Human Herpesvirus 6A Is a Risk Factor for Multiple Sclerosis

Body fluid markers for multiple sclerosis and differential diagnosis from atypical demyelinating disorders

INTRODUCTION

Body fluid markers could be helpful to predict the conversion into clinically definite multiple sclerosis (MS) in people with a first demyelinating event of the central nervous system (CNS). Consequently, biomarkers such as oligoclonal bands, which are integrated in the current MS diagnostic criteria, could assist early MS diagnosis.

AREAS COVERED

This review examines existing knowledge on a broad spectrum of body fluid markers in people with a first CNS demyelinating event, explores their potential to predict conversion to MS, to assess MS disease activity, as well as their utility to differentiate MS from atypical demyelinating disorders such as neuromyelitis optica spectrum disorder and myelin oligodendrocyte glycoprotein associated disease.

EXPERT OPINION

This field of research has shown a dramatic increase of evidence, especially in the last decade. Some biomarkers are already established in clinical routine (e.g. oligoclonal bands) while others are currently implemented (e.g. kappa free light chains) or considered as breakthroughs (e.g. neurofilament light). Determination of biomarkers poses challenges for continuous monitoring, especially if exclusively detectable in cerebrospinal fluid. A handful of biomarkers are measurable in blood which holds a significant potential.

Causal associations of COVID-19 on neurosurgical diseases risk: a Mendelian randomization study

Many researchers have explored the potential association between one neurosurgical disease and coronavirus disease 2019 (COVID-19), but few systematically analyzed the association and causality between COVID-19 and various neurosurgical diseases. A Mendelian randomization analysis was conducted to evaluate the causal association between COVID-19 (including critically ill COVID-19, hospitalized COVID-19, and respiratory syndrome coronavirus 2 (SARS-CoV-2) infection) and 30 neurosurgical diseases within European populations. The consequences of inverse variance weighted models suggest that genetic susceptibility of critically ill COVID-19 may increase the risk of cerebral infarction (odds ratio [OR] = 1.02; p-value = 0.006), genetic susceptibility of SARS-CoV-2 infection may increase the risk of stroke (OR = 1.02; p-value = 0.047), and conversely, genetic susceptibility of hospitalized COVID-19 may reduce the risk of pituitary adenoma and craniopharyngioma (OR = 0.90; p-value = 0.032). In addition, evidences revealed potential associations between genetic susceptibility of COVID-19 and spinal stenosis (OR = 1.03; p-value = 0.028), diffuse brain injury (OR = 1.21; p-value = 0.040) and focal brain injury (OR = 1.12; p-value = 0.040). By testing for heterogeneity and pleiotropy, the above causal conclusions are robust. In summary, our analysis shows that COVID-19 has an independent and powerful causal influence on multiple neurosurgical disorders.

Human herpesvirus 6A and axonal injury before the clinical onset of multiple sclerosis

Recent research indicates that multiple sclerosis is preceded by a prodromal phase with elevated levels of serum neurofilament light chain (sNfL), a marker of axonal injury. The effect of environmental risk factors on the extent of axonal injury during this prodrome is unknown. Human herpesvirus 6A (HHV-6A) is associated with an increased risk of developing multiple sclerosis. The objective of this study was to determine if HHV-6A serostatus is associated with the level of sNfL in the multiple sclerosis prodrome, which would support a causative role of HHV-6A. A nested case-control study was performed by crosslinking multiple sclerosis registries with Swedish biobanks. Individuals with biobank samples collected before the clinical onset of multiple sclerosis were included as cases. Controls without multiple sclerosis were randomly selected, matched for biobank, sex, sampling date and age. Serostatus of HHV-6A and Epstein-Barr virus was analysed with a bead-based multiplex assay. The concentration of sNfL was analysed with single molecule array technology. The association between HHV-6A serology and sNfL was assessed by stratified t-tests and linear regressions, adjusted for Epstein-Barr virus serostatus and sampling age. Within-pair ratios of HHV-6A seroreactivity and sNfL were calculated for each case and its matched control. To assess the temporal relationship between HHV-6A antibodies and sNfL, these ratios were plotted against the time to the clinical onset of multiple sclerosis and compared using locally estimated scatterplot smoothing regressions with 95% confidence intervals (CI). Samples from 519 matched case-control pairs were included. In cases, seropositivity of HHV-6A was significantly associated with the level of sNfL (+11%, 95% CI 0.2-24%, P = 0.045) and most pronounced in the younger half of the cases (+24%, 95% CI 6-45%, P = 0.007). No such associations were observed among the controls. Increasing seroreactivity against HHV-6A was detectable before the rise of sNfL (significant within-pair ratios from 13.6 years versus 6.6 years before the clinical onset of multiple sclerosis). In this study, we describe the association between HHV-6A antibodies and the degree of axonal injury in the multiple sclerosis prodrome. The findings indicate that elevated HHV-6A antibodies both precede and are associated with a higher degree of axonal injury, supporting the hypothesis that HHV-6A infection may contribute to multiple sclerosis development in a proportion of cases.

