Human herpesvirus-6 (HHV-6)-associated hemophagocytic syndrome

Lymphoproliferative Syndromes Associated with Human Herpesvirus-6A and Human Herpesvirus-6B

Human herpesvirus 6A and 6B (HHV-6A and HHV-6B) have been noted since their discovery for their T-lymphotropism. Although it has proven difficult to determine the extent to which HHV-6A and HHV-6B are involved in the pathogenesis of many diseases, evidence suggests that primary infection and reactivation of both viruses may induce or contribute to the progression of several lymphoproliferative disorders, ranging from benign to malignant and including infectious mononucleosis-like illness, drug induced hypersensitivity syndrome/drug reaction with eosinophilia and systemic symptoms (DIHS/DRESS), and nodular sclerosis Hodgkin's lymphoma. Herein, we discuss the conditions associated with the lymphoproliferative capacity of HHV-6, as well as the potential mechanisms behind them. Continued exploration on this topic may add to our understanding of the interactions between HHV-6 and the immune system and may open the doors to more accurate diagnosis and treatment of certain lymphoproliferative disorders.

Pathogenesis of Severe Neutropenia in Patients With Primary Human Herpesvirus 6B Infection

BACKGROUND

Although myelosuppression caused by human herpesvirus 6B (HHV-6B) reactivation in transplant recipients has been extensively investigated, the pathophysiological mechanisms of severe neutropenia in primary HHV-6B infection remain unclear.

PROCEDURE

Fifty-four patients with primary HHV-6B infection were evaluated. Hematological examinations and blood sampling were conducted on days 1-4 (pre) and 5-10 (post) after the onset of illness. Severe neutropenia was defined as a neutrophil count less than 500 cells/μL. Patient characteristics, clinical data, and cytokines and chemokines levels were compared between the patients with (n = 16) and without (n = 38) severe neutropenia.

RESULTS

Severe neutropenia was detected in samples that were collected between days 5 and 10 after illness. Significantly lower platelet counts (pre, P = 0.048; post, P = 0.032) and regulated on activation, normal T cell expressed and secreted levels (post, P = 0.007) were detected in the patients with neutropenia. Aspartate aminotransferase levels (P = 0.008), and interferon γ-inducible protein-10 (P < 0.0001), monocyte chemoattractant protein-1 (P = 0.005), and monokine induced by interferon γ (P = 0.011) levels were significantly higher in post samples collected from the patients with neutropenia. No differences were observed in any patient characteristics and serum cytokines levels. No bacterial infections were detected during the observation period.

CONCLUSIONS

Chemokines may play an important role in the pathogenesis of severe neutropenia in patients with primary HHV-6B infection.

Acute encephalopathy with biphasic seizures and late reduced diffusion associated with hemophagocytic syndrome

We reported a girl with HHV-6 infection associated with both acute encephalopathy with biphasic seizures and late reduced diffusion, and hemophagocytic syndrome. She had a prolonged convulsion after a one-day history of febrile illness. Cerebrospinal fluid or brain CT showed no abnormalities on admission and her consciousness was recovered on the next day. However, a prolonged seizure and deterioration of consciousness appeared on the sixth day of illness. Diffusion-weighted images revealed marked reduction of water diffusion in the bilateral frontal areas. HHV-6 infection was virologically proven by polymerase chain reaction. She was treated with gamma-globulin, steroid pulse therapy, and brain hypothermia. In addition, decrease in white blood cells and platelet counts, and elevation of liver enzymes and ferritin were noted on the fourth day of illness. Hemophagocytic macrophages were revealed by bone marrow aspiration on the sixth day. Her hematological and blood chemistry abnormalities recovered gradually after steroid pulse therapy. An elevation of interleukin-6, -8, and -10, and tumor necrosis factor in the serum and that of interleukin-4, -6, and-8 in the cerebrospinal fluid were observed at the onset of a late seizure. These facts suggested that hypercytokinemia will be related to the pathogenesis of acute encephalopathy of our patient.

Development of hemophagocytic lymphohistiocytosis in triplets infected with HHV-8

Hemophagocytic lymphohistiocytosis (HLH) is a rare disorder of immune dysregulation, characterized by end-organ damage from lymphocytic infiltration and macrophage activation. All known mutations associated with the HLH occur in genes critical in the perforin-granzyme pathway. Herein, we report HLH occurring in 2 female triplet infants who also had associated human herpesvirus type 8 (HHV-8) infections. The subjects had identical novel compound-heterozygous mutations in the Perforin alleles, resulting in undetectable perforin expression and NK-cell cytotoxicity. Both infants also had evidence of infection with HHV-8. These reports are, to our knowledge, the first cases of HLH in triplets and the first reported cases of HHV-8 infection associated with HLH in non-renal transplant and non-HIV-infected subjects.

Update on human herpesvirus 6 biology, clinical features, and therapy

Human herpesvirus 6 (HHV-6) is a betaherpesvirus that is closely related to human cytomegalovirus. It was discovered in 1986, and HHV-6 literature has expanded considerably in the past 10 years. We here present an up-to-date and complete overview of the recent developments concerning HHV-6 biological features, clinical associations, and therapeutic approaches. HHV-6 gene expression regulation and gene products have been systematically characterized, and the multiple interactions between HHV-6 and the host immune system have been explored. Moreover, the discovery of the cellular receptor for HHV-6, CD46, has shed a new light on HHV-6 cell tropism. Furthermore, the in vitro interactions between HHV-6 and other viruses, particularly human immunodeficiency virus, and their relevance for the in vivo situation are discussed, as well as the transactivating capacities of several HHV-6 proteins. The insight into the clinical spectrum of HHV-6 is still evolving and, apart from being recognized as a major pathogen in transplant recipients (as exemplified by the rising number of prospective clinical studies), its role in central nervous system disease has become increasingly apparent. Finally, we present an overview of therapeutic options for HHV-6 therapy (including modes of action and resistance mechanisms).

