Tag: Epstein-Barr virus

Categories : GastrointestinalTags :

Chicken and Egg: Which Comes First, Epstein–Barr Virus or Crohn’s Disease?

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Irritable bowel syndrome. Credit: Scientific Animations CC4.0

Crohn’s disease, a debilitating inflammatory bowel disease, has many known contributing factors, including bacterial changes in the microbiome that foster an inflammatory environment. Now, for the first time, Crohn’s disease has been tied to a virus – specifically, Epstein-Barr virus (EBV), best known for causing infectious mononucleosis (mono).

Researchers had already observed increased levels of EBV in the intestine of patients with Crohn’s disease and had also found associations between EBV and autoimmune diseases other than Crohn’s, including lupus, multiple sclerosis, and rheumatoid arthritis.

But which came first? EBV or Crohn’s disease?

‘It was a classic chicken and egg problem,” says Anubhab Nandy, PhD, a research fellow in the Division of Gastroenterology, Hepatology, and Nutrition at Boston Children’s Hospital.

A longitudinal study just published in Gastroenterology systematically looked at the role of viruses in Crohn’s and found strong evidence that EBV infection predisposes people to develop Crohn’s.

Tracking EBV and Crohn’s

Nandy and colleagues analyzed data from a cohort of initially healthy military recruits, aged 20 to 24, who provided periodic serum samples throughout their service. They tested the samples with VirScan, a high-throughput assay developed by study coauthor Stephen Elledge, PhD, at Harvard Medical School. VirScan enables detection of antibodies against a wide range of viruses, providing insights into viral exposures.

Compared with healthy controls, military personnel whose samples were positive for anti-EBV antibodies were three times more likely to eventually develop Crohn’s disease. Interestingly, evidence of EBV exposure preceded their Crohn’s diagnosis by five to seven years.

“We went into this study not looking for EBV; we were looking for any virus that might elicit inflammatory bowel disease,” says Scott Snapper, MD, PhD, the study’s senior investigator and director of the Inflammatory Bowel Disease Center at Boston Children’s. “Then, when EBV was a hit, we looked very specifically at immune responses to EBV with more detailed tests.”

These tests bore out and strengthened the VirScan findings.

The team next looked for anti-EBV antibodies in a second cohort – more than 5000 children (median age; 11 years) who were first-degree relatives of people with Crohn’s disease. In this cohort, EBV was not a statistically significant predictor of a subsequent Crohn’s disease diagnosis. Snapper speculates that having first-degree relatives with Crohn’s could already have put them at increased risk due to shared genetic or environmental factors, muddying the association with EBV.

EBV and the immune system

Another possibility is that EBV affects children’s immune systems differently, perhaps because children are less likely to develop infectious mono when exposed. “Responding to certain organisms early in life may boost the immune system in a way that prevents immune-mediated disease,” Snapper says.

Nandy and Snapper now want to figure out what EBV does to people at a molecular level to make them more susceptible to Crohn’s disease.

One possibility is that the virus has certain genes or molecules that interact with human genes involved in susceptibility to autoimmune conditions. Another may relate to an anti-inflammatory protein produced by EBV, remarkably similar to mammalian IL-10. People exposed to that protein may make antibodies against it, preventing their own IL-10 from working and leaving them susceptible to inflammatory disease.

“Mechanistically, we need to understand exactly how EBV alters the immune system leading to Crohn’s disease,” Snapper says. “If you could figure out the mechanisms, you could come up with new therapies.”

Source: Boston Children’s Hospital

Categories : Immune SystemTags :

Multiple Sclerosis Drug Ocrelizumab Works by Reshaping the Immune System

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Myelin sheath damage. Credit: Scientific Animations CC4.0

When ocrelizumab became the first FDA-approved treatment for early forms of multiple sclerosis (MS) in 2017, it offered patients immense hope. The long-awaited drug is a monoclonal antibody that depletes B cells – the immune cells that drive MS progression. Exactly how ocrelizumab does this, however, remains unclear.