Economic and Social Standing of Individuals in Iran Diagnosed with Multiple Sclerosis

BACKGROUND

Multiple sclerosis (MS) may be affected by socioeconomic status (SES). This study aims to explore the determinants of SES among Iranian patients with MS and examine how these factors relate to disability and disease progression.

METHODS

All patients with MS listed in the nationwide MS registry of Iran (NMSRI) until January 8, 2022, were included in this population-based study.

RESULTS

Among the 5153 patients, most were female (74.5%), married (70.8%), and did not hold an academic degree (53.8%). Unemployment (OR: 3.75) and being unmarried (OR: 2.60) were significantly associated with Expanded Disability Status Scale (EDSS)≥6, and the time to progression was shorter in the unemployed group (P value: 0.03). There was also a significant negative correlation between the time to progression and the age at disease onset.

CONCLUSION

The study suggests that providing financial and social support to MS patients and their families through investment could reduce both individual and societal burdens.

Higher frequency of Human herpesvirus-6 (HHV-6) viral DNA simultaneously with low frequency of Epstein-Barr virus (EBV) viral DNA in a cohort of multiple sclerosis patients from Rio de Janeiro, Brazil

Multiple sclerosis (MS) is a chronic neuroinflammatory and neurodegenerative disease of the central nervous system (CNS). The etiology of MS is not well understood, but it's likely one of the genetic and environmental factors. Approximately 85% of patients have relapsing-remitting MS (RRMS), while 10-15% have primary progressive MS (PPMS). Epstein-Barr virus (EBV) and Human herpesvirus 6 (HHV-6), members of the human Herpesviridae family, are strong candidates for representing the macroenvironmental factors associated with MS) pathogenesis. Antigenic mimicry of EBV involving B-cells has been implicate in MS risk factors and concomitance of EBV and HHV-6 latent infection has been associated to inflammatory MS cascade. To verify the possible role of EBV and HHV-6 as triggering or aggravating factors in RRMS and PPMS, we compare their frequency in blood samples collected from 166 MS patients. The presence of herpes DNA was searched by real-time PCR (qPCR). The frequency of EBV and HHV-6 in MS patients were 1.8% (3/166) and 8.9% (14/166), respectively. Among the positive patients, 100% (3/3) EBV and 85.8% (12/14) HHV-6 are RRMS and 14.4% (2/14) HHV-6 are PPMS. Detection of EBV was 1.2% (2/166) and HHV-6 was 0.6% (1/166) in blood donors. About clinical phenotype of these patients, incomplete multifocal myelitis, and optic neuritis were the main CNS manifestations. These are the first data about concomitant infection of these viruses in MS patients from Brazil. Up to date, our findings confirm a higher prevalence in female with MS and a high frequency of EBV and HHV-6 in RRMS patients.

Association analysis between symptomology and herpesvirus IgG antibody concentrations in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and multiple sclerosis

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and multiple sclerosis (MS) are two complex and multifactorial diseases whose patients experience persistent fatigue, cognitive impairment, among other shared symptoms. The onset of these diseases has also been linked to acute herpesvirus infections or their reactivations. In this work, we re-analyzed a previously-described dataset related to IgG antibody responses to 6 herpesviruses (CMV - cytomegalovirus; EBV - Epstein-Barr virus; HHV6 - human herpesvirus-6; HSV1 and HSV2 - herpes simplex virus-1 and -2, respectively; VZV - varicella-zoster virus) from the United Kingdom ME/CFS biobank. The primary goal was to report the underlying symptomology and its association with herpesvirus IgG antibodies using data from 4 disease-trigger-based subgroups of ME/CFS patients (n = 222) and patients with MS (n = 46). The secondary objective was to assess whether serological data could distinguish ME/CFS and its subgroup from MS using a SuperLearner (SL) algorithm. There was evidence for a significant negative association between temporary eye insight disturbance and CMV antibody concentrations and for a significant positive association between bladder problems and EBV antibody concentrations in the MS group. In the ME/CFS or its subgroups, the most significant antibody-symptom association was obtained for increasing HSV1 antibody concentration and brain fog, a finding in line with a negative impact of HSV1 exposure on cognitive outcomes in both healthy and disease conditions. There was also evidence for a higher number of significant antibody-symptom associations in the MS group than in the ME/CFS group. When we combined all the serological data in an SL algorithm, we could distinguish three ME/CFS subgroups (unknown disease trigger, non-infection trigger, and an infection disease trigger confirmed in the lab at the time of the event) from the MS group. However, we could not find the same for the remaining ME/CFS group (related to an unconfirmed infection disease). In conclusion, IgG antibody data explains more the symptomology of MS patients than the one of ME/CFS patients. Given the fluctuating nature of symptoms in ME/CFS patients, the clinical implication of these findings remains to be determined with a longitudinal study. This study is likely to ascertain the robustness of the associations during natural disease course.

The Role of Microorganisms in the Etiopathogenesis of Demyelinating Diseases

Multiple sclerosis (MS), neuromyelitis optica (NMO) and myelin oligodendrocyte glycoprotein antibody disease (MOGAD) are inflammatory diseases of the central nervous system (CNS) with a multifactorial aetiology. Environmental factors are important for their development and microorganisms could play a determining role. They can directly damage the CNS, but their interaction with the immune system is even more important. The possible mechanisms involved include molecular mimicry, epitope spreading, bystander activation and the dual cell receptor theory. The role of Epstein-Barr virus (EBV) in MS has been definitely established, since being seropositive is a necessary condition for the onset of MS. EBV interacts with genetic and environmental factors, such as low levels of vitamin D and human endogenous retrovirus (HERV), another microorganism implicated in the disease. Many cases of onset or exacerbation of neuromyelitis optica spectrum disorder (NMOSD) have been described after infection with Mycobacterium tuberculosis, EBV and human immunodeficiency virus; however, no definite association with a virus has been found. A possible role has been suggested for Helicobacter pylori, in particular in individuals with aquaporin 4 antibodies. The onset of MOGAD could occur after an infection, mainly in the monophasic course of the disease. A role for the HERV in MOGAD has been hypothesized. In this review, we examined the current understanding of the involvement of infectious factors in MS, NMO and MOGAD. Our objective was to elucidate the roles of each microorganism in initiating the diseases and influencing their clinical progression. We aimed to discuss both the infectious factors that have a well-established role and those that have yielded conflicting results across various studies.

Excision of Integrated Human Herpesvirus 6A Genomes Using CRISPR/Cas9 Technology

Human herpesviruses 6A and 6B are betaherpesviruses that can integrate their genomes into the telomeres of latently infected cells. Integration can also occur in germ cells, resulting in individuals who harbor the integrated virus in every cell of their body and can pass it on to their offspring. This condition is termed inherited chromosomally integrated HHV-6 (iciHHV-6) and affects about 1% of the human population. The integrated HHV-6A/B genome can reactivate in iciHHV-6 patients and in rare cases can also cause severe diseases including encephalitis and graft-versus-host disease. Until now, it has remained impossible to prevent virus reactivation or remove the integrated virus genome. Therefore, we developed a system that allows the removal of HHV-6A from the host telomeres using the CRISPR/Cas9 system. We used specific guide RNAs (gRNAs) targeting the direct repeat region at the ends of the viral genome to remove the virus from latently infected cells generated in vitro and iciHHV-6A patient cells. Fluorescence-activated cell sorting (FACS), quantitative PCR (qPCR), and fluorescence in situ hybridization (FISH) analyses revealed that the virus genome was efficiently excised and lost in most cells. Efficient excision was achieved with both constitutive and transient expression of Cas9. In addition, reverse transcription-qPCR (RT-qPCR) revealed that the virus genome did not reactivate upon excision. Taken together, our data show that our CRISPR/Cas9 approach allows efficient removal of the integrated virus genome from host telomeres. IMPORTANCE Human herpesvirus 6 (HHV-6) infects almost all humans and integrates into the telomeres of latently infected cells to persist in the host for life. In addition, HHV-6 can also integrate into the telomeres of germ cells, which results in about 80 million individuals worldwide who carry the virus in every cell of their body and can pass it on to their offspring. In this study, we develop the first system that allows excision of the integrated HHV-6 genome from host telomeres using CRISPR/Cas9 technology. Our data revealed that the integrated HHV-6 genome can be efficiently removed from the telomeres of latently infected cells and cells of patients harboring the virus in their germ line. Virus removal could be achieved with both stable and transient Cas9 expression, without inducing viral reactivation.

Shared genetics and causal associations between COVID-19 and multiple sclerosis

Neuroinflammation caused by COVID-19 negatively impacts brain metabolism and function, while pre-existing brain pathology may contribute to individuals' vulnerability to the adverse consequences of COVID-19. We used summary statistics from genome-wide association studies (GWAS) to perform Mendelian randomization (MR) analyses, thus assessing potential associations between multiple sclerosis (MS) and two COVID-19 outcomes (severe acute respiratory syndrome coronavirus 2 [SARS-CoV-2] infection and COVID-19 hospitalization). Genome-wide risk genes were compared between the GWAS datasets on hospitalized COVID-19 and MS. Literature-based analysis was conducted to construct molecular pathways connecting MS and COVID-19. We found that genetic liability to MS confers a causal effect on hospitalized COVID-19 (odd ratio [OR]: 1.09, 95% confidence interval: 1.03-1.16) but not on SARS-CoV-2 infection (1.03, 1.00-1.05). Genetic liability to hospitalized COVID-19 confers a causal effect on MS (1.15, 1.02-1.30). Hospitalized COVID-19 and MS share five risk genes within two loci, including TNFAIP8, HSD17B4, CDC37, PDE4A, and KEAP1. Pathway analysis identified a panel of immunity-related genes that may mediate the links between MS and COVID-19. Our study suggests that MS was associated with a 9% increased risk for COVID-19 hospitalization, while hospitalized COVID-19 was associated with a 15% increased risk for MS. Immunity-related pathways may underlie the link between MS on COVID-19.