Antibody status to HHV-6 in children with leukaemia

DNA damage signalling from the placenta to foetal blood as a potential mechanism for childhood leukaemia initiation

For many diseases with a foetal origin, the cause for the disease initiation remains unknown. Common childhood acute leukaemia is thought to be caused by two hits, the first in utero and the second in childhood in response to infection. The mechanism for the initial DNA damaging event are unknown. Here we have used in vitro, ex vivo and in vivo models to show that a placental barrier will respond to agents that are suspected of initiating childhood leukaemia by releasing factors that cause DNA damage in cord blood and bone marrow cells, including stem cells. We show that DNA damage caused by in utero exposure can reappear postnatally after an immune challenge. Furthermore, both foetal and postnatal DNA damage are prevented by prenatal exposure of the placenta to a mitochondrially-targeted antioxidant. We conclude that the placenta might contribute to the first hit towards leukaemia initiation by bystander-like signalling to foetal haematopoietic cells.

Human Herpesvirus 6 and Malignancy: A Review

In order to determine the role of human herpesvirus 6 (HHV-6) in human disease, several confounding factors, including methods of detection, types of controls, and the ubiquitous nature of the virus, must be considered. This is particularly problematic in the case of cancer, in which rates of detection vary greatly among studies. To determine what part, if any, HHV-6 plays in oncogenesis, a review of the literature was performed. There is evidence that HHV-6 is present in certain types of cancer; however, detection of the virus within tumor cells is insufficient for assigning a direct role of HHV-6 in tumorigenesis. Findings supportive of a causal role for a virus in cancer include presence of the virus in a large proportion of cases, presence of the virus in most tumor cells, and virus-induced in-vitro cell transformation. HHV-6, if not directly oncogenic, may act as a contributory factor that indirectly enhances tumor cell growth, in some cases by cooperation with other viruses. Another possibility is that HHV-6 may merely be an opportunistic virus that thrives in the immunodeficient tumor microenvironment. Although many studies have been carried out, it is still premature to definitively implicate HHV-6 in several human cancers. In some instances, evidence suggests that HHV-6 may cooperate with other viruses, including EBV, HPV, and HHV-8, in the development of cancer, and HHV-6 may have a role in such conditions as nodular sclerosis Hodgkin lymphoma, gastrointestinal cancer, glial tumors, and oral cancers. However, further studies will be required to determine the exact contributions of HHV-6 to tumorigenesis.

A systematic review and meta-analysis of the association between childhood infections and the risk of childhood acute lymphoblastic leukaemia

Background:

To determine whether childhood infections were associated with the development of childhood acute lymphoblastic leukaemia (ALL).

Methods:

We included studies that assessed any infection in childhood prior to the diagnosis of ALL in children aged 0–19 years compared to children without cancer. The primary analysis synthesised any infection against the odds of ALL, and secondary analyses assessed the frequency, severity, timing of infections, and specific infectious agents against the odds of ALL. Subgroup analyses by data source were investigated.

Results:

In our primary analysis of 12 496 children with ALL and 2 356 288 children without ALL from 38 studies, we found that any infection was not associated with ALL (odds ratio (OR)=1.10, 95% CI: 0.95–1.28). Among studies with laboratory-confirmed infections, the presence of infections increased the odds of ALL by 2.4-fold (OR=2.42, 95% CI: 1.54–3.82). Frequency, severity, and timing of infection were not associated with ALL.

Conclusions:

The hypothesis put forward by Greaves and others about an infectious aetiology are neither confirmed nor refuted and the overall evidence remains inadequate for good judgement. The qualitative difference in the subgroup effects require further study, and future research will need to address the challenges in measuring infectious exposures.

The seroprevalence of Kaposi's sarcoma associated herpes virus and human herpes virus-6 in pediatric patients with cancer and healthy children in a Turkish pediatric oncology center

BACKGROUND

Many studies have tried to be establish a pathogenic role for human herpesvirus-6 and -8 (HHV-6, HHV-8) in malignant diseases, but whether these viruses plays a role in these pathologies remains unclear. HHV-6 and HHV-8 seropositivity were shown in a healthy population. There is no published data in Turkey about seroprevalence of these viruses. We aimed to determine the seroprevalence of HHV-6 and HHV-8 in pediatric cancer patients and to compare with healthy Turkish children's viral seroprevalence.

PATIENTS AND METHODS

Ninety-three pediatric cancer patients and 43 age-matched healthy children were included in the study. All sera were screened for antibodies to HHV-6 and HHV-8 by ELISA.

RESULTS

HHV-8 immunoglobulin G (IgG) was positive in 3.3% of lymphoma patients, in 4.8% of acute lymphoblastic leukemia (ALL) patients, in 4.8% of retinoblastoma patients and in 7% of healthy children. There was no significant difference in HHV-8 seroprevelance between these groups. HHV-6 seroprevalence was 81% in ALL patients, 70% in lymphoma group, 81% in retinoblastoma patients and 69.8% in healthy children. Although there was no significant difference in HHV-6 prevalence between healthy children and pediatric cancer patients, HHV-6 seropositivity tended to be higher in retinoblastoma patients under age of 4 years (odds ratio: 2.925).

