̽��ֱ�� of Cambridge - virus

Gone fishing: highly accurate test for common respiratory viruses uses DNA as ‘bait’

sc604 — Mon, 16 Jan 2023 16:00:00 +0000

̽��ֱ��test uses DNA ‘nanobait’ to detect the most common respiratory viruses – including influenza, rhinovirus, RSV and COVID-19 – at the same time. In comparison, PCR (polymerase chain reaction) tests, while highly specific and highly accurate, can only test for a single virus at a time and take several hours to return a result.

While many common respiratory viruses have similar symptoms, they require different treatments. By testing for multiple viruses at once, the researchers say their test will ensure patients get the right treatment quickly and could also reduce the unwarranted use of antibiotics.

In addition, the tests can be used in any setting, and can be easily modified to detect different bacteria and viruses, including potential new variants of SARS-CoV-2, the virus which causes COVID-19. ̽��ֱ��results are reported in the journal Nature Nanotechnology.

̽��ֱ��winter cold, flu and RSV season has arrived in the northern hemisphere, and healthcare workers must make quick decisions about treatment when patients show up in their hospital or clinic.

“Many respiratory viruses have similar symptoms but require different treatments: we wanted to see if we could search for multiple viruses in parallel,” said Filip Bošković from Cambridge’s Cavendish Laboratory, the paper’s first author. “According to the World Health Organization, respiratory viruses are the cause of death for 20% of children who die under the age of five. If you could come up with a test that could detect multiple viruses quickly and accurately, it could make a huge difference.”

For Bošković, the research is also personal: as a young child, he was in hospital for almost a month with a high fever. Doctors could not figure out the cause of his illness until a PCR machine became available.

“Good diagnostics are the key to good treatments,” said Bošković, who is a PhD student at St John’s College, Cambridge. “People show up at hospital in need of treatment and they might be carrying multiple different viruses, but unless you can discriminate between different viruses, there is a risk patients could receive incorrect treatment.”

PCR tests are powerful, sensitive and accurate, but they require a piece of genome to be copied millions of times, which takes several hours.

̽��ֱ��Cambridge researchers wanted to develop a test that uses RNA to detect viruses directly, without the need to copy the genome, but with high enough sensitivity to be useful in a healthcare setting.

“For patients, we know that rapid diagnosis improves their outcome, so being able to detect the infectious agent quickly could save their life,” said co-author Professor Stephen Baker, from the Cambridge Institute of Therapeutic Immunology and Infectious Disease. “For healthcare workers, such a test could be used anywhere, in the UK or in any low- or middle-income setting, which helps ensure patients get the correct treatment quickly and reduce the use of unwarranted antibiotics.”

̽��ֱ��researchers based their test on structures built from double strands of DNA with overhanging single strands. These single strands are the ‘bait’: they are programmed to ‘fish’ for specific regions in the RNA of target viruses. ̽��ֱ��nanobaits are then passed through very tiny holes called nanopores. Nanopore sensing is like a ticker tape reader that transforms molecular structures into digital information in milliseconds. ̽��ֱ��structure of each nanobait reveals the target virus or its variant.

̽��ֱ��researchers showed that the test can easily be reprogrammed to discriminate between viral variants, including variants of the virus that causes COVID-19. ̽��ֱ��approach enables near 100% specificity due to the precision of the programmable nanobait structures.

“This work elegantly uses new technology to solve multiple current limitations in one go,” said Baker. “One of the things we struggle with most is the rapid and accurate identification of the organisms causing the infection. This technology is a potential game-changer; a rapid, low-cost diagnostic platform that is simple and can be used anywhere on any sample.”

A patent on the technology has been filed by Cambridge Enterprise, the ̽��ֱ��’s commercialisation arm, and co-author Professor Ulrich Keyser has co-founded a company, Cambridge Nucleomics, focused on RNA detection with single-molecule precision.

“Nanobait is based on DNA nanotechnology and will allow for many more exciting applications in the future,” said Keyser, who is based at the Cavendish Laboratory. “For commercial applications and roll-out to the public we will have to convert our nanopore platform into a hand-held device.”

“Bringing together researchers from medicine, physics, engineering and chemistry helped us come up with a truly meaningful solution to a difficult problem,” said Bošković, who received a 2022 PhD award from Cambridge Society for Applied Research for this work.

̽��ֱ��research was supported in part by the European Research Council, the Winton Programme for the Physics of Sustainability, St John’s College, UK Research and Innovation (UKRI), Wellcome, and the National Institute for Health and Care Research (NIHR) Cambridge Biomedical Research Centre.

