Human herpesvirus-6 infection in children with cancer

Frequency and clinical impact of viraemia in paediatric patients undergoing therapy for cancer

In contrast to transplant recipients, there is a paucity of data regarding frequency and clinical significance of viraemia in children receiving conventional chemotherapy. In a prospective observational study, we assessed the frequency of and clinical impact of viraemia with cytomegalovirus (CMV), Epstein-Barr virus (EBV), adenovirus, human herpesvirus-6 (HHV6) and herpes-simplex virus 1/2 (HSV1/2) in paediatric cancer patients at diagnosis, at a routine examination during intensive chemotherapy, and during febrile neutropenia (FN). Seventy-nine patients (median age 6 years; 66 children with haematological malignancies) were included in the study. Overall, 362 blood samples were analysed, 72 from the time at diagnosis (11.1% with positive PCR result), 118 during a regular control after chemotherapy (11.0% positive), and 159 during FN (8.8% positive). The overall positivity rate was 9.6% (CMV 3.3%, HHV6 2.7%, HSV 2.2%, EBV 0.8% and adenovirus 0.3%). There were no significant differences between FN episodes with and without viraemia in terms of duration of fever or neutropenia/lymphopenia, severity of mucositis (> II0), incidence of diarrhea and ICU admission. Our results indicate that viraemia in paediatric cancer patients generally does not have a major clinical impact, and may help in the decision regarding the indication of routine evaluation for viraemia in febrile neutropenic, but otherwise asymptomatic children.

Comparative Analysis of Roseoloviruses in Humans, Pigs, Mice, and Other Species

Viruses of the genus Roseolovirus belong to the subfamily Betaherpesvirinae, family Herpesviridae. Roseoloviruses have been studied in humans, mice and pigs, but they are likely also present in other species. This is the first comparative analysis of roseoloviruses in humans and animals. The human roseoloviruses human herpesvirus 6A (HHV-6A), 6B (HHV-6B), and 7 (HHV-7) are relatively well characterized. In contrast, little is known about the murine roseolovirus (MRV), also known as murine thymic virus (MTV) or murine thymic lymphotrophic virus (MTLV), and the porcine roseolovirus (PRV), initially incorrectly named porcine cytomegalovirus (PCMV). Human roseoloviruses have gained attention because they can cause severe diseases including encephalitis in immunocompromised transplant and AIDS patients and febrile seizures in infants. They have been linked to a number of neurological diseases in the immunocompetent including multiple sclerosis (MS) and Alzheimer's. However, to prove the causality in the latter disease associations is challenging due to the high prevalence of these viruses in the human population. PCMV/PRV has attracted attention because it may be transmitted and pose a risk in xenotransplantation, e.g., the transplantation of pig organs into humans. Most importantly, all roseoloviruses are immunosuppressive, the humoral and cellular immune responses against these viruses are not well studied and vaccines as well as effective antivirals are not available.

HHV-6B infection, T-cell reconstitution, and graft-vs-host disease after hematopoietic stem cell transplantation

Successful and sustained CD4⁺ T-cell reconstitution is associated with increased survival after hematopoietic cell transplantation (HCT), but opportunistic infections may adversely affect the time and extent of immune reconstitution. Human herpesvirus 6B (HHV-6B) efficiently infects CD4⁺ T cells and utilizes as a receptor CD134 (OX40), a member of the TNF superfamily that antagonizes regulatory T-cell (T_reg) activity. Reactivation of HHV-6B has been associated with aberrant immune reconstitution and acute graft-versus-host disease (aGVHD) after HCT. Given that T_reg counts are negatively correlated with aGVHD severity, we postulate that one mechanism for the poor CD4⁺ T-cell reconstitution observed shortly after transplant may be HHV-6B infection and depletion of peripheral (extra-thymic) CD4⁺ T cells, including a subpopulation of T_reg cells. In turn, this may trigger a series of adverse events resulting in poor clinical outcomes such as severe aGVHD. In addition, recent evidence has linked HHV-6B reactivation with aberrant CD4⁺ T-cell reconstitution late after transplantation, which may be mediated by a different mechanism, possibly related to central (thymic) suppression of T-cell reconstitution. These observations suggest that aggressive management of HHV-6B reactivation in transplant patients may facilitate CD4⁺ T-cell reconstitution and improve the quality of life and survival of HCT patients.

Human Herpesvirus-6B Reactivation Is a Risk Factor for Grades II to IV Acute Graft-versus-Host Disease after Hematopoietic Stem Cell Transplantation: A Systematic Review and Meta-Analysis

