# Boosting efficacy of oral vaccine candidates by enabling spore display of nitrated antigens

> **NIH NIH DP2** · UNIVERSITY OF DELAWARE · 2022 · $1,406,279

## Abstract

Project Summary
Many diseases could be prevented or treated by enlisting the immune system to recognize a specific antigen.
Bacterial diseases warrant heightened attention as many bacterial pathogens lack efficacious vaccines and
exhibit rising rates of antibiotic resistance. These pathogens often find many ways of evading immune system
detection, including varying their most immunogenic antigens. While many virulence-related proteins can be
strongly conserved across pathogen serotypes, they often exhibit weak immunogenicity that is insufficient to
draw the response of the immune system. In this project, we ask: Are there strategies to shine a light on live
bacterial antigens for increased recognition by immune cells? Furthermore, can we couple these strategies to
shelf-stable delivery vectors that are simple to administer to patients across the world?
We propose a transformational approach to expand the list of candidate antigens for use in live bacterial vaccine
vectors by teaching Bacillus subtilis to produce and harness an immunogenic amino acid. This amino acid has
been demonstrated to terminate immune self-tolerance when substituted on the surface of autologous proteins
in mice. Site-specific introduction of nitrated residues within proteins has resulted in presentation of a neoepitope
that is recognized by helper T cells for subsequent activation of B cells that produce polyclonal antibodies. It
stands to reason that the immunogenicity of many weakly immunogenic foreign antigens could be increased
using this strategy, though this has not yet been tested. One challenge is that prior studies also established a
critical but poorly understood role of the MHC Class II locus in enabling immune response to nitrated antigens.
Our project will investigate the potential of spore-displayed nitrated antigens as a transformational vaccination
platform for bacterial disease, with the Shigella invasion protein antigens as a model system. We will first perform
animal studies with Shigella antigens that are weakly immunogenic but strongly conserved across pathogen
serotypes to determine if nitration can increase their immunogenicity. To better understand where nitrated
residues should be placed for optimal recognition by immune cell machinery, we will develop a high-throughput
microbial display platform to screen MHC-II preference towards unnatural peptide ligands. In parallel, we will
develop tools to enable site-specific incorporation of the immunogenic amino acid within proteins fused to the
spore coat of B. subtilis. Recombinant spores of this non-pathogenic organism can be orally administered and
maintain immunization efficacy after exposure to harsh conditions. The spore-based platform has promise to
overcome limitations in the manufacture, transport, and administration of vaccines; however, the platform has
low immunogenicity. Our strategy to form nitrated residues using this platform could overcome that limitation.
From this project, we will gain i...

## Key facts

- **NIH application ID:** 10472983
- **Project number:** 1DP2AI176137-01
- **Recipient organization:** UNIVERSITY OF DELAWARE
- **Principal Investigator:** Aditya Mohan Kunjapur
- **Activity code:** DP2 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $1,406,279
- **Award type:** 1
- **Project period:** 2022-09-08 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10472983

## Citation

> US National Institutes of Health, RePORTER application 10472983, Boosting efficacy of oral vaccine candidates by enabling spore display of nitrated antigens (1DP2AI176137-01). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10472983. Licensed CC0.

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