PhD defence by Yogesh Basavaraju

On Monday 17 June 2024, Yogesh Basavaraju will defend his PhD thesis "Develop and validate novel MHC-II-based T cell detection technologies to interrogate CD4 T cell reactivity and determine key characteristics of neoepitope immunogenicity".

Time & place: 13:00, building 303, aud. 43

Principal supervisor: Professor Sine Reker Hadrup
Co-supervisor: Tripti Tamhane

Assessment committee:
Professor Peter Heegaard, DTU Health Tech
Professor Sebastian Springer, Constructor University Bremen
Professor Christian Freund, Freie University Berlin

Chairperson:
Associate Professor Sunil Kumar Saini, DTU Health Tech

Abstract:

The human immune system is a complex network that plays a role in body’s defense against pathogens and cancer. It comprises of innate and adaptive immunity. Adaptive immunity comprises of lymphocytes – T cells and B cells. Two types of T cells – CD8 T cells (cytotoxic) and CD4 T cells (T-helper cells) play an important role in cancer and infections. The T cells detect antigens that are presented on major histocompatibility complex (MHC), and upon recognizing the antigen-MHC complex they are activated, thus eliciting an immune response against the antigen. The role of these antigen-specific T cells responding to antigen challenge is a topic of intense studies, and critical for development and mechanistic insight to therapeutic strategies and disease development. Detecting such antigen-specific T cells is important for designing and optimizing therapies.

Large-scale detection technologies developed to asses CD8 T cell detection have not yet been adapted to enable the identification of CD4 T cells at a large scale. Some of the challenges are the availability of soluble MHCII and the ability to load antigens at a large scale to screen for antigen-specific CD4 T cells. Here we have established an MHCII expression and peptide exchange platform in the presence of human leukocyte antigen-DM (HLA-DM). We then used DNA barcodes to mark the peptide-MHCII multimers thereby able to detect CD4 T cell binding by DNA barcoding. We detected viral-specific CD4 T cells and validated them by conventional tetramer staining. This DNA-barcoded technology was also used for screening peptides loaded on MHC class I molecules in the setting of chronic lymphocytic leukemia to detect CD8 T cell responses for peptides derived from B-cell receptor immunoglobulin regions.

All this is possible with the use of soluble reagents, therefore, to address the instability of such soluble heterodimeric reagents we explored a novel approach of using a nanobody (single-domain antibodies) and its epitope as fusion partners in enhancing the functional stability of heterodimers. In nanobody-epitope fused MHCI and MHCII, we demonstrate the enhancement of their ability to detect antigen-specific CD8 and CD4 T cell respectively compared to their wild-type construct.

In conclusion, we contribute to the field of immunology and immunotherapy by providing novel approaches for large-scale screening of antigenic CD4 T cells and using nanobody-epitope fusion to enhance heterodimeric stability.