Interdisciplinary Initiatives Program Round 6 - 2012

Jorg Goronzy, Immunology & Rheumatology
William Greenleaf, Genetics

Generation of immunological memory is a central feature of the adaptive immune system and the basis for the success of vaccination. With increasing age, induction of successful T cell memory after vaccination is impaired. Moreover, memory cell function changes with age and/or duration of the infection. Epigenetic chromatin modifications lie at the heart of T cell memory. Indeed, the increased speed with which memory T cells respond to T cell receptor stimulation is modulated by chromatin marks that "poise" memory cells in a state competent for rapid reactivation and re-expression of effector molecules. However, investigation of the epigenetic landscape within subsets of memory T cells specifically sensitized for viral pathogens is currently methodologically intractable owing to the relatively small number of cells that can be isolated. To address this limitation, we will develop a platform for investigating the position and post-translational modifications of histones within small populations of isolated T cells by coupling fluorescence activated cell sorting (FACS) with new and existing methods for immunoprecipitating relevant modified histones and preparing the isolated DNA fragments for high throughput sequencing. We aim to use this platform to determine whether histone modifications associated with T memory cell differentiation depend on the age at which the primary infection occurs. Specifically, we will determine whether old naïve T cells are competent to acquire chromatin marks as do young naïve T cells when developing into memory T cells. As a second objective, we will determine whether memory cell-associated chromatin marks are unstable with age or duration of the infection. We will compare T memory cell responses to two different herpes viruses, varicella zoster virus (VZV) and cytomegalovirus (CMV). Both viruses are associated with age-associated pathologies, but in very different ways. CMV-specific responses are inflated with age, leading to non-specific inflammation, while VZV responses decline leading to reactivation of the virus. We will define chromatin signatures in memory T cells that are associated with these different age-dependent response patterns.