Immunopeptidomics reveals conserved and abundant Francisella tularensis proteins as immunogenic CD4 T cell antigens in mice
6 affiliations
- 1Department of Molecular Pathology and Biology, Military Faculty of Medicine, University of Defence, Hradec Kralove, Czech Republic
- 2Laboratory of Immunobiology, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
- 3Laboratory of Adaptive Immunity, Institute of Molecular Genetics of the Czech Academy of Sciences, Prague, Czech Republic
- 4Biomedical Research Center, University Hospital Hradec Kralove, Hradec Kralove, Czech Republic
- 5Laboratory of Immunotherapy, Institute of Microbiology of the Czech Academy of Sciences, Prague, Czech Republic
- 6Department of Cell Biology, Faculty of Science, Charles University, Prague, Czech Republic
Abstract
Human tularemia is caused by infection with the intracellular bacterium Francisella tularensis. The ability of the bacterium to cause a severe pneumonic form of the disease has led to concerns in the field of biodefense and efforts to develop a vaccine. F. tularensis LVS provides partial protection against fully virulent strains, with CD4+ T cells playing a significant role in this protection, however the recognized bacterial antigens remain largely unknown. To identify these antigens, we screened MHC class II peptides presented by infected dendritic cells using mass spectrometry-based immunopeptidomics. We identified 57 MHC-II peptides from 23 different F. tularensis LVS proteins. Most of these proteins were highly expressed in the bacterial proteome. Subsequent screening for IFN-γ responses identified ten peptides as immunogenic epitopes of CD4+ T cells following immunization of mice with F. tularensis LVS, thereby revealing previously unknown specificity and breadth of the induced immune responses. Five epitopes, derived from the antigens FTL_1678, DacD, DnaK, FTL_1498, and MinD, represented the dominant epitopes that elicited a response in at least 80% of immunizations. Finally, a peptide vaccine containing these epitopes proved to be immunogenic in mice and contributed to the early control of bacterial replication following challenge with the virulent F. tularensis FSC200 strain, although this alone was insufficient to ensure complete protection. Using immunopeptidomics, we have thus identified several immunogenic CD4+ T cell epitopes and antigens of F. tularensis LVS. Beyond their potential role in the protective immune response, the identified epitopes may also enable the development of tools for characterizing antigen-specific CD4+ T cells in vaccination studies or T cell biology research. Author summary: The establishment of effective T cell-mediated immunity is essential for the elimination of infections caused by intracellular bacterial pathogens. Identifying bacterial targets for T cells is important for determining the spectrum and specificity of immune responses, developing diagnostic tools, and designing vaccines. For the intracellular bacterium Francisella tularensis, the causative agent of tularemia, knowledge of the antigens and epitopes recognized by T cells is limited. In this study, we use immunopeptidomics to identify bacterial peptides presented by MHC class II from infected dendritic cells and a mouse model of tularemia to evaluate their immunogenicity. We uncovered several immunogenic epitopes and antigens of CD4+ T cells in the F. tularensis LVS strain and evaluated the protective potential of these epitopes against infection with the virulent F. tularensis FSC200 strain. Our study provides new insights into the specificity, dominance, and breadth of CD4+ T cell immune responses induced by F. tularensis LVS.
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BibTeX
@article{laskova2026immunopeptidomics,
title = {{Immunopeptidomics reveals conserved and abundant Francisella tularensis proteins as immunogenic CD4 T cell antigens in mice}},
author = {Pavlina Laskova and Stanislava Porkertova and Ondrej Ballek and Lucie Balonova and Jana Pavloskova and Ales Neuwirth and Ivona Pavkova and Ivo Fabrik and Pavol Lukac and Luca Vannucci and Dominik Filipp and Jiri Stulik and Marek Link},
journal = {PLOS Pathogens},
year = {2026},
month = sep,
doi = {10.1371/journal.ppat.1014597},
url = {https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014597},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Immunopeptidomics reveals conserved and abundant Francisella tularensis proteins as immunogenic CD4 T cell antigens in mice
AU - Pavlina Laskova
AU - Stanislava Porkertova
AU - Ondrej Ballek
AU - Lucie Balonova
AU - Jana Pavloskova
AU - Ales Neuwirth
AU - Ivona Pavkova
AU - Ivo Fabrik
AU - Pavol Lukac
AU - Luca Vannucci
AU - Dominik Filipp
AU - Jiri Stulik
AU - Marek Link
PY - 2026
DA - 2026/09/29
JO - PLOS Pathogens
DO - 10.1371/journal.ppat.1014597
UR - https://journals.plos.org/plospathogens/article?id=10.1371/journal.ppat.1014597
AB - Human tularemia is caused by infection with the intracellular bacterium Francisella tularensis. The ability of the bacterium to cause a severe pneumonic form of the disease has led to concerns in the field of biodefense and efforts to develop a vaccine. F. tularensis LVS provides partial protection against fully virulent strains, with CD4+ T cells playing a significant role in this protection, however the recognized bacterial antigens remain largely unknown. To identify these antigens, we screened MHC class II peptides presented by infected dendritic cells using mass spectrometry-based immunopeptidomics. We identified 57 MHC-II peptides from 23 different F. tularensis LVS proteins. Most of these proteins were highly expressed in the bacterial proteome. Subsequent screening for IFN-γ responses identified ten peptides as immunogenic epitopes of CD4+ T cells following immunization of mice with F. tularensis LVS, thereby revealing previously unknown specificity and breadth of the induced immune responses. Five epitopes, derived from the antigens FTL_1678, DacD, DnaK, FTL_1498, and MinD, represented the dominant epitopes that elicited a response in at least 80% of immunizations. Finally, a peptide vaccine containing these epitopes proved to be immunogenic in mice and contributed to the early control of bacterial replication following challenge with the virulent F. tularensis FSC200 strain, although this alone was insufficient to ensure complete protection. Using immunopeptidomics, we have thus identified several immunogenic CD4+ T cell epitopes and antigens of F. tularensis LVS. Beyond their potential role in the protective immune response, the identified epitopes may also enable the development of tools for characterizing antigen-specific CD4+ T cells in vaccination studies or T cell biology research. Author summary: The establishment of effective T cell-mediated immunity is essential for the elimination of infections caused by intracellular bacterial pathogens. Identifying bacterial targets for T cells is important for determining the spectrum and specificity of immune responses, developing diagnostic tools, and designing vaccines. For the intracellular bacterium Francisella tularensis, the causative agent of tularemia, knowledge of the antigens and epitopes recognized by T cells is limited. In this study, we use immunopeptidomics to identify bacterial peptides presented by MHC class II from infected dendritic cells and a mouse model of tularemia to evaluate their immunogenicity. We uncovered several immunogenic epitopes and antigens of CD4+ T cells in the F. tularensis LVS strain and evaluated the protective potential of these epitopes against infection with the virulent F. tularensis FSC200 strain. Our study provides new insights into the specificity, dominance, and breadth of CD4+ T cell immune responses induced by F. tularensis LVS.
SN - 1553-7374
ER -