Michael K. Racke, MD

 Anne, to wrap things up, do you have any words of wisdom? Or do you want to put Alberto on the spot and have him wrap things up?

 I’ll definitely put Alberto on the spot. We have him here as our guest, and I’d like to know more about what he thinks might be treatments in our lifetime. Or do we have to get rid of the virus in babies and do a long experiment, when we’ll all be dead at the end?

 I don’t know, but I wouldn’t give up trying. I agree with the skepticism. I agree with you, Avi, but we still have to try. If we can, we should try, because the possibility that we can get a better treatment if not a cure targeting the virus may sound remote, but it’s possible. I wouldn’t want to give that up as a priority.

 Avi, I’m going to play devil’s advocate. If we look at other viral illnesses that cause demyelinating disease, and in mice—Theiler [murine encephalomyelitis] virus, coronavirus, or mouse hepatitis virus—how does that compare with the findings for EBV [Epstein-Barr virus] and MS [multiple sclerosis]?

 I’m not answering that. I have no idea.

 I don’t know those models that well, but you need a persistent viral infection. It’s true that a lot of it is immune mediated. With the Theiler virus, you get this slowly progressive chronic neurodegeneration and there’s virus in the CNS [central nervous system].

 Although, Stephen Miller showed that you can get epitope spreading there too, and some antimyelin.

 That could still be a genetic background phenomenon in why it’s progressive as opposed to getting attacked.

 When you guys figure it out and have a treatment, tell me in which patient the treatment can be used. Then I’ll be happy to prescribe it as long as it’s safe.

 Avi, are there other animal models that people have used? I don’t know of any examples of a demyelinating disease in mice where people are trying to make a model for EAE [experimental autoimmune encephalomyelitis] where the virus isn’t there.

 Yes, the virus has to be there. HHV-6 [human herpesvirus 6] is the same thing that Steve did in marmosets. You have to put the virus in there in order to cause the demyelination.

The virus may be very difficult to find in the brain. For example, diminutive RNA hepatitis virus isn’t easy to find in the brain.

 Yes. There’s a massive immune attack. There’s the canine distemper virus story; there’s another 1. There’s a lot of stuff that people had done in the past with these viruses.

 I have a question for the immunologist. If the main mechanism is in you, why is it so difficult to find the antigen? I’ve looked at this literature, but I can’t find the answers. It’s been 30 or more years of trying to find it, and it’s not being found.

 It depends on you what you believe. People have been able to demonstrate in multiple sclerosis that people have memory T cells to myelin antigens. That doesn’t necessarily mean that’s causing disease. It could be an epiphenomena, epitope spreading after some virus started it. The other thing that’s interesting is the way these interact the same with vitamin D. Including yours, there are plenty of papers that suggest that if you get Epstein-Barr virus and had low vitamin D, that enhances it even more. What did the vitamin D do in this picture? It would be interesting. You weren’t able to look at vitamin D levels in the same samples, were you?

 Yes. Vitamin D deficiency will roughly double the risk of the MS. If you have the optimal level compared with the lowest level, there’s a 2-fold variation of risk.

 I think Mike was saying in the recent study.

 In the same population, but not in this paper and not in the EBV negative, we’re going to do that.

 But the point is if you were EBV negative with low vitamin D, you still don’t get MS.

 You have to be EBV positive. But if you’re EBV positive with low vitamin D, you’re much more likely to get MS.

 It’s 2-fold higher compared with people with good vitamin D levels.

 Alberto, you’ve made me a believer, and that’s hard to do. I’m a skeptic at heart. That’s fantastic work, and a lot of years in the making. I learned a lot during this panel session. I want to give a shoutout to Alberto, who’s going to be presenting within the Whitaker Lecture at this year’s CMSC [Consortium of Multiple Sclerosis Centers Annual Meeting], which I’m excited about. For those of you who are listening, please attend the CMSC. It’s going to be in National Harbor, Maryland, right outside Washington, DC.

We’ve had a rich discussion. I thank all the panelists, friends and colleagues for beautifully going back and forth about EBV and the implications at the bench side and the bedside. On behalf of our panelists, I want to thank all of you for watching this special 

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Looking to the future of multiple sclerosis care, the panel of thought leaders pose important questions that remain to be answered in the research and treatment of multiple sclerosis.

Future Directions in Research and Treatment

 Do you feel like there may be some difference with progressive onset MS [multiple sclerosis] vs relapse onset? Alberto, you mentioned we have such highly effective drugs for relapsing-remitting MS. In my view, we have limited to none for progressive MS. If you were to put your money somewhere for therapeutics in the EBV [Epstein-Barr virus] world, if we feel that has some causal effect, where would you look? Would you look toward progressive MS and try to utilize treatments toward that phenotype? I don’t know the answer. What are your thoughts?

 That’s a very good question. I agree that progressive MS is where we’d like to be able to intervene and change course. On the other hand, it could be too late, going back to the discussion we had before. Maybe the more you wait, the less the disease process becomes virus dependent. It’s a dilemma that doesn’t have a good answer. The only way to know the answer would be to try, with all the difficulties there are, either very early treatment or treatment in progressive patients and see what happens. We don’t have a good substitute for clinical experimental evidence, because we can discuss the mechanisms forever, but it’s enough to miss 1 link. The effect may be the opposite of what you expect. In the history of the treatment of MS, there have been some examples of that. There are things that we thought to be beneficial that we now know to be harmful because you missed a little piece of the very complex picture.