In a new study published in The Journal of Clinical Investigation, Yale scientists begin to answer this question. By using single-cell RNA sequencing, a technique that provides a window into the gene expression in individual cells, the researchers laid out a detailed view of how ocrelizumab achieves its therapeutic effects.

“The surprise was that the drug doesn’t work at all the way we thought it was working,” says David A. Hafler, MD, Professor of Neurology at Yale School of Medicine, who led the study. “We knew what the end result was and that the drug was enormously effective in patients. But what’s driving the drug’s action is a type of white blood cell in the central nervous system. No one would ever hypothesise that.”

The roles of T cells and B cells in multiple sclerosis

B and T cells have closely intertwined roles in the immune system. B cells are critical cells that recognise foreign objects, bind them, and present them to T cells, which then signal other immune cells to take action. But this relationship goes awry in disease.

Scanning electron micrograph of a B cell. Credit: NIH

In MS, abnormally active B cells trigger T cells to attack the myelin sheath, the protective layer of nerve fibres, leading to neurological symptoms, such as loss of vision, muscle weakness, and cognitive impairment. More than two decades ago, Hafler and his team discovered this was due to defects in regulatory T cells, which normally put the brake on immune responses, but when defective, unleash immune cells that mistakenly target the body’s own tissues.

In the early stages of MS, both B and T cells are deemed to be the drivers of the disease. Once the disease progresses to a neurodegenerative stage, other inflammatory processes become more prominent.

“Once you enter the neurodegenerative phase of the disease, it is much more difficult to stop the process,” Hafler says. “What we’ve learned is that the earlier you treat the disease, the better the outcome.”

Ocrelizumab binds to the surface of B cells, leading to their destruction. And especially for people in the early stages of MS, it can be quite effective. “The drug works incredibly well,” Hafler says. But Hafler and his team found that ocrelizumab was doing far more than just controlling B cells.

In the new study, the researchers analysed the blood and cerebrospinal fluid of 18 patients, all of whom had an early-onset form of multiple sclerosis in which patients cycle between periods of disease remission and relapse. The scientists measured the cell type-specific changes in protein expression before and after the patients received six months of ocrelizumab, in an effort to identify immune molecules that might change in response to the drug.

They discovered that the reduction in B cells driven by ocrelizumab led to an increase in the pro-inflammatory molecule TNF-α. This was unexpected because TNF-α has been shown to trigger the immune system and exacerbate inflammation in certain diseases. In fact, medications that block the activity of TNF-α are typically used for treating various autoimmune diseases such as rheumatoid arthritis and inflammatory bowel disease.

As they looked further, the researchers found that by inducing TNF-α, ocrelizumab led to an increase in a specific type of regulatory T cell. This, in turn, curbed the circulation of T cells that attack the myelin.

“This unpredicted increase in TNF-α shows that ocrelizumab works in a paradoxical way,” says Hafler.

Understanding the cause of multiple sclerosis

One of the current working models of MS suggests that the disease originates from the Epstein-Barr virus. “How the Epstein-Barr virus triggers the disease is a point that we don’t yet understand,” Hafler says. However, there is a strong body of evidence to show that the virus infects B cells. Therefore, understanding how a B cell-depleting drug affects T cell activity may lead to further explanations.

The current finding also explains why a fifth of the genes linked to MS risk involve the TNF pathway and why many of those genetic changes are protective in other diseases, such as inflammatory bowel diseases.

“This shows that biology has a richness to it,” Hafler says. “When these molecules are made, where they’re made, and what cell they’re working on have very different effects.”

Hafler suspects that ocrelizumab might be acting through other mechanisms as well, an inkling that motivates his lab to continue their investigation. “For something to work that well, there must be other things going on,” he says.

The team is now beginning to study the pathogenesis of MS in a large cohort of women who have at least one parent with the disease. By following the genetic evolution of the disease, the scientists are hoping to better understand how B cells change the immune landscape in real time.