Human herpesvirus 6: molecular biology and clinical features

Human herpesvirus 6 (HHV-6) exists as distinct variants HHV-6A and HHV-6B. The complete genomes of HHV-6A and HHV-6B have been sequenced. HHV-6B contains 97 unique genes. CD46 is the cell receptor for HHV-6, explaining its broad tissue tropism but its restricted host-species range. HHV-6 utilizes a number of strategies to down-regulate the host immune response, including molecular mimicry by production of a functional chemokine and chemokine receptors. Immunosuppression is enhanced by depletion of CD4 T lymphocytes via direct infection of intra-thymic progenitors and by apoptosis induction. Infection is widespread in infants between 6 months and 2 years of age. A minority of infants develop roseola infantum, but undifferentiated febrile illness is more common. Reactivation from latency occurs in immunocompromised hosts. Organ-specific clinical syndromes occasionally result, but indirect effects including interactions with other viruses such as human immunodeficiency virus type 1 and human cytomegalovirus or graft dysfunction in transplant recipients may be more significant complications in this population. Recent advances in quantitative PCR are providing additional insights into the natural history of infection in paediatric populations and immunocompromised hosts.

Hemophagocytic syndrome associated with multiple myeloma

Hemophagocytic syndrome (HPS) is an uncommon reactive disorder characterized by proliferation of histiocytes that actively engulf other hematopoietic cells causing cytopenia. It complicates several diseases including hematological neoplasias. We report the case of a 54-year-old woman who was admitted to our hospital with fever of unknown origin. Her clinical picture was characterized by renal failure, splenomegaly and pancytopenia. Findings on bone marrow examination showed HPS associated with multiple myeloma. A review of the literature revealed that only one case has previously been published.

[Complex effects of cavinton on climacteric symptoms]

The use of nonhormonal drugs in order to ameliorate climacteric symptoms makes it possible to treat also those women in whom there are some contraindications or lack of compliance for taking hormonal replacement therapy. The drugs with complex effects on the whole body functions are more widely used recently. The aim of the present study is to assess the therapeutic effect of Cavinton (vinpocetin) on the degree of climacteric symptoms and to verify its complex beneficial influence. The study comprises of three groups of women in early menopause--control group (n = 30), treatment groups with normolipidaemia (n = 32) and with hyperlipidaemia (n = 29). All women presented with moderately expressed climacteric symptoms as assessed by Kupperman menopausal index and Hamilton-Anxiety-Skala (HAMA). The women in the 2nd and 3rd groups have been taking Cavinton in an oral dose of 5 mg three times daily for 3 months. The following parameters of lipid metabolism were determined in the beginning and at the end of the study: total, HDL- and LDL-cholesterol, triglycerides, and two indexes of lipid atherogenic risk--total/HDL-cholesterol ratio and atherogenic index (AI) = total--HDL/LDL-cholesterol. The menopausal complaints were assessed by Kupperman index and HAMA. Blood vessels reactivity was determined by pulsation index (PI). Statistically significant decrease in total cholesterol and LDL-cholesterol levels as well as amelioration of atherogenic indexes was observed in the 3rd group. Kupperman index and HAMA decreased significantly on the 45th day and the 3rd month in the women under treatment. No significant changes in PI were observed but a tendency towards a decrease was seen in the 3rd group. Our data suggest that Cavinton possesses complex beneficial effects in climacteric women significantly ameliorating climacteric symptoms as well as some parameters of lipid metabolism in women with hyperlipidaemia.

Haemophagocytic syndrome associated with infections

Haemophagocytic syndromes (HS) are the clinical manifestation of an increased macrophagic activity with haemophagocytosis. Pathophysiology is related to a deregulation of T-lymphocytes and excessive production of cytokines. The main clinicobiological features are fever, hepatosplenomegaly, adenopathies, skin rash, neurological features, cytopenias, hypertriglyceridaemia, hyperferritinaemia and coagulopathy. Diagnosis is based on examination of the bone marrow which shows benign histiocytes actively phagocytosing haemopoietic cells. Acquired HS are mostly associated with an underlying disease such as immunodeficiency, haematological neoplasias and autoimmune diseases. Infection-associated HS was originally described by Risdall in 1979, in viral disease. Since the initial description HS has also been documented in patients with bacterial, parasitic or fungal infections. Epstein-Barr virus (EBV) is the causative agent in most cases. In EBV-associated HS, which sometimes has a fatal course, unregulated T-cell reaction or uncontrolled B-cell proliferation may release cytokines. Management of HS consists of early diagnosis, careful screening for, and prompt treatment of, infections and detection and therapy of any underlying disease. Prognosis of infection-associated haemophagocytic syndrome (IAHS) is better than that in other types of secondary HS. Management of cytokine imbalance should be useful to improve the outcome and reduce the mortality rate in these cases.