Biology subjects

Hedgepeth, E. J.

Publications and source records attributed to Hedgepeth, E. J..

2 recordsLinked to original sources

bioRxiv2026

Generation and MHC class II loading of an endogenous influenza epitope revealed by a T cell receptor-like antibody

CD4+ T cells coordinate immune responses to infections and cancers and initiate many autoimmune diseases, yet the intracellular pathways that generate the peptide antigens they recognize remain incompletely understood. Progress has been limited in part by the scarcity of reagents that directly detect defined peptide:MHC class II (pMHC-II) complexes. Here, we established an mRNA vaccine-based pipeline to generate and characterize T cell receptor (TCR)-like antibodies. One result was 1D6, a monoclonal antibody specific for NA25:Ab, an influenza A/PR8 neuraminidase-derived epitope presented by MHC-II. 1D6 bound NA25:Ab with high affinity and specificity. 1D6 recognizes NA25:Ab through binding determinants partially distinct from those used by the cognate TCR. Using this reagent, we confirmed the proteasome dependence of NA25 presentation and showed that NA25:Ab accumulates in intracellular MHC-II loading compartments without a major requirement for canonical macroautophagy, pointing to an unconventional mode of antigen presentation. These findings establish TCR-like antibodies as powerful tools for dissecting noncanonical MHC-II antigen processing pathways. One Sentence SummaryAn mRNA immunization strategy generated a highly specific antibody to study how a noncanonical natural epitope from influenza virus is produced and loaded onto MHC-II.

immunology↗

bioRxiv2025

Endogenous antigen processing promotes mRNA vaccine CD4+ T cell responses

Lipid nanoparticle (LNP)-encapsulated nucleoside-modified mRNA vaccines elicit robust CD4+ T cell responses, which are essential for antiviral immunity1-3. While peptides presented to CD4+ T cells via major histocompatibility complex class II (MHC II) are traditionally thought to be derived from extracellular sources that are processed by antigen presenting cells (APCs) through the classical exogenous pathway4,5, the precise mechanisms of mRNA-LNP vaccine-specific CD4+ T cell priming remain unknown. Here, we investigated the role of alternative, endogenous antigen presentation pathways6,7 in inducing CD4+ T cell responses to mRNA-LNP vaccines. APCs treated with mRNA-LNP vaccines were consistently superior in activating T cells under conditions of endogenous, rather than exogenous, presentation. Immunization with an mRNA-LNP vaccine that excludes antigen expression in APCs resulted in lower antigen-specific CD4+ T cell, T follicular helper cell, and antibody responses than mice receiving control vaccine. In contrast, depletion of vaccine antigen from exogenous sources such as muscle cells resulted in little to no reduction in antigen-specific CD4+ T cells. Our findings demonstrate that direct presentation of endogenous antigen on MHC II is crucial to mRNA-LNP vaccine-induced immune responses and adds to a growing body of literature that redefines the paradigm of MHC II-restricted antigen processing and presentation.

immunology↗