“This study is only one piece of the puzzle,” Hafler says. “We’ll continue to look for other pieces.”

Source: Yale School of Medicine

Categories : Neurodegenerative DiseasesTags :

Epstein-Barr Virus: How does a Common Infection Trick the Immune System into Attacking the Brain in People with MS?

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An electron micrograph showing three Epstein-Barr virus (EBV) particles colourised red-orange. Credit: NIAID

Olivia Thomas, Karolinska Institutet; Graham Taylor, University of Birmingham, and Jill Brooks, University of Birmingham

Almost 3 million people worldwide have multiple sclerosis (MS) – an autoimmune disease caused by the immune system mistakenly attacking the brain and central nervous system.

While treatments for MS have improved over the years, there’s still no cure. This is largely because researchers still don’t fully understand what goes wrong in the immune system to cause MS. But our latest research has revealed new insights into the way certain immune cells behave in people with MS. This discovery brings us closer to understanding why some people get MS – and may also be a crucial step in developing better treatments and even cures.

Although the causes of MS aren’t fully understood, we know that genetics, lifestyle and environment factors can all influence MS risk. But the biggest risk factor for developing MS appears to be a common virus called Epstein-Barr virus (EBV).

EBV typically infects people during childhood without causing any symptoms – so most early infections go unnoticed. But if the infection occurs during adolescence, it may cause glandular fever (infectious mononucleosis) which, although debilitating in the short-term, usually has no long-term effects.

Most viral infections are rapidly cleared by the body’s immune system, but EBV is cleverer than most viruses. Although the immune system controls the infection, it is unable to completely eradicate the virus as it hides inside a type of immune cell called a B cell (which normally produce antibodies that bind to and destroy invading viruses or bacteria). Once you’re infected with EBV you carry it for life – although for most people this causes no problems.

By adulthood about 95% of people are infected with EBV, but in people with MS nearly 100% are infected. Large epidemiological studies have shown that EBV infection increases the risk of developing MS over 30-fold. For people who have had glandular fever the risk is even higher. Research has also shown that in people with MS, EBV infection occurs before the very earliest stages of disease.

Many researchers now believe being infected with EBV is more than a risk factor in MS – it’s essential.

But how does EBV cause MS – and why does a common virus only cause MS in a few people? Several theories are currently being investigated.

One theory is that in some people the immune cells activated by EBV mistakenly attack parts of the brain and central nervous system. This process, called molecular mimicry, also occurs in other autoimmune diseases, such as Guillain-Barré syndrome. This could explain why drugs which prevent immune cells from entering the brain are shown to dramatically improve MS symptoms.

Research into EBV molecular mimicry in MS has mainly focused on the viral protein EBNA1. Without EBNA1 EBV cannot live in B cells, and MS patients have higher levels of antibodies towards EBNA1.

But EBV makes over 80 different proteins during its life cycle. In our latest work we investigated immune responses to these other viral proteins in people with MS.

Altered immunity

We compared the immune responses of 31 people with MS, 33 healthy people and 11 people who had recently recovered from glandular fever. We wanted to see if each group reacted to EBV infections differently.

We found that antibodies targeting EBNA1 and another viral protein called VCA were higher in people with MS compared to the other groups. People with MS were also more likely to have antibodies targeting several other viral proteins. This suggests EBV antibodies are more altered in MS than previously thought – but it isn’t certain whether these antibodies are fighting infection or if they have a role in MS disease.

Scanning electron micrograph of a T cell lymphocyte. Credit: NIH / NIAID

Antibodies aren’t the full story. Previous research has suggested another type of immune cell, called a T cell, may also play an important role as they’re found in high numbers in MS brain lesions. As such, we wanted to understand whether T cells which fight EBV were different in people with MS.

