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Human herpesvirus 6 (HHV-6) is a highly neuro- and lymphotropic virus with an increasing number of diseases associated with it. Most children are infected at the age of 6 to 15 months. Primary infection manifests classically as exanthema subitum. This is, however, only one aspect of the clinical spectrum of the disease. Neurological symptoms are common and the virus may persist in several tissues and cells and be reactivated in various immunosuppressive conditions. In addition, HHV-6 may be involved in many chronic diseases. The two variants HHV-6A and HHV-6B appear to have different disease associations. To conclude, diseases associated with or caused by HHV-6 seem to expand. HHV-6 needs attention and active research both in children and in adults.

Background: Two human herpesviruses, human herpesvirus 6 (HHV-6), and Epstein-Barr virus (EBV), have been repeatedly linked to multiple sclerosis (MS). Objective: The aim of this study was to investigate HHV-6 and EBV reactive oligoclonal bands (OCBs), and viral DNA in the intrathecal compartment in MS. Methods: The reactivity of OCBs in cerebrospinal fluid (CSF) for EBV and HHV-6 antigens and stability of virus reactive OCBs over time were studied in a well-characterized MS patient cohort. Associations between virus reactive OCBs and viral DNA in CSF (and any clinical and/or radiological findings) were investigated. Results: Of patients with MS, 38% had OCBs reactive to either one of the viruses studied, compared to none in the patients with other inflammatory neurological diseases ( p=0.005). The banding pattern of virus reactive OCBs remained the same over time. Furthermore, MS patients with viral DNA in CSF had more contrast enhancing lesions (CELs). Conclusion: The stable presence of herpesvirus reactive OCBs in CSF further strengthens the association of MS with these viruses. The finding that herpesviruses might be linked to the appearance of active lesions warrants investigation of new therapeutic strategies to treat these viruses in MS.

Demyelinating diseases of the central nervous system (CNS) often include elevated IgG production in intrathecal space presenting as oligoclonal bands (OCBs) in cerebrospinal fluid (CSF). In most demyelinating diseases, e.g. in multiple sclerosis (MS), the underlying cause is not known. We used isoelectric focusing and affinity immunoblot to study the specificity of CSF OCBs to human herpesvirus-6 (HHV-6) in patients with demyelinating diseases of the CNS including MS. Eighty patients with positive OCB finding were included in the study. The OCBs reacted with the HHV-6 antigen in 18 cases (23%). Twelve of 46 MS patients (26%), 5 of 24 other demyelinating diseases (21%) and 1 of 10 other neurological disorders (10%) had HHV-6 specific OCBs in CSF. A specific intrathecal HHV-6 A and B antibody production was shown in a proportion of patients with demyelinating diseases and might suggest a role in the pathogenesis of these diseases.

The evolution of coagulation and fibrinolysis has not been thoroughly evaluated in allogeneic SCT. In this pilot study, we characterized the adaptive mechanisms of coagulation and fibrinolysis during allogeneic SCT and 3-month follow-up and studied possible associations with outcome, including acute GVHD. Thirty patients underwent SCT for a haematological malignancy after myeloablative conditioning. Nineteen patients received the transplant from an HLA-identical sibling and 11 from an unrelated donor. GVHD prophylaxis consisted of CYA and MTX, with methylprednisolone in sibling transplants. Serial coagulation and fibrinolytic activity markers were assessed, including prothrombin fragments 1+2 (F1+2), thrombin time, D-dimer, tissue-type plasminogen-activator (tPA) and plasminogen-activator inhibitor (PAI-1). Early during conditioning therapy, F1+2 and D-dimer increased threefold indicating thrombin generation and fibrin turnover. TPA activity peaked before engraftment, concurring with diminished PAI-1. At 10 days after transplantation shortened thrombin time (

Background and purpose: To elucidate the role of human herpesvirus-6 (HHV-6) in the development of multiple sclerosis (MS). Patients and methods: Nine patients with MS and with acute or chronic HHV-6 infection were evaluated. Results: Intrathecal antibody production to HHV-6 and oligoclonal IgG bands in the cerebrospinal fluid (CSF) was observed in two patients with a clinically definite MS and chronic HHV-6 infection (based on the presence of HHV-6 specific antibodies in the CSF). A temporal association between the symptoms of clinically possible MS and acute primary HHV-6A infection (based on avidity of HHV-6 specific antibodies) was observed in two patients. Conclusions: Human herpesvirus-6 infection may be an associated agent in some MS cases. Viral studies are needed to identify a possible viral etiology and give specific therapy.

