|Ph.D Student||Fridman Anna|
|Subject||Study of MHC Class II Epitope Presentation with|
Antibodies that Mimic TCR Specificity
|Department||Department of Biology||Supervisor||Professor Yoram Reiter|
|Full Thesis text|
MHC class II (MHC-II) molecules are expressed on antigen-presenting cells (APCs) and present peptides derived from extracellular proteins to CD4 T cells. Binding of T cells to MHC via T cell receptor (TCR) initiates signaling cascade resulting in antigen-specific activation of T cell clones. In order to study MHC-II T cell epitopes one can use antibodies that mimic CD4 TCR specificity, while binding MHC-II/peptide complexes. These antibodies, termed T-Cell Receptor-Like (TCR-like) antibodies, combine two arms of the immune system: high-affinity soluble antibody molecules endowed with a fine specificity of T cells receptor.
Recently, novel TCR-like antibodies against autoreactive T-cell epitopes associated with Type 1 diabetes and Multiple Sclerosis autoimmune diseases were isolated in our laboratory by phage display approach. These TCR-like antibodies were characterized and found to be of high significance for two major research lines: (i) for basic molecular studies as a tool to investigate auto-antigen presentation during autoimmune inflammatory processes with the ability to detect and image APCs that present the auto-antigen. (ii) For translational-clinical applications, where these antibodies were shown to inhibit/block the proliferation of autoreactive T cells in-vitro and in-vivo by binding to the disease associated autoantigen with stronger affinity compared to the autoreactive TCRs.
The goal of this study was to broaden our TCR-like antibody approach in order to study MHC-II epitope presentation in two experimental models associated with autoimmunity and immunity to viral infection. These models enabled us to explore and develop novel antigen-specific research tools to study molecular mechanisms related to antigen presentation as well as novel antigen-specific therapeutic strategies.
For the autoimmune model we focused on Rheumatoid Arthritis, a T cell mediated autoimmune disease of the joints. This disease is triggered by autoantigens presentation (e.g. Type II collagen (CII)) on MHC-II molecules by APCs. While presented by HLA-DR4 molecule, residues 261-273 of CII represent an immunodominant T cell epitope.
For the viral model we focused on Influenza infection. After vaccination with inactivated Influenza virus from Hemagglutinin (HA) 3 subtype, one can find elevated frequency of CD4 T cells directed towards immunodominant HLA-DR4/HA-306-318 epitope in immunized HLA-DR4 subjects. Therefore, TCR-like antibodies against HLA-DR4/HA-306-318 viral epitope can be of high significance for the study of antigen presentation on APCs during a natural course of Influenza infection.
By screening of phage display library we isolated TCR-like antibodies against HLA-DR4/CII-261-273 and HLA-DR4/HA-306-318 recombinant complexes. These antibodies, termed P4A11 and H1, respectively, were able to bind native DR4/CII-261-273 or HLA-DR4/HA-306-318 epitopes as presented by peptide-pulsed DR4 APCs. Most significant, P4A11 and H1 inhibited the recognition between CII-261-273, or HA-306-318, pulsed DR4 APCs and their cognate T cell hybridoma and prevent their activation.
In addition, by using these TCR-like antibodies we were able to detect APCs presenting the HLA-DR4/CII-261-273 or HLA-DR4/HA-306-318 epitopes in splenocytes derived from CII or HA immunized DR4 transgenic mice.
In this study we demonstrated a proof of concept for the utility of our TCR-like antibodies for translational-clinical applications and for basic studies related to antigen presentation, as a tool for direct visualization of APCs.