1. My lab is interested in understanding the mechanisms underlying the induction and maintenance of memory CD8+ T cells, the factors responsible for sustaining effector function and the mechanisms for their persistence. CD8+T lymphocytes are crucial for both clearance of intracellular pathogens and limiting the growth of virally infected cells and tumors. The CD8+T cell response to a pathogen results in the formation of a memory population of cells, which serves as a protective barrier against future insults by the same pathogen and is the basis for long-lasting protective immunity. At present we know that following resolution of bacterial and viral infections, a population of long-lived memory CD8+ T cells persist in both secondary lymphoid tissues and non-lymphoid tissues. Seminal studies show that memory T cells can be classified into two subpopulations: (1) central memory T cells (TCM) which reside predominantly in secondary lymphoid organs, and (2) effector memory T cells (TEM) that are generally excluded from lymphoid tissues but preferentially migrate into the tissues and peripheral organs. The distribution of memory CD8+ T cells into TCM and TEM subpopulations is not absolute and holds important consequences for immunity.
(a) Viral and Bacterial Infections:
Our ultimate goal is to elicit CD8+ T cell responses that have the capacity to reduce the severity of infection and thereby lower mortality rates associated with infectious disease. What is not completely understood and imperative for vaccine development is whether the tissue microenvironment influences memory CD8 T cell differentiation, which subpopulations of memory CD8+T cells continue to protect against subsequent infections, how these CD8+ T cell populations are generated and maintained, and ultimately how these CD8+ T cell populations can be generated in the right tissue by vaccination. Our studies and those of others have shown that CD4+ and CD8+ memory T cells reside in non-lymphoid tissues and are functionally distinct from their counterparts in secondary lymphoid. Secondary lymphoid memory CD8+ T cells are poorly lytic ex vivo. More recently, we showed that secondary splenic memory CD8+ T cells acquire lytic activity after entry into non-lymphoid tissues and thus add to the pool of memory cells found in non-lymphoid tissues. The basis for this modulation of effector function is unknown but could be due to the active process of migration or to the tissue microenvironment. We hypothesize that a significant functional reprogramming of memory CD8+ T cells occurs in non-lymphoid tissues, allowing non-lytic CD8+TCM and TEM to gain effector function upon entering non-lymphoid tissues in the absence of antigen.
How CD8+TEM and CD8+TCM are maintained in lymphoid and non-lymphoid tissues is also under investigation. CD8+ TCM have been reported to homeostatically proliferate more than CD8+ TEM and thus able to compensate for their gradual attrition through apoptosis. On the other hand we predict that CD8+ TEM in the non-lymphoid tissues may rely more on survival signals to maintain their numbers. We are currently examining whether different subpopulations of memory CD8+ T cells (TCM and TEM) found in lymphoid and non-lymphoid tissues are equally resistant to apoptosis.
(b) Immune response to solid tumors:
Our strategy in this project is to concentrate on (1) determining the normal interactions between the tumor and the immune system and (2) ask what happens when immunotherapy is effective. The logic of this is that the cells that mediate this effective response must be the type that new immuno-therapeutics should be designed to elicit. Our major hypothesis is that the failure of immunotherapies in clinical trials is due to an incomplete understanding of the identity of the most appropriate therapeutic cell type(s) and the factors that drive their differentiation. Specifically, we hypothesize that there is a failure to induce effective anti-tumor memory CD8 T cell populations. Memory CD8 T cells possess those essential criteria we would ask of mediators of an effective immune response derived by immunotherapy (i.e. they respond quickly and to small amounts of recall antigen and are long-lived). In particular, a subset of memory CD8+ T cells (TM), the effector TM (TEM), may be the most potent anti-tumor effect to elicit in immunotherapies as they home to peripheral tissues rather than lymphoid organs and have direct cytolytic capacity. We will use a murine model where tumor cell lines have been transfected with hemagglutinin (HA) which allows us to use TCR transgenic mice specific for HA to directly assess tumor specific T cell responses to determine the impact anti-tumor CD4 T cells have on the phenotype and function of anti-tumor CD8 T cells. Using a system in which tumor antigen can be turned off (and thereby enabling the dissociation of antigen load from the other effects of tumor growth) we will determine the effect of tumor antigen versus tumor microenvironment has on the induction of anti-tumor memory CD8 T cells. Our understanding of anti-tumor CD8 T cell memory generation in cancer lags behind the more comprehensive analyses that have occurred in infectious disease models. Successful completion of this project will help rectify this deficiency by providing important insight into the development of memory T cells during tumor growth.
