Looking back over 50 years of Epstein-Barr virus
Kat: This is the Cancer Research UK podcast for April 2014. This month, we’ve got a special edition looking back over 50 years of the Epstein-Barr virus – the first virus found to cause cancer in humans – with some of the key researchers involved. Plus our heroes and zeros.
Hello and welcome, I’m Dr Kat Arney. This March marked the 50 year anniversary of a remarkable paper published by the Lancet, in which three pioneering young scientists identified the first human tumour virus. The virus was later named after two of the trio, and christened the Epstein-Barr virus, or EBV for short.
Emma Smith brings us this report from a conference celebrating the discovery, and looking at the progress that’s been made in tackling cancers caused by the virus over the past 5 decades.
Emma: The beginnings of the discovery of EBV can be found in the work of a British medical officer, Denis Burkitt. Based in Uganda, he described the details of an aggressive and usually fatal cancer that affected children.
The tumours were a type of cancer called lymphoma – later named Burkitt’s lymphoma after him – and were caused by white blood cells dividing uncontrollably. The peculiar thing he noted was the strong geographical pattern to the disease, it only occurred in areas with a certain climate.
On March 22, 1961, Burkitt visited England and gave a lecture at a London medical school. In the audience sat a young scientist called Anthony Epstein. As soon as he heard the lecture, he became extremely excited, and here he tells us why:
Anthony: The only thing that could play a part and be determined by temperature and rainfall was something biological. And I immediately thought in my head, because I had worked with tumour viruses before, of a cancer causing virus carried by some kind of arthropod vector – arthropod that is to say, something like a mosquito or a tick for instance.
Emma: Epstein met with Burkitt and arranged for samples of the tumour to be shipped to England so they could be studied using the country’s first commercially available electron microscope – a tool so powerful that even tiny virus particles can be detected with it.
But much to their frustration there was no virus to be seen, and they were not able to grow the tumour cells in the lab to study them more closely. That is until one day, when fog caused the plane carrying a tumour sample to be diverted. The sample was longer in transit than normal, and Epstein told us what he found when it arrived.
Anthony: The samples were always in a small bottle, they weren’t fixed or anything of course, and there was transit fluid to keep them from drying out and so on. This time when I looked at the transit fluid it was cloudy. And one thought, “Oh, bacteria have got in there, perhaps a sample from the jaw already infected, and that the long journey had allowed bacterial proliferation. This is not worth doing anything with, chuck it away and go home.”
But I put a drop of this stuff onto a glass slide with a coverslip, looked at it as a wet preparation, and instead of seeing huge numbers of bacteria, the cloudiness was induced by free-floating tumour cells that had come detached from the cut edges of the sample.
Emma: Reminded of research he’d seen elsewhere, Epstein tried growing the cells that had come free from the tumour, and finally he succeeded. It was when he looked at the tumour cells grown in the laboratory under the electron microscope that he first spotted tell-tale virus particles, but at first he didn’t know the significance of his discovery.
Anthony: Well it was impossible to know what it was. I knew it was a herpes virus, but what herpes virus? I mean, I don’t know what virology you know, but there are at the moment nigh on nine human herpes viruses. At that time I think there were four or five. So what is this? It is of any importance? Well the fact that a herpes virus was replicating in a culture, without wiping the culture out – which all the known herpes viruses would have done – made me feel that this was something special.
Emma: With the help of scientists in the US, Epstein and his colleagues revealed the new virus to the world and slowly gathered the evidence that it was behind Burkitt’s lymphoma. But there were many surprises to come.
It’s now known that EBV has links to cancers of the back of the nose and throat, also known as nasopharyngeal cancers, as well as other types of lymphoma. And it’s emerging EBV might play a role in stomach cancer too.
Yet there’s a bigger mystery. Research has shown that more than 95 per cent of adults across the globe are infected with EBV. But, clearly, 95 per cent of people don’t get EBV-related cancers. Figuring out why the virus causes cancer in a minority of people was still a huge puzzle, so scientists turned to the virus’ genetic code – its DNA – for clues.
The genetic code, or sequence, of EBV was published in 1984 by a team led by Fred Sanger – the founding father of DNA sequencing. Sanger had an unorthodox method of choosing what to sequence next, as Professor Paul Farrell – one of the authors of the paper explains.
Paul: Fred had a rather straightforward way of deciding what to sequence next – he just chose something that was three time bigger than the last thing he’d sequenced!
Emma: A Cancer Research UK funded scientist, Beverly Griffin, had all the pieces of DNA ready to go and persuaded Sanger that this should be the next thing to sequence. It took eight or nine people three years to complete, but it gave researchers crucial information about the virus. For example, as Paul Farrell explains, one surprise was the extent to which the virus uses RNA to give instructions to the cell it has infected.