Graft-versus-host disease (GVHD) is an important cause of morbidity and mortality after allogeneic hematopoietic cell transplantation (HCT). Many studies have suggested that human herpesvirus-6B (HHV-6B) plays a role in acute GVHD (aGVHD) after HCT. Our objective was to systematically summarize and analyze evidence regarding HHV-6B reactivation and development of aGVHD. PubMed and EMBASE databases were searched using terms for HHV-6, HCT, and aGVHD, yielding 865 unique results. Case reports, reviews, articles focusing on inherited chromosomally integrated HHV-6, poster presentations, and articles not published in English were excluded. The remaining 467 articles were reviewed for the following requirements: a statistical analysis of HHV-6B reactivation and a GVHD was described, HHV-6B reactivation was defined by PCR, and blood (plasma, serum, or peripheral blood mononuclear cells) was used for HHV-6B PCR. Data were abstracted from publications that met these criteria (n = 33). Publications were assigned to 1 of 3 groups: (1) HHV-6B reactivation was analyzed as a time-dependent risk factor for subsequent aGVHD (n = 14), (2) aGVHD was analyzed as a time-dependent risk factor for subsequent HHV-6B reactivation (n = 1), and (3) analysis without temporal specification (n = 18). A statistically significant association (P < .05) between HHV-6B reactivation and aGVHD was observed in 10 of 14 studies (71%) in group 1, 0 of 1 study (0%) in Group 2, and 8 of 18 studies (44.4%) in Group 3. Of the 14 studies that analyzed HHV-6B as a risk factor for subsequent aGVHD, 11 performed a multivariate analysis and reported a hazard ratio, which reached statistical significance in 9 of these s tudies. Meta-analysis of these 11 studies demonstrated a statistically significant association between HHV-6B and subsequent grades II to IV aGVHD (hazard ratio, 2.65; 95% confidence interval, 1.89 to 3.72; P < .001).HHV-6B reactivation is associated with aGVHD, and when studies have a temporal component to their design, HHV-6B reactivation is associated with subsequent aGVHD. Further research is needed to investigate whether antiviral prophylaxis reduces incidence or severity of aGVHD.

Absence of human herpesvirus 6B detection in association with illness in children undergoing cancer chemotherapy

The lymphotropic herpesviruses, cytomegalovirus (CMV), Epstein-Barr virus (EBV), and human herpesvirus 6B (HHV-6B) can reactivate and cause disease in organ transplant recipients; the contributions of HHV-6A and HHV-7 to disease are less certain. Less is known about their pathogenic roles in children undergoing treatment for malignancies. Children with newly diagnosed cancer were followed for 24 months. Clinical information and blood samples were collected during routine visits and during acute visits for fever or possible viral infections. Lymphotropic herpesvirus DNA in blood was measured by polymerase chain reaction (PCR). Although HHV-6B DNA was detected at least once in about half of the patients; the other viruses were seldom detected. There was no association between HHV-6B detection and individual acute clinical events, however, HHV-6B detection was more common in children who experienced more frequent acute clinical events. In children being treated for various malignancies, HHV-6B detection was common, but was not associated with individual events of acute illness. Thus, if HHV-6B is not assessed longitudinally, clinical events may be misattributed to the virus. The elevated frequency of detection of HHV-6B in sicker children is consistent with prior reports of its detection during apparently unrelated acute clinical events. J. Med. Virol. 88:1427-1437, 2016. © 2016 Wiley Periodicals, Inc.

The roles of viruses in brain tumor initiation and oncomodulation

While some avian retroviruses have been shown to induce gliomas in animal models, human herpesviruses, specifically, the most extensively studied cytomegalovirus, and the much less studied roseolovirus HHV-6, and Herpes simplex viruses 1 and 2, currently attract more and more attention as possible contributing or initiating factors in the development of human brain tumors. The aim of this review is to summarize and highlight the most provoking findings indicating a potential causative link between brain tumors, specifically malignant gliomas, and viruses in the context of the concepts of viral oncomodulation and the tumor stem cell origin.

Beta-herpesviruses in febrile children with cancer

We conducted a cross-sectional study of beta-herpesviruses in febrile pediatric oncology patients (n = 30), with a reference group of febrile pediatric solid-organ transplant recipients (n = 9). One (3.3%) of 30 cancer patients and 3 (33%) of 9 organ recipients were PCR positive for cytomegalovirus. Four (13%) of 30 cancer patients and 3 (33%) of 9 transplant recipients had human herpesvirus 6B (HHV-6B) DNAemia, which was more common within 6 months of initiation of immune suppression (4 of 16 vs. 0 of 14 cancer patients; p = 0.050). HHV-6A and HHV-7 were not detected. No other cause was identified in children with HHV-6B or cytomegalovirus DNAemia. One HHV-6B-positive cancer patient had febrile disease with concomitant hepatitis. Other HHV-6B-positive children had mild "viral" illnesses, as did a child with primary cytomegalovirus infection. Cytomegalovirus and HHV-6B should be included in the differential diagnosis of febrile disease in children with cancer.

Human herpesvirus 6B infection of the large intestine of patients with diarrhea

Four patients had severe diarrhea after undergoing stem cell transplantation. Human herpesvirus 6B (HHV-6B) DNA was detected in large intestine tissue specimens and in peripheral blood mononuclear cells. In situ hybridization was positive for HHV-6B DNA in the nuclei of goblet cells and, sometimes, in the histiocytes in the submucous region of the large intestine, which suggests that HHV-6B may infect and reactivate in these cells.

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.

Screening for herpesvirus genomes in common acute lymphoblastic leukemia

There is epidemiological evidence that infection may play a role in the etiology of childhood leukemia in particular common B cell precursor acute lymphoblastic leukemia. A panel of 20 leukemic samples (panel 1) was examined for the presence of four lymphotropic herpesviruses using conventional molecular techniques. A second independent panel of 27 leukemic samples (panel 2), along with 28 control peripheral blood samples from children with other forms of cancer, was tested for the presence of the same four viruses using sensitive real-time quantitative PCR. While herpesvirus genomes were detected, they were present at very low levels; detection rates and levels were similar in the leukemic and control panels. In addition we surveyed 18 leukemic samples (five from panel 1, six from panel 2 and a further seven samples not previously analyzed) using a degenerate PCR assay capable of detecting the genomes of known herpesviruses plus putative new members of the family. No novel herpesvirus genomes were detected suggesting that a herpesvirus is unlikely to be etiologically involved as a transforming agent in common acute lymphoblastic leukemia.