2. A Humanized Mouse Model for Breast Cancer.
Despite improvements in breast cancer therapy, patients with advanced or metastatic disease have a poor survival rate. One new approach to inhibiting growth of breast cancer tumors is to target mammaglobin-A, a breast cancer-associated antigen expressed by approximately 80% of breast tumors. Several CD8+ cytotoxic T lymphocyte (CTL) epitopes of mammaglobin-A have been identified and CTLs generated against these epitopes lyse breast cancer cell lines. This shows that these epitopes are naturally presented by breast tumors. My lab is currently developing a humanized mouse model of breast cancer. These mice are humanized by engraftment of human hematopoietic stem cells from healthy donors or breast cancer patients. We will use humanized mice that have been immunized with cDNA containing the full-length mammaglobin-A (containing both CD8 and CD4 mammaglobin-A epitopes) and these mice will be subsequently inoculated with breast cancer cell lines expressing mammaglobin-A. We postulate that characterization of the cellular immune responses to the mammaglobin-A antigen will provide us an opportunity to study human biological processes in vivo (in humanized mice) and test DNA-based vaccination strategies against breast cancer. Such developments will eventually lead to methods for early detection and diagnosis of breast cancer, and the development of a vaccine to induce a protective immune response in high-risk individuals.
Marzo A.L, Yagita H, and Lefrancois L. Cutting Edge: Migration to nonlymphoid tissues results in functional conversion of central to effector memory CD8 T cells. J Immunol. 2007; 179:36-40.
Lefrancois L and Marzo A.L. The descent of memory T-cell subsets.
Nat Rev Immunol. 2006 Aug;6(8):618-23.
Marzo AL, Klonowski KD, Le Bon A, Borrow P, Tough DF and Lefrancois L.
Initial T cell frequency dictates memory CD8 T cell lineage commitment.
Nat Immunol. 2005 Aug;6(8):793-9.
Marzo A L, Vezys V, Klonowski KD, Lee SJ, Muralimohan G, Moore M, Tough DF, and Lefranois L. Fully functional memory CD8 T cells in the absence of CD4 T cells.
J. Immunol. 2004 Jul 15; 173(2):969-75.
Marzo A.L.,Vezys V, Williams K, Tough DF, and Lefranois L. Tissue-level regulation of Th1 and Th2 primary and memory CD4 T cells in response to Listeriainfection.
J. Immunol. 2002 May 1;168(9): 4504-10.
Masopust D, Vezys V, Marzo AL, Lefrancois L. Preferential localization of effector memory cells in nonlymphoid tissue. Science. 2001 Mar 23;291(5512):2413-7.
Robinson BW, Scott BM, Lake RA, Stumbles PA, Nelson DJ, Fisher S, Marzo AL. Lack of ignorance to tumor antigens:evaluation using nominal antigen transfection and T-cell receptor transgenic lymphocytes in Lyons-Parish analysisimplications for tumor tolerance.
Clin Cancer Res. 2001 Mar;7(3Suppl):811s-817s.
Marzo A.L., Lake R.A., Lo D., Sherman L., McWilliam A., Nelson D., Robinson B.W.S., and Scott, B. Tumor antigens are constitutively presented in the draining lymph nodes.
J Immunol. 1999 May 15;162(10):5838-5845.
Members of the Marzo Laboratory:
Ryan Sowell: Research Technician III; Ryan_Sowell@rush.edu
Magda Rogozinska: Research Technician III; Magdalena_Rogozinska@rush.edu
Nadine Lerret : Graduate student; Nadine_Lerret@rush.edu
Rana Saber: Graduate student; Rana_Saber@rush.edu