Reference:
Filip Bošković et al. ‘Simultaneous identification of viruses and viral variants with programmable DNA nanobait.’ Nature Nanotechnology (2022). DOI: 10.1038/s41565-022-01287-x

A new test that ‘fishes’ for multiple respiratory viruses at once using single strands of DNA as ‘bait’, and gives highly accurate results in under an hour, has been developed by Cambridge researchers.

Good diagnostics are the key to good treatments

Filip Bošković

Natalia Gdovskaia via Getty Images

Doctor examining a patient

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

Yes

Llama ‘nanobodies’ could hold key to preventing deadly post-transplant infection

sc604 — Thu, 22 Jul 2021 09:07:34 +0000

Around four out of five people in the UK are thought to be infected with HCMV, and in developing countries this can be as high as 95%. For the majority of people, the virus remains dormant, hidden away inside white blood cells, where it can remain undisturbed and undetected for decades. If the virus reactivates in a healthy individual, it does not usually cause symptoms. However, for people who are immunocompromised – for example, transplant recipients who need to take immunosuppressant drugs to prevent organ rejection – HCMV reactivation can be devastating.

At present, there is no effective vaccine against HCMV, and anti-viral drugs often prove ineffective or have very serious side-effects.

Now, in a study published in Nature Communications, researchers at Vrije Universiteit Amsterdam in the Netherlands and at the ̽��ֱ�� of Cambridge have found a way to chase the virus from its hiding place using a special type of antibody known as a nanobody.

Nanobodies were first identified in camels and exist in all camelids – a family of animals that also includes dromedary, llamas and alpacas. Human antibodies consist of two heavy and two light chains of molecules, which together recognise and bind to markers on the surface of a cell or virus known as antigens. For this special class of camelid antibodies, however, only a single fragment of the antibody – often referred to as single domain antibody or nanobody – is sufficient to properly recognize antigens.

Dr Timo De Groof from Vrije Universiteit Amsterdam, the study’s joint first author, said: “As the name suggests, nanobodies are much smaller than regular antibodies, which make them perfectly suited for particular types of antigens and relatively easy to manufacture and adjust. That’s why they’re being hailed as having the potential to revolutionise antibody therapies.”

̽��ֱ��first nanobody has been approved and introduced onto the market by biopharmaceutical company Ablynx, while other nanobodies are already in clinical trials for diseases like rheumatoid arthritis and certain cancers. Now, the team in ̽��ֱ��Netherlands and the UK have developed nanobodies that target a specific virus protein (US28), one of the few elements detectable on the surface of a HCMV latently infected cell and a main driver of this latent state.

Dr Ian Groves from the Department of Medicine at the ̽��ֱ�� of Cambridge said: “Our team has shown that nanobodies derived from llamas have the potential to outwit human cytomegalovirus. This could be very important as the virus can cause life-threatening complications in people whose immune systems are not functioning properly.”

In laboratory experiments using blood infected with the virus, the team showed that the nanobody binds to the US28 protein and interrupts the signals established through the protein that help keep the virus in its dormant state. Once this control is broken, the local immune cells are able to 'see' that the cell is infected, enabling the host’s immune cells to hunt down and kill the virus, purging the latent reservoir and clearing the blood of the virus.

Dr Elizabeth Elder, joint first author, who carried out her work while at the ̽��ֱ�� of Cambridge, said: “ ̽��ֱ��beauty of this approach is that it reactivates the virus just enough to make it visible to the immune system, but not enough for it to do what a virus normally does – replicating and spreading. ̽��ֱ��virus is forced to put its head above the parapet where it can then be killed by the immune system.”

Professor Martine Smit, also from from the Vrije Universiteit Amsterdam, added: “We believe our approach could lead to a much-needed new type of treatment for reducing – and potentially even preventing – CMV infectious in patients eligible for organ and stem cell transplants.”

̽��ֱ��research was funded by the Dutch Research Council (NWO), Wellcome and the Medical Research Council, with support from the NIHR Cambridge Biomedical Research Centre.

Reference
De Groof TWM, Elder E, et al. Targeting the latent human cytomegalovirus reservoir for T-cell mediated killing with virus specific nanobodies. Nature Communications (2021). DOI: 10.1038/s41467-021-24608-5

Scientists have developed a ‘nanobody’ – a small fragment of a llama antibody – that is capable of chasing out human cytomegalovirus (HCMV) as it hides away from the immune system. This then enables immune cells to seek out and destroy this potentially deadly virus.

