Human herpes virus 6 and multiple sclerosis

Rehabilitation on cerebellar ataxic patients with multiple sclerosis: A systematic review

Multiple Sclerosis (MS) is a chronic inflammatory, autoimmune disease of the Central Nervous System with a vast spectrum of clinical phenotypes. A major aspect of its clinical presentation is cerebellar ataxia where physiotherapy and treatment modalities play a significant role on its management. This systematic review aims to investigate the physiotherapeutic rehabilitation techniques regarding the management of cerebellar ataxia due to MS and secondary to stratify each protocol as part of a multi structural personalized rehabilitation approach based on the gravity of the symptoms. A Pubmed Medline, Scopus and Web of Science research was performed using the corresponding databases. The results were screened by the authors in pairs. In our study, six (6) non-pharmacological interventional protocols, 3 Randomized Controlled Trials and 3 pilot studies, were included with a total of 145 MS patients. Physiotherapeutic techniques, such as NDT-Bobath, robotic and visual biofeedback re-education protocols and functional rehabilitation techniques were included. In most cases cerebellar ataxic symptoms were decreased post-treatment. The overall quality of the studies included was of moderate level (level B). Rehabilitation in cerebellar ataxia due to MS should be based on multicentric studies with the scope of adjusting different types of treatments and physiotherapeutic techniques based on the severity of the symptom.

Human Herpesvirus 6A Is a Risk Factor for Multiple Sclerosis

The role for human herpesvirus (HHV)-6A or HHV-6B in multiple sclerosis (MS) pathogenesis has been controversial. Possibly because the damage of the virus infection may occur before onset of clinical symptoms and because it has been difficult to detect active infection and separate serological responses to HHV-6A or 6B. Recent studies report that in MS patients the serological response against HHV-6A is increased whereas it is decreased against HHV-6B. This effect seems to be even more pronounced in MS patients prior to diagnosis and supports previous studies postulating a predomination for HHV-6A in MS disease and suggests that the infection is important at early stages of the disease. Furthermore, HHV-6A infection interacts with other factors suspected of modulating MS susceptibility and progression such as infection with Epstein-Barr virus (EBV) and Cytomegalovirus (CMV), tobacco smoking, HLA alleles, UV irradiation and vitamin D levels. The multifactorial nature of MS and pathophysiological role for HHV-6A in inflammation and autoimmunity are discussed.

Human herpesvirus 6 infection as a trigger of multiple sclerosis: an update of recent literature

BACKGROUND

This is an update on the existing evidence regarding a relationship between infection with human herpesvirus 6 (HHV-6) and multiple sclerosis (MS) in order to contribute on the attempt to define the nature and strength of that relationship.

RESULTS

Study quality was assessed using the criteria proposed by Moore and Wolfson and by the classification criteria used by the Canadian Task Force on the Periodic Health Examination. Studies were categorized both by experimental technique and by quality (high [A], intermediate [B], and low [C]) as determined by the Moore and Wolfson criteria. Overall, 27 (90%) of 30 studies, 18 (86%) of which were classified as A quality, reached a statistically significant result. According to the Canadian Task Force classification, all studies were categorized as evidence of qualityII-1. Limitations of the available experimental techniques and perspectives for future research are discussed.

CONCLUSIONS

The current review continues to emphasize the need for further, objective, evidence-based examination of the relationship between HHV-6 infection and multiple sclerosis.

Human Endogenous Retrovirus as Therapeutic Targets in Neurologic Disease

Human endogenous retroviruses (HERVs) are ancient retroviral DNA sequences established into germline. They contain regulatory elements and encoded proteins few of which may provide benefits to hosts when co-opted as cellular genes. Their tight regulation is mainly achieved by epigenetic mechanisms, which can be altered by environmental factors, e.g., viral infections, leading to HERV activation. The aberrant expression of HERVs associates with neurological diseases, such as multiple sclerosis (MS) or amyotrophic lateral sclerosis (ALS), inflammatory processes and neurodegeneration. This review summarizes the recent advances on the epigenetic mechanisms controlling HERV expression and the pathogenic effects triggered by HERV de-repression. This article ends by describing new, promising therapies, targeting HERV elements, one of which, temelimab, has completed phase II trials with encouraging results in treating MS. The information gathered here may turn helpful in the design of new strategies to unveil epigenetic failures behind HERV-triggered diseases, opening new possibilities for druggable targets and/or for extending the use of temelimab to treat other associated diseases.

Microglial Phenotypes and Functions in Multiple Sclerosis

Microglia are the resident immune cells that constantly survey the central nervous system. They can adapt to their environment and respond to injury or insult by altering their morphology, phenotype, and functions. It has long been debated whether microglial activation is detrimental or beneficial in multiple sclerosis (MS). Recently, the two opposing yet connected roles of microglial activation have been described with the aid of novel microglial markers, RNA profiling, and in vivo models. In this review, microglial phenotypes and functions in the context of MS will be discussed with evidence from both human pathological studies, in vitro and in vivo models. Microglial functional diversity-phagocytosis, antigen presentation, immunomodulation, support, and repair-will also be examined in detail. In addition, this review discusses the emerging evidence for microglia-related targets as biomarkers and therapeutic targets for MS.

Viral-induced suppression of self-reactive T cells: Lessons from neurotropic coronavirus-induced demyelination

Genetic and environmental factors, i.e. infections, have been proposed to contribute to disease induction and relapsing events in multiple sclerosis (MS), an autoimmune demyelinating disease of the central nervous system (CNS). While research has mainly focused on virus associated autoimmune activation, less is known about prevention of autoimmunity, especially following resolving infections associated with CNS tissue damage. This review discusses novel insights on control of self-reactive (SR) T cells activated during neurotropic coronavirus-induced demyelination. A new concept is introduced that SR T cells can be dampened by distinct regulatory mechanisms in the periphery and the CNS, thereby preventing autoimmune disease.

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Virus-induced demyelination activates myelin specific T cells.

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Virus-induced regulatory mechanisms limit pathogenic self-reactive R CD4 T cells.

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Self-reactive CD4 T cells are controlled by distinct mechanisms in the CLN and CNS.