CONCLUSION

HHV-6 seroprevalence was higher than HHV-8 seropositivity in our study. Viral studies related HHV-6 seroprevelance in retinoblastoma patients would be useful to clarify if there is any etiological association between HHV-6 and retinoblastoma.

EBV, HCMV, HHV6, and HHV7 screening in bone marrow samples from children with acute lymphoblastic leukemia

Acute lymphoblastic leukemia (ALL) is the most common cancer in childhood worldwide and Mexico has reported one of the highest incidence rates. An infectious etiology has been suggested and supported by epidemiological evidences; however, the identity of the involved agent(s) is not known. We considered that early transmitted lymphotropic herpes viruses were good candidates, since transforming mechanisms have been described for them and some are already associated with human cancers. In this study we interrogated the direct role of EBV, HCMV, HHV6, and HHV7 human herpes viruses in childhood ALL. Viral genomes were screened in 70 bone marrow samples from ALL patients through standard and a more sensitive nested PCR. Positive samples were detected only by nested PCR indicating a low level of infection. Our result argues that viral genomes were not present in all leukemic cells, and, hence, infection most likely was not part of the initial genetic lesions leading to ALL. The high statistical power of the study suggested that these agents are not involved in the genesis of ALL in Mexican children. Additional analysis showed that detected infections or coinfections were not associated with prognosis.

β-HHVs and HHV-8 in Lymphoproliferative Disorders

Similarly to Epstein-Barr virus (EBV), the human herpesvirus-8 (HHV-8) is a γ-herpesvirus, recently recognized to be associated with the occurrence of rare B cell lymphomas and atypical lymphoproliferations, especially in the human immunodeficiency virus (HIV) infected subjects. Moreover, the human herpesvirus-6 (HHV-6), a β-herpesvirus, has been shown to be implicated in some non-malignant lymph node proliferations, such as the Rosai Dorfman disease, and in a proportion of Hodgkin’s lymphoma cases. HHV-6 has a wide cellular tropism and it might play a role in the pathogenesis of a wide variety of human diseases, but given its ubiquity, disease associations are difficult to prove and its role in hematological malignancies is still controversial. The involvement of another β-herpesvirus, the human cytomegalovirus (HCMV), has not yet been proven in human cancer, even though recent findings have suggested its potential role in the development of CD4⁺ large granular lymphocyte (LGL) lymphocytosis. Here, we review the current knowledge on the pathogenetic role of HHV-8 and human β-herpesviruses in human lymphoproliferative disorders.

Human herpesvirus 6 in hematological malignancies

Pathogenetic roles of human herpesvirus (HHV)-6 in lymphoproliferative diseases have been of continued interest. Many molecular studies have tried to establish a pathogenic role for HHV-6 in lymphoid malignancies. However, whether HHV-6 plays a role in these pathologies remains unclear, as positive polymerase chain reaction results for HHV-6 in those studies may reflect latent infection or reactivation rather than presence of HHV-6 in neoplastic cells. A small number of studies have investigated HHV-6 antigen expression in pathologic specimens. As a result, the lack of HHV-6 antigen expression on neoplastic cells argues against any major pathogenic role of HHV-6. The role of HHV-6 in childhood acute lymphoblastic leukemia (ALL) has also been of interest but remains controversial, with 2 studies documenting higher levels of HHV-6 antibody in ALL patients, and another 2 large-scale studies finding no significant differences in HHV-6 seroprevalences between ALL patients and controls. Alternatively, HHV-6 is increasingly recognized as an important opportunistic pathogen. HHV-6 reactivation is common among recipients of allogeneic stem cell transplantation (SCT), and is linked to various clinical manifestations. In particular, HHV-6 encephalitis appears to be significant, life-threatening complication. Most HHV-6 encephalitis develops in patients receiving transplant from an unrelated donor, particularly cord blood, typically around the time of engraftment. Symptoms are characterized by short-term memory loss and seizures. Magnetic resonance imaging typically shows limbic encephalitis. Prognosis for HHV-6 encephalitis is poor, but appropriate prophylactic measures have not been established. Establishment of preventive strategies against HHV-6 encephalitis represents an important challenge for physicians involved with SCT.

IgM and avidity of IgG antibodies in primary HHV-6 infections

Primary HHV-6 infection could be diagnosed by enzyme immunoassay from a single serum using IgG avidity test based on results obtained from 43 patients, 26 with seroconversion and 17 with variable antibody levels. The avidity was less than 30% in all patients with seroconversion. HHV-6 IgM appeared non-specific.

[HHV-6 infection and acute lymphoblastic leukemia in a child]

We report the case of a child who was infected by HHV-6 and who started an acute lymphoblastic leukemia two months later. This case reminds that an etiologic role have been suggested for many viral infections in some leukemias in childhood, particularly the human herpesvirus 6 (HHV-6).