Our team has shown that nanobodies derived from llamas have the potential to outwit human cytomegalovirus

Ian Groves

Jessica Knowlden on Unsplash

Llamas

Yes

Beyond the pandemic: reduce the risk of animal viruses jumping to humans

lw355 — Thu, 30 Jul 2020 07:40:07 +0000

Cambridge zoologists Bill Sutherland and Silviu Petrovan warn that we must dramatically change the way we interact with animals to reduce the risk of this happening again.

'Significant breakthrough' in understanding the deadly nature of pandemic influenza

sjr81 — Tue, 18 Sep 2018 14:59:28 +0000

Influenza is one of the main infectious diseases in humans. Seasonal influenza viruses account for about 650,000 deaths per year, whereas pandemic strains such as the 1918 H1N1 pandemic virus have been linked to 50-100 million deaths worldwide. Highly pathogenic avian influenza viruses such as the H5N1 and H7N9 strains have a mortality rate of about 50% in humans.

̽��ֱ��reasons for difference in disease severity and lethality caused by seasonal influenza viruses on the one hand, and pandemic and highly pathogenic avian influenza viruses on the other hand is still poorly understood. Previous research has indicated that in infections with the 1918 pandemic virus or infections with an H5N1 avian virus, a powerful immune response is established that leads to death.

This led Dr Aartjan te Velthuis of the ̽��ֱ�� of Cambridge and his colleagues Prof Ervin Fodor, Dr Josh Long and Dr David Bauer of the ̽��ֱ�� of Oxford, to ask what viral molecule can trigger this powerful immune response.

̽��ֱ��British groups first looked to how viruses are detected by the cell. Normally, an infected cell spots the presence of a virus by sensing the genetic material of the virus, RNA in the case of flu.

Work by Dr Richard Randall, a co-author on the manuscript from the ̽��ֱ�� of St Andrews, has shown that influenza viruses are good at hiding their RNA. This observation prompted te Velthuis and his colleagues to look for flu RNA that the virus was not able to hide from the cellular pathogen sensing system. What they found was truncated pieces of the viral genome that the virus had produced in error. ̽��ֱ��researchers called these pieces mini viral RNAs.

Fodor and his colleagues next investigated whether different influenza viruses produce mini viral RNAs at different frequencies and whether there was a link with the strong innate immune response that, for instance, the 1918 pandemic virus induces.

A combination of in vitro and in vivo experiments performed at Oxford and Cambridge, as well as by collaborators Leo Poon of the ̽��ֱ�� of Hong Kong, Debby van Riel of the Erasmus Medical Centre, and Emmie de Wit of the Rocky Mountain Laboratories, revealed indeed a strong correlation between the ability of an influenza virus to generate mini viral RNAs and the amount of inflammation and cell death the virus infection caused.

“We think it is a significant breakthrough and that it is particularly exciting that we are finding this factor a hundred years after the 1918 pandemic,” said Dr te Velthuis.

̽��ֱ��research groups are now continuing their efforts to investigate whether there is a causal link between influenza virus mortality and the production of mini viral RNAs. Together with their latest work, these efforts may help us understand better how influenza viruses cause disease, how we can identify dangerous influenza viruses, and how to develop new antivirals against influenza virus infections.

̽��ֱ��work was funded by the Wellcome Trust, Royal Society, Medical Research Council, NIH, and the Netherlands Organization for Scientific Research.

Researchers at the ̽��ֱ�� of Cambridge and the ̽��ֱ�� of Oxford have discovered a new molecule that plays a key role in the immune response that is triggered by influenza infections. ̽��ֱ��molecule, a so-called mini viral RNA, is capable of inducing inflammation and cell death, and was produced at high levels by the 1918 pandemic influenza virus. ̽��ֱ��findings appeared in Nature Microbiology yesterday (September 17).

We think it is a significant breakthrough and that it is particularly exciting that we are finding this factor a hundred years after the 1918 pandemic.

Aartjan te Velthuis

Yes

Licence type:

Attribution-Noncommercial-ShareAlike

Opinion: Want to eradicate viruses? They made us who we are

ljm67 — Tue, 28 Feb 2017 16:52:22 +0000

It is cold and flu season so many of us are currently under the weather with a virus. But what exactly is a virus? And are they even alive?

Outside a host cell, these weird microscopic particles, or virions, only consist of a tiny piece of genetic information (about 10,000 times less than that contained in the human genome) and a protein or lipid (fatty molecule) shell. Whether these particles are living things is the subject of much debate, as they don’t meet many of the usual criteria for life.