Cerebrospinal Fluid in a Small Cohort of Patients with Multiple Sclerosis Was Generally Free of Microbial DNA

Multiple sclerosis (MS) is a common cause of non-traumatic neurologic disability with high incidence in many developed countries. Although the etiology of the disease remains elusive, it is thought to entail genetic and environmental causes, and microbial pathogens have also been envisioned as contributors to the phenotype. We conducted a metagenomic survey in cerebrospinal fluid (CSF) from 28 MS patients and 15 patients suffering other type of neurological conditions. We detected bacterial reads in eight out of the 15 non-MS patients and in a single MS patient, at an abundance >1% of total classified reads. Two patients were of special interest: one non-MS patient harbored ~73% bacterial reads, while an MS patient had ~83% bacterial reads. In the former case, Veillonella parvula, a bacterium occasionally found associated with meningitis was the predominant species, whilst Kocuria flava, apparently an environmental bacterium, predominated in the latter case. Thirty-four out of 43 samples contained <1% bacterial reads, which we regard as cross- or environmental contamination. A few viral reads corresponding to Epstein-Barr virus, cytomegalovirus, and parvovirus were also identified. Our results suggest that CSF of MS patients is often (but not always) free of microbial DNA.

Association between human herpesvirus & human endogenous retrovirus and MS onset & progression

This review discusses the role of Epstein-Barr virus (EBV), human herpesvirus 6 (HHV6) and human endogenous retroviruses (HERVs) in the onset and progression of multiple sclerosis (MS). Although EBV has been established as one of the causal factors in MS onset, its role in MS progression is still uncertain. Moreover, interactions between EBV and other risk factor on MS development still need more investment. With less consistent evidence than EBV, HHV6 has also been implicated in the pathogenesis of MS; moreover, it showed a closer connection with the disease activity. Recent studies found that HERVs were associated with the development and progression of MS. Some antiviral treatments have shown promise for clinical interventions in the future. Future studies are yet needed to fully clarify the role of these agents in MS onset and disease course and the modes by which they realise these effects.

Multiple sclerosis in women having children by multiple partners. A population-based study in Denmark

We investigated whether having children with multiple men is a risk factor for being diagnosed with multiple sclerosis (MS). We studied a cohort of 151 328 women, of whom 64 704 had different men fathering their children and 86 624 the same partner for all births. Women were included if they had a second or higher parity child between 1973 and 1996. The follow-up for MS ended in 1997. There were a total of 213 cases of MS diagnosed during the study period. We analysed data through Poisson regression models. Women having children with different men were not at higher risk of being diagnosed with MS, with the possible exception of a short period after having a baby with a new partner. Women having children with more than one man may have a higher risk of a pregnancy accelerating the diagnosis of MS but are probably not at an overall higher risk of MS.

Self-reactive CD4(+) T cells activated during viral-induced demyelination do not prevent clinical recovery

Background

Microbial infections have been implicated in initiating and enhancing severity of autoimmune diseases including the demyelinating disease multiple sclerosis (MS). Nevertheless, the incidence of both acute and persisting viral infections without evidence of autoimmune sequelae suggests that this process is well controlled. The conditions promoting or stemming self-reactive (SR) T cells following viral-induced tissue damage thus need to be better defined. Using a non-fatal viral mouse model of encephalomyelitis associated with demyelination and disability, yet ultimate clinical improvement, this study set out to monitor uptake and presentation of endogenous myelin antigens, as well as induction and fate of SR T cells.

Methods

Activation and central nervous system (CNS) recruitment of myelin-specific CD4 T cells was analyzed by flow cytometry during encephalomyelitis induced by a glia tropic murine coronavirus. Potential antigen-presenting cells (APC) ingesting myelin were characterized by flow cytometry and their ability to activate SR T cells tested by co-culture with carboxyfluorescein succinimidyl ester (CFSE)-labeled myelin-specific CD4 T cells. Endogenous SR T cell kinetics was analyzed within both cervical lymph nodes and CNS by Enzyme-Linked ImmunoSpot (ELISPOT) following viral infection.

Results

The data demonstrate the presence of APC capable of activating SR T cells in both draining lymph nodes and the CNS temporally correlating with overt demyelination. While both the CNS-infiltrating myeloid population and microglia ingested myelin, only CNS-infiltrating APC were capable of presenting endogenous myelin antigen to SR T cells ex vivo. Finally, SR T cell activation from the endogenous T cell repertoire was most notable when infectious virus was controlled and paralleled myelin damage. Although SR T cell accumulation peaked in the persistently infected CNS during maximal demyelination, they were not preferentially retained. Their gradual decline, despite ongoing demyelination, suggested minimal re-stimulation and pathogenic function in vivo consistent with the lack of autoimmune symptoms.

Conclusions

The results demonstrate the potential for CNS tissue destruction to induce and recruit SR T cells to the injury site and support a host suppressive mechanism limiting development of autoimmunity.

EBV & HHV6 reactivation is infrequent and not associated with MS clinical course

BACKGROUND

Among the environmental factors associated with multiple sclerosis (MS) causation, some of the strongest associations are with Epstein-Barr virus (EBV), and to a lesser extent human herpesvirus 6 (HHV6). Associations with clinical course are less conclusive, however.

METHODS

We evaluated serum anti-EBV-EA-R IgG and anti-HHV6 IgM, and EBV and HHV6 viral load (VL) for their associations with relapse, disability, and progression in disability in a prospective cohort of 198 participants with clinically definite MS.

RESULTS

Anti-EBV-EA-R IgG was detected in 81.8% of cases at study entry, and titers remained essentially unchanged during the study. Anti-HHV6 IgM was detected in only one participant, and EBV-VL (29%) and HHV6-VL (1.8%) were detected in a minority of samples, and where detected levels were low. Our previously demonstrated association between anti-HHV6 IgG and relapse hazard was not affected by adjustment for parameters of reactivation. We found no evidence that any of the viral markers were associated with disability or progression in disability. In relation to relapse, only EBV-VL was positively associated, although this was strongly influenced by a single individual.

CONCLUSION

Using a prospective cohort design, we found no convincing evidence that reactivation parameters of EBV or HHV6 were associated with subsequent MS relapse hazard or progression in disability, confirming previous findings, and indicating that herpesvirus reactivation is not an important driver of relapse or disability in this established MS population.

