| Abstract |
Human cytomegalovirus (HCMV) is a herpes virus, related to the virus that causes cold sores. HCMV infects almost everybody, without causing obvious disease and is usually mistaken for a mild flu. Most people never realise they are infected, but in some very specific cases, they will experience serious illness. HCMV is one of the few viruses that can cross placenta and infect unborn babies. Every year in UK around 5000 babies are infected this way. Of these, around 50 die and 1000 develop disabilities like hearing loss, blindness or brain damage. In fact, HCMV is responsible for most cases of developmental disorders in babies. In adults, HCMV is a serious problem for patients with HIV-AIDS and transplant patients. Even with care, a high proportion of patients will experience widespread disease, leading to damage to the lungs, eyes, gut or transplanted organs, and severe complications or even death. HCMV screening, antiviral and supportive treatments are top priorities for clinicians managing all these patient groups. It is estimated that caring for HCMV-patients in UK costs around £500 million every year. So far, scientists haven't developed a vaccine or drugs that cure HCMV or treat it without severe side effects. Perhaps since we don't know enough about HCMV. It is known that all cases of HCMV disease have one thing in common - an immune system that does not work at its best. HCMV infection lasts for life and our immune system keeps it constantly in check to prevent disease. But the virus always manages to hang around and takes advantage of any opportunity when the immune system breaks down, to grow and cause illness. Even in apparently healthy infected people, the virus changes their immune system with unknown consequences for our long-term wellbeing. Studying HCMV's interactions with our immune system is therefore very interesting and important. So far, we have been quite successful and discovered how 10 HCMV genes stop white blood cells called Natural Killer cells from killing the infection. This search is hard, because HCMV is the largest and most complex human virus. HCMV keeps over 100 genes just to interfere with our immune system and each gene has evolved many functions. As these functions are only needed in people they are often 'lost' from the virus genome when grown in cells, for example the large gene region called UL/b' which we wish to study. We don't yet understand how or why HCMV loses its genes in culture, but it's quite fortunate for us. For instance, one of the first genes lost when the virus is grown in cells, called UL141, is the most potent immune inhibitor. Focusing on genes that 'get lost first' is a very effective way of deciding which ones to study. UL141 is in the centre of the 22 genes that make up the UL/b' region. We have been interested in studying this region for a while and made a lot of effort developing technology for it. First, we 'decoded' or sequenced the genetic material of virus from patients and followed how it changed during culture. We found that UL141 gets lost first and is then followed by the rest of UL/b'. To make sure that the virus for our experiments doesn't change, we keep it preserved in bacteria and only grow it once in tissue culture when we need a stock of virus. Because the virus genome in bacteria is easy to cut and paste, we were able to make a library of 22 virus mutants, each missing one UL/b' gene. This way, if we mark each virus sample differently, we can analyse them all together using an instrument called a mass spectrometer. This is a good way to look at all proteins in the cell at the same time and can tell us what our virus proteins do to the cell and how they do it. We therefore always start with proteomics when looking at functions that we know nothing about. Ultimately, our studies will tell us how the virus works, how it interacts with our immune system, what is the best way to make a vaccine, or what is the best way to kill the virus. |