While there isn’t any formal agreement on what defines life, most definitions include the ability to adapt to the environment, to reproduce, to respond to stimuli, and to use energy.

While the virus particle may fall short of the definition of life depending on the criteria used, for some virologists like myself, thinking of the virion as the “virus” is like calling a sperm or unfertilised egg a “person”. Sure, a sperm is an essential step towards creating a person, but few people would argue that a sperm or unfertilised egg should be described as the finished product.

Flu: part virus, part human. Shutterstock

Much like a sperm, virions are produced in the millions. Many will never reach their destination and are lost and degrade in the environment. It is only when the virus binds to and enters a target cell that its cycle of replication can begin.

A virion doesn’t even always contain a majority of the molecules a virus can create. For example, the norovirus virion contains just three different types of protein and one type of RNA (a nucleic acid like DNA which uses a different sugar to form its backbone). Infected cells, however, make at least eight different viral proteins and four different viral RNAs.

Nor does the virus particle itself usually result in the symptoms of disease. Typically, when you catch a virus, your symptoms come from either infected cells dying, or your immune response to those infected cells.

For these reasons, some virologists consider the infected cell, rather than the virion, to be the virus.

I am virus

While this idea sounds outlandish, from conception to grave, your cells are intricately associated with viruses. Even if you don’t have a cold or the flu, you are still part-virus as human DNA plays host to a range of different viruses.

These are retroviruses, the best-known example of which is HIV. While HIV only entered the human population relatively recently, viruses very much like it have been infecting us and the creatures we evolved from since long before humans even existed.

While HIV infects immune cells, when a retrovirus instead infects the cells that produce eggs or sperm, the viral DNA can be inherited by any offspring. Over millions of years, these viruses have lost their ability to produce infectious particles, but have in some cases found other vital roles, and are now indispensable for human life.

One well-studied example is a protein called Syncytin-1, which is vital for the development of the placenta. This was originally a retroviral protein which entered the monkey population which gave rise to humans around 24m years ago. If we deleted this protein from our DNA, humanity would rapidly go extinct as we could no longer produce a functional placenta.

Transplanting pig organs into humans carries a risk of viral infection. Shutterstock

All these viruses which inserted into our DNA long ago are termed endogenous retroviruses (ERVs). In humans, ERVs have long since lost the ability to produce infectious virions, but this is not the case in all animals. Pig ERVs, for example, can produce infectious particles and are a concern when considering the use of pig organs for transplant, as these are known to be able to infect human cells in the lab.

Blurred lines

If a virus is the infected cell, rather than the virion, you could even think of the viruses that can infect us as more than 99.9% human. This is because they need many of the human proteins or other molecules present in your cells and encoded in your DNA to make more virus.

A human cell is vastly more complex than even the largest virus, and viruses can make use of this to compensate for their own simplicity. Viruses and their host cells share many common needs. They need to be able to produce RNA, protein, lipids and have access to the raw materials to generate these. As a host cell already contains all the needed components to achieve this, a virus can simply provide its own instructions, in the form of the viral genome, and let the cell do most of the work.

It takes many more cellular proteins to make a virus, than it does viral proteins. A virus only needs to provide instructions for the few components the host cell cannot produce. An example of this would be viruses which have a virion with a lipid membrane, such as influenza. This membrane is usually recycled from host cell membranes. ̽��ֱ��addition of a couple of viral proteins converts this into the membrane coat of the virion.

This use of host components by viruses also makes it clear why it has been so difficult to develop effective antiviral drugs. Much as with cancer treatment, there is very little to distinguish infected cells from normal human cells, which makes coming up with a drug that will only target infected cells extremely challenging. To be effective, you have to target that tiny part of the infected cell that is purely virus, without harming the remainder.

So are viruses alive? It’s still not settled, and really depends on what you think a virus is. What does seem clear, however, is that the viruses which infect us can be seen as part human, and we are part virus.

Edward Emmott, Research Associate in Virology, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

We are still part-virus, writes Edward Emmott, Research Associate in Virology, for ̽��ֱ��Conversation. Human DNA plays host to a range of different viruses. And this could help explain why it has been so difficult to develop effective antiviral drugs.

NIAID

HIV-infected T cell

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Licence type:

Attribution

Virus attracts bumblebees to infected plants by changing scent

fpjl2 — Thu, 11 Aug 2016 18:05:25 +0000

Plant scientists at the ̽��ֱ�� of Cambridge have found that the cucumber mosaic virus (CMV) alters gene expression in the tomato plants it infects, causing changes to air-borne chemicals – the scent – emitted by the plants. Bees can smell these subtle changes, and glasshouse experiments have shown that bumblebees prefer infected plants over healthy ones.