SJL mice infected with Acanthamoeba castellanii develop central nervous system autoimmunity through the generation of cross-reactive T cells for myelin antigens

We recently reported that Acanthamoeba castellanii (ACA), an opportunistic pathogen of the central nervous system (CNS) possesses mimicry epitopes for proteolipid protein (PLP) 139–151 and myelin basic protein 89–101, and that the epitopes induce experimental autoimmune encephalomyelitis (EAE) in SJL mice reminiscent of the diseases induced with their corresponding cognate peptides. We now demonstrate that mice infected with ACA also show the generation of cross-reactive T cells, predominantly for PLP 139–151, as evaluated by T cell proliferation and IA^s/dextramer staining. We verified that PLP 139–151-sensitized lymphocytes generated in infected mice contained a high proportion of T helper 1 cytokine-producing cells, and they can transfer disease to naïve animals. Likewise, the animals first primed with suboptimal dose of PLP 139–151 and later infected with ACA, developed EAE, suggesting that ACA infection can trigger CNS autoimmunity in the presence of preexisting repertoire of autoreactive T cells. Taken together, the data provide novel insights into the pathogenesis of Acanthamoeba infections, and the potential role of infectious agents with mimicry epitopes to self-antigens in the pathogenesis of CNS diseases such as multiple sclerosis.

Monitoring of active human herpes virus 6 infection in Iranian patients with different subtypes of multiple sclerosis

Background. Recently, it has been suggested that human herpes virus 6 (HHV6) may play a role in the pathogenesis of multiple sclerosis (MS). Our purpose is to determine the incidence of reactivated HHV6 in MS patients. Methods. Viral sequence analyzed by qPCR in the peripheral blood mononuclear cells (PBMCs), serum, and saliva samples of different subtypes of MS patients (n = 78) and healthy controls (n = 123). HHV6 IgG and IgM antibody levels measured by ELISA technique in the plasma samples of both groups. Likewise, cerebrospinal fluid (CSF) samples of some MS patients (n = 38) were analyzed for viral sequence. Results. Results demonstrate increased levels of anti-HHV6-IgG (78.2% versus 76.4% in controls; P = NS), and IgM (34.6% versus 6.5% in controls; P < 0.05) in MS patients. Furthermore, RRMS and SPMS patients showed relatively higher anti-HHV6 IgG and IgM compared to PPMS (P < 0.001). Moreover, load of cell-free viral DNA was higher in RRMS and SPMS patients and detected in 60.2% (47/78) of MS patients, compared with 14.6% (18/123) of healthy controls (P < 0.001). Moreover, load of cell-free viral DNA was higher in RRMS and SPMS patients and detected in 60.2% (47/78) of MS patients, compared with 14.6% (18/123) of healthy controls (P < 0.001). Conclusions. The results extend the observation of an increased frequency of systemic reactivated HHV6 infection in MS patients with developed stages of disease.

The long and evolving relationship between viruses and multiple sclerosis

Multiple sclerosis (MS) is a demyelinating disorder of unknown etiology, possibly caused by a virus or is virus-triggered. Several viruses, including herpesviruses, were suggested as etiologic agents or risk factors for exacerbation in the course of illness but none have been shown to be irrefutably linked. Recently the interest of researchers and clinicians in the association between viruses and MS was reawakened by the development of progressive multifocal leukoencephalopathy, a demyelinating and fatal disease caused by JC polyomavirus replication, in natalizumab-treated MS patients. In this review, we will illustrate the evidence underlying the viral hypothesis for MS pathogenesis and will review the main features of the potential viral candidates. We will also describe the risks associated with newer MS therapies and with viral/bacterial vaccinations.

Small RNA deep sequencing identifies microRNAs and other small noncoding RNAs from human herpesvirus 6B

Roseolovirus, or human herpesvirus 6 (HHV-6), is a ubiquitous human pathogen infecting over 95% of the population by the age of 2 years. As with other herpesviruses, reactivation of HHV-6 can present with severe complications in immunocompromised individuals. Recent studies have highlighted the importance of herpesvirus-derived microRNAs (miRNAs) in modulating both cellular and viral gene expression. An initial report which computed the likelihood of various viruses to encode miRNAs did not predict HHV-6 miRNAs. To experimentally screen for small HHV-6-encoded RNAs, we conducted large-scale sequencing of Sup-T-1 cells lytically infected with a laboratory strain of HHV-6B. This revealed an abundant, 60- to 65-nucleotide RNA of unknown function derived from the lytic origin of replication (OriLyt) that gave rise to smaller RNA species of 18 or 19 nucleotides. In addition, we identified four pre-miRNAs whose mature forms accumulated in Argonaute 2. In contrast to the case for other betaherpesviruses, HHV-6B miRNAs are expressed from direct repeat regions (DR(L) and DR(R)) located at either side of the genome. All miRNAs are conserved in the closely related HHV-6A variant, and one of them is a seed ortholog of the human miRNA miR-582-5p. Similar to alphaherpesvirus miRNAs, they are expressed in antisense orientation relative to immediate-early open reading frames (ORFs) and thus have the potential to regulate key viral genes.

Role of vitamin D in multiple sclerosis: implications for disease management

SUMMARY This review discusses the evidence on the role of vitamin D in multiple sclerosis (MS) and whether vitamin D supplementation is effective for the management of MS. People with MS are at high risk of vitamin D deficiency, osteoporosis and fractures. Observational data suggest that higher vitamin D levels are associated with lower relapse risk and there is promising evidence on its effect on MRI measures, disability progression, mental health and fatigue. However, there is currently insufficient randomized controlled trial evidence to recommend vitamin D supplementation with the aim to improve those outcomes. There is sufficient evidence to justify assessing and correcting vitamin D and calcium levels to optimize bone health in people with MS at high absolute risk of fracture.

Anti-HHV-6 IgG titer significantly predicts subsequent relapse risk in multiple sclerosis

BACKGROUND

Some of the strongest associations with MS onset are for human herpesviruses, particularly Epstein-Barr virus (EBV) and human herpesvirus 6 (HHV-6). Their role in MS clinical course is less clear, however.