 Anne, Avi, and Mike, what about if you were to say, “Let’s bring this to a clinical trial,” and you could only go into 1 population? Alberto mentioned it’s very hard to do placebo-controlled trials, at least in relapsing MS, which I totally agree with. You could have a whole other conversation of ethics surrounding that. But in progressive MS, maybe that’s the opportunity for a lot of reasons. I don’t know what others think.

 Let me say something. The clinical trial will never work for herpesviruses. The reason is that none of these drugs get rid of the virus is that they only suppress viral replication. If you have active herpes viral replications, you’ll suppress it. You don’t get rid of the virus, even if you treat herpes and encephalitis. You never get rid of the herpesvirus. The herpesvirus is still there.

 Don’t you think that I could make the argument that that’s how interferons worked? They got their name because they interfere with viral replication. With both alpha and beta interferon, everybody was saying, “It works because it modifies the immune system.” I could say, “No, what it’s doing is interfering with viral replication, and that’s how it’s mediating its effect.” Getting to Scott’s point, I’d say that it’s inhibiting the activation of virus that resulted in exacerbations. If you look at interferons, the treatment effect is much better against exacerbations and reducing MRI activity than it is against progression. I’d treat relapsing-remitting MS first and see if I could improve that as opposed to thinking that it had some effect to immediately inhibit progressive disease.

 When you have a relapse, do you have an increase in viral load for EBV?

People have looked at it. We looked at it.

 That was a setup question. Avi, I had a feeling.

 But by that time—I go back to your point about epitope spreading. That may be that the mechanism of how EBV treatment would have to work is at the beginning to prevent the disease. Once I’ve had inflammation and had all the machination going for the pathogenesis of MS, I can now get rid of EBV, and the disease is going on its own.

 You can never get rid of EBV. That’s the thing. With all herpesviruses, once you’re infected with it, it doesn’t matter what antiviral agent you use. You’ve got it until the day you die. At least currently.

 What about if you got rid of every single B cell?

 It doesn’t matter. The B cell is only 1 of the cells where EBV lies. EBV can infect a number of other cell types.

 Are you arguing that the Atara Biotherapeutics drug wouldn’t work because you could never get rid of it?

 If you have a T-cell response against an infected cell, that’s a different story. If you have some antigen that’s still being expressed and you can get to the reservoirs, you theoretically could. But with an antiviral, you won’t. Theoretically, it’s possible that with a cytotoxic T-cell response, you could get rid of a latent reservoir. It’s not true latency because you still have antigens expressed during the latent period. It’s like a persistent infection. That’s possible.

 The key question is what the mechanism is, because you mentioned viral reactivation. This is a question for you, Avi. How many B cells need to get a lytic reactivation of EBV in the brain to cause damage? Because my understanding of these low viruses from other examples is that you don’t need a massive virus. Even a tiny number of infected cells that are inducing lytic replication could cause a lot of damage. Some of this condition is difficult to find the virus in the brain. I don’t know what you think about that.

 It’s a theoretical possibility yet demonstrated in the virus. That has been very difficult. A lot of people have tried and never found it. When that Italian paper came out with EBV and the lymphoid follicles, you might remember that a lot of people look for it in the meninges. I had a postdoc who came from Jack Antel’s lab, and we spent 2 or 3 years with Richard Ambinder, an EBV expert at Johns Hopkins Medicine. We never found any virus in the brain. Jack Antel looked at it himself. A number of people looked at it. We couldn’t find EBV. We were very eager to find it.

 Avi, what caught my attention is that you said, “The reservoir.” I’m thinking about route of administration for therapeutics and where you may make a greater impact depending on the different subtype of MS. Meaning if you have progressive MS, we think about the blood-brain barrier not being as leaky as relapsing-remitting MS. Could there be a difference in the treatment effect with some of the vaccines that may be developed with where they’re given? With B-cell depletion, rituximab has been tried intravenously but also intrathecally. Maybe I’m just tired and not making a lot of sense, but I think about that. Because if we’re going try to help people with MS with different types of MS, there are some people in whom the route of administration is going to make a difference.

 The point that Mike was trying to make is that once the immune system is triggered, whatever vaccine or other treatment you’re going to do, it may not make a lot of difference if it’s an immune-mediated phenomenon that’s driving the pathophysiology. If you think it’s a viral-mediated phenomenon and the virus is key to the pathophysiology, then if you can suppress it, it will make a difference. But demonstrating that has been very difficult. It’s not from a lack of trying. People have been looking for EBV for decades in all kinds of stages of multiple sclerosis. That relationship has been very hard. Alberto is the first person who’s been able to demonstrate it serologically in this population. But in established multiple sclerosis, there’s a huge body of literature. It’s been very hard.

 Yes, but what he demonstrated is that there was a response to the virus. It didn’t mean that the virus had to be in the brain. The other argument could be that it’s in a B cell in the bone marrow, for example. You’re looking in the brain, but nobody was looking at a bone marrow biopsy at that time.

Expert panelists review the viability of new treatments in development for multiple sclerosis.

Debating the Possibility of Epstein-Barr Virus–Targeted Treatments for MS

 Anne, you were ready to jump into the conversation. When Mike started talking about NfL [neurofilament light chain], I could see you were like, “It’s not specific to MS.”