Scientists say that by indirectly manipulating bee behaviour to improve pollination of infected plants by changing their scent, the virus is effectively paying its host back. This may also benefit the virus: helping to spread the pollen of plants susceptible to infection and, in doing so, inhibiting the chance of virus-resistant plant strains emerging.

̽��ֱ��authors of the new study, published today in the journal PLOS Pathogens, say that understanding the smells that attract bees, and reproducing these artificially by using similar chemical blends, may enable growers to protect or even enhance yields of bee-pollinated crops.

“Bees provide a vital pollination service in the production of three-quarters of the world’s food crops. With their numbers in rapid decline, scientists have been searching for ways to harness pollinator power to boost agricultural yields,” said study principal investigator Dr John Carr, Head of Cambridge’s Virology and Molecular Plant Pathology group.

“Better understanding the natural chemicals that attract bees could provide ways of enhancing pollination, and attracting bees to good sources of pollen and nectar – which they need for survival,” Carr said.

He conducted the study with Professor Beverley Glover, Director of Cambridge ̽��ֱ�� Botanic Garden, where many of the experiments took place, and collaborators at Rothamsted Research.

CMV is transmitted by aphids – bees don’t carry the virus. It’s one of the most prevalent pathogens affecting tomato plants, resulting in small plants with poor-tasting fruits that can cause serious losses to cultivated crops.

Not only is CMV one of the most damaging viruses for horticultural crops, but it also persists in wild plant populations, and Carr says the new findings may explain why:

“We were surprised that bees liked the smell of the plants infected with the virus – it made no sense. You’d think the pollinators would prefer a healthy plant. However, modelling suggested that if pollinators were biased towards diseased plants in the wild, this could short-circuit natural selection for disease resistance,” he said.

“ ̽��ֱ��virus is rewarding disease-susceptible plants, and at the same time producing new hosts it can infect to prevent itself from going extinct. An example, perhaps, of what’s known as symbiotic mutualism.”

̽��ֱ��increased pollination from bees may also compensate for a decreased yield of seeds in the smaller fruits of virus-infected plants, say the scientists.

̽��ֱ��findings also reveal a new level of complexity in the evolutionary ‘arms race’ between plants and viruses, in which it is classically believed that plants continually evolve new forms of disease-resistance while viruses evolve new ways to evade it.

“We would expect the plants susceptible to disease to suffer, but in making them more attractive to pollinators the virus gives these plants an advantage. Our results suggest that the picture of a plant-pathogen arms race is more complex than previously thought, and in some cases we should think of viruses in a more positive way,” said Carr.

Plants emit ‘volatiles’, air-borne organic chemical compounds involved in scent, to attract pollinators and repulse plant-eating animals and microbes. Humans have used them for thousands of years as perfumes and spices.

̽��ֱ��researchers grew plants in individual containers, and collected air with emissions from CMV-infected plants, as well as ‘mock-infected’ control plants.

Through mass spectrometry, researchers could see the change in emissions induced by the virus. They also found that bumblebees could smell the changes. Released one by one in a small ‘flight arena’ in the Botanic Gardens, and timed with a stopwatch by researchers, the bees consistently headed to the infected plants first, and spent longer at those plants.

“Bees are far more sensitive to the blends of volatiles emitted by plants and can detect very subtle differences in the mix of chemicals. In fact, they can even be trained to detect traces of chemicals emitted by synthetic substances, including explosives and drugs,” said Carr.

Analysis revealed that the virus produces a factor called 2b, which reprograms genetic expression in the tomato plants and causes the change in scent.

Mathematical modelling by plant disease epidemiologist Dr Nik Cunniffe, also in the Department of Plant Sciences at Cambridge, explored how the experimental findings apply outside the glasshouse. ̽��ֱ��model showed how pollinator bias for infected plants can cause genes for disease-susceptibility to persist in plant populations over extremely large numbers of generations.

̽��ֱ��latest study is the culmination of work spanning almost eight years (and multiple bee stings). ̽��ֱ��findings will form the basis of a new collaboration with the Royal Horticultural Society, in which they aim to increase pollinator services for cultivated crops.

With the global population estimated to reach nine billion people by 2050, producing enough food will be one of this century’s greatest challenges. Carr, Glover and Cunniffe are all members of the Cambridge Global Food Security Initiative at Cambridge, which is involved in addressing the issues surrounding food security at local, national and international scales.