Background The triggering agent of multiple sclerosis is still unknown and many viruses, including human herpesvirus-6 (HHV-6), are under suspicion. In earlier study we found patients who had HHV-6 reactive OCBs in their CSF. We wanted to investigate whether HHV-6 has an active role in diseases with demyelination. Objective To analyze the HHV-6-reactive cases in detail and investigate the possible independent role of HHV-6 in the development of central nervous system involvements with demyelination. Study design We studied serum and CSF samples that were collected over a period of one year, from all patients who had oligoclonal bands (OCB) in cerebrospinal fluid (CSF) and were examined in the Department of Neurology, University Central Hospital of Helsinki, Finland. Clinical evaluation was accomplished blinded of HHV-6 analysis and follow-up time was two years. All patients underwent MRI of the head and clinically indicated CSF analysis. Results The 17 patients with HHV-6-reactive OCBs were significantly younger and had significantly more IgG-OCBs in comparison to patients without HHV-6-reactive OCBs. Initial diagnoses in patients with HHV-6-reactive OCBs remained the same during the follow-up time. Conclusion Patients with HHV-6-positive OCBs appear to form a separable group. In progressive neurological diseases HHV-6 may have a role in long-term infection with demyelination.

Multiple sclerosis (MS) is a heterogeneous disease that develops as an interplay between the immune system and environmental stimuli in genetically susceptible individuals. There is increasing evidence that viruses may play a role in MS pathogenesis acting as these environmental triggers. However, it is not known if any single virus is causal, or rather several viruses can act as triggers in disease development. Here, we review the association of different viruses to MS with an emphasis on two herpesviruses, Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6). These two agents have generated the most impact during recent years as possible co-factors in MS disease development. The strongest argument for association of EBV with MS comes from the link between symptomatic infectious mononucleosis and MS and from seroepidemiological studies. In contrast to EBV, HHV-6 has been found significantly more often in MS plaques than in MS normal appearing white matter or non-MS brains and HHV-6 re-activation has been reported during MS clinical relapses. In this review we also suggest new strategies, including the development of new infectious animal models of MS and antiviral MS clinical trials, to elucidate roles of different viruses in the pathogenesis of this disease. Furthermore, we introduce the idea of using unbiased sequence-independent pathogen discovery methodologies, such as next generation sequencing, to study MS brain tissue or body fluids for detection of known viral sequences or potential novel viral agents.

The small RNA segment of some hantaviruses (family Bunyaviridae) encodes two proteins: the nucleocapsid protein and, in an overlapping reading frame, a non-structural (NSs) protein. The hantavirus NSs protein, like those of orthobunya- and phleboviruses, counteracts host innate immunity. Here, for the first time, the NSs protein of a hantavirus (Tula virus) has been observed in infected cells and shown to localize in the perinuclear area. Transiently expressed NSs protein showed similar localization, although the kinetics was slightly different, suggesting that to reach its proper location in the infected cell, the NSs protein does not have to cooperate with other viral proteins.

HHV-6 infection has been associated with neurological symptoms in children. Two variants of human herpes virus 6, HHV-6A and HHV-6B, have been identified. Their role in neurological infections is poorly understood. We studied 53 children with suspected encephalitis for HHV-6A (strain GS) and HHV-6B (strain Z29) antibodies using an indirect immunofluorescence test. Primary infection was separated from past infection by an IgG-avidity test. The identified primary infections were studied for HHV-6 specific DNA by PCR. Forty-one children of 53 had IgG antibodies to HHV-6. Six children had low avidity of HHV-6 IgG antibodies indicating acute primary infection; four to type A, one to B, and one to both types. By serology, HHV-6 viral etiology was suggested in 6/53 (11.3%) of cases. One of the six patients with primary infection had HHV-6 DNA in serum and two in CSF. The children with primary HHV-6 infection were significantly younger than the whole series, 2.3 years vs. 6.4 years. We conclude that primary HHV-6 infection appears to be an important associated or causative agent in neurological infections of young children, and it can be confirmed from a single serum specimen using the IgG-avidity test.

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.

