Merkel cell polyomavirus and Langerhans cell neoplasm

BACKGROUND

The relationship between various external agents such as pollen, food, and infectious agents and human sensitivity exists and is variable depending upon individual's health conditions. For example, we believe that the pathogenetic potential of the Merkel cell polyomavirus (MCPyV), the resident virus in skin, is variable and depends from the degree of individual's reactivity. MCPyV as well as Epstein-Barr virus, which are normally connected with humans under the form of subclinical infection, are thought to be involved at various degrees in several neoplastic and inflammatory diseases. In this review, we cover two types of Langerhans cell neoplasms, the Langerhans cell sarcoma (LCS) and Langerhans cell histiocytosis (LCH), represented as either neoplastic or inflammatory diseases caused by MCPyV.

METHODS

We meta-analyzed both our previous analyses, composed of quantitative PCR for MCPyV-DNA, proteomics, immunohistochemistry which construct IL-17 endocrine model and interleukin-1 (IL-1) activation loop model, and other groups' data.

RESULTS

We have shown that there were subgroups associated with the MCPyV as a causal agent in these two different neoplasms. Comparatively, LCS, distinct from the LCH, is a neoplastic lesion (or sarcoma) without presence of inflammatory granuloma frequently observed in the elderly. LCH is a proliferative disease of Langerhans-like abnormal cells which carry mutations of genes involved in the RAS/MAPK signaling pathway. We found that MCPyV may be involved in the development of LCH.

CONCLUSION

We hypothesized that a subgroup of LCS developed according the same mechanism involved in Merkel cell carcinoma pathogenesis. We proposed LCH developed from an inflammatory process that was sustained due to gene mutations. We hypothesized that MCPyV infection triggered an IL-1 activation loop that lies beneath the pathogenesis of LCH and propose a new triple-factor model.

Herpes-virus infection in patients with Langerhans cell histiocytosis: a case-controlled sero-epidemiological study, and in situ analysis

Background

Langerhans cell histiocytosis (LCH) is a rare disease that affects mainly young children, and which features granulomas containing Langerhans-type dendritic cells. The role of several human herpesviruses (HHV) in the pathogenesis of LCH was suggested by numerous reports but remains debated. Epstein-barr virus (EBV, HHV-4), & Cytomegalovirus (CMV, HHV-5) can infect Langerhans cells, and EBV, CMV and HHV-6 have been proposed to be associated with LCH based on the detection of these viruses in clinical samples.

Methodology

We have investigated the prevalence of EBV, CMV and HHV-6 infection, the characters of antibody response and the plasma viral load in a cohort of 83 patients and 236 age-matched controls, and the presence and cellular localization of the viruses in LCH tissue samples from 19 patients.

Principal Findings

The results show that prevalence, serological titers, and viral load for EBV, CMV and HHV-6 did not differ between patients and controls. EBV was found by PCR in tumoral sample from 3/19 patients, however, EBV small RNAs EBERs –when positive-, were detected by in situ double staining in bystander B CD20⁺ CD79a⁺ lymphocytes and not in CD1a⁺ LC. HHV-6 genome was detected in the biopsies of 5/19 patients with low copy number and viral Ag could not be detected in biopsies. CMV was not detected by PCR in this series.

Conclusions/Significance

Therefore, our findings do not support the hypothesis of a role of EBV, CMV, or HHV-6 in the pathogenesis of LCH, and indicate that the frequent detection of Epstein-barr virus (EBV) in Langerhans cell histiocytosis is accounted for by the infection of bystander B lymphocytes in LCH granuloma. The latter observation can be attributed to the immunosuppressive micro environment found in LCH granuloma.

Development of Langerhans cell histiocytosis associated with chronic active Epstein-Barr virus infection

Chronic active Epstein-Barr virus (CAEBV) infection is characterized by a status of lymphoproliferative disease of EBV-infected cells, resulting in chronic or recurrent infectious mononucleosis-like symptoms. CAEBV is always accompanied by life-threatening complications. We report the case of a 2-year-old female patient with CAEBV who subsequently developed Langerhans cell histiocytosis (LCH) presenting with bilateral exophthalmos, bone, and skin involvement. In situ hybridization for EBER revealed EBV-infected B-cells present in lesional tissue implying that interactions between EBV-infected B-cells and lesional Langerhans cells may be associated with the development of LCH.

Persistent long-term human herpesvirus 6 (HHV-6) infection in a patient with langerhans cell histiocytosis

Langerhans cell histiocytosis (eosinophilic granuloma) was first diagnosed in the adolescence of a male patient presented. Several years later persisting human herpesvirus 6 (HHV-6) infection was recognized. The HHV-6 infection could be verified retrospectively in his historical histological samples; the continuous presence of HHV-6 could be established through 17 years of disease course. The patient was operated several times during this period for painful relapses, and developed diabetes insipidus. At variable time points during the clinical course, Varicella zoster (VZV), Epstein-Barr virus (EBV) and human herpesvirus 8 (HHV-8) infections were temporarily detected from blood samples and biopsy specimens. HHV-6 was the only virus continuously identified throughout the entire follow-up period. Antiviral therapy effectively cleared EBV and HHV-8, but HHV-6 remained detectable throughout the disease course. Since DNA sequences of HHV-6 could be detected in the pathologic histiocytes of eosinophilic granuloma, and from other samples taken later on, it is suggested that long-term HHV-6 infection may be associated with development or progression of Langerhans cell histiocytosis.

