Viral Immunology

Cytomegalovirus

Human cytomegalovirus (HCMV) is an important pathogen with high prevalence worldwide. It is the leading infectious cause of congenital malformation, is associated with life-threatening disease in immunocompromised individuals, in particular AIDS sufferers and transplant recipients, and is a causative agent of hepatitis, colitis, post-transplantation arteriosclerosis and infectious mononucleosis. The US Institute of Medicine has designated HCMV as a highest priority (Level I) vaccine target.Cytomegalovirus

Useful links

This Week In Virology (TWIV)

Giant Virus site

AdZ Adenovirus Cloning System

Immune Evasion by HCMV

The NK activating receptor CD155 (top panel) is downregulated by HCMV infection (bottom panel) As a herpes virus, primary infection is followed by lifelong persistence during which the immune systems must act to limit the consequences of infection. Through co-evolution, HCMV has developed an intimate relationship with our immune system, and the virus has been established as a paradigm for viral immune evasion.

Natural Killer (NK) cells are implicated in both the innate and adaptive immunity and make a crucial contribution in combating HCMV disease. Patients with defects in NK cell function exhibit extreme sensitivity to HCMV infection. We identified UL40 as the first virus gene definitively demonstrated to induce protection against NK attack. Our studies have also identified the novel HCMV NK evasion function CD155, that has been lost from laboratory-adapted strains of the virus, and which contributes to immune evasion by at least 2 distinct pathways. A major aspect of our work is to uncover the mechanisms by which HCMV modulates the immune system to promote its own survival.

In vivo modelling of CMV infection

To examine the immune responses that control CMV infection in vivo, we utilize the murine CMV model (MCMV) of infection. We are particularly interested in understanding how the virus exploits host immune regulatory mechanisms to enable persistence within the body. We have identified that the immune modulatory cytokine interleukin-10 (IL-10) is up-regulated upon infection and restricts the accumulation of antiviral T cells at sites of prolonged viral replication and latency, consequently facilitating persistence of the virus. Ultimately, we hope that understanding how antiviral immune responses are suppressed during CMV infection, and identifying what immune mechanisms contribute to protection will assist in the design of effective vaccination and immune-therapeutic strategies to counter HCMV infection.

Genetics of HCMV

At 235kb, the HCMV genome is the largest of any human virus

HCMV has the largest genome of any characterised human virus. The complete DNA sequence for the laboratory strain AD169 determined 20 years ago has proved invaluable in HCMV research. However, strain AD169 and other lab strains have accumulated major defects during propagation in vitro. Many genes, including predicted NK evasion functions, are non-essential for in vitro replication and have been deleted or mutated. It has therefore been important to define the intact HCMV genome. In collaboration with Dr Andrew Davison’s laboratory (University of Glasgow), the complete sequence of an HCMV clinical isolate - strain Merlin - from Cardiff was sequenced and annotated. Merlin is now the international reference strain in NCBI Refseq, and we have subsequently cloned the Merlin genome a bacterial artificial chromosome (BAC). Together with collaborative studies detailing the changes that occur during in vitro passage of HCMV, we are now able to analyse pathogenesis, immune evasion, tropism and virus genome evolution using virus that closely represents the clinical agent. The Merlin BAC has already provided insight into clinical HCMV by allowing us to identify the HCMV gene RL13 as a potent inhibitor of viral replication in vitro. We’ve even been featured on the ITV News! To obtain the Merlin BAC please contact Dr Richard Stanton.

Adenovirus Vectors

This laboratory has exploited replication-deficient adenovirus (Ad) vectors extensively over the last 20 years to study gene function, to generate immune responses and to detect immune responses. Recently, our research has extended to developing Adenovirus type 4 (Ad4) vector systems. Live oral Ad 4 and Ad7 vaccines have been used effectively and safely by the US military to prevent outbreaks of acute respiratory disease. In collaboration with Dr Andrew Davison’s laboratory (Univ Glasgow) the sequence of human adenovirus vaccine strain was characterised. We have also developed a new adenovirus cloning system, the AdZ system, which enables us to modify the Ad backbone and to clone multiple genes into Ad vectors rapidly and easily. Vectors with both Ad5 and Ad4 backbones are available, with full protocols and details found here. For more information or to obtain the vectors, please contact Dr Richard Stanton.

Principal Investigators