̽��ֱ��use of state-of-the-art experimental glasshouses at Cambridge Botanic Garden, and equipment at Cambridge and Rothamsted, was funded by the Leverhulme Trust.

Study of bee-manipulating plant virus reveals a “short-circuiting” of natural selection. Researchers suggest that replicating the scent caused by infection could encourage declining bee populations to pollinate crops – helping both bee and human food supplies.

Modelling suggested that if pollinators were biased towards diseased plants in the wild, this could short-circuit natural selection for disease resistance

John Carr

John Carr/Alex Murphy

Researcher Sanjie Jiang inside the 'flight arena' in the glasshouse of the Cambridge ̽��ֱ�� Botanic Garden.

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Silent killer

lw355 — Fri, 13 Sep 2013 13:14:24 +0000

To catch the herpes virus human cytomegalovirus (HCMV) you must be exposed to someone who has it. This isn’t difficult: it is carried by around 65% of the population. Once in the body, HCMV persists for life owing to its clever ability to avoid our immune system and to go into hiding inside our cells in a latent state. Now, research is identifying changes in these cells that could lead to a new route to eradicating the virus.

“HCMV can be acquired very early in childhood, and the number of people infected gradually rises throughout life,” said Professor John Sinclair, a molecular virologist in the Department of Medicine. “ ̽��ֱ��active virus can not only be passed from an infected mother to her child in breast milk but can easily be transferred from child to child in saliva – one child puts a toy in their mouth, then it’s passed to another child who does the same, and the virus is passed on. It’s also a sexually transmitted disease, so there’s another increase in infections when people become sexually mature.”

Once acquired, the virus goes into a latent state in the body. If it reactivates in healthy people, their immune responses prevent it from causing disease. But when the immune system is suppressed, active HCMV becomes dangerous. It is a major cause of illness and death in organ and bone marrow transplant patients, who are given drugs to deliberately suppress their immune system and prevent their body rejecting the transplant. With an increasing demand for transplants in the UK, HCMV is set to become a growing problem.

“If it’s not treated well, or it develops resistance to antiviral drugs, HCMV can lead to pneumonitis – inflammation of the lung tissue – and, in the most extreme case, it replicates all over the body and the patient ends up with multiple organ failure,” said Dr Mark Wills, a viral immunologist working alongside Sinclair in the Department of Medicine.

“Tissue from donors carrying the virus often has to be used for transplants because there are so few donors and so many people carrying the virus,” said Sinclair. “By transplanting bone marrow, or an organ from someone with the infection, you’re giving the patient the virus and you’re immune-suppressing them. That’s the worst of both worlds.”

And HCMV is not a worry just for transplant patients. “HCMV is now the leading cause of infectious congenital disease – that is, disease present at birth,” said Sinclair. Women in early pregnancy who are newly infected with HCMV or whose HCMV reactivates are at real risk, and this can lead to disease in their unborn baby. HCMV also targets HIV-AIDS patients, where a progressive failure of the immune system allows this opportunistic infection to thrive.

There is no vaccine to prevent HCMV infection, and the antiviral drugs available to treat it have significant toxicity and only limited effectiveness. In addition to the problem of viral resistance, drugs can only target HCMV in its active state, which means the virus can never be fully eradicated. “You can suppress the virus down to a very low level, but you can never get rid of the latent reservoir with the currently available antiviral drugs,” said Wills.

Sinclair and Wills, who have just received their fifth consecutive five-year grant from the Medical Research Council (MRC), have focused on understanding how the virus maintains this latent infection in specialised cells of the immune system and how the immune system is prevented from eliminating the virus from the body.

“ ̽��ֱ��belief has always been that, in its latent state, HCMV was just sitting there doing nothing, waiting to reactivate,” said Sinclair. “But we’ve started to identify major changes in latently infected cells, and we think these are targetable with novel drugs and immunotherapies.

“One change is in a transporter protein normally used by the cell to pump out things it needs to get rid of,” he added. “If you put the chemotherapy drug vincristine on a healthy cell, the cell will pump it out and survive. Working with Paul Lehner at the Cambridge Institute for Medical Research we found that, during latent infection, this transporter protein is less effective, making the cell more prone to killing by vincristine.” Their results were published in Science in April 2013.

“In addition to treatment with drugs, we’re looking into immunotherapies – treatments based on using the patient’s immune system,” said Wills. “Clearly, the difficulty is that all healthy people have very good immune responses to the virus, yet we all still carry it and can never get rid of it. There must be a problem here – the virus is deliberately trying to evade the immune system by manipulating it.”