Paul: A big thing that has come through is that this virus, and some others related to it, are using a lot of functional RNA to affect the hosT-cell. The significance of this is that the RNAs are not ‘seen’ by the adaptive immune system, so it’s a way in which the virus seems to be able to influence the hosT-cells without being seen by the immune system.
The biggest vehicle for this, if you like, are microRNAs – the small RNAs that are now recognised to be a whole layer of gene regulation we didn’t know about twenty years ago, and EBV is really the king of microRNAs. It makes about 45 different microRNAs that regulate cell genes. And in nasopharyngeal cancer, the cancer which is very frequent in Southeast Asia associate with EBV, it expressed very high levels of these microRNAs in the cancers. So many people, including me, think that it’s very likely that this is one of the mechanisms by which the virus contributes to the disease.
Emma: Farrell also explains how understanding the genetics of the virus could lead to new treatments for people with EBV-linked cancers.
Paul: The way to be convinced what the virus is doing in the disease is simply to understand the molecular mechanism. And obviously that gives an opportunity for therapeutic targets. Usually inventing new treatments for cancer cells is very difficult because the cancer cells are so subtly different from normal cells it’s very hard to find any drug that will distinguish the two. But here we’ve got a situation where the number of normal cells infected by EBV in a carrier happens to be extraordinarily low.
For example in me, one in 10,000 of my B-cells carries EBV, so it’s an incredibly low carriage. But if you look in one of the cancers, then every cancer cell, essentially, carries the virus, so it’s a fantastic marker of the cancer cells. So in terms of trying to target therapy, it seems like a real gift in terms of the opportunity to invent new therapeutics. We’ve just got to be able to understand the mechanism of action of the genes that are being expressed in the cancer.
Emma: This groundwork of research into EBV – from its discovery to the detail of its DNA – has had important consequences for people with EBV-linked cancers, in the form of new treatments.
One avenue of tackling EBV-driven cancers began in the 1990s in Memphis, Tennessee, where a pioneering young doctor called Cliona Rooney was desperately looking for ways to help her young patients who had received a bone marrow transplant and developed unusual lymphomas.
Because the children were receiving bone marrow from unrelated donors, the immune cells in the donated marrow can recognise the patient as foreign and start attacking the children’s’ organs, known as graft versus host disease. To prevent this doctors took out a type of white blood cell called a T-cell, but this caused it own problems as Cliona explains.
Cliona: And so the T-cell depletion virtually eliminated the graft versus host disease, but because they had eliminated the T-cells, they also removed T-cells that were responsible for protecting patients against virus-associated diseases. And one of the viruses that was a particular problem was Epstein-Barr virus. And after primary infection you carry the virus in your body for your whole life in your B-cells and epithelial cells. And mostly most people don’t have a problem.
But the reason you don’t have a problem is because you’ve got very potent T-cells that can recognise the virus proteins in the infected B-cells and kill them. But when you remove your T-cells, there’s nothing to kill of the virus-infected B-cells, and these B-cells grow out as a lymphoma.
When Cliona was at St Jude’s around two in 10 of her patients were getting lymphomas caused by EBV, and back then there were no treatments for these patients. In her fight to save one young girl’s life she decided to try a radical new approach.
Cliona: In fact, the first patient had received every treatment that was available and they were ineffective. So in the meantime I had got blood from the patient’s donor, which was her sister actually, and I made EBV-specific T-cells, and we grew them up and called the FDA as said, “We’ve got these T-cells and this patient’s got lymphoma and there’s nothing to be done” and the FDA said we could infuse them, and we’d just grown them in the research laboratory.
Emma: Sadly, the little girl died as her lymphoma was already at a late stage, but remarkably the T-cells grown to target EBV had started attacking the tumours. Based on this they got funding to try this innovative approach in other patients, and got fantastic results both in preventing EBV lymphomas developing if patients were given EBV T-cells at the time of transplant, and treating children who had developed EBV-driven lymphomas.
Cliona: So what we found was that the T-cells were very effective, they were safe, they didn’t really have any severe adverse events – which when you compare with chemotherapy and radiotherapy is pretty amazing. Their hair didn’t fall out, they didn’t feel sick, and they didn’t get fevers. And so they were very effective. That was really the beginning of using virus-specific T-cells for the treatment of Epstein-Barr virus.
Emma: Cliona Rooney is still carrying out research to improve this technique, making it quicker and protecting bone marrow recipients from other viruses that, whilst don’t cause cancer, can likewise prove fatal. The other exciting potential use of their therapy has is treating people who have other types of EBV-related cancers, like Hodgkin’s lymphoma. The difference between them and the transplant patients is that they have T-cells that are specific for EBV, but they’re not doing their job.
