described that HHV6 might trigger PCT. A contribution of HHV6 to the pathogenesis of sporadic PCT could have dramatic implications on our current therapeutic approach.

A high circulating copy number of HHV-6 due to chromosomal integration in a child with acute lymphoblastic leukemia

We report a case of a 3.5-year-old female with a very high copy number of human herpesvirus 6 (HHV-6) detected by PCR in blood during acute lymphoblastic leukemia induction therapy. The patient was unsuccessfully treated with antiviral drugs. HHV-6 genome was shown to be constitutively integrated into chromosome 22q-tel, likely to be inherited from the mother who was found to carry high HHV-6 copy number. This case highlights the importance of excluding HHV-6 chromosomal integration before diagnosing HHV-6 infection or reactivation in immunocompromised patients.

Insight into the mechanism of human herpesvirus 7 U21-mediated diversion of class I MHC molecules to lysosomes

The U21 open reading frame from human herpesvirus-7 encodes a membrane protein that associates with and redirects class I MHC molecules to the lysosomal compartment. The mechanism by which U21 accomplishes this trafficking excursion is unknown. Here we have examined the contribution of localization, glycosylation, domain structure, and the absence of substrate class I MHC molecules on the ability of U21 to traffic to lysosomes. Our results suggest the existence of a cellular protein necessary for U21-mediated rerouting of class I MHC molecules.

Herpesviruses detection by quantitative real-time polymerase chain reaction in bronchoalveolar lavage and transbronchial biopsy in lung transplant: viral infections and histopathological correlation

The monitoring of herpesvirus infection plays a central role in lung transplantation (LT). Herein we evaluated the prevalence of human cytomegalovirus (HCMV), human herpesvirus-6 (HHV-6), human herpesvirus-7 (HHV-7), and Epstein-Barr Virus (EBV) DNA in bronchoalveolar lavage (BAL) and transbronchial biopsy (TBB) specimens from LT patients. We associated the findings with the occurrence of interstitial pneumonia, acute rejection, or organizing pneumonia. Viral DNA was detected using real-time polymerase chain reaction (PCR) on 76 paired samples (BAL and TBB) from 27 patients who were receiving a universal combined prophylaxis (cytomegalovirus [CMV] immunoglobulin [Ig] + gancyclovir or valgancyclovir). Histopathological analysis was performed in accordance with the International Society for Heart and Lung Transplantation (ISHLT) criteria. Overall, HCMV results were positive in 25/76 (32.9%) specimens (BAL and/or TBB); HHV-6 in 16 (21.1%); HHV-7 in 40 (52.6%); and EBV in 13 (17.1%). Interstitial pneumonia was diagnosed in 6/76 (7.9%) cases: 5 (83.3%) were positive to HCMV (combined specimens; P < .0001); 5 (83.3%) to HHV-7; and 2 (33.3%) to EBV. An acute rejection episode was diagnosed in 19/76 (25%) cases: 7 (36.8%) were positive to HCMV; 5 (26.3%) to HHV-6; 10 (52.6%) to HHV-7, and 3 (15.8%) to EBV. No significant association was observed between virus detection or load and acute rejection. Organizing pneumonia was diagnosed in 4/76 (5.3%) cases: 1 (25%) positive to HCMV; 4 (100%) to HHV-6 (P < .05); 2 (50%) to HHV-7; and none to EBV. In conclusion, the prevalence of HCMV tended to be lower than that reported in the literature, confirming the importance of universal combined prophylaxis. HCMV was a relevant agent for interstitial pneumonia; although the small numbers limit the statistical analysis, our data did not support an association between herpesviruses and acute rejection episodes, whereas the role of HHV-6 in the pathogenesis of organizing pneumonia deserves further study. Viral detection on TBB could represent an adjunctive tool to complement that on BAL.

Heterogeneous pathways of maternal-fetal transmission of human viruses (review)