METHODS

Prospective cohort of 198 persons with clinically definite MS, followed 2002-5, and serum samples obtained from all subjects at study entry to measure anti-HHV-6 and anti-EBV (Epstein-Barr nuclear antigen [EBNA] and viral capsid antigen [VCA]) IgG titers. Association with relapse evaluated using survival analysis; association with disability/progression evaluated using linear regression or multilevel mixed-effects linear regression.

RESULTS

For the 145 persons with relapsing-remitting MS followed beyond one review, anti-HHV-6 IgG titer was positively associated with the hazard of relapse with a dose-dependent trend (p = 0.003), not affected by adjustment for anti-EBV IgG titers, neither of which were independently associated with relapse. There was no significant association between anti-human herpesvirus IgG titers and baseline-measured disability scores, or change in disability scores; however, anti-HHV-6 IgG titers were 2.8 times higher among progressive-course females than progressive-course males.

DISCUSSION

These findings suggest that, in addition to a potential etiological role in MS, HHV-6 infection or the immune response to HHV-6 antigens may have an effect on the risk of MS relapses and possibly on progressive courses of MS. The observed effect was directly related to anti-HHV-6 IgG titers and may indicate that either HHV-6 infection or factors associated with an altered humoral immune response to HHV-6 may have an effect on MS clinical course. Anti-HHV-6 IgG titer may be a useful prognostic factor in relapsing-remitting MS clinical course.

The role of infections in the pathogenesis and course of multiple sclerosis

Interplay between susceptibility genes and environmental factors is considered important player in the genesis of multiple sclerosis (MS). Among environmental factors, a role for an infectious pathogen has long been considered central to the disease process. This opinion has support both from epidemiological data and the findings of immunological abnormalities in spinal fluid that reflect an immune response to an as yet undetermined antigen, possibly a pathogen, in the cerebrospinal fluid. Our review will outline the current understanding of the role of infection in the causation and progression of MS. We will review the data that point to an infectious cause of MS and consider the specific agents Chlamydophila (Chlamydia) pneumoniae, Human Herpes Virus 6, and Epstein-Barr Virus, that are implicated in either the development or progression of MS.

Human herpesvirus 6 infection as a trigger of multiple sclerosis

We systematically reviewed the existing evidence to determine whether a relationship exists between infection with human herpesvirus 6 (HHV-6) and multiple sclerosis (MS) and, if so, to define the strength of that relationship. The following terms were used in searches of the Entrez-PubMed database (1966-2009): human herpes virus 6, HHV 6, demyelination, multiple sclerosis, pathogenesis, diagnosis, serology, cerebrospinal fluid, IgG antibodies, IgM antibodies, PCR, and lymphoproliferative techniques. Study quality was assessed using the criteria proposed by Moore and Wolfson and by the classification criteria used by the Canadian Task Force on the Periodic Health Examination. Studies were categorized both by experimental technique and by quality (high [A], intermediate [B], and low [C]) as determined by the Moore and Wolfson criteria. Overall, 25 (41%) of 61 studies, 15 (60%) of which were classified as A quality, reached a statistically significant result. According to the Canadian Task Force classification, all studies were categorized as evidence of quality II-1. Limitations of the available experimental techniques and perspectives for future research are discussed. The current review supports the need for further, objective, evidence-based examination of the relationship between HHV-6 infection and multiple sclerosis.

A mechanism of virus-induced demyelination

Myelin forms an insulating sheath surrounding axons in the central and peripheral nervous systems and is essential for rapid propagation of neuronal action potentials. Demyelination is an acquired disorder in which normally formed myelin degenerates, exposing axons to the extracellular environment. The result is dysfunction of normal neuron-to-neuron communication and in many cases, varying degrees of axonal degeneration. Numerous central nervous system demyelinating disorders exist, including multiple sclerosis. Although demyelination is the major manifestation of most of the demyelinating diseases, recent studies have clearly documented concomitant axonal loss to varying degrees resulting in long-term disability. Axonal injury may occur secondary to myelin damage (outside-in model) or myelin damage may occur secondary to axonal injury (inside-out model). Viral induced demyelination models, has provided unique imminent into the cellular mechanisms of myelin destruction. They illustrate mechanisms of viral persistence, including latent infections, virus reactivation and viral-induced tissue damage. These studies have also provided excellent paradigms to study the interactions between the immune system and the central nervous system (CNS). In this review we will discuss potential cellular and molecular mechanism of central nervous system axonal loss and demyelination in a viral induced mouse model of multiple sclerosis.

Chlamydophila pneumoniae Infection and Its Role in Neurological Disorders

Chlamydophila pneumoniae is an intracellular pathogen responsible for a number of different acute and chronic infections. The recent deepening of knowledge on the biology and the use of increasingly more sensitive and specific molecular techniques has allowed demonstration of C. pneumoniae in a large number of persons suffering from different diseases including cardiovascular (atherosclerosis and stroke) and central nervous system (CNS) disorders. Despite this, many important issues remain unanswered with regard to the role that C. pneumoniae may play in initiating atheroma or in the progression of the disease. A growing body of evidence concerns the involvement of this pathogen in chronic neurological disorders and particularly in Alzheimer's disease (AD) and Multiple Sclerosis (MS). Monocytes may traffic C. pneumoniae across the blood-brain-barrier, shed the organism in the CNS and induce neuroinflammation. The demonstration of C. pneumoniae by histopathological, molecular and culture techniques in the late-onset AD dementia has suggested a relationship between CNS infection with C. pneumoniae and the AD neuropathogenesis. In particular subsets of MS patients, C. pneumoniae could induce a chronic persistent brain infection acting as a cofactor in the development of the disease. The role of Chlamydia in the pathogenesis of mental or neurobehavioral disorders including schizophrenia and autism is uncertain and fragmentary and will require further confirmation.

The U24 protein from human herpesvirus 6 and 7 affects endocytic recycling

Modulation of T-cell receptor expression and signaling is essential to the survival of many viruses. The U24 protein expressed by human herpesvirus 6A, a ubiquitous human pathogen, has been previously shown to downregulate the T-cell receptor. Here, we show that U24 also mediates cell surface downregulation of a canonical early endosomal recycling receptor, the transferrin receptor, indicating that this viral protein acts by blocking early endosomal recycling. We present evidence that U24 is a C-tail-anchored protein that is dependent for its function on TRC40/Asna-1, a component of a posttranslational membrane insertion pathway. Finally, we find that U24 proteins from other roseoloviruses have a similar genetic organization and a conserved function that is dependent on a proline-rich motif. Inhibition of a basic cellular process by U24 has interesting implications not only for the pathogenicity of roseoloviruses but also for our understanding of the biology of endosomal transport.