Cliona: In a patient who’s got an EBV lymphoma, you can detect T-cells that are specific for the protein, but the tumour is growing. So we’re trying to understand why that it. And what we’ve found, and many other investigators, is that the tumours are very immunosuppressive. They’re able to create a local environment that is very suppressive to T-cells. So the T-cells that go to the tumour will be switched off by it. What we’re trying to do now is take T cells from those patients and reactivate them in tissue culture, and we can do that and reactive them and infuse them back into the patients.
Emma: And early results look promising...
Cliona: We showed that these T-cells could eliminate EBV-positive lymphomas in over 50 per cent of cases and produce significant tumour responses in over 70 per cent. And these were patients who’d rally undergone all the standard therapies for lymphoma – for example, high dose chemotherapy and radiation and autologous bone marrow transplant, and after that you’re really looking for experimental therapies, which ours was. And they’re really very effective. So what we’re trying to do now is develop better ways to make the T-cells, and try to make them even more effective so we can cure even more patients, and patients with bulkier disease. So we can genetically modify T-cells quite easily, and I think this is the way we’re going to try to go forward.
Emma: The other promising new treatments emerging are vaccines. There are two approaches to this attack – vaccines to treat people who have already developed EBV-linked cancers, and vaccines to prevent EBV infections causing cancer.
Here’s Cancer Research UK scientist Graham Taylor, who’s leading a clinical trial testing whether a vaccine to boost the immune response against EBV is an effective treatment for people with nasopharyngeal cancer.
Graham: We’ve complete two clinical trials, and these are phase 1 clinical trials which is the first step in the drug development pathway to making a new medicine. We vaccinated a total of 33 patients – 18 in Hong Kong and 15 in the UK – and all of these patients had EBV-positive nasopharyngeal carcinoma. Now this is a cancer that occurs in the cavity that’s behind the nose – the nasopharynx. And although it’s quite a rare cancer in Western countries, it’s quite common in Southeast Asia, countries like southern China, Hong Kong and all throughout Southeast Asia.
All these patients had completed standard therapy for their disease, which is a type of chemotherapy called cisplatin, and radiation. Once they’d completed that therapy they received the vaccine, three doses of the vaccine in the upper arm, and we monitored the immune response that was stimulated by the vaccine. And in a number of patients, particularly those that got higher doses of vaccine, we saw a large increase in the T-cell response. One patient had a small amount of residual tumour after that chemotherapy and radiotherapy, and there we saw some preliminary evidence that there might be some tumour cell death occurring after the vaccination.
Emma: The trial is still at an early stage, but we’re looking forward to seeing results as the trial progresses.
On the other side of the pond, Professor Jeff Cohen, from the National Institutes of Health, has been working towards developing a vaccine to lessen the health burden caused by EBV across the globe. His focus is trying to reduce the estimated 200,000 people developing cancer caused by EBV worldwide every year.
It’s also a goal to reduce the impact of another sickness EBV can cause if caught as a young adult, and that’s glandular fever, or mononucleosis. Around 125,000 new cases are diagnosed every year in the US alone, and while it’s rarely life-threatening, glandular fever can make people feel very poorly and leave them unable to work for long periods of time. Professor Cohen gives us a quick update on his progress.
Jeff: If you think about the vaccines that have been successful for preventing virus infections, all of them are either live attenuated vaccines or are virus-like particles. And we don’t think it’s feasible in 2014 to make a live attenuated vaccine, because Epstein-Barr virus contains a number of oncogenes.
So instead we’re working on a vaccine that would be a virus-like particle, meaning that you’d have many copies of a virus protein on a particle. Again, only the human papillomavirus vaccine and the hepatitis B vaccine are sub-unit vaccines, but these again are virus-like particles. So those two vaccines do prevent cancer – hepatitis B-associated liver cancer and human papillomavirus-associated cervical cancer.
Emma: But is EBV really that easy to wipe out? It is the most common human virus, infecting more than nine in 10 adults globally.
Jeff: I think it would be very difficult to entirely wipe out the virus. This virus has been with us for many, many years and has evolved a number of strategies to evade the immune system. Again, it’s always surprising to me how Epstein-Barr virus, like other herpes viruses, can induce a good immune response – we have antibodies in our blood that neutralise the virus and prevent it from infecting cells. We also have lymphocytes in our bodies called T-cells that can kill virus-infected cells.