Evidence for human herpesvirus 6 variant A antibodies in multiple sclerosis: diagnostic and therapeutic implications

Human herpesvirus 6 (HHV-6) has been linked to the pathogenesis of multiple sclerosis (MS). HHV-6 antibodies in serum and cerebrospinal fluid (CSF) of 27 patients with clinically definite MS (CDMS) were compared with age- and sex-matched controls, including various other neurological diseases and symptoms (OND). In addition, we studied a series of 19 patients with clinically or laboratory supported possible MS (CPMS). Seroprevalence to HHV-6A was 100% in patients with MS, both in CDMS and CPMS, compared to 69.2% in patients with OND (P = .001 and .007). The mean immunoglobulin G (IgG) titers were significantly higher in patients with CDMS and CPMS than in controls (P = .005 and .00002). The proportion of acute primary infections without CSF involvement was similar in all groups; however, primary infections with intrathecal HHV-6 antibody production were more frequent in MS. In CSF, HHV-6A-specific antibodies were present in three (11.5%) and four (21.1%) patients with CDMS and CPMS, compared to none with OND (P = .06 and .01, respectively). Serological suggestions to HHV-6A infection occurred more often in both CDMS and CPMS than in OND (14.8% versus 21.1% versus 3.8%). We conclude that a subpopulation of MS patients, and even a greater proportion of possible MS subjects, has serological evidence of HHV-6A infection, which might provide new markers for diagnosis and therapy.

Antibodies against six human herpesviruses in relation to seven cancers in black South Africans: a case control study

Background

Infections with certain human herpesviruses have been established as risk factors for some cancer types. For example, Epstein-Barr Virus is considered a cause of Burkitt's lymphoma and other immunosuppression related lymphomas, Hodgkin lymphoma, and nasopharyngeal cancer. Several other human herpesviruses have been linked to cancers but the totality of evidence is inconclusive.

Methods

We conducted a systematic sub-study from within an ongoing case control study of adult black South Africans to investigate the relationship between antibodies to six human herpesviruses and seven cancer groups that may be caused by infectious agents. Subjects had incident cancers of the oral cavity(n = 88), the cervix(n = 53), the prostate(n = 66), Hodgkin lymphoma(n = 83), non-Hodgkin lymphoma(n = 80), multiple myeloma(n = 94) or leukaemia(n = 203). For comparison, patients with other cancers(n = 95) or cardiovascular disease(n = 101) were randomly selected from within the study. Patients were interviewed and their blood was tested for IgG antibodies against HSV-1, HSV-2, VZV, EBV-EBNA, CMV and HHV-6 using enzyme linked immunosorbent assays. Because these viruses are highly prevalent in this population, optical density results from the assays were used as an indirect, quantitative measure of antibody level.

Results

There was significant variation in the mean log antibody measures for HSV-2, VZV, CMV and HHV-6 between the disease groups. However, none of the specific cancer groups had significantly higher mean log antibody measures for any of the viruses compared to either control group. In a more detailed examination of seven associations between cancers and herpesviruses for which there had been prior reports, two statistically significant associations were found: a decreasing risk of myeloid leukaemia and an increasing risk of oral cancer with increasing tertiles of antibodies against HHV-6 compared to all other patients (p-trend = 0.03 and 0.02, respectively). Odds ratios for the top tertile compared to the bottom tertile were 0.58 (95%CI 0.3 – 1.0) for myeloid leukaemia and 2.21 (95% CI 1.1 – 4.3) for oral cancer.

Conclusion

In this population, using these tests for IgG, neither mean antibody measure nor high antibody measure against human herpesviruses 1–6 was strongly associated with any of the seven cancer groups. However, we may not have had sufficient power to detect weak associations or associations with a sub-type of cancer if they were present.

Human herpes virus 6 or Epstein-Barr virus were not detected in Guthrie cards from children who later developed leukaemia

To investigate if children who later developed acute lymphoblastic leukaemia (ALL) were prenatally infected with HHV-6 and/or EBV, Guthrie cards taken at birth were analysed by PCR. Guthrie cards from 54 patients with ALL and 47 healthy controls matched for age and birth place were tested negative for both HHV-6 and EBV DNA. All samples contained amplifiable DNA when tested by HLA-DQ PCR. Our negative findings suggest that childhood ALL is unlikely to be associated with an in utero infection with EBV or HHV-6.

Human herpesvirus 6 (HHV6) infection

Human herpes virus-6 was first reported in 1986 and is the sixth member of the herpes virus family. HHV-6 consists of two closely related variants HHV-6A and HHV-6B. The majority of infections occur in healthy infants with most infections caused by HHV-6B. The virus preferentially infects CD4+T-lymphocytes and the surface marker CD46 acts as a co-receptor. Infection is followed by persistence and latency in different cells and organs including monocytes/macrophages, salivary glands, the brain and the kidneys. In this article we will discuss the clinical manifestations of HHV-6 infection in healthy children and the syndromes associated with HHV-6 reactivation in immunocompromised patients. Evidence of association between HHV-6 infection and different clinical entities such as multiple sclerosis, malignancy, infectious momononucleosis, drug hypersensitivity syndromes and skin eruptions is discussed. Published data on the use and efficacy of antiviral agents in complicated infections and infections in immunocompromised patients is presented.