Human herpesvirus-6 infections and infection-preventative measures in transplant recipients

Like the other herpesviruses, human herpesvirus (HHV)-6 is capable of persisting in the host after primary infection and can reactivate under immunosuppressed conditions. In stem cell transplantation recipients, HHV-6 reactivation is observed in 40–50% of patients and is linked to various clinical manifestations, including rash, delayed platelet engraftment and encephalopathy. HHV-6 reactivation is also relatively common in solid organ transplantation recipients, and is associated with graft dysfunction and subsequent development of human cytomegalovirus disease. In particular, HHV-6 has been recognized as a life-threatening pathogen for the development of encephalopathy after stem cell transplantation. Ganciclovir, foscarnet and cidofovir are effective against HHV-6 in vitro. However, success rates are not high for patients who have developed encephalopathy. Plasma HHV-6 DNA-guided pre-emptive approaches have not been successful owing to the dynamic kinetics of HHV-6 reactivation. Establishment of optimal strategies is needed to prevent HHV-6-associated complications, in particular encephalopathy.

Detection of herpesvirus DNA in cerebrospinal fluid and correlation with clinical symptoms

BACKGROUND

Novel PCR techniques can detect minute quantities of herpesvirus DNA in cerebrospinal fluid (CSF). The clinical significance of such findings is not always clear.

PATIENTS AND METHODS

(a) Investigation of clinical characteristics of 76 patients with herpesvirus DNA detection in CSF. (b) Screening for herpesvirus DNA in CSF samples of 208 patients without clinical signs of herpesvirus infection.

RESULTS

(a) Eleven of 76 herpesvirus-DNA-positive patients did not show symptoms usually associated with the detected virus (HSV-1/2, n = 5; EBV, n = 6). (b) Two of 208 patients without hint for herpesvirus infection had HHV-6 DNA of low concentration in CSF.

CONCLUSIONS

The detection of low-level herpesvirus replication in CSF by highly sensitive PCR assays requires critical evaluation.

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.

Human herpes virus 6 and multiple sclerosis: a Finnish twin study

OBJECTIVE

To investigate the possible association of human herpes virus 6- (HHV6) infection and multiple sclerosis (MS).

BACKGROUND

Despite intensive investigations of genetic and environmental factors, the etiopathogenesis of MS remains unknown. HHV6 is a possible candidate in that it is neurotropic, able to induce demyelination and become latent and be reactivated. We had access to The Finnish National Twin Cohort, which provided a unique opportunity to study the association between HHV6 and MS in genetically homogenous patients.

METHODS

Thirty-four serum samples from 17 MS twin pairs and 12 cerebrospinal fluid (CSF) samples from six MS twin pairs were tested by PCR specific for HHV6. Immunoglobulin (Ig) G and M response against HHV6 in serum and CSF were analysed using ELISA method. The samples were collected during a remission of the disease.

RESULTS

No HHV6 DNA was found in any serum (n=34) or CSF (n=12) samples. Eighty-eight percent of the twins with MS and 86% of the healthy twin siblings were positive for IgG in serum. One twin with MS was also positive for IgM in serum, whereas none of the healthy twins was IgM positive. All CSF samples were negative for IgG and IgM in both groups.

CONCLUSIONS

During a clinical remission of MS the detection of antibodies against HHV6 in CSF and HHV6 DNA in serum, CSF supernatant or CSF leukocytes is unlikely. However, the results do not exclude a possibility of HHV6 reactivation during MS exacerbation or acute HHV6 infection being one of the triggering agents in development of MS long before its clinical manifestation.

Induction of experimental autoimmune encephalomyelitis in Lewis rats by a viral peptide with limited homology to myelin basic protein

Viral infections are thought to play an important role in the pathogenesis of multiple sclerosis potentially through molecular mimicry, but direct evidence from humans and animal models remains inadequate. Based on the fact that amino acid homology has been found between viral and host encephalitogenic protein, we designed four viral peptides (peptides of HBV polymerase protein, large T protein of JC virus, EB virus DNA polymerase and alkaline exonuclease of Human herpesvirus 6) with limited homology to myelin basic protein and explored their clinical, immunological and histological characteristics in Lewis rats. The immunization with JC virus peptide induced slight clinical signs of EAE in Lewis rats. Immunological examination indicated that rats immunized with JC virus peptide triggered T-cell cross-reactivity against MBP68-86, but failed to induce antibody cross-reactivity with MBP68-86. Histological staining exhibited the infiltration of inflammatory T cells and the activation of microglia in spinal cords of rats immunized with MBP68-86 and JC virus peptide. Other three peptides had negative findings in Lewis rats. These results suggested that molecular mimicry could be an important factor in the pathogenesis of EAE induced with JC virus peptide by expanding a population of reactive T cells that recognize MBP68-86 in Lewis rats inferring a possible pathogenesis for molecular mimicry in MS.

Social conflict exacerbates an animal model of multiple sclerosis

A growing body of evidence suggests that social conflict is associated with inflammatory disease onset and exacerbations in multiple sclerosis (MS) patients and in animal models of MS. This review illustrates how animal research can be used to elucidate the biobehavioral mechanisms underlying the adverse health effects of social conflict. The authors review studies indicating that social conflict exacerbates a virally initiated animal model of MS. This research suggests that the deleterious effects of social conflict may be partially mediated by stress-induced increases in pro-inflammatory cytokine levels in the central nervous system. In addition, they provide evidence that the adverse health effects of social conflict can be prevented by blocking the stress-induced increases in cytokine activity. This suggests that interventions designed to prevent or reverse the stress-induced increases in cytokine activity may be able to prevent or reverse some of the negative health effects of social conflict in humans.