 That’s 1 thing, but I was thinking about all those children who get Epstein-Barr virus [EBV] when they’re under 5 years old. If they’re destined to get MS [multiple sclerosis], they’re going to have a long latent period. Why would that be in some people vs a year or 2 in another person? That gets back to my question to Alberto about people who have symptomatic mononucleosis when they’re in their teens or early 20s. What’s different about that that seems to convey an even larger risk?

 Individuals with mononucleosis have massive EBV infection with an extremely high viral load and even more overwhelming cytotoxicity response. For a few weeks, you have a storm of B cells and T cells proliferating. One important thing is that at that stage, some of these B cells infiltrate within the CNS [central nervous system] and go to the brain. Maybe they establish there’s some nature in which they can survive inside the brain. This is 1 of the hypotheses that has been proposed. I don’t think it’s surprising that mononucleosis is associated with higher risk of MS, given that EBV is a cause of MS, because you have much more virus than in people who are symptomatic and much more aggressive immune response against the virus. That makes some sense in a common way. Not in a technical way, but in an intuitive way. Like with COVID-19, where an overwhelming infection is more likely to get you more sick. But the delay is a very good question.

There are cases of MS that occur 10, 15, and 20 years after the infection. What’s going on in that time? One possibility of this dynamic is that the relation between the virus and immune system isn’t static, at least not in all people. The virus tends to reactivate, and periodically the immune system will suppress it. In this process of reactivation and suppression, maybe something emerged, whether it’s a bit of spreading molecular mimicry or collateral damage. At some point in this dynamic, a pathological direction is taken. I’m not an immunologist. I’m giving you possible intuitive things from a distance.

 I was going to ask Avi, because that’s very curious to me to have such different latencies between the prime infection and then the autoimmune disease. Avi, beyond what Alberto just mentioned, what other things come to mind that could explain that huge latency between pediatric-onset MS and someone in their 60s developing MS, at least symptomatic MS?

 I don’t know the answer, but the phenomenon is well known. You get chickenpox as a child, but you get shingles when you’re older. There are a lot of other things. It’s the same thing with people who associate herpesvirus with Alzheimer disease. You’re getting HSV-1 [herpes simplex virus 1] infection very early, while Alzheimer disease occurs so late. Who knows if that association is true. But it’s the same idea of long latency.

With viral infections in the CNS, you can get long latencies. We’ve seen patients who get infected with dengue very early on and then many years later start developing encephalitis and neurodegeneration from it. Nipah virus is the same thing. You have 20 years of latency before you can get encephalitis. That’s a well-known phenomenon. I don’t know what’s happening during that time. Maybe the virus is latent and gets reactivated at some point and then the immune system reacts very differently upon the time of reactivation. It’s quite possible. Or something else is happening. All these proteinopathy people will say it’s promoting protein aggregation, and it takes a certain threshold to get to and then triggers things. I don’t know the answer, but these are possibilities.

Alberto Ascherio, MD, DrPH, addresses the range of latency periods for Epstein-Barr virus and the impact on onset multiple sclerosis.

Understanding Varying Latency Periods for Epstein-Barr Virus and Onset of MS

 Anne, I’m going to ask you this question, because this is going to come up. Once people become more aware of this study and other studies moving forward, we’re going to get tons of questions from patients. Just like with any new study that comes out, the patient is going to ask, “What can I do to get rid of this virus?” All of us are wondering whether that’s going to make a difference if you get rid of the virus. How are you going to answer these questions? It’s putting the cart before the horse, but what’s your approach going to be?

 I’ll certainly mention that B-cell depletion—B cells are where the virus resides latently—seems to have a beneficial effect. Maybe it’s because we don’t get rid of all them, but when they come back, the disease comes back. It’s not as though you never have disease again. I’m going to tell them about some of the studies that people are talking about and beginning to do—early phase studies to try to get rid of EBV [Epstein-Barr virus]–affected B cells in particular with the early phase ATA188 study, which is utilizing T cells to go after B cells that are EBV infected. We don’t have any results. That was all started by Mike Pender many years ago when he started growing CD8 cells that were autologous to the patient and would attack EBV-containing B cells in that same patient. I don’t know that he has any great results on that yet. He probably hasn’t done enough patients. But studies like that might provide some insights, and also might give a little hope to patients who already have MS [multiple sclerosis]. If there ever was a sterilizing vaccine, that most likely wouldn’t help them once they got it.

 As far as my approach, I’ll tell you what I’m going to do. I’m going to get Alberto’s cell phone number. I have your cell phone number. I’ll say, “Talk to Alberto first so he can tell you how important EBV is,” and then you’ll do exactly what you just said, and then I’ll get off the hook. No—

 Send that telephone number to me also, please.

 That’s right. In terms of next steps, there still needs to be a lot of work. It’s like with a lot of things in MS. We’re at the tip of the iceberg, and we have a lot of exciting data, but where do we go next? Alberto, where do we need to go with the work you’ve done and others are doing to take it from the stratosphere to the clinic? It’s challenging to try to translate it to the clinic.

