Utilising proteomics to develop anti-HCMV immunotherapy

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Human cytomegalovirus (HCMV) is a herpesvirus that infects almost everyone worldwide. Infection is lifelong, during which time it is controlled by the immune system. While the majority of infections do not cause symptoms, HCMV is nevertheless a major cause of disease in certain groups of people. If caught during pregnancy, the virus can pass to the foetus and can result in deafness, mental retardation, or even death of the unborn child. In the UK up to 1000 babies per year have severe permanent disabilities due to HCMV, more than Down's syndrome or foetal alcohol syndrome. HCMV is a major cause of severe life-threatening disease in individuals with poor immune systems, notably transplant patients and people with HIV/AIDs. HCMV has also been associated with the most common form of brain cancer, hardening of the arteries, premature aging of the immune system, hepatitis and inflammatory bowel problems. Antiviral drugs have toxic side effects, and viruses rapidly become resistant to them. There is an urgent need for better therapeutic options.CMV is the most complex human virus. Unfortunately we, and others, have shown that the virus changes whenever it is grown in the laboratory. This means that researchers have not been able to study the actual virus that causes clinical disease, and this has limited the development of vaccines and therapy. To solve this problem we took a clinical virus, sequenced its genome and designated it strain Merlin. This has been adopted as the worldwide HCMV reference strain. My work has characterised how this virus changes when grown in the lab and enabled me to devise a unique system to stop these changes happening. For the first time, scientists can perform experiments with a virus that accurately mimics the virus that causes disease. I will now use this virus, along with state-of-the-art technology, to define all HCMV proteins that can be targeted for vaccination or therapy.To date vaccines have aimed to prevent initial infection with the virus. These studies need to target proteins present in the virus, yet the entire set of proteins present in clinical virus is completely unknown. Using our viruses we can now define the complete set of proteins available for targeting.Although these vaccine strategies may reduce the chances of becoming infected, they cannot stop infection completely. Once a person is infected, a different strategy is required - one that enables cells to be killed after they are infected. The immune system can only kill infected cells if it can recognise them, yet we don't know how the virus changes infected cells. Using our state-of-the-art techniques and viruses, we will now determine exactly how HCMV changes the surface of an infected cell. We will determine which of these changes are the best targets for killing infected cells, and engineer antibodies that can be given to patients to enable their immune system to recognise these cells, and kill them - thereby controlling the HCMV infection.Although we are in a unique position to develop and test these therapeutic reagents against infected cells, our novel viruses still suffer from a limitation. Virus is naturally spread by being secreted in bodily fluids (e.g. urine, saliva). To understand and control the process by which the virus spreads between people, we must be able to mimic this process in the lab. Yet when we grow clinical virus in the lab, very little virus is secreted. We have shown that this is because of a viral gene called RL13. We will investigate how RL13 stops secretion of virus, how this can be circumvented in the lab, and how it is circumvented when virus is secreted in patients. This will enable the production of large amounts of secreted virus that, as closely as possible, represents virus secreted from patients. This is crucial to enable laboratories to investigate the way HCMV spreads between people, and to develop ways of stopping it happening.