Brains and peripheral blood mononuclear cells of multiple sclerosis (MS) patients hyperexpress MS-associated retrovirus/HERV-W endogenous retrovirus, but not Human herpesvirus 6

Multiple sclerosis (MS)-associated retrovirus (MSRV)/HERV-W (human endogenous retrovirus W) and Human herpesvirus 6 (HHV-6) are the two most studied (and discussed) viruses as environmental co-factors that trigger MS immunopathological phenomena. Autopsied brain tissues from MS patients and controls and peripheral blood mononuclear cells (PBMCs) were analysed. Quantitative RT-PCR and PCR with primers specific for MSRV/HERV-W env and pol and HHV-6 U94/rep and DNA-pol were used to determine virus copy numbers. Brain sections were immunostained with HERV-W env-specific monoclonal antibody to detect the viral protein. All brains expressed MSRV/HERV-W env and pol genes. Phylogenetic analysis indicated that cerebral MSRV/HERV-W-related env sequences, plasmatic MSRV, HERV-W and ERVWE1 (syncytin) are related closely. Accumulation of MSRV/HERV-W-specific RNAs was significantly greater in MS brains than in controls (P=0.014 vs healthy controls; P=0.006 vs pathological controls). By immunohistochemistry, no HERV-W env protein was detected in control brains, whereas it was upregulated within MS plaques and correlated with the extent of active demyelination and inflammation. No HHV-6-specific RNAs were detected in brains of MS patients; one healthy control had latent HHV-6 and one pathological control had replicating HHV-6. At the PBMC level, all MS patients expressed MSRV/HERV-W env at higher copy numbers than did controls (P=0.00003). Similar HHV-6 presence was found in MS patients and healthy individuals; only one MS patient had replicating HHV-6. This report, the first to study both MSRV/HERV-W and HHV-6, indicates that MSRV/HERV-W is expressed actively in human brain and activated strongly in MS patients, whilst there are no significant differences between these MS patients and controls for HHV-6 presence/replication at the brain or PBMC level.

Infection, vaccines and other environmental triggers of autoimmunity

The etiology of autoimmune diseases is still not clear but genetic, immunological, hormonal and environmental factors are considered to be important triggers. Most often autoimmunity is not followed by clinical symptoms unless an additional event such as an environmental factor favors an overt expression. Many environmental factors are known to affect the immune system and may play a role as triggers of the autoimmune mosaic.Infections: bacterial, viral and parasitic infections are known to induce and exacerbate autoimmune diseases, mainly by the mechanism of molecular mimicry. This was studied for some syndromes as for the association between SLE and EBV infection, pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection and more. Vaccines, in several reports were found to be temporally followed by a new onset of autoimmune diseases. The same mechanisms that act in infectious invasion of the host, apply equally to the host response to vaccination. It has been accepted for diphtheria and tetanus toxoid, polio and measles vaccines and GBS. Also this theory has been accepted for MMR vaccination and development of autoimmune thrombocytopenia, MS has been associated with HBV vaccination. Occupational and other chemical exposures are considered as triggers for autoimmunity. A debate still exists about the role of silicone implants in induction of scleroderma like disease.Not only foreign chemicals and agents have been associated with induction of autoimmunity, but also an intrinsic hormonal exposure, such as estrogens. This might explain the sexual dimorphism in autoimmunity.Better understanding of these environmental risk factors will likely lead to explanation of the mechanisms of onset and progression of autoimmune diseases and may lead to effective preventive involvement in specific high-risk groups. So by diagnosing a new patient with autoimmune disease a wide anamnesis work should be done.

Microglia and multiple sclerosis

Microglia participate in all phases of the multiple sclerosis (MS) disease process. As members of the innate immune system, these cells have evolved to respond to stranger/danger signals; such a response within the central nervous system (CNS) environment has the potential to induce an acute inflammatory response. Engagement of Toll-like receptors (TLRs), a major family of pattern-recognition receptors (PRRs), provides an important mechanism whereby microglia can interact with both exogenous and endogenous ligands within the CNS. Such interactions modulate the capacity of microglia to present antigens to cells of the adaptive immune system and thus contribute to the initiation and propagation of the more sophisticated antigen-directed responses. This inflammatory response introduces the potential for bidirectional feedback between CNS resident and infiltrating systemic cells. Such interactions acquire particular relevance in the era of therapeutics for MS because the infiltrating cells can be subjected to systemic immunomodulatory therapies known to change their functional properties. Phagocytosis by microglia/macrophages is a hallmark of the MS lesion; however, the extent of tissue damage and the type of cell death will dictate subsequent innate responses. Microglia/macrophages are armed with a battery of effector molecules, such as reactive nitrogen species, that may contribute to CNS tissue injury, specifically to the injury of oligodendrocytes that is associated with MS. A therapeutic challenge is to modulate the dynamic properties of microglia/macrophages so as to limit potentially damaging innate responses, to protect the CNS from injury, and to promote local recovery.

Network communications: lymphotoxins, LIGHT, and TNF

Lymphotoxins (LT) provide essential communication links between lymphocytes and the surrounding stromal and parenchymal cells and together with the two related cytokines, tumor necrosis factor (TNF) and LIGHT (LT-related inducible ligand that competes for glycoprotein D binding to herpesvirus entry mediator on T cells), form an integrated signaling network necessary for efficient innate and adaptive immune responses. Recent studies have identified signaling pathways that regulate several genes, including chemokines and interferons, which participate in the development and function of microenvironments in lymphoid tissue and host defense. Disruption of the LT/TNF/LIGHT network alleviates inflammation in certain autoimmune disease models, but decreases resistance to selected pathogens. Pharmacological disruption of this network in human autoimmune diseases such as rheumatoid arthritis alleviates inflammation in a significant number of patients, but not in other diseases, a finding that challenges our molecular paradigms of autoimmunity and perhaps will reveal novel roles for this network in pathogenesis.

Immunology of multiple sclerosis

Multiple sclerosis (MS) develops in young adults with a complex predisposing genetic trait and probably requires an inciting environmental insult such as a viral infection to trigger the disease. The activation of CD4+ autoreactive T cells and their differentiation into a Th1 phenotype are a crucial events in the initial steps, and these cells are probably also important players in the long-term evolution of the disease. Damage of the target tissue, the central nervous system, is, however, most likely mediated by other components of the immune system, such as antibodies, complement, CD8+ T cells, and factors produced by innate immune cells. Perturbations in immunomodulatory networks that include Th2 cells, regulatory CD4+ T cells, NK cells, and others may in part be responsible for the relapsing-remitting or chronic progressive nature of the disease. However, an important paradigmatic shift in the study of MS has occurred in the past decade. It is now clear that MS is not just a disease of the immune system, but that factors contributed by the central nervous system are equally important and must be considered in the future.