By analysing blood samples we found that, although EBV T cell numbers were similar in MS and healthy people, these cells behaved differently in people with MS. T cells from people with MS produced slightly higher amounts of an inflammatory substance called interleukin-2. The body normally produces this substance in response to injury or infection, but too much interleukin-2 can cause chronic disease.

We also looked at molecular mimicry, wondering whether EBV T-cells mistakenly target brain proteins rather than fighting the virus.

Surprisingly, we found that in both people with MS and healthy people, their EBV T cells reacted to multiple proteins found in the brain. Notably, most people had EBV T cells that targeted a protein called myelin oligodendrocyte glycoprotein, or Mog, which surrounds the nerves.

Looking at one person with MS in more detail, we found individual T cells that directly recognised both EBNA1 and Mog. This means that, rather than just fighting infection, some EBV T cells could also target nerve cells in the brain.

This widespread misdirection between EBV T cells and the brain goes some way to suggest how infection with this common virus can lead to MS. But its presence in healthy people is slightly confusing. One possible explanation could be that EBV T cells are better able to cross the blood-brain barrier (a tight-knit lining of cells that protect the brain) in people with MS. This idea is something we’re keen to explore in future research.

While there’s still much we don’t know about these misdirected EBV T cells in the brain, our latest findings provide fresh evidence for researchers and hopefully will lead to the development of new, targeted treatments for MS.

Olivia Thomas, Assistant Professor, Department of Clinical Neuroscience, Karolinska Institutet; Graham Taylor, Associate Professor in Viral and Tumour Immunology, University of Birmingham, and Jill Brooks, Research Fellow, Institute of Cancer and Genomic Sciences, University of Birmingham

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Categories : Diseases, Syndromes and ConditionsTags :

New Approach to Epstein-Barr Virus and Resulting Disease

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An electron micrograph showing three Epstein-Barr virus (EBV) particles colourised red-orange. Credit: NIAID

The Epstein-Barr virus can cause a spectrum of diseases, including a range of cancers. Emerging data now show that inhibition of a specific metabolic pathway in infected cells can diminish latent infection and therefore the risk of downstream disease, as reported by researchers from the University of Basel and the University Hospital Basel in the journal Science.

Exactly 60 years ago, pathologist Anthony Epstein and virologist Yvonne Barr announced the discovery of a virus that has carried their names ever since. The Epstein-Barr virus (EBV) made scientific history as the first virus proven to cause cancer in humans. Epstein and Barr isolated the pathogen, which is part of the herpesvirus family, from tumour tissue and demonstrated its cancer-causing potential in subsequent experiments.

Most people are carriers of EBV: 90% of the adult population are infected with the virus, usually experiencing no symptoms and no resulting illness. Around 50% become infected before the age of five, but many people don’t catch it until adolescence. Acute infection with the virus can cause glandular fever – also known as “kissing disease” – and can put infected individuals out of action for several months. In addition to its cancerogenic properties, the pathogen is also suspected to be involved in the development of autoimmune diseases such as multiple sclerosis.

As yet, no drug or approved vaccination can specifically thwart EBV within the body. Now, a research group from the University of Basel and the University Hospital Basel has reported a promising starting point for putting the brakes on EBV. Their results have been published in the journal Science.

EBV hijacks the metabolism of infected cells

Researchers led by Professor Christoph Hess have deciphered how the immune cells infected with EBV – the so-called B cells – are reprogrammed. Known as “transformation,” this process is necessary for the infection to become chronic and cause subsequent diseases such as cancer. Specifically, the team discovered that the virus triggers the infected cell to ramp up the production of an enzyme known as IDO1. This ultimately leads to greater energy production by the power plants of infected cells: the mitochondria. In turn, this additional energy is needed for the increased metabolism and the rapid proliferation of B cells reprogrammed by EBV in this way.

Clinically, the researchers focused on a group of patients who had developed EBV-triggered blood cancer following organ transplantation. To prevent a transplanted organ from being rejected, it is necessary to weaken the immune system using medications. This, in turn, makes it easier for EBV to gain the upper hand and cause blood cancer, referred to as post-transplant lymphoma.