 Right. There are 2 areas of research in which we’re involved. One is treatment. I’m not a clinician, but they’ve been collaborating with clinical groups trying to promote trials of antiviral drugs effective against EBV in people with MS. It’s incredibly challenging. You probably know better than I do. For ethical reasons, given the very powerful treatments that are available, it’s not possible to do placebo-controlled trials. Basically, we’re suggesting trials of antivirals added on to standard treatment, but the standard treatment for relapsing-remitting MS is so effective against the relapses in the new lesions that it may be very difficult to demonstrate any benefit. It’s a bit unfortunate. We may have a hypothetical impact on strategy to treat MS, but it’s going to be very difficult to test it and to see if it works. It may work, but it may not work.

Specifically, there are some antivirals that in vitro seemed to have high activity against EBV. They’re considered very safe, like tenofovir alafenamide, which is a useful pre-exposure prophylaxis of HIV. We’ve been collaborating with the hypothesis of, can we test this in people with the MS? My role is as a collaborator, but we don’t do clinical studies. The other area is going in the other direction. Given that people get infected with EBV, can we predict who’s going to get MS? Can we find a biomarker, any signature? Going back to what Michael and Anne commented on before, can we identify the profile of antibody responses or other biomarkers that will identify who’s going to get MS? Because that could be very useful for secondary prevention. Maybe the disease process has started. We see it about to start, and we can do something to delay or prevent it. These are the 2 big areas.

 What you just said caught my attention with the NfL [neurofilament light chain] levels going up. Everyone is excited about NfL. There’s a lot of work that needs to be done there, especially in MS. You wonder if there will be a differential effect in those who are EBV positive. But I can almost envision a graph where NfL levels are going up in those who are destined to get MS, and it stays low in those who don’t.

 Scott, when the NfL goes up, they have MS. That’s arguing that there’s damage happening in the nervous system. The CMSC [Consortium of Multiple Sclerosis Centers]—I’m trying to think if you participated in this—had a workshop at the last annual meeting looking at NfL as a biomarker. Not just for MS but also for Alzheimer disease and the neurodegenerative disorders, basically anywhere you’re killing neurons or damaging neurons, NfL gets into the blood.

The power of what Alberto has showed is that it could be a long time between when they first got exposed to EBV to when they clinically got MS, but you already see it early on. We always say that people probably get presymptomatic MS when there are lesions already happening. He’s using NfL as that marker to say, “Look, you get EBV.” Then you get those already showing that there’s some inflammation happening in the brain, and it can be a long time until the person has their first clinical exacerbation. But he’s already made the link that EBV led to the next step, which was damage in the nervous system that he’s measured with the NfL.

 You’re saying exactly what I said, so I’m agreeing with you, or you’re agreeing with me. What I was proposing is if the NfL level is normal and they’re EBV positive, then the chance of them having MS or developing MS could be considerably lower than someone who’s already having—

Alberto Ascherio, MD, DrPH; Anne Cross, MD; and Michael Racke, MD, discuss implications for patient communication and other advances from bench to bedside.

Translating New Advances to the Clinic

 Going back to what I alluded to, if this happens to be the heavy hitter, so to speak, then where can we intervene to prevent the development of MS [multiple sclerosis] in an individual who may be at higher risk? Or if someone already has MS, is there opportunity to decrease the severity of the disease? Or if it’s someone who has progressive disease, is there an opportunity to limit the disease progression? I’m curious to hear the panel’s thoughts. Anyone can answer. I struggle with the patient who comes in who has children and, from a genetic predisposition, their child is already at a little higher risk. Then they have mononucleosis. Can we intervene earlier to prevent disease? I don’t know if someone wants to jump on that.

 For years, I’ve been talking to my patients about making certain that their children weren’t vitamin D deficient, whether that truly has an effect or not. It wouldn’t be a bad thing to make sure they aren’t vitamin D deficient. The same thing is to keep them from smoking or getting obese. I’ve always said to them, “And there’s Epstein-Barr virus and mononucleosis,” but I don’t know how you’re going to stop them from getting that. Because Epstein-Barr virus [EBV] is also associated with other diseases and cancers, I’m hoping we’ll eventually have an effective and safe vaccine that we can give to people, maybe just those who are susceptible, or maybe everyone to help prevent it.

 Just tell your kids, “Don’t kiss anyone. Stay away from people.” The kissing disease; that’s what I remember growing up and hearing, which isn’t feasible.

 That’s because the councils are so large, they’re kissing one another. It’s not from kissing.

 That’s right. Anne, you mentioned a potential treatment, a vaccine. There are some things in development. Avi, because you’re the preeminent neurovirologist and viruses are close to your heart, where we are with the science in developing the vaccine that may be specific to EBV? Where we need to go?

 A number of companies are interested in making a vaccine. Merck is making a vaccine. I met with them once pre-COVID-19, and they were very interested. They’ve already made headway. There are several other companies. Steve Jacobson has been working with another company, and they’re making a vaccine. I don’t know how close they are to doing human trials, but it seems that they’re pretty close. Anne, I don’t know if you have additional information on them.

 You could probably talk about this better than we can. With the enrolled study, Atara Biotherapeutics has an EBV potential therapeutic that’s T-cell directed, but I don’t know if anyone can talk about it. It’s interesting. Maybe I misread this, but I heard Moderna is also developing an mRNA [vaccine], which could be very interesting as well.

 Yes, they’re making mRNA vaccines for a lot of pathogens. They can just type it and use it.

