News at Medicine - October 2014 - Grad alumnus involved in research on immunology and cell biology

Grad alumnus involved in research on immunology and cell biology
October 15, 2014
Dr. Cliff Guy, who did his PhD at Memorial under the supervision of Dr. Thomas Michalak, is an author on a number of significant papers.
Dr. Guy is currently a staff scientist and managing director of the Imaging Facility, Department of Immunology at St. Jude Children’s research hospital. The facility supports the research interests of over 70 scientists with broad interests in the field of immunology and cell biology. 
The paper Distinct TCR signaling pathways drive proliferation and cytokine production in T cells was published in Nature Immunology. “A properly functioning immune system is a lesson in balance, providing protection against disease without attacking healthy tissue,” said Dr. Guy. “Work led by St. Jude scientists and published recently in Nature Immunology has identified a mechanism that helps T cells find that sweet spot where the strength of the immune response matches the threat.”
The finding offers important insight into the immune response. The work also lays the foundation for advancing understanding and treatment of problems that arise when the system malfunctions, including autoimmune disorders that occur when the immune system targets healthy tissue or chronic infectious diseases and cancer that result from an insufficient immune response. 
The approach used to generate these mice was recently published in the journal Nature Protocols: Generation of T cell receptor-retrogenic mice: improved retroviral-mediated stem cell gene transfer.
This protocol utilizes retroviral stem cell gene transfer into murine bone marrow followed by reconstitution of immune-deficient RAG1 knockout mice. “Additionally, we utilize a self-cleaving 2A peptide motif to express up to 4 different proteins from the same genetic construct, in equivalent ratios,” said Dr. Guy. “In this manner, we are able to generate an immune replete mouse expressing T cells of any desired specificity, or expressing any number of modified proteins, in approximately six weeks. This is in comparison with traditional approaches which may require more than a year to generate a similar mouse.”
In a series of collaborative papers, Dr. Guy said the research team has published extensively on the effector mechanisms used by regulatory T cells (Tregs): IL-35-mediated induction of a potent regulatory T cell population, in Nature Immunology. And the composition and signaling of the IL-35 receptor are unconventional.
“Together, these two papers highlighted how a novel cytokine, IL-35, which was discovered by Dario Vignali’s group in 2008, contribute to maintenance of peripheral T cell quiescence via ‘infectious tolerance,’ explained Dr. Guy. “Interestingly, the composition of the IL-35 receptor and its utilization of signaling molecules was determined to rather unique in comparison with other members of this cytokine family.”
In the paper Stability and function of regulatory T cells is maintained by a neuropilin-1-semaphorin-4a axis, published in Nature, the team determined that expression of neuropilin-1 on Tregs is crucial for their function, especially in inflammatory environments. “The interaction of neuropilin-1 with its ligand semaphoring-4a was necessary to abrogate signaling via the PI3K pathway through the recruitment of PTEN, resulting in stability and maintenance of Tregs,” said Dr. Guy. “In the absence of this pathway, mice were largely resistant to the development of a variety of malignancies, suggesting the possibility that immunotherapy targeting Treg function via this and other key molecular pathways would be of therapeutic benefit.
The paper Viral suppressors of the RIG-I-mediated interferon response are pre-packaged in influenza virions, was released recently in the journal Nature Communications. “We were able to blunt the immune response by interfering with the interferon response,” said Dr. Guy. “As soon as three hours after infection, and prior to the replication of new viruses, the infecting viruses are able to deliver their genetic cargo along with immune modulatory proteins. This complex is delivered specifically to the mitochondria where it blunts the antiviral response. Mutation of this protein such that it lacked the necessary motif, resulted in a less pathogenic infection.” This study is the first to utilize fluorescence-based stochastic optical reconstruction microscopy (STORM) to identify viral genomes in complex with antiviral proteins, whilst being situated on the outer mitochondrial membrane.