In the paper, which has now been published, the researchers were able to show that EBV upregulates the enzyme IDO1 already months before post-transplant lymphoma is diagnosed. This finding may help to develop biomarkers for the disease.

Second chance for a failed drug

“Previously, IDO1 inhibitors have been developed in the hope that they could help to treat established cancer – which has unfortunately turned out not to be the case. In other words, there are already clinically tested inhibitors against this enzyme,” explains Christoph Hess. Accordingly, this class of drugs might now receive a second chance in applications aimed at dampening EBV infection and thereby tackling EBV-associated diseases. Indeed, in experiments with mice, IDO1 inhibition with these drugs reduced the transformation of B cells and therefore the viral load and the development of lymphoma.

“In transplant patients, it’s standard practice to use drugs against various viruses. Until now, there’s been nothing specific for preventing or treating Epstein-Barr virus associated disease,” says Hess.

Source: University of Basel

Categories : Neurodegenerative DiseasesTags :

Epstein–Barr Virus Antibodies may Trigger Multiple Sclerosis

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Source: CC0

Researchers at Karolinska Institutet have found further links between Epstein–Barr virus and multiple sclerosis. A study published in Science Advances shows that some individuals have antibodies against the virus that mistakenly attack a protein in the brain and spinal cord.

Many years ago, the Epstein–Barr virus (EBV), which infects most people early in life and then usually lies dormant was linked to multiple sclerosis (MS) but the reason remained a mystery. Increasing evidence, including two papers published in Science and Nature last year, suggests that EBV infection precedes MS and that antibodies against the virus may be involved. However, the molecular mechanisms seem to vary between patients and remain largely unknown.

“MS is an incredibly complex disease, but our study provides an important piece in the puzzle and could explain why some people develop the disease,” says Olivia Thomas, postdoctoral researcher at the Department of Clinical Neuroscience, Karolinska Institutet and shared first author of the paper. “We have discovered that certain antibodies against the Epstein-Barr virus, which would normally fight the infection, can mistakenly target the brain and spinal cord and cause damage.”

The researchers analysed blood samples from more than 700 patients with MS and 700 healthy controls. They found that antibodies that bind to a certain protein in the Epstein-Barr virus, EBNA1, can also bind to a similar protein in the brain and spinal cord called CRYAB, whose role is to prevent protein aggregation during conditions of cellular stress such as inflammation. These misdirected, cross-reactive antibodies may damage the nervous system and cause severe symptoms in MS patients, including problems with balance, mobility and fatigue. The antibodies were present in about 23 percent of MS patients and 7% of control individuals.

“This shows that, whilst these antibody responses are not required for disease development, they may be involved in disease in up to a quarter of MS patients,” says Olivia Thomas. “This also demonstrates the high variation between patients, highlighting the need for personalised therapies. Current therapies are effective at reducing relapses in MS but unfortunately, none can prevent disease progression.”

“We are now expanding our research to investigate how T cells fight EBV infection and how these immune cells may damage the nervous system in multiple sclerosis and contribute to disease progression,” says joint first author of the paper Mattias Bronge, affiliated researcher at the Department of Clinical Neuroscience, Karolinska Institutet.

Source: Karolinska Institutet

Categories : Diseases, Syndromes and Conditions Immune SystemTags :

Scientists Solve Epstein-Barr Virus Mystery

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Photo by National Cancer Institute on Unsplash

Medical science has not yet been able to explain why the Epstein-Barr virus triggers infectious mononucleosis (IM) in some people with initial infections and not in others. But now researchers have identified a unusual T cell response to the virus as the cause, and as a potential target for the development of vaccines. The findings were recently published in the journal Blood.