 Moderna has a phase 1 study going on with an EBV vaccine. It’s useful to separate the discussion between prevention and treatment, because the data are pretty compelling that if you could completely prevent EBV infection, you’d prevent MS. A vaccine doesn’t necessarily prevent disease, as we know from COVID-19. The discussion on the vaccine would be whether we can have a vaccine that confers long-lasting sterile immunity. If we can, that would prevent MS.

If we have a vaccine that can affect the immune response but doesn’t completely prevent infection, then the effect of the risk of MS will depend on the specifics of the vaccine, how it affects the immune response, and the mechanisms that relate EBV to MS. That’s the big unknown. I hope to learn and discover from you guys. Given that EBV is causing MS, how does that happen? That’s the $1 billion question. Once you have MS, is it still early enough to change the virus host relation, or is it too late? Is it a hit and run, as Avi mentioned? Is it that the virus triggers an immune response that becomes physically autonomous, and it doesn’t need the virus anymore and takes its own way? I don’t know that. I wish I knew. That’s what keeps me awake at night, trying to think.

We have clues in both directions. There are some hints. We know the virus is there, that it doesn’t go away. We know they’re depleting the B cells that are the site of persistence of the virus. It’s a dramatic therapeutic effect. The virus is there in a latent form, but it’s very active. Its immunosuppression will cause lymph proliferation. Even if the mechanism of damage is from the new response against the virus, these elements suggest that the virus is still playing a role in keeping that immune response active and strong and possibly cytotoxic, either molecular mimicry or collateral damage, or even transformation of the B cells themselves because it’s an oncogenic virus. Maybe the EBV virus could transform B cells in the way that dysregulate the…. It’s also possible that all this is history. Once you have MS, you can even wipe away the virus but unfortunately it’s too late. I don’t know the answer to that.

 I like how you’re separating prevention, and then once someone has MS, the propagation of the immune responses, whether it’s EBV related or not. Avi and Mike, do you have any comments on that? There’s some work being done looking at that with Larry Steinman’s group, that recent paper that Mike alluded too. I don’t know if that provides any more insight to that question.

 It gets back to the idea of whether it’s molecular mimicry. If it’s molecular mimicry and you’ve gotten rid of the fires, but you already have T cells that are recognizing some other self-antigen, then I could evoke Avi’s epitope spreading and get rid of EBV; it doesn’t matter. I even would make the argument that I’ve done a lot of work in autologous hematopoietic stem cell transplantation, and some of those people get cured. Why is it that they get cured? Maybe the other argument is, why is it that there are some people who break away? I’ve always used the argument. I’d tell the patients, “I’m trying to make you your identical twin who doesn’t have MS.” That’s still making the argument that you have to have an infectious agent like EBV. If I clean your immune system, for whatever reason, you have to get EBV again or whatever viruses you need to once again recapitulate the events to get MS. For some reason, in three-quarters of the patients, that doesn’t happen and they don’t get MS anymore. There’s a lot of work to be done to try to understand how viruses cause disease, and certainly for demyelinating disease.

The expert panelists comment on intervention efforts underway to address multiple sclerosis prevention and treatment.

Therapeutic Implications Regarding the Role of Epstein-Barr Virus in MS

 Anne, I see on your face that you want to ask a question. You’re all allowed to ask questions. I don’t have to be the only person asking questions.

 This is a burning question. Alberto, in 1 of your earlier papers you showed that the risk was particularly higher in persons who got Epstein-Barr virus [EBV] or at least a symptomatic mononucleosis when they were a little older, maybe in their teens or so. It seems like in this study, these persons who were developing an Epstein-Barr virus infection were in their teens or slightly older. Do you think the age of getting it is meaningful?

 The data are about the history of mononucleosis. We don’t know the age of infection for people who are symptomatic except in our study. The previous literature showed that history of mononucleosis is associated with a 2.3-fold increased risk of MS [multiple sclerosis]. I’m being precise on the 2.3 because there have been several meta-analyses, and it’s remarkably consistent. It’s a strong risk factor, but this is more for Mike or Avi to comment on the possibility that the immune response to EBV when you get mononucleosis is bigger than in people who have a symptomatic EBV infection. I don’t think we fully understand the mechanism behind this association in this case between mononucleosis and MS risk.

 That’s interesting. Avi, I don’t know if you want to comment on whether someone is symptomatic or asymptomatic. This could be with any virus exposure. I’m sure we’re going to learn with COVID-19 also about the long-hauler situation in those who are asymptomatic vs symptomatic or mild vs severe. That’s curious.

 There are 2 things. First, with any infection, as Alberto was saying, you get different types of clinical presentations. Let’s say the flu runs through your family. You’ll find 1 family member who gets really sick, another who has relatively mild symptoms, and someone who’s asymptomatic. It’s the same family with different types of presentations. Your workplace is the same thing. If somebody comes in infected and infects everybody, some fall sick and some don’t. There’s a host response to infections that’s different. Maybe the host genetics or host factors might dictate the response that people get. Is that relevant for multiple sclerosis?

Alberto is trying to make the case that if you’re older and have a very strong immune reaction, maybe that’s contributing to the pathophysiology. If that’s the case, you might see what’s called epitope spreading. Particularly if you have persistent infection or a very robust infection, you may get antibodies against multiple epitopes. If it’s persistent over a period of time, you’ll get more epitopes, against which you’ll get an immune response. Alberto, in your peptide library or however you’ve looked at it, have you looked to see what epitopes you get antibodies against? Does that change over a period of time?