Sinclair and Wills are trying to understand how the virus does this while in its latent state. Their findings show that HCMV disrupts the proper activation of the immune system by manipulating small signalling molecules called cytokines and chemokines, which normally help to kick-start the process of removing a foreign invader. “Now we know this, we can start to think about intervening,” said Wills.

“We’ve also found that latently infected cells are producing a number of viral proteins,” added Wills. “That’s a dangerous strategy for the virus, because these proteins could be presented on the surface of the cells they’re hiding in, which would attract immune cells like T cells to kill them. Our initial research showed that there are T-cell responses – so why aren’t the viral cells being eliminated? It’s paradoxical.” In further investigations, they uncovered another mechanism in which the virus was promoting a certain subtype of T cell that suppresses the immune system. “So now we’re working to remove the immunosuppressive component of that immune response by either removing or neutralising the function of the immunosuppressive T-cell subtype, to enable the other components of the body’s immune response to target the infected cells,” added Wills.

By targeting latent infection, this work holds great promise for developing better methods of treatment for HCMV and for the design of a vaccine. “If you intervene just before a transplant, and use this immunotherapeutic technique to target the latently infected cells, in combination with the drugs, you can purge the infected cells,” said Sinclair. “This massively reduces the potential that HCMV will reactivate in the person receiving the transplant, because effectively you’re not giving them the virus,” he added.

They have proved this concept in the laboratory and their new MRC grant will enable them to trial its effectiveness in a model system as a stepping stone to human clinical trials. “A decade ago we couldn’t have even contemplated doing this type of work,” said Sinclair, “but now we have worked out what’s going on during latent infection, we can try to target these changes. Being able to clear the latent infection is key to eradicating much of the disease caused by HCMV that we see in the clinic.”

Many of us are infected with a virus we’ll never clear. While we’re healthy, it’s nothing to worry about, but when our immune system is suppressed it could kill us.

̽��ֱ��virus is deliberately trying to evade the immune system by manipulating it

Mark Wills

̽��ֱ��District

HCMV

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes

Offensive manoeuvres in the war against HIV

lw355 — Mon, 25 Feb 2013 10:31:53 +0000

It was in Los Angeles in 1981 that the first report emerged of an unusual cluster of patients whose immune systems appeared to have failed. This report is now acknowledged as the first scientific account of an infectious disease that was to become the HIV/AIDS global epidemic, infecting 60 million people and killing 25 million to date

Three decades later, and with more than 20 antiretroviral drugs to combat HIV, treatment can now significantly prolong life and reduce the rate of viral transmission. For some patients, life expectancy with uninterrupted treatment is now similar to that of someone who is not infected with HIV – not the death sentence it once was – and the global rate of new infections is at last declining.

Yet, current therapies do not fully restore health and, in resource-poor settings, patients often lack access to antiretroviral drugs. Moreover, because the virus has the ability to insert its genetic material into the genetic material of the patient’s cells, ‘latent’ viruses can re-emerge at any point, necessitating lifelong drug treatment.

“There is no imminent prospect of a vaccine, and there may not be one in the way that we have for measles and mumps, where our own immune system can clear the virus,” explained Andrew Lever, Professor of Infectious Diseases in the Department of Medicine and Honorary Consultant Physician at Addenbrooke’s Hospital. “ ̽��ֱ��bottom line is 60 million immune systems have had a crack at eradicating HIV and all have failed.”

̽��ֱ��virus is both adaptable and versatile, escaping drug treatment by mutating the structure of its proteins. Patients require combinations of drugs – an approach known as highly active antiretroviral therapy (HAART) – because this reduces the chance that a virus will mutate sufficiently to escape all.

Continued research efforts are therefore urgently required, as Lever explained: “ ̽��ֱ��big areas in HIV research are finding new drugs to complement the ones we’ve got already, so as to outrun the virus in terms of resistance, and finding a means to eradicate the latent virus.”

Lever’s research, which has been investigating the mechanisms of HIV infection for almost 25 years, is helping to tackle both of these challenges.

Structural traps

Anti-HIV drugs typically target viral proteins that are involved in the process of entering or exiting the cell. But, as Lever explained, this lies at the heart of resistance to the virus: “Proteins are very adaptable. Time and again the virus escapes the drug by altering its protein structure so that it still functions but the drug no longer recognises it. We decided instead to target the virus’ RNA genetic material.”

Lever’s previous studies had provided fundamental insights into the way in which RNA is packaged, a process that he realised could provide a remarkable opportunity for a completely new type of antiretroviral therapeutic.