Several viruses can pass the maternal-fetal barrier, and cause diseases of the fetus or the newborn. Recently, however, it became obvious, that viruses may invade fetal cells and organs through different routes without acute consequences. Spermatozoa, seminal fluid and lymphocytes in the sperm may transfer viruses into the human zygotes. Viruses were shown to be integrated into human chromosomes and transferred into fetal tissues. The regular maternal-fetal transport of maternal cells has also been discovered. This transport might implicate that lymphotropic viruses can be released into the fetal organs following cellular invasion. It has been shown that many viruses may replicate in human trophoblasts and syncytiotrophoblast cells thus passing the barrier of the maternal-fetal interface. The transport of viral immunocomplexes had also been suggested, and the possibility has been put forward that even anti-idiotypes mimicking viral epitopes might be transferred by natural mechanisms into the fetal plasma, in spite of the selective mechanisms of apical to basolateral transcytosis in syncytiotrophoblast and basolateral to apical transcytosis in fetal capillary endothelium. The mechanisms of maternal-fetal transcytosis seem to be different of those observed in differentiated cells and tissue cultures. Membrane fusion and lipid rafts of high cholesterol content are probably the main requirements of fetal transcytosis. The long term presence of viruses in fetal tissues and their interactions with the fetal immune system might result in post partum consequences as far as increased risk of the development of malignancies and chronic pathologic conditions are discussed.

Multiplex real-time PCR for the simultaneous detection of herpes simplex virus, human herpesvirus 6, and human herpesvirus 7

A simultaneous detection system to quantify HSV, HHV-6, and HHV-7 DNA via multiplex real-time PCR using different fluorochromes was developed. The minimum quantitative level established via this multiplex assay was four copies per reaction for HSV type 1, four copies for HHV-6, and three copies for HHV-7, respectively. The dynamic range encompassed at least six orders of magnitude. The system was specific and reproducible even in the presence of large amounts of other viral DNA. We then applied this multiplex real-time PCR assay to 105 CSF specimens obtained from subjects less than 15 years old in whom a diagnosis of viral encephalitis/encephalopathy was suspected on clinical grounds. The detection rate for each viral DNA was 6.7% for HSV, 9.5% for HHV-6, and 1.9% for HHV-7. These results indicate that our system is reliable and may be useful for the rapid diagnosis of viral encephalitis/encephalopathy.

The epidemiology of acute encephalitis

Encephalitis means inflammation of the brain matter. Despite being a rare condition, encephalitis is of public health importance worldwide because it has high morbidity and mortality. Yet, many details about its epidemiology have yet to be elucidated. This review attempts to summarise what is known about the epidemiology of the infective causes of encephalitis and is based on a literature search of the Medline archives. Infection is the most common cause identified, with viruses being the most important known aetiological agents. Incidence varies between studies but is generally between 3.5 and 7.4 per 100,000 patient-years. Encephalitis affects peoples of all ages; however, incidence is higher in the paediatric population. Although both sexes are affected, most studies have shown a slight predominance in males. Encephalitis occurs worldwide; some aetiologies have a global distribution (herpesviruses) while others are geographically restricted (arboviruses). Although definite epidemiological trends are evident, it is difficult to make generalisations as few population-based studies exist, most cases are not reported to health authorities, and many possible pathogens are implicated but in most cases a cause is never found. A better understanding of the epidemiology of this devastating disease will pave the way for better prevention and control strategies.

Downregulation of the T-cell receptor complex and impairment of T-cell activation by human herpesvirus 6 u24 protein

We have performed a screen aimed at identifying human herpesvirus 6 (HHV-6)-encoded proteins that modulate immune recognition. Here we show that the U24 protein encoded by HHV-6 variant A downregulates cell surface expression of the T-cell receptor (TCR)/CD3 complex, a complex essential to T-cell activation and the generation of an immune adaptive response. In the presence of U24, the TCR/CD3 complex is endocytosed but is not recycled back to the plasma membrane. Instead, it accumulates in early and late endosomes. Interestingly, whereas CD3 downregulation from the cell surface is normally associated with T-cell activation, U24 downregulates CD3 independently of T-cell activation. Moreover, we found that U24-expressing T cells are resistant to activation by antigen-presenting cells. HHV-6 has evolved a unique mechanism of inhibition of T-cell activation that may impair the establishment of an adaptive immune response. Furthermore, lymphocyte activation creates an environment favorable to the reactivation and replication of lymphotropic herpesviruses. Thus, by inhibiting T-cell activation, HHV-6 might limit its reactivation and thus minimize immune recognition.

Co-infection with Mycoplasma pneumoniae and human herpesvirus 6 (HHV-6) in an immunocompetent child with meningoencephalitis: a random association?

Encephalitis can represent a complication of both Mycoplasma and Human Herpesvirus type 6 infections and, although uncommon, is associated with significant morbidity and mortality. We describe a 13-year-old girl with fever, headache and mental changes with a pattern of concomitant Mycoplasma and Human Herpesvirus-6 infection. The hypothetical relationship between this dual infection and the central nervous system disease is discussed.