Yet with all those defences active, we still shed virus into our saliva and infect other people. So I think it’s going to be difficult to completely wipe out the virus, but I think we can have a vaccine that would result in a friendlier virus – that is, a virus that infects us but doesn’t cause mononucleosis, and isn’t associated with a number of malignancies.
Emma: So it’s been an exciting five decades of EBV research – from its founding discovery and the realisation that human viruses could cause cancer, through to new treatments for people with EBV-linked cancers. But what do our experts think the next 50 years holds?
Let’s start by asking the man who shared his name with the virus, Anthony Epstein.
Anthony: What’s left to discover? Well, in much sooner than 50 years it’ll be completely clear the molecular pathways involved by the virus in causing malignant change. That will be discovered quite soon. The other thing, which ought to have been done long ago and will be done soon, is an anti-viral vaccine, to prevent infection and the consequences therefore of the malignant change caused by the virus.
Emma: For Cliona Rooney, the future lies in understanding how the virus – and the cancers it causes – interact with the immune system.
Cliona: Other tumours that are not associated with viruses also evade the immune response, and we don’t have such good target antigens. So we can develop target antigens. But in the meantime our studies with Epstein-Barr virus show us how we can evade the tumour’s ability to avoid the immune response. And some of these are proteins that are made by the virus that can overcome immunity, but the tumour itself also has a lot of strategies to overcome the immune response.
And for me, because I’m interested in treating patients, I think that this is going to be the most important way that we can actually test different ways t attack tumours. And if we can show they’re effective for Epstein-Barr virus-related tumours, then we can start using them on non-virus associated tumours that affect many more people, like lung cancer, prostate cancer, pancreatic cancer etc etc.
Emma: It’s a view shared by Graham Taylor.
Graham: What’s really exciting is the possibility to treat those patients better, defining the best combination of adoptive T-cell therapy for some patients, vaccination for others, maybe combining the two – that really excites me. Generating better outcomes for patients is what we’re all after, ad so my prediction over the next 50 years is that as well as chemotherapy and radiotherapy, we’ll be using the immune system to target these cancers – not just virus-associated cancers, but other cancers that are not linked to viruses as far as we know.
Emma: And what hope for a vaccine to prevent EBV infection in the first place? Jeff Cohen thinks there is reason to hope.
Jeff: I think in 50 years we will have a vaccine for Epstein-Barr virus that will reduce many of the complications associated with the virus. I think we will continue to learn more about how this virus is associated with cancer, and how it affects B-lymphocytes in the body. And I think the virus has taught us a tremendous amount of cell biology in terms of how B-cells proliferate and how a B-cell can become immortalised. And I think we’re going to learn a lot more about cell biology by studying this virus as well as potential ways to tame the virus within our bodies.
Kat: That was Emma Smith with Anthony Epstein, Cliona Rooney, Graham Taylor, Jeff Cohen and Paul Farrell. And big thanks to Ben Thompson at the Society for General Microbiology for help with the recordings.
And finally, it’s time for our heroes and zeros. Our heroes this month are all the people who donated more than £8 million towards our life-saving research through the #nomakeupselfie campaign on social media. We didn’t start the trend, but we were overwhelmed by your pictures – all you gorgeous bare-faced women, all you men who plastered on the slap, the with-makeup selfies from the ladies who don’t normally wear it, the kids and pets who joined in too, the guys with their socks and everyone else. You’re all amazing, and we can’t thank you enough.
The money is going to fund ten of our clinical trials, bringing new treatments to patients across the UK, and it adds up to a staggering 50 years of research time in total. You can find out more about where the money is going – and what happened to the people who accidentally texted to find out about adopting a polar bear! – on our blog. Just follow the link in the Soundcloud player.
And our zeroes this month are carrots – or, more specifically, a story claiming that eating carrots reduces the risk of prostate cancer. In fact, the scientific paper the story is based on is an analysis of a number of studies looking at carrots and cancer risk. Many of the studies included in the analysis were relatively small, several of them actually didn’t show any significant effect of eating carrots on prostate cancer risk, others showed only a small reduction in risk, or even an increased risk of the disease, and there were other significant statistical variables. So this study doesn’t provide strong evidence that carrots have any special risk-reducing properties when it comes to prostate cancer.
But while bingeing on carrots may not do much for your prostate cancer risk specifically, it’s important to remember that eating a healthy, balanced diet rich in fruit and vegetables – including carrots - can help to reduce the risk of many types of cancer.
That’s all for this month, we’ll see you again next month for a look at all the latest cancer news.
We’d also like to answer your questions in our podcast, so please email them to email@example.com, post on our Facebook page, or tweet us – that’s @CR_UK. And if you’re listening to this on Soundcloud, please leave us a comment with your feedback. Thanks very much and bye for now.