 Yes, we could look at that. So far, we see that with all the epitopes that are different, the mechanisms of control are coming from EBV. It’s not 1; there are over 40 epitopes that are in peptides, different EBV proteins, maybe not 1 but 2 other EBV proteins. We’re starting to look at the history and evidence of change over time in terms of the epitope spread. Unfortunately, we know when these individuals were infected, but we don’t have the clinical information to differentiate those who were symptomatic or not symptomatic. That’s not being made available to us. It probably exists in some registry, but we couldn’t access that information.

 If I could interject for a second, it sounds to me in some ways it’s a little similar. I don’t know if you saw the paper from Dr Thomas Wisniewski’s group with COVID-19. If you look at people who had severe infections—people who were hospitalized and had encephalopathy—they had dramatically elevated NfL [neurofilament light chain]. Presumably, the NfL is being elevated because there’s an inflammatory response within the central nervous system causing some damage that now allows you to detect the NfL in the peripheral blood. We probably see this in a lot of instances where there’s something happening in the brain. The thing that’s interesting—we were talking about getting into this earlier—is if you take Alberto’s work on vitamin D and take the vitamin D, EBV, and maybe even HHV-6 [human herpesvirus 6], if people have had all 3 of those things, their risk goes even higher. The important fact is what Alberto said, that of all these factors, there are things that can add to it, but maybe this is 1 of the primary factors. Of all the factors we’ve seen, perhaps this is the 1 that carries the most weight.

A panel of experts probe the variations in immune response to Epstein-Barr virus in patients with multiple sclerosis.

Examining Immune Response to Epstein-Barr Virus

 Alberto, I want to circle back to you because I’m curious about your thoughts. Mike touched on this. Your paper said that it’s necessary to have exposure to EBV [Epstein-Barr virus] to develop MS [multiple sclerosis]. In your view, what are some other additional factors that would play into leading someone to MS? Meaning unhealthy lifestyle choices or if someone is a smoker or overweight. Does that add into the mix to even increase that 30-plus-fold that EBV seems to add?

 It’s rare for a virus to be sufficient to cause a disease. I agree with Michael, but EBV and MS in this sense are similar to human papillomavirus and cervical cancer, the hepatitis D virus and liver cancer, or many viruses and encephalitis. It’s quite common for a virus to cause a disease in a small minority or in a proportion of people. The sufficiency is almost never given. I also try to stay away from saying it’s necessary, because unless we define a disease as being caused by a specific agent—for example, if you define measles, it’s the infection with the measles virus. If you define measles clinically, even if it’s a very characteristic disease, you’ll find children with a fever and all the symptoms, and it isn’t caused by the measles virus. I tend to stay away from that because there will be an individual with all the features of MS, and there will be 1 of 800 who’s in our study but isn’t EBV positive and who has a disease that isn’t caused by MS.

Getting more precisely to your question, in the past 20 years, we’ve been looking at risk factors for MS in individuals who are EBV positive because that’s the large majority of the population. We and others have identified vitamin D sufficiency, cigarette smoking, childhood obesity, and genetic predisposition as the main factors that influence the risk of MS. Each factor has a magnitude of effect around 2-fold, maybe 3-fold, for the HLA-DR15 allele. They contribute to the risk, but EBV is by far the strongest.

 That’s what caught my attention with your study. When we think about MS and preventing MS, once someone has MS, we have good immune therapies to prevent relapses, new spots on MRI, etc. But if we can develop treatments, that may prevent MS in an individual who may be at high risk of developing MS. With someone who’s EBV positive and was exposed to EBV, we should be encouraging them to make healthy lifestyle choices: to stop smoking if they’re a smoker and to exercise if they’re not exercising. But that may get us only so far, as you nicely mentioned about the increased risk or folds between EBV and other factors.

Alberto Ascherio, MD, DrPH, highlights key risk factors leading to increased prevalence of multiple sclerosis.

Exploring Contributing Risk Factors to MS

 Mike, you’re an immunologist. You’ve done a lot of benchwork. From your perspective, when we think about priming the immune system and the various factors that go into priming the immune system to develop an autoimmune condition like MS [multiple sclerosis], how do you see that? How do you explain that to an individual? I’m still trying to wrap my head around 1 causative factor leading to MS, because I’ve always thought about it as a perfect storm. Can you talk to us a little about that?

 There are a couple of things. (By the way, very nice work, Alberto.) When things of autoimmunity, when things like molecular mimicry—there was a paper by Jack Strominger and Kai Wucherpfennig years ago that looked at cross-reactivity between T cells in patients with MS vs a number of infectious agents, and of course, peptides from EBV [Epstein-Barr virus] came up. There’s recently been a paper from Bill Robinson and Larry Steinman’s group showing cross-reactivity and an antibody response between EBNA, which is the EBV nuclear antigen, and a molecule called glial cell adhesion molecule.

The other thing people don’t necessarily talk about as much is the idea that infections also shape the immune repertoire with an idea that it’s not just that I have to have molecular mimicry. I have to have infections in such a way that under certain conditions, if everything happens in the right way and under the right conditions, I can get an autoimmune response that’s dysregulated. For example, lots of papers have tried to link not only Epstein-Barr virus but also human herpesvirus type 6. There have been plenty of papers. Thomas Olson had a paper suggesting that CMV was protective. For Anne and me, 

How could some of these infections affect the immune repertoire in a way that you can get EAE [experimental autoimmune encephalomyelitis]? One thing that was interesting was a paper by Ray Welsh that showed that if you had multiple infections, that was in some sense protective, as opposed to if you had 1 infection. I’d almost say that Epstein-Barr virus—correct me if I’m misinterpreting this—is necessary but not sufficient. I hope that’s true, because I had infectious mononucleosis. You have to have it, but there have to be other things. You mentioned genetic background. That’s how you end up getting the frequency of MS occurring that’s much less than the population of people who got infected with EBV, similar to how there are plenty of people who are smokers who, for whatever reason, end up having protective factors, perhaps genetics, so that they don’t get lung cancer.

 I want to get Anne into the conversation. In your clinic, since Alberto’s paper got published—it’s widely available, and there’s a lot of buzz around it—what are you hearing from patients? Are you hearing from patients in the clinic who want to know more about this story? There are potential treatments in the pipeline that could be helpful. What are you hearing?

 Congratulations, Alberto, on your fantastic piece of work that took so long to put together. So far, I’m not hearing a huge amount, but that’s partly because the paper is new. However, with some of my sophisticated patients, I’m hearing questions, including, “What could this mean in terms of treatment and even prevention down the road? Could there be vaccinations against Epstein-Barr?” It probably hasn’t been out long enough for a lot of patients to know about it, but I’m sure it’s coming down the pike.

Anne Cross, MD, and Michael Racke, MD, discuss how the immune system is primed in multiple sclerosis.

Priming the Immune System for MS

 I’m going to propose a question to Avi because he’s 1 of the preeminent virologists I know. Avi, why has it been so important throughout the years to study viruses in general? When we think about autoimmune diseases, and specifically MS [multiple sclerosis], how can this help put things together? Viruses may be priming the immune system, deviating someone’s immune system toward autoimmunity, or having a protective effect. Could you comment on that?

 Sure. Thank you very much for that question, Scott. When you’re a hammer, everything is a nail. When you’re a virologist, those are the most important things. The pandemic has made us wonder, “Why has nobody cared about viruses?” First, I want to congratulate Alberto on this fascinating work that he published. It’s such an important piece of work. People have tried to draw this association between EBV [Epstein-Barr virus] and MS for a very long time. You might remember that people showed lymphoid follicles in the meninges with EBV and then a lot of epidemiological association with EBV and lots of other viruses too. In MS, a lot of viruses have been implicated over the years, and EBV seems to be the 1 that continues to hold up. A lot of things fell by the wayside, like HTLV-1. You can remember a lot of these things over the years.

People love viral etiologies of diseases because you think that if there’s a viral etiology, maybe you can cure, or maybe the disease course will change after you treat the virus. For every disease, people have tried to look for transmissible agents, including for Alzheimer disease, Parkinson disease, and ALS [amyotrophic lateral sclerosis]. People used to take brain tissue they injected into macaques and chimps and all kinds of stuff to see if they can transmit it. The idea of slow viruses existed for decades and has been shown to be the case for Kuru disease and then for Creutzfeldt–Jakob disease. It was later discovered that it wasn’t the virus; it was actually an infectious protein.

But the idea that there may be viruses associated with neurodegenerative diseases continues. Herpesviruses have been associated with Alzheimer disease. That hasn’t been proven, but there’s a lot of work being done along those lines. These things can have long latent periods. You get infected, and as Alberto showed, you don’t develop MS the next day. There are long latent periods, and that makes it particularly difficult to draw those kinds of associations. But long latency can occur, and then it could be a trigger. Viruses can be a trigger. As you mentioned, Scott, they can trigger autoimmune phenomenon, and those autoimmune phenomena can take their own course and cause the disease. It could be either of those 2 possibilities.

 I have a Venn diagram that I show when I’m giving a talk on anything immunology related and the autoimmune process, that shows the perfect storm to set someone down the path of autoimmunity. At least for MS, the immune system is at center stage. Maybe there’s some genetic predisposition. We have identified hundreds of genes. Then we have the environmental risk, in which EBV has kept coming back, as you mentioned. It’s a new old kid on the block.

Avindra Nath, MD, explains the importance of understanding virology when treating autoimmune diseases.

Viruses and Autoimmune Disease

 Hello, and thank you for joining us for this special 

. Today we’ll be discussing the practical and clinical implications of a recent novel published study, the first of its kind, drawing the association between multiple sclerosis [MS] and EBV [Epstein-Barr virus]. Joining me is a wonderful group of experts with different vantage points: 1 of the main authors of the study, Dr Alberto Ascherio, a professor of medicine at Brigham and Women’s Hospital and Harvard Medical School in Boston, Massachusetts; Dr Anne Cross, a professor of neurology and chair of the division of neuroimmunology at Washington University in St. Louis [Missouri]; Dr Avi Nath, a senior investigator and clinical director of the National Institute of Neurological Disorders and Stroke; and Dr Mike Racke, the medical director for neurology at Quest Diagnostics [in Seacaucus, New Jersey] and a past president of the CMSC [Consortium of Multiple Sclerosis Centers]. I’m Scott Newsome, a neurologist from Johns Hopkins Medicine in Baltimore, Maryland.