Langerhans cell histiocytosis and human herpes virus 6 (HHV-6), an analysis by real-time polymerase chain reaction

Patients with Langerhans cell histiocytosis (LCH) usually present to orthopedic surgeons because this disease most commonly affects bone. The pathogenesis of LCH is unknown, although roles for environmental, infectious, immunologic, and genetic causes have been postulated. More specifically, there is limited data suggesting that human herpes virus 6 (HHV-6) may be a potential etiologic agent. Frozen biopsy material was obtained from 13 patients with LCH and 20 patients without the disease. After ensuring histologic adequacy of the material, the tissue was tested for HHV-6 by qualitative and quantitative real-time TaqMan PCR. Four of 13 patients with LCH had evidence of HHV-6 DNA in their tissue while 7 of 20 control patients tested positive for HHV-6 genome. Viral loads are reported for the positive patients; no statistical difference was observed in the presence or quantity of HHV-6 DNA found in either population, suggesting that the prevalence of HHV-6 in the tissue of LCH patients is the same as that found in tissue from individuals without disease.

Identical twin brothers concordant for Langerhans' cell histiocytosis and discordant for Epstein-Barr virus-associated haemophagocytic syndrome

We report on identical twin brothers, one of whom presented at 14 months of age with fever and clinical, laboratory and histological evidence of Epstein-Barr virus-associated haemophagocytic syndrome (EBV-AHS) and 4 months later with typical signs and symptoms of Langerhans' cell histiocytosis (LCH). The other twin, without previous symptoms, also displayed at that time LCH associated with signs of recent EBV infection, but without symptoms of haemophagocytic syndrome. No mutation in the SH2D1A gene, as observed in X-linked lymphoproliferative disease, or in the perforin gene as observed in some cases of hereditary haemophagocytic syndrome, was found.

CONCLUSION

the occurrence of haemophagocytic syndrome and Langerhans' cell histiocytosis, although genetically based, can be triggered by environmental agents and viruses, in particular Epstein-Barr virus.

Expression of Epstein-Barr virus in Langerhans? cell histiocytosis*1

Langerhans' cell histiocytosis (LCH) is a proliferative histiocytic disorder of unknown etiology. We previously reported that Epstein-Barr virus (EBV) infects and proliferates in macrophages, and investigated the possibility that EBV exhibits etiologic effects in LCH. To detect EBV expression, paraffin sections from 17 LCH cases were examined by mRNA in situ hybridization for EBV BamHIW, Epstein-Barr virus nuclear antigen-2 (EBNA2), and Epstein-Barr virus-encoded small nonpolyadenylated RNA (EBER1) sequences, and by indirect immunofluorescence staining for EBNA2, latent membrane protein 1 (LMP1), and BamHIZ-coding leftward-reading frame 1 (BZLF1). To detect EBV DNA, polymerase chain reaction (PCR)-Southern blotting was used. All cases showed positive hybridization signals by BamHIW mRNA in situ hybridization. Also, 13 and 14 cases showed positive signals for EBNA2 and EBER1 RNA in situ hybridization, respectively. Furthermore, almost all cases exhibited fluorescence after immunofluorescence staining with monoclonal anti-EBNA2 and anti-BZLF1 antibodies, and 15 cases were positive after treatment with monoclonal anti-LMP1 antibody. PCR-Southern blotting detected an amplified EBER1 sequence in all 9 cases examined. EBV expression was confirmed in LCH using in situ hybridization and immunofluorescence. Furthermore, EBV DNA was also detected by PCR-Southern blotting. These positive results of BZLF1 suggest that EBV replicates in LCH tissues.

Langerhans cell histiocytosis: a primary viral infection of bone? Human herpes virus 6 latent protein detected in lymphocytes from tissue of children

To better understand the etiology of Langerhans cell histiocytosis (LCH), the authors analyzed tissue from 35 children diagnosed with LCH for the presence of viral proteins and DNA by immunohistochemistry (IHC) and in situ hybridization (ISH). Eighteen control biopsies were obtained from patients without LCH. Confirmatory ISH was randomly performed on four positive and two negative cases determined by IHC. Twenty-five (71.4%) tissue samples with LCH involvement stained by IHC with the 101-kDa antibody against human herpesvirus-6 (HHV-6). None were positive with antibodies against the p41/38 or gp110 viral proteins. Five (27.7%) positive control tissues demonstrated presence of the 101-kDa viral protein in a similar fashion. The difference in the prevalence of HHV-6 in LCH-positive tissues (25/35) when compared with control tissues from patients without LCH involvement (5/18) was statistically significant. ISH confirmed the IHC in all six tissues tested. These findings demonstrate an association between HHV-6 and LCH, suggesting a role for the HHV-6B in the etiology of this disease.

Etoposide as the basic and interferon-alpha as the maintenance therapy for Langerhans cell histiocytosis: a RTC

The treatment of patients who suffer from a disseminated form of Langerhans cell histiocytosis (LCH) is still controversial. So far, few larger randomized studies have been performed. The authors present 3 patients with a disseminated form of LCH--4 months, 9 months, and 2 years old, respectively. The lesional Langerhans cells in each patient showed positive immunohistochemical reaction to S-100 protein and the presence of Birbeck granules was confirmed by electron microscopy. All the patients were treated with etoposide (VP-16), 200 mg/m2 for 3 consecutive days, with 15 cycles at intervals of 3 weeks between each cycle, followed by maintenance therapy with IFN-alpha. All 3 patients reached complete stabile remission. The patients were young, at high risk, with multiple-organ involvement of LCH, and two of them had obvious signs of organ dysfunction at presentation, suggesting a poor prognosis. All remain disease-free several years after therapy. The results suggest that INF-alpha may prevent recurrences in high-risk patients.

Evaluation of human herpesvirus type 8 infection in childhood langerhans cell histiocytosis

The etiology of Langerhans cell histiocytosis (LCH) is unknown. Viral causes, including human herpesvirus type 6 (HHV6), have been suggested but remain unproved. The recently discovered human herpesvirus type 8 (HHV8), the cause of Kaposi's sarcoma, infects dendritic cells in the bone marrow associated with multiple myeloma. Evidence for an association of HHV8 infection with LCH in children was studied by two approaches: indirectly by HHV8-specific serologic assays and directly by detection of HHV8 sequences using polymerase chain reaction in affected bone marrow samples. Using three different assays specific for HHV8 antibodies, 3 of 10 (30%) children with LCH had detectable HHV8 antibodies, which was not different from the prevalence of 5 of 30 (17%) in healthy controls of similar age (P = 0.65). Of bone marrow samples from three additional children with LCH, all had amplifiable DNA but were negative for HHV8 sequences. These studies of a small number of patients do not demonstrate an increased prevalence of HHV8 infection in children with LCH, and they do not suggest a causal role for HHV8 in the etiology of LCH.

Human cytomegalovirus infection in foci of Langerhans cell histiocytosis

Langerhans cell histiocytosis (LCH) has been thought to be a disorder of immune regulation, and increasingly, evidence showing that the tissue damage in LCH involves lymphokines and pro-inflammatory cytokines is reported. We detected human cytomegalovirus (HCMV)-DNA in LCH cells in the foci of LCH lesions by immunohistochemistry, in situ hybridization and PCR. HCMV was detected in the nuclei and/or cytoplasm of LCH cells in 9 of 27 LCH cases by immunostaining. HCMV was probably an early antigen. In situ hybridization revealed signals for HCMV-DNA only in the nuclei of LCH cells in 10 of the 27 LCH cases. PCR analysis was performed in 20 of the LCH cases, and HCMV-DNA was detected in 7 of these. All 7 positive cases were also positive for HCMV by ISH and IHC. These findings suggested that early phase infection or reactivation of HCMV occurred in the LCH lesions. HCMV infection may be accompanied by impaired cytokine production. Our study also suggested a relationship between HCMV infection and expression of TNFalpha. In tissues affected by LCH, dermatopathic lymphadenopathy or malignant fibrous histiocytoma and in normal tissues no signals for Epstein-Barr virus-RNA were detected. These findings suggest that in some cases LCH is associated with HCMV infection.

An update on clonality, cytokines, and viral etiology in Langerhans cell histiocytosis

Many etiologies have been proposed for Langerhans cell histiocytosis (LCH). Recent scientific studies have clearly provided new insights into the etiology and pathogenesis of the disease. The possible role of viruses has not been completely negated, but no viral genomes have been consistently detected in LCH lesions. Other studies do not indicate that LCH arises from a primary defect in the immune system, although altered immune responses and immune dysfunction may play a role in the pathophysiology of the disease. Definitive results have been gained from molecular studies of clonality, however. These have definitively established that LCH is a clonal histiocytic disease rather than a reactive polyclonal disorder.

Ultrastructural studies in Langerhans cell histiocytosis: a search for evidence of viral etiology

The ultrastructure of lesional cells in biopsy material from 50 cases of Langerhans cell histiocytosis (LCH) was studied for the effects of virus and/or cytokines. Viral "footprints," which actually represent ultrastructural signs of the effects of cytokines on cells, were found in 76% of the cases. These were detected in lesional Langerhans cells, endothelial cells, and lymphocytes and consisted of tubuloreticular structures, cylindrical confronting cisternae, and curvilinear membranous formations. No virus particles or virus-specific cell products were found. These studies suggest that LCH cells are subject to cytokine stimulation but provide no evidence to implicate a virus in the disease process.