Early and late HHV-6 gene transcripts in multiple sclerosis lesions and normal appearing white matter

Multiple sclerosis is an inflammatory demyelinating disease of the CNS, the aetiology of which is believed to have both genetic and environmental components. We have investigated one of the candidate viruses for the environmental component of multiple sclerosis, the neurotropic human herpesvirus 6 (HHV-6). Utilizing fluorescent in situ hybridization (FISH) techniques, we have examined human post-mortem tissues for the presence of immediate early and late viral gene expression in multiple sclerosis patient normal appearing white matter (NAWM), lesional tissue and normal control brain samples. HHV-6 gene transcription was detected in all tissue samples and was restricted to oligodendrocytes, as determined by double mRNA FISH analysis. Quantitative analysis of viral mRNA expression indicated that both NAWM and lesional multiple sclerosis samples exhibited significantly higher levels of HHV-6 expression compared with the normal control samples. Lesional samples exhibited the highest levels of viral gene expression, with NAWM exhibiting an intermediate level between lesional and control tissues. Immunofluorescence against early and late HHV-6 proteins verified active translation of HHV-6 viral mRNA in oligodendrocytes. Southern blot analysis of nested polymerase chain reactions using extracted genomic DNA and cDNA confirmed the presence of the HHV-6 genome in all individuals, with the active expression profile mirroring the FISH results. The frequent high level of HHV-6 infection in multiple sclerosis samples suggests a possible role in pathogenesis.

Association of human endogenous retroviruses with multiple sclerosis and possible interactions with herpes viruses

The hypothesis that human endogenous retroviruses (HERVs) play a role in autoimmune diseases is subject to increasing attention. HERVs represent both putative susceptibility genes and putative pathogenic viruses in the immune-mediated neurological disease multiple sclerosis (MS). Gammaretroviral HERV sequences are found in reverse transcriptase-positive virions produced by cultured mononuclear cells from MS patients, and they have been isolated from MS samples of plasma, serum and CSF, and characterised to some extent at the nucleotide, protein/enzyme, virion and immunogenic level. Two types of sequences, HERV-H and HERV-W, have been reported. No known HERV-H or HERV-W copy contains complete ORFs in all prerequisite genes, although several copies have coding potential, and several such sequences are specifically activated in MS, apparently resulting in the production of complete, competent virions. Increased antibody reactivity to specific Gammaretroviral HERV epitopes is found in MS serum and CSF, and cell-mediated immune responses have also been reported. Further, HERV-encoded proteins can have neuropathogenic effects. The activating factor(s) in the process resulting in protein or virion production may be members of the Herpesviridae. Several herpes viruses, such as HSV-1, VZV, EBV and HHV-6, have been associated with MS pathogenesis, and retroviruses and herpes viruses have complex interactions. The current understanding of HERVs, and specifically the investigations of HERV activation and expression in MS are the major subjects of this review, which also proposes to synergise the herpes and HERV findings, and presents several possible pathogenic mechanisms for HERVs in MS.

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).

Simultaneous presence of endogenous retrovirus and herpes virus antigens has profound effect on cell-mediated immune responses: implications for multiple sclerosis

Retroviruses have been suggested as possible pathogenic factors in multiple sclerosis (MS), supported by the observation that endogenous retroviruses are activated in MS patients. Different members of the herpes family of which several are neurotropic have also been suggested as factors in MS pathogenesis. Further, interactions between retroviruses and herpes viruses have been implied in the development of MS. The objective of the study was investigation of cell-mediated immune responses of MS patients to retrovirus and herpes virus antigens, particularly antigen combinations, with analyses of the influence of retrovirus antigens on cellular immunological reactivity toward other viral antigens. Cellular immunity as measured by blast transformation assays was analyzed using freshly isolated peripheral blood mononuclear cells from 47 MS patients and 36 healthy volunteers. Combinations of the endogenous retrovirus HERV-H and herpes virus antigens resulted in highly increased cellular immune responses among both the MS patients and healthy subjects. The increase was synergistic in character in most samples. Very pronounced effects were obtained using HHV-6A and HSV-1 antigens. Blast transformation assays combining antigens from two different herpes viruses or combinations of measles and herpes antigens showed no synergy. The obtained data indicate a pronounced synergistic effect on the cellular immune response when retrovirus and herpes antigens are present together. The cause of the synergy is unknown so far. The effect on the immune response may influence the disease progression.

Theiler's virus infection: a model for multiple sclerosis

Both genetic background and environmental factors, very probably viruses, appear to play a role in the etiology of multiple sclerosis (MS). Lessons from viral experimental models suggest that many different viruses may trigger inflammatory demyelinating diseases resembling MS. Theiler's virus, a picornavirus, induces in susceptible strains of mice early acute disease resembling encephalomyelitis followed by late chronic demyelinating disease, which is one of the best, if not the best, animal model for MS. During early acute disease the virus replicates in gray matter of the central nervous system but is eliminated to very low titers 2 weeks postinfection. Late chronic demyelinating disease becomes clinically apparent approximately 2 weeks later and is characterized by extensive demyelinating lesions and mononuclear cell infiltrates, progressive spinal cord atrophy, and axonal loss. Myelin damage is immunologically mediated, but it is not clear whether it is due to molecular mimicry or epitope spreading. Cytokines, nitric oxide/reactive nitrogen species, and costimulatory molecules are involved in the pathogenesis of both diseases. Close similarities between Theiler's virus-induced demyelinating disease in mice and MS in humans, include the following: major histocompatibility complex-dependent susceptibility; substantial similarities in neuropathology, including axonal damage and remyelination; and paucity of T-cell apoptosis in demyelinating disease. Both diseases are immunologically mediated. These common features emphasize the close similarities of Theiler's virus-induced demyelinating disease in mice and MS in humans.