Human herpesvirus-6A and -6B encode viral immunoevasins that downregulate class I MHC molecules

Like all other members of the herpesvirus family, the closely related human herpesviruses-6 and -7 (HHV-6,7) persist in their host throughout life. In so doing, without exception, every member of the herpesvirus family has evolved mechanisms to avoid detection by the immune system. In particular, human cytomegalovirus (HCMV), mouse cytomegalovirus (MCMV), human herpesvirus-8 (HHV-8), and herpes simplex virus (HSV) all encode multiple proteins that interfere with proper MHC class I antigen presentation. The mechanisms employed by these viruses to effect removal of MHC class I from the cell surface vary. The U21 open reading frame from HHV-7 diverts class I MHC molecules to an endolysosomal compartment using an as-yet unknown mechanism. The two variants of HHV-6, HHV-6A and -6B, both possess a U21 open reading frame which contain only approximately 30% amino acid identity to the U21 sequence from HHV-7. Here we describe the characterization of the U21 gene products from HHV-6A and HHV-6B. Like HHV-7 U21, both of the HHV-6 U21 molecules bind to and divert class I MHC molecules to an endolysosomal compartment, effectively removing them from the cell surface, and providing a possible means of escape from immune detection.

[Human herpes virus type 6, etiology of an acute encephalitis in childhood: case report]

Primary infection with human herpesvirus-6 (HHV-6) causes the classical roseola infantum. Otherwise the infection is clinically silent but it may sometimes be responsible for central nervous system involvement. In order to illustrate such a type of lesions, we report on a 16-month-old girl with acute leucoencephalitis. The disease started with pyrexia 40 degrees C, followed by an episode of seizure, erythematous rash on the trunk and then coma. Brain MRI showed wide lesions on white matter. HHV-6 DNA was detected by PCR in the CSF and serum at the acute stage, and tests for HHV-6 antibody showed a significant increase of IgG antibody titre between acute and convalescent sera. One month later complete clinical recovery was observed while the MRI showed a partial disappearance of the lesions. The sero-conversion associated with the detection of the viral DNA in the serum identified a primary HHV-6 infection and the detection of viral nucleic acid in CSF gives arguments for the responsibility of the virus in the pathogenesis. When facing an acute leuco-encephalitis in infants, it is important to perform exhaustive virology investigations to rule out the implication of HHV-6 as well as other commonly incriminated pathogens (EBV, CMV, mycoplasma, enterovirus) to avoid accusing wrongly the vaccines.

Childhood viral exanthems

Many viral infections exhibit cutaneous lesions. Recognition of the exanthems associated with these infections and the broader clinical scenarios in which they occur can lead to more rapid diagnosis and appropriate treatment for affected patients.

Human herpesvirus 6 chromosomal integration in immunocompetent patients results in high levels of viral DNA in blood, sera, and hair follicles

Six immunocompetent patients with human herpesvirus 6 (HHV-6) chromosomal integration had HHV-6 and beta-globin DNA quantified in various samples by PCR. The mean HHV-6 DNA concentration (log(10) copies/milliliter) in blood was 7.0 (>/=1 HHV-6 DNA copies/leukocyte), and in serum it was 5.3 (>/=1 HHV-6 DNA copies/lysed cell). The mean HHV-6 DNA load (log(10) copies)/hair follicle was 4.2 (>/=1 copies/hair follicle cell), demonstrating that viral integration is not confined to blood cells. The characteristically high HHV-6 DNA levels in chromosomal integration may confound laboratory diagnosis of HHV-6 infection and should be given due consideration.

Estimating immunoregulatory gene networks in human herpesvirus type 6-infected T cells

The immune response to viral infection involves complex network of dynamic gene and protein interactions. We present here the dynamic gene network of the host immune response during human herpesvirus type 6 (HHV-6) infection in an adult T-cell leukemia cell line. Using a pathway-focused oligonucleotide DNA microarray, we found a possible association between chemokine genes regulating Th1/Th2 balance and genes regulating T-cell proliferation during HHV-6B infection. Gene network analysis using an integrated comprehensive workbench, VoyaGene, revealed that a gene encoding a TEC-family kinase, ITK, might be a putative modulator in the host immune response against HHV-6B infection. We conclude that Th2-dominated inflammatory reaction in host cells may play an important role in HHV-6B-infected T cells, thereby suggesting the possibility that ITK might be a therapeutic target in diseases related to dysregulation of Th1/Th2 balance. This study describes a novel approach to find genes related with the complex host-virus interaction using microarray data employing the Bayesian statistical framework.