Multiple sclerosis (MS) is a chronic inflammatory disease of the central nervous system of unknown etiology. Several viruses have been suggested as playing a role in the pathogenesis of MS. The aim of this study was to investigate the interrelationship of human herpesvirus 6 (HHV-6) and plasminogen activation at the cellular level in MS plaques.Brain tissue specimens obtained from autopsies of 15 patients with MS and 10 controls were studied immunohistochemically for HHV-6 and cytomegalovirus (CMV) antigen and tissue plasminogen activator (tPA) protein. The presence of Ebstein-Barr virus (EBV) EBER RNA was studied using RNA in situ hybridization.HHV-6 antigen was identified in the cells of 67% (10/15) of MS brain sections and 30% (3/10) of the control sections. All samples were negative for CMV antigen and all samples with intact RNA were negative for EBV EBER RNA as demonstrated by in situ hybridization. tPA expression was found to be increased in MS plaques compared with the control samples. Interestingly, in 5 MS samples both HHV-6 antigen and tPA stained clearly, compared with none in the controls, but HHV-6 and tPA only occasionally co-localized in the same cells.At the cellular level, HHV-6 and plasminogen activation seem to co-localize in MS.

Allogeneic stem cell transplantation (SCT) seems to result in activation of coagulation and fibrinolysis. We characterised the outcome of SCT and graft versus host disease (GvHD) in association with the adaptive mechanisms of coagulation and fibrinolysis. 30 patients given myeloablative conditioning with cyclophosphamide and total body irradiation underwent allogeneic SCT for a hematological malignancy. 19 patients received the transplant from a sibling and 11 from an unrelated donor. GvHD prophylaxis consisted of cyclosporine and methotrexate, and in addition methylprednisolone in case of a sibling donor. Eight patients developed GvHD during the 3-month follow-up. Several coagulation and fibrinolysis activities were serially assessed: antithrombin, protein C (PC), FVIII, prothrombin fragments 1+2 (F1+2), D-dimer, tissue plasminogen activator (tPA) and plasminogen activator inhibitor (PAI-1). During the conditioning therapy as an early sign of thrombin generation, F1+2 increased 3-fold and D-dimer 4-fold, compatible with enhanced fibrin turnover. The activity of tPA reached its maximum already before the engraftment and that of PAI-1 diminished accordingly. FVIII increased steadily from normal to reach maximum (up to 273% ±104%, median ±SD, p10 U/ml) predicted the non-relapse mortality (p=0.013). In conclusion, early activation of coagulation and fibrinolysis is followed by increased FVIII and PC activities in SCT. Early marked thrombin generation and elevated PAI-1 associated with the non-relapse mortality and low PC activity with the appearance of acute GvHD.

Intrathecal antibody synthesis is a well-documented phenomenon in infectious neurological diseases as well as in demyelinating diseases. Intrathecal antibody synthesis against HTLV-1 has been reported in HAM/TSP, but little is known about the role of B cells and humoral immune responses in the central nervous systems (CNS) of HAM/TSP patients. Here we demonstrate profiles of HTLV-1-specific antibodies in cerebrospinal fluid (CSF) of HAM/TSP patients. Of 36 HAM/TSP patients, antibody responses against Gag and Tax were detected in CSF of all the patients. CSF/Serum antibody ratio was elevated in anti-Gag (mean 1.20) more than in anti-Tax (mean 0.85), but importantly HAM/TSP patients with lesions or atrophy in spinal cord showed higher CSF/ Serum anti-Gag antibody ratio. Antibody response against Env was detected in CSF of 94.4% of patients, but CSF/ serum anti-Env ratio was significantly lower than those of anti-Gag and anti-Tax (mean 0.18). 19 patients were further studied for oligoclonal band (OCB) specificity to HTLV-1 antigens and all of them were found to have bands specific for at least one antigen studied. Significantly higher proportion of patients had Gag- or Envspecific OCBs than Tax-specific OCBs. Interestingly, CXCL13 (B cell attracting chemokine-1) was increased in CSF of HAM/TSP patients, which was associated with higher HTLV-1-specific antibody responses in CSF and was correlated with decrease of plasma blasts in peripheral blood. These results highlight the importance of the B cell compartment in HAM/TSP where production of HTLV-1-specific antibody may be required to control viral persistence and/or may be associated with HAM/ TSP disease progression.