For the virus RNA to be packaged and released from the cell as an intact virus particle, it must twist itself into a three-dimensional knot-like structure. It was this structure which Lever and colleagues discovered is used as a packaging signal by the virus. To form the structure, the sequence of the RNA must be highly conserved between viruses. As a result, opportunities for ‘escape mutation’ are limited. A virus protein called Gag uses the knot-like structure to pick out the viral RNA from the thousands of cellular RNAs that are an integral part of the process by which a cell translates the information in its DNA into molecules that enable the cell to function.

Interfering with Gag binding can potentially stop the virus spreading from cell to cell. In collaboration with Professor Shankar Balasubramanian and Dr Neil Bell in the Department of Chemistry, and researchers at the ̽��ֱ�� of Sussex, Lever is now using this phenomenon as the basis for designing novel antiviral drugs. In parallel, work with Professor David Klenerman in the Department of Chemistry is providing the first high-resolution data on the precise conformation of the RNA structure.

̽��ֱ��goal is to create a ‘structural trap’ in which small-molecule drugs lock the RNA in a conformation that can no longer interact properly with Gag. Targeting the function of RNA through its 3D structure is a new direction for antiviral drug discovery, and sufficiently challenging to receive funding from the Medical Research Council Milstein Fund – specifically intended for ‘high-risk, high-reward’ studies.

Using an assay they developed for measuring the interaction between Gag and RNA, the team is now screening a library of small drug-like molecules for those with potential to interfere with the process. “Although it’s very early stages, the molecular hypothesis that we started with for targeting this structure has taken us to a situation where we have molecules that look like they are doing something interesting in the assay,” said Balasubramanian. “Being able to target RNA in this way would be a paradigm shift in terms of new therapeutics for HIV, and other infectious diseases.”

Will RNA-directed therapeutics overcome viral resistance? “It’s a good question and untested,” added Balasubramanian. “Once we find a good small molecule that disrupts binding and packaging then we can address exactly this question.”

Curing HIV

Drug discovery is a key area for the future. However, the scientists also have their eyes on an even bigger prize – a cure for HIV – and a new collaboration between five UK Biomedical Research Centres (BRCs) is now working towards understanding how to rid the body of latent virus.

“Because latent virus exists only as genetic material, essentially indistinguishable from the genetic material of the patient’s cells, it’s effectively hidden. ̽��ֱ��patient’s immune system can’t see these infected cells and the drugs can’t target them,” explained Lever. “ ̽��ֱ��reservoir of infection sits there for years because it’s in very long-lived immune cells. Even if you suppress the virus right down using drug treatment, as soon as you stop the drugs it bounces right back with viruses that, based on their genetic sequence, are historically very old, so these have been latent for a long time.”

̽��ֱ��new project, CHERUB (Collaborative HIV Eradication of Viral Reservoirs: UK BRC), funded by the National Institute for Health Research, brings together researchers from Imperial College, King’s College Biobank, ̽��ֱ�� of Cambridge, ̽��ֱ�� College London and ̽��ֱ�� of Oxford, and is the first pan-BRC cooperative project to compete internationally in a new field of biomedical research.

Lever leads the Cambridge contribution along with Dr Mark Wills and Dr Axel Fun from the Department of Medicine. “Until we learn how to eradicate the latent virus then all we can do is contain it,” Lever explained. “CHERUB will work in collaboration with NHS Trusts and the pharmaceutical industry to recruit new patient cohorts for studies that range from fundamental laboratory research through to large-scale clinical trials of novel agents.”

̽��ֱ��Cambridge researchers will develop an assay to detect latent virus that will be used to provide a measure of the relative success of drugs, as well as expand current research areas to learn new ways to rouse the virus from its latency.

“All HIV patients have latent virus – it’s a fact of life,” added Lever. “You can suppress active viruses with current conventional drugs so that the patient’s immune system recovers but you can’t get rid of the latent virus. ̽��ֱ��aim now is to suppress the virus to the point where the immune system recovers but at the same time to wake up and eradicate the virus from the latently infected cells. And then we are talking about a cure.”

For more information, please contact Louise Walsh at the ̽��ֱ�� of Cambridge Office of External Affairs and Communications.

Although anti-HIV drugs can significantly prolong life, patients must take the drugs for the rest of their lives. New approaches to therapeutics may hold the answer to finding a cure for HIV.

̽��ֱ��bottom line is 60 million immune systems have had a crack at eradicating HIV and all have failed.

Andrew Lever

Cynthia Goldsmith, Centers for Disease Control and Prevention

HIV-1 budding from a cultured cell

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes