50 years of Epstein-Barr virus

In March 1964 The Lancet medical journal published a remarkable piece of research from three scientists called Anthony Epstein, Yvonne Barr, and Burt Achong. They had discovered the first human virus that can cause cancer, which later came to bear two of their names: Epstein-Barr virus (EBV).

In this third post in our Cancer and Infections series we look at the remarkable story of its discovery – a tale full of brilliant scientific minds and lucky coincidences – that revealed it to the world.

Out of Africa

The story of EBV and its role in cancer began with the work of a surgeon called Denis Burkitt. During World War II he was posted to Africa, and subsequently settled in Uganda for a few years to practise medicine there.

In 1958 Burkitt first reported a specific type of cancer that was common in young children living across central Africa. These aggressive tumours – later named after him as Burkitt’s lymphoma – were caused by white blood cells multiplying out of control.

The children were often brought to hospital with dental problems or swellings of the face and neck. The tumours grew rapidly and, sadly, did not respond to any treatments available at that time.

Thanks in part to funding from the British Empire Cancer Campaign – a predecessor of Cancer Research UK – Burkitt was able to continue his research and study which children developed this new type of cancer in more precise detail.

He noted that although no single tribe of African children was more affected, there was a very strong geographical pattern that matched particularly rainy areas with a high year-round temperature.

This strong link to environmental conditions, very similar to the pattern of malaria, led Burkitt and his colleagues to believe that the lymphoma was being transmitted by an insect-borne virus. But he had no evidence to back his theory up.

• The story of EBV

A chance meeting

On March 22, 1961, Burkitt visited England and gave a lecture at a London medical school detailing his findings for other doctors and scientists. Sitting listening to his lecture, titled “The Commonest Children’s Cancer in Tropical Africa — A Hitherto Unrecognised Syndrome”, was a young Cancer Research UK doctor called Anthony Epstein.

Epstein had a particular interest in understanding disease using tests carried out in the lab, and he was an expert on using a new and very powerful tool – the electron microscope.

He had also been working on the Rous sarcoma virus that caused tumours in chickens, and understood how viruses could drive the development of cancer in some circumastances.

He was determined to be the first to find a cancer-causing virus in humans, and was greatly excited by Burkitt’s theory that the new type of lymphoma might be linked to a virus.

Following the lecture, the pair talked over tea and arranged samples of tumours taken from children with Burkitt’s lymphoma to be shipped from Uganda to Epstein’s lab in London.

After a few long and frustrating years trying in vain to find a virus in the samples, Epstein made a breakthrough – thanks to poor weather conditions.

Fog caused one of his samples to be diverted to another airport, and because of the longer journey some of the cells from the tumour shook free. Alongside a young researcher who joined his lab, called Yvonne Barr, they finally managed to grow these free-floating cancer cells to study.

And with the help of a colleague called Burt Achong, the “Eureka” moment finally came when they looked at the Burkitt’s lymphoma cells down the powerful electron microscope and saw some were filled with tiny virus particles.

Mysteries to solve

Epstein’s discovery, although ground-breaking, was just the first step in a long and baffling road ahead.

He and his team set up a joint project with a man and wife duo from the US – Werner and Gertrude Henle – who were experts in studying viruses.

In 1965 they confirmed that Epstein had spotted a brand new human virus, and it was officially christened Epstein-Barr virus.

But there was a problem. Under the microscope, it appeared that only one in every 100 cells from Burkitt’s lymphoma tumours were infected with EBV, and some tumour samples had no detectable virus at all. This cast serious doubt on the theory that the virus was causing the cancer.

Undeterred, the Henles and their team carried out further experiments. They found that infected cells – a type of white blood cell called a B cell – could transmit the virus to uninfected B cells and cause them to become cancerous.

This was positive evidence in favour of their virus theory, so they kept pursuing this line of research with dogged determination.

Eventually they had the proof they needed when a blood test was developed that could detect infected cells. Satisfyingly, all the children with Burkitt’s lymphoma tested positive for EBV infection.

But, much to their shock, so did nine out of every 10 adults living in America, none of whom had Burkitt’s lymphoma. So what was going on?

The answer came after a lab technician working in the Henle’s lab became ill with glandular fever.

Before her illness, she’d always tested negative for EBV, but afterwards she was positive. It was a smoking gun, and larger studies confirmed that every case of glandular fever (a widespread disease) was caused by EBV infection.

Cause or coincidence?

One fundamental question remained – was the EBV infection causing Burkitt’s lymphoma, or was the disease just creating a nice pool of cells for the virus to infect and its presence was a mere coincidence? And why did only a minority of infected African children develop lymphoma, when so many were infected with EBV?

To try and get definitive proof, scientists from France set up a study of thousands of children in Uganda to see whether EBV infection led to Burkitt’s lymphoma.

By 1972, they had enrolled 42,000 children in their study, collecting samples of blood to look at when they became infected with EBV.

Over the next five years, some of children in the study developed Burkitt’s lymphoma – all of whom had signs of unusually heavy EBV infections long before the tumour appeared. This was strong evidence that EBV had a role in Burkitt’s lymphoma but it was clear other factors were also at play.

The final clue to the mystery fell into place in 1976, when scientists at the Karolinska Institute in Sweden studied the chromosomes (lengths of DNA) in cells from Burkitt’s lymphoma tumours. They noticed that the same chunk of one particular chromosome had broken off and re-attached to a different chromosome in all the cells.

It turned out that the chunk of chromosome that had broken off contained c-myc, a cancer-driving gene (oncogene).

C-myc usually tells cells to divide when they’re needed, and its activity is tightly controlled, but in the Burkitt’s lymphoma cells it had landed next to genes that are always turned on in white blood cells. This meant that c-myc became permanently switched on too, giving the cells instructions to keep growing.

And so the jigsaw was complete. Persistent viral infections, like EBV, were sending children’s B cells into over-drive making them divide rapidly for long periods of time.

This was often made worse by additional infections children had at the same time, like chronic malaria.

It meant their B cells were constantly copying their DNA and just by chance genetic mistakes involving c-myc occurred. The combination of the genetic mistake and EBV greatly increased the risk of Burkitt’s lymphoma developing.

Wait…there’s more

Our funding had helped Burkitt and Epstein take the initial steps in finding the first human virus to directly cause cancer in humans, and opened up a whole new field of research. And there were more surprises in store.

Using the molecular tools that had been developed over the years, researchers found that EBV infection was strongly linked to cancers of the back of the nose and throat (nasopharyngeal cancers) too.

Large studies carried out in China, where this cancer is common, revealed that tests for EBV could identify people at an early stage of disease before symptoms had developed, and even spot those at high risk.

But, as is the case for Burkitt’s lymphoma, there are other elements at play too. A combination of genes, diet and EBV infection together increases the chances of developing this type of cancer.

More recently, evidence has begun to emerge that EBV infection is also linked to a percentage of stomach cancers – the second leading cause of cancer-related deaths across the world.

In 1991 scientists first noticed a rare but distinctive type of stomach cancer that had very similar characteristics to nasopharyngeal cancer. When they tested the samples, nearly all of them were positive for EBV.

A large analysis from 2009 concluded that around one in every 10 stomach cancers contained EBV. Research is ongoing to decipher what role the virus is playing in this type of cancer and how it weaves together with other risk factors like diet, genetics and H. pylori infection.

The global burden

Thanks to Burkitt’s intrepid studies 50 years ago in Africa and Epstein’s persistence, we now know that EBV infection plays a role in several diverse types of cancer, including lymphomas, nasopharyngeal cancers and some stomach cancers.

Despite it being a bumpy road full of twists and turns, their perseverance opened the door to new avenues of research and ways to treat cancer by targeting virus-infected cells. In the next post in our series on infections and cancer, we peer into the future of EBV research and the promise it holds for curing and preventing cancers.

Emma

Key reference

• Epstein M.A., Achong B.G. & Barr Y.M. (1964). VIRUS PARTICLES IN CULTURED LYMPHOBLASTS FROM BURKITT’S LYMPHOMA, The Lancet, 283 (7335) 702-703. DOI: 10.1016/S0140-6736(64)91524-7

Note

Reference for Burkitt’s 1958 report of a common cancer affecting children in Africa: Burkitt, D. (1958) A sarcoma involving the jaws in African children. Br J Surg. 46(197):218-23.

Image credits: Lecture image, microscopic virus image, B cell image and infected cells image all from Wikimedia Commons