[Value of the polymerase chain reaction in the diagnosis of herpes infections of the nervous system]

OBJECTIVE

To assess the performance of a polymerase chain reaction (PCR) method in cerebrospinal fluid (CSF) for the diagnosis of nervous system infections caused by herpesvirus, and to estimate the incidence of encephalitis due to herpes simplex virus type 1 in the adult population of the island of Gran Canaria.

METHODS

We studied 330 CSF specimens from 312 patients (281 HIV-negative and 31 HIV-positive) remitted to investigate clinically suspected encephalitis or meningitis, or to study neuropathy or demyelinating disease. A multiplex PCR technique was used to detect herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), varicella-zoster virus (VZV), human cytomegalovirus (CMV), Epstein-Barr virus and human herpesvirus type 6. The patients' clinical records were reviewed to establish the definite diagnosis.

RESULTS

Nine samples from eight patients (2.6%) showed positive results (9.7% of patients with pathological CSF and none with normal CSF). The eight patients had clinical and analytic findings of herpesvirus nervous system infection: HSV-1 DNA in four patients with encephalitis, HSV-2 DNA in one patient with meningitis, VZV DNA in two patients with meningitis and CMV DNA in one HIV-positive patient with encephalitis. Herpesvirus was the cause of 50% of encephalitis cases and 10% of meningitis cases. The incidence of HSV-1 encephalitis was five cases per million inhabitants per year.

CONCLUSIONS

Diagnosis of herpesvirus nervous system infections by PCR in CSF is not appropriate when CSF parameters are normal. We found a higher incidence of herpesvirus encephalitis than has been reported in other studies.

Potent, selective and cell-mediated inhibition of human herpesvirus 6 at an early stage of viral replication by the non-nucleoside compound CMV423

CMV423 (2-chloro-3-pyridin-3-yl-5,6,7,8-tetrahydroindolizine-1-carboxamide) is a new antiviral agent with potent and selective in vitro activity against the beta-herpesvirus human cytomegalovirus (HCMV), but not against alpha- or gamma-herpesviruses. Here we report that its activity also extends to human herpesvirus 6 (HHV-6) and 7 (HHV-7). When compared in vitro to ganciclovir and foscarnet (the standard drugs recommended for treatment of HHV-6 infections), CMV423 showed a superior selectivity, due to its high activity (antiviral IC(50): 53nM) and low cytotoxicity (CC(50): 144microM), both in continuous cell lines and in CBLCs infected with HHV-6. From mechanistic experiments at the level of viral mRNA and protein expression, we learned that CMV423 targets an event following viral entry but preceding viral DNA replication. Its antiviral action was dependent on the cell line used, implying involvement of a cellular component. When compared to a panel of known protein kinase inhibitors, CMV423 was found to share anti-HHV-6 characteristics with herbimycin A, which affects tyrosine kinase activity through heat shock protein 90 (Hsp90) inhibition. We demonstrated that high concentrations of CMV423 have an inhibitory effect on the total cellular protein tyrosine kinase activity, and that CMV423 and herbimycin A, when combined, act synergistically against HHV-6. The activities of cyclin-dependent kinases, protein kinases A and C, and the HHV-6-encoded pU69 kinase were not affected. We, therefore, conclude that CMV423 exerts its activity against HHV-6 through inhibition of a cellular process that is critical at early stages of viral replication and that may affect protein tyrosine kinase activity.

Quantitative analysis of human herpesvirus 6 cell tropism

Although HHV-6A and -6B are known to replicate preferably in human T-lymphocytes, in vitro infection of several other cell types has been described. Also, the finding that both variants use the ubiquitous molecule CD46 as a membrane receptor fully supports the possibility of a broad cellular tropism. However, productive infection, which requires complete progression through the viral replication cycle, depends on multiple cellular processes. Our studies were aimed at determining the differences in replication efficiency according to the cell type infected and at relating these differences to the sequential transcriptional events preceding DNA replication. A strong expression of immediate-early, early, and late genes was only seen in the T-lymphoblastoma lines. In the other cell lines, there was no clear correlation between the level of transcription and the final outcome of replication. Finally, we investigated the cytopathic effects of HHV-6 on different cell types of neural origin (oligodendrocytes, astrocytes, and neurons) in greater detail, and found that although all three sustained HHV-6 replication, HHV-6A was more neurovirulent than HHV-6B. This was confirmed in primary human oligodendrocyte cultures.

Infectious agents and multiple sclerosis--are Chlamydia pneumoniae and human herpes virus 6 involved?

A good deal of evidence suggests an infectious component in the development of multiple sclerosis (MS) and, to date, some 20 bacteria and viruses have been associated with the disease. Recent independent sets of studies have implicated the respiratory bacterium Chlamydia pneumoniae and human herpes virus 6 (HHV-6) in the pathogenesis of MS. However, as is the case for essentially all earlier microbial associations, experimental evidence linking either this bacterium or this virus to MS is equivocal. We review the published reports concerning involvement of C. pneumoniae and HHV-6 in MS, and data relating to possession of the APOE epsilon 4 allele, which some studies indicate might influence how these or other pathogens affect disease genesis. Based on the large set of inconsistent observations available and given important new information regarding the neuropathology of MS, we contend that no conclusion is possible at this point regarding the potential role of either C. pneumoniae or HHV-6 in MS. We therefore propose future studies that should clarify whether, and if so how, these and other organisms function in the pathogenesis of this disease.

Effects of blender rotational speed and discharge on the homogeneity of cohesive and free-flowing mixtures

The roles of blender rotational speed and blender discharge on the homogeneity of free-flowing art sand and of a cohesive placebo formulation were investigated in the tote blender. For three practical operating speeds, 6, 10, and 14 RPM, spanning the entire range of commercial equipment, the homogeneity of the free-flowing mixture was independent of rotational speed and blender size. On the other hand, the homogeneity of the cohesive pharmaceutical powder mixture was dependent on vessel rotational speed in a complex fashion, with 10 RPM producing a better final mixture than either 5 or 15 RPM. The homogeneity of the free-flowing sand mixture was preserved when discharged into a vertical bin, while the homogeneity of the fine pharmaceutical powder mixture significantly improved after discharge from the tote blender.