# Determining the role of lipooligosaccharide on the Opa structural ensemble and the formation of an Opa-CEACAM complex

> **NIH NIH F32** · UNIVERSITY OF VIRGINIA · 2022 · $70,360

## Abstract

Project Summary
Neisseria gonorrhoeae (Gc) and Neisseria meninigitidis (Nm) are pathogenic bacteria causing the sexually
transmitted infection gonorrhea and meningococcal meningitis respectively. Gc is a seriously world-wide health
concern, especially considering the rise of antibiotic resistance in Gc strains. Nm is a less severe threat,
however development of vaccines and antibiotics to prevent and treat Nm infection is still needed.
Understanding Neisseria infection and pathogen-host interactions at the basic molecular level becomes crucial
for these essential tasks. Opacity-associated (Opa) proteins in Neisseria are known to trigger engulfment of the
bacteria into human cells via their interaction with members of the carcinoembryonic antigen-related cellular
adhesion molecule (CEACAM or CCM) family. The structure of Opa has been characterized by our lab, but
attempts to characterize the Opa-CCM molecular complex have conflicted with the established knowledge of
the field. There is evidence that lipooligosaccharide (LOS), a