# Structure, function and antigenicity of B. pertussis virulence factors

> **NIH NIH R01** · UNIVERSITY OF TEXAS AT AUSTIN · 2022 · $564,342

## Abstract

Project Summary
Despite widespread use of a vaccine, infection with the bacterium Bordetella pertussis continues to claim the
lives of ~200,000 infants annually worldwide and cause significant morbidity and mortality in developed countries,
including the US. To develop improved vaccines and therapeutics, we need to better understand how this
organism causes disease and identify new vaccine antigens. The adenylate cyclase toxin (ACT) is a leading
candidate for inclusion in future pertussis vaccines. ACT is a large (1706 residue), bi-functional toxin with a cell-
invasive domain fused to a pore-forming repeat-in-toxin (RTX) hemolysin domain. The RTX domain is composed
of five blocks of ~8 nonapeptide motifs separated by linkers of different length and sequence. ACT efficiently
targets leukocytes by binding αMβ2 integrins via a site localized to the RTX domain. Receptor binding triggers
translocation of the 40 kDa N-terminal adenylate cyclase domain across the host cell membrane where it rapidly
converts nearly all intracellular ATP to cAMP, thereby compromising phagocytic and other leukocyte anti-
bacterial activities.
Although the general features of ACT function have been described, there are few data to support a molecular
understanding of any step in the intoxication process for ACT specifically or for RTX proteins more generally.
The structural features by which the RTX blocks mediate specific protein–protein interactions, such as receptor
binding, and the epitopes and mechanisms by which antibodies inhibit ACT function are not well defined. Our
panel of high-affinity antibodies that recognize neutralizing and non-neutralizing epitopes on ACT provide a
unique opportunity to address these questions. The long-term goal of this research is to understand structural
mechanisms of the complex cellular intoxication process used by the Bordetella adenylate cyclase toxin to
incapacitate immune cells. The specific objective is to provide a molecular description of the interaction of
ACT’s RTX domain with its receptor and with neutralizing and non-neutralizing antibodies. This will provide
mechanistic insights into ACT function and define important vaccine targets such as epitopes susceptible to
antibody-mediated neutralization, the receptor-binding site, and pre-translocation conformations. Such
information is necessary for the implementation of rational design strategies that seek to more effectively present
such targets to the immune system. The expected outcomes include the first structures of an RTX protein
containing more than two repeat blocks and the first RTX–antibody and RTX–receptor structures. We will also
evaluate structural pathways for RTX antibody escape and species specificity and the impact of such changes on
cellular toxicity of the intact ACT protein and bacterial infection using a mouse model. Since there are currently
no structural data defining antibody or receptor epitopes for any RTX protein, this work will transform our
understa...

## Key facts

- **NIH application ID:** 10448307
- **Project number:** 5R01AI155453-02
- **Recipient organization:** UNIVERSITY OF TEXAS AT AUSTIN
- **Principal Investigator:** JENNIFER A MAYNARD
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $564,342
- **Award type:** 5
- **Project period:** 2021-07-09 → 2026-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10448307

## Citation

> US National Institutes of Health, RePORTER application 10448307, Structure, function and antigenicity of B. pertussis virulence factors (5R01AI155453-02). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10448307. Licensed CC0.

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