# ANALYSIS OF THE E COLI HEMOLYSIN AND RELATED TOXINS

> **NIH NIH R01** · UNIVERSITY OF WISCONSIN-MADISON · 1991 · $222,188

## Abstract

A family of exotoxins (RTX) produced by a variety of important human and
animal pathogens, such as Escherichia coli, Bordetella pertussis,
Actinobacillus actinomycetemcomitans and Pasteurella haemolytica has been
recently recognized.  The RTX toxins with the possible exception of the B.
pertussis RTX toxin, form pores in target cell plasma membranes which lead
to cell lysis.  The RTX toxins can be distinguished from one another by
differences in cell- and host-specificity.  The main objective of the
research is to understand the bases for RTX toxin pore formation and cell-
and host-specificity.  The most thoroughly studied member and prototype of
the family is the E. coli hemolysin (HlyA).  hlyA mutations and reciprocal
hybrids of different RTX structural genes will be isolated.  The  HlyA
mutant and hybrid proteins will analyzed in a variety of functional tests
that will examine their ability to form channels in cells and artificial
lipid bilayers and determine their target-cell specificity characteristics.
A particular class of HlyA mutants will be studied in detail.  These
mutants retain hemolytic activity but have lost the ability to lyse
nucleated cells.  The mutants will allow an assessment of the relative
contribution of the hemolytic versus leukotoxic activities to virulence by
testing them in a rat model of E. coli intra-abdominal sepsis and in vitro
tests of HlyA activities (inhibition of macrophage antigen processing and
presentation, channel formation, target-cell binding etc.).  The topography
of HlyA inserted into plasma membranes will be studied by protease-
protection experiments and flow cytometry using a panel of anti-HlyA
monoclonal antibodies with epitopes mapped to specific HlyA regions.  HlyC
is necessary for production of cytolytically active HlyA.  To study this
poorly understood event, a monoclonal antibody (D12) specific for "active"
HlyA will be used to screen HlyA mutants.  A second long term objective of
the work is the identification and characterization of additional RTX
determinants among pathogenic bacteria.  Exoproteins produced by Neisseria
meningitidis and Hemophilus influenzae type b (Hib) have been identified
which are antigenically related to RTX toxins.  The N. meningitidis RTX-
like protein will be characterized in a collaborator's laboratory.  To
isolate the RTX-like Hib genes, an existing recombinant library of Hib
genomic DNA will be screened with anti-RTX antibodies and RTX gene probes.
to assess the significance of the Hib RTX-like protein in Hib pathogenesis,
isogenic Hib strains altered in their ability to produce the putative RTX
protein will be constructed and tested in an infant rat intranasal-
challenge model of sepsis and meningitis.  The Hib RTX-like exoprotein will
be also tested in in vitro assays of cytoxicity and pore formation.  The
structure and function of HlyA and its RTX relatives and the role of the
RTX toxins in the pathogenesis of significant human and animal diseases are
not under...

## Key facts

- **NIH application ID:** 3129906
- **Project number:** 2R01AI020323-09
- **Recipient organization:** UNIVERSITY OF WISCONSIN-MADISON
- **SAM.gov UEI:** LCLSJAGTNZQ7
- **Principal Investigator:** Rodney A. Welch
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1991
- **Award amount:** $222,188
- **Award type:** 2
- **Project period:** 1983-08-01 → 1996-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3129906

## Citation

> US National Institutes of Health, RePORTER application 3129906, ANALYSIS OF THE E COLI HEMOLYSIN AND RELATED TOXINS (2R01AI020323-09). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3129906. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*