Modulation of Natural Killer Cell By Human Cytomegalovirus
Lead Research Organisation:
CARDIFF UNIVERSITY
Department Name: School of Medicine
Abstract
Cytomegalovirus (CMV) is related to the herpes virus that causes cold sores. Like herpes, CMV is carried for life and can reactivate at any time to cause disease. Most people worldwide are infected with CMV, yet do not know. However, in hospitals, CMV is well known and a major problem. CMV can cause severe multi-organ disease in individuals whose immune system has been compromised by infections (e.g. HIV AIDS), suppressed by drugs (for bone marrow, heart or kidney transplants) and also when it infects unborn children in the womb. CMV is the most complex of any human virus with 167 genes. What do they all do? Surprisingly, most of are not needed by virus to grow, rather they may be there to attack our immune system.
Natural Killers (NK) cells are crucial in fighting infections (CMV in particular) and cancers. NK cells detect signals on the surface cells that indicate whether things are OK or not. If they are not, NK cells are fierce ? rapidly both killing the problem cell and triggering the immune system to respond. Only recently have we begun to understand what signals NK cells are responding to ? and there are many. Surprisingly, CMV has helped tell us how NK cells work.
Eight CMV genes have been identified that prevent NK cells from killing. These CMV genes affect the expression of cellular proteins recognised by NK cells. Our laboratory has been heavily involved in this work. Because HCMV has an enormous genome, finding these genes is been tough. We know the virus encodes many more NK evasion functions, although not how many. Over the past 5 years, we have worked hard to develop a hyper-efficient system to screen the whole genome, and now this system is ready.
We want to identify and characterise as many NK evasion genes as possible. How these genes work, will tell us how NK cells work. There is also good evidence in a mouse model that these genes are essential for the virus to cause disease. With scientists in the US, we intend to determine whether this is true in primates. This study is important to understanding how CMV causes disease. However, by identifying and knocking these NK evasion genes out of the virus, it may yet be possible to develop a CMV vaccine.
Natural Killers (NK) cells are crucial in fighting infections (CMV in particular) and cancers. NK cells detect signals on the surface cells that indicate whether things are OK or not. If they are not, NK cells are fierce ? rapidly both killing the problem cell and triggering the immune system to respond. Only recently have we begun to understand what signals NK cells are responding to ? and there are many. Surprisingly, CMV has helped tell us how NK cells work.
Eight CMV genes have been identified that prevent NK cells from killing. These CMV genes affect the expression of cellular proteins recognised by NK cells. Our laboratory has been heavily involved in this work. Because HCMV has an enormous genome, finding these genes is been tough. We know the virus encodes many more NK evasion functions, although not how many. Over the past 5 years, we have worked hard to develop a hyper-efficient system to screen the whole genome, and now this system is ready.
We want to identify and characterise as many NK evasion genes as possible. How these genes work, will tell us how NK cells work. There is also good evidence in a mouse model that these genes are essential for the virus to cause disease. With scientists in the US, we intend to determine whether this is true in primates. This study is important to understanding how CMV causes disease. However, by identifying and knocking these NK evasion genes out of the virus, it may yet be possible to develop a CMV vaccine.
Technical Summary
Human cytomegalovirus (HCMV) has the largest genome (~236Kb) of any characterised human virus encoding 167 putative open reading frames (ORFs). Although this pathogen is carried by majority of the world?s population, the much of the HCMV genome remains uncharacterised. The complexity of the genome makes the mapping of even recognised viral functions to specific HCMV genes extremely problematical. Natural Killer (NK) cells are crucial in controlling cytomegalovirus infections. A substantial proportion of the HCMV genome acts to suppress NK recognition; to date eight HCMV NK evasion functions have been characterised even though only a fraction of the genome has been sampled. We propose exploiting DNA recombineering technology to generate a bank of 167 replication-deficient adenovirus (Ad) vectors each encoding a discrete, epitope-tagged HCMV ORF. Both Ad recombinants and HCMV proteins expressed in a prokaryotic system will be used to generate specific antibodies to support expression studies. A compete HCMV gene bank of Ad recombinants will be an invaluable resource for the HCMV research community. Our specific goal is to perform functional NK assays, using CD107 mobilisation and intracellular interferon-gamma staining, to identify HCMV gene function capable of promoting and suppressing NK recognition. Constructs encoding rhesus CMV homologues of HCMV NK evasion functions will also be evaluated to facilitate studies in the closest tractable in vivo model for HCMV.