T cells normally fight the proliferation of the Epstein-Barr virus (EBV) in humans as part of an antiviral immune response. In this response, certain EBV components (peptides) are presented to the T cells by a specific molecule (HLA-E), which is found on the surface of cells infected with EBV. This triggers a non-classical T-cell response that leads to the destruction of the infected cells. Due to a genetic variation (HLA-E*0103/0103), about one third of the population naturally has more HLA-E molecules on EBV-infected cells.

A recently published study has shown that the risk of developing IM following first-time infection with the Epstein-Barr virus depends strongly on this EBV-specific immune response.

“Our research revealed that people with the HLA-E*0103/0103 genetic variation have a lower risk of developing infectious mononucleosis than those who do not have the variation. Our experiments in the lab showed that this gene variation is associated with a highly pronounced EBV-specific -non-classical — immune response,” explained Hannes Vietzen from MedUni Vienna’s Center for Virology, the first author of the study.

Preventive and diagnostic possibilities

EBV is one of the most common viral infections in humans. On initial infection, the virus causes IM in some children and young adults; this disease is characterised by non-specific symptoms, such as fever, as well as exhaustion that in some cases can last for several months. Until now, it was unclear why a first-time EBV infection only leads to IM in a minority of people, while most do not present any symptoms whatsoever. The immune response that the researchers identified could also be a target for research into preventive measures: “This immune response was still measurable years after the initial EBV infection and generally provides long-lasting protection against reinfection with Epstein-Barr, so it might be worth focusing our attention on this mechanism with a view to developing new vaccines in future,” said Hannes Vietzen, looking ahead.

Another finding from the study could also open up new diagnostic options: “The combination of the unfavourable HLA-E genetic variation with certain EBV peptides also appears to play an important role in the development of EBV-associated lymphomas in transplant recipients,” Hannes Vietzen commented. “Analysis of the EBV strains found in these patients could be helpful in identifying high-risk patients at an early stage and treating them in good time.”

Source: Medical University of Vienna

Categories : Neurodegenerative DiseasesTags :

MS Likely Caused by Epstein-Barr Virus

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Source: NCI on Unsplash

Multiple sclerosis (MS) is likely caused by infection with the Epstein-Barr virus (EBV), according to a new Harvard University study.

“The hypothesis that EBV causes MS has been investigated by our group and others for several years, but this is the first study providing compelling evidence of causality,” said senior author Professor Alberto Ascherio. “This is a big step because it suggests that most MS cases could be prevented by stopping EBV infection, and that targeting EBV could lead to the discovery of a cure for MS.” The findings were published in Science.

Currently incurable, MS is a chronic inflammatory disease of the central nervous system that attacks the myelin sheaths protecting neurons in the brain and spinal cord. One of the top suspects for its cause is EBV, a herpes virus that can cause infectious mononucleosis and establishes a latent, lifelong infection of the host. Establishing a causal relationship between the virus and the disease has been hard because EBV infects approximately 95% of adults, MS is relatively rare, and the onset of MS symptoms begins about ten years after EBV infection. To determine the connection between EBV and MS, the researchers conducted a study among over 10 million US military personnel, identifying 955 who were diagnosed with MS during their period of service.

The team analysed serum samples taken twice a year by the military and determined the soldiers’ EBV status at time of first sample and the relationship between EBV infection and MS onset during the period of active duty. In this cohort, the risk of MS increased 32-fold after infection with EBV but remained unchanged after infection with other viruses. Serum levels of neurofilament light chain, a biomarker of the nerve degeneration typical in MS, increased only after EBV infection. The findings cannot be explained by any known risk factor for MS and suggest EBV as the leading cause of MS.

The delay between EBV infection and the onset of MS may be partly a result of the disease’s symptoms being undetected early on and partly the evolving relationship between EBV and the host’s immune system, which is repeatedly stimulated whenever latent virus reactivates.

“Currently there is no way to effectively prevent or treat EBV infection, but an EBV vaccine or targeting the virus with EBV-specific antiviral drugs could ultimately prevent or cure MS,” Prof Ascherio said.

Source: Harvard University