Let’s get started. At center stage, the star of the show is Alberto, because of this wonderful study that you and your team recently published. Could you describe to the audience why you thought this study was so important to pursue? Can you also provide us with a CliffsNotes version of the study design, methods, and anything else you want to tell us about the study?

 Thank you for the introduction, Scott. The idea that EBV is related to MS has been around for a long time, but it’s been an idea difficult to sell to most MS specialists. Until now, MS was considered an autoimmune disease of unknown etiology, and only a few of us consistently tried to put EBV within the picture. One reason it’s so difficult is that EBV is a nearly ubiquitous virus. The common thought is that because it infects nearly everybody, how can it be the cause of MS, which affects only 1 of 300 people? I always found that question a bit puzzling, because I say, “Do you think if everybody was a smoker, cigarette smoking would cease to cause lung cancer?” Obviously not. The difficultly is more in demonstrating the link. Conceptually, it’s not that something ubiquitous can cause a rare disease, which is a common occurrence for many viruses. But how do you prove it?

This is the first study that could rely on a very large population of EBV-negative individuals who weren’t infected with EBV. These were young adults who could be followed prospectively, and we could see in an experiment of nature whether those who get infected have a different risk of developing MS compared with those who aren’t infected. The results are striking. If you’re not infected with EBV, you virtually don’t get MS. It’s only after EBV infection that your risk of MS jumps more than 34-fold.

The study concept is very simple. It took 20 years to conduct in collaboration between multiple institutions, with multiple obstacles in the course. But the concept is basic, comparing EBV-negative with EBV-positive subjects. We included several controls. One is cytomegalovirus [CMV], which is transmitted in a similar manner to EBV. We used that as a negative control. We found that with individuals infected with CMV, there’s no relation to MS. The occurrence of MS is entirely independent from CMV infection. If anything, CMV seemed to have a very modest protective effect on the occurrence of MS.

We also looked at neurofilament light chain [NfL]. The neurofilament light chain in serum is a sensitive biomarker of neurodegeneration. It’s not specific for MS, but when you get an elevation in serum NfL, it suggests that something is happening in the brain, that it’s the beginning of a pathological process. The reason we measure NfL is because there’s a prodromal period in MS. The common objection we got when we were presenting the hypothesis of EBV in MS was, “How can you exclude the possibility that those individuals who have prodromal MS and a dysregulated immune system are more likely to get infected with EBV?” NfL helps establish the temporal sequence. In individuals who develop MS, we see that it’s EBV infection first followed by NfL elevation and later by MS onset. We never see NfL elevation preceding EBV infection. This strengthened the evidence that EBV comes first and the beginning of the pathological process is secondary in time to EBV.

Finally, because several infectious agents have been proposed as being related to MS, we looked at the overall antibody response against human viruses—over 100,000 peptides that cover all the pathological human viruses—and we compared the antibody responses between MS cases and control with the same age, sex, and ethnicity. We found that the peptides that differentiated MS cases from the controls were only EBV peptides. I was surprised by how striking the results were. I expected a lot of noise and false-positive heat with different peptides from different viruses, but the response to EBV is so strong that it overwhelmed everything else. Only EBV peptides stood out in MS. Putting everything together, I don’t think there’s any other plausible explanation, so I’m pretty convinced about this. I’ve seen people expressing concern in the media. I’m yet to hear someone proposing an alternative explanation other than EBV causing MS.

 Thank you. I enjoyed reading your paper. You broke it down very nicely. I was going to ask you a couple of questions, which we’ll get to later. But I know there are some challenges when you do studies like this where people will think that there’s an association vs a cause and effect, which I’m sure is some of the constructive criticism that comes your way. Because if you show an association, that doesn’t necessarily mean there’s a causal link. But we’ll hear a little later from colleagues about that. In your view, what is the most significant piece of your paper? You mentioned that this is 20 years in the making, which is quite impressive. I don’t think people understand how much goes into work like what you guys did. What are the top 2 most significant things of your study?

 The key observation is that your risk of MS is 0 until you get infected with EBV. If I may comment on your question of association, it makes a big difference when you’re looking at an association that’s a 20% increase compared with 1.2 or 2 and a relative risk of 30. When an association gets to a certain level, at some point you find that you don’t have an alternative explanation. A good example is smoking and lung cancer. There’s no experimental evidence of randomized people to smoking or not smoking. It’s an association, but it’s an association that’s been accepted. The link between several viruses and other diseases before the vaccine became available has also been based on association studies, so the strength of the association is 1 of the basic elements.

As we said in the paper, confounding is the beast that people are concerned about in epidemiological studies. To induce a relative risk of 30, a confounder would need to have an association with MS, increase the risk of MS by over 64 times, and be correlated with increased risk of EBV infection by over 64 times. I haven’t heard anyone proposing anything coming remotely close to something that could have the strengths of association with both the exposures and the outcome of interest.

 Thank you. You mentioned CMV as being a control. In the pediatric world, there have been some works looking at EBV and CMV and the relative association or protective effect.

Alberto Ascherio, MD, DrPH, recaps key findings and learning from a recently published study that he coauthored demonstrating a causal relationship between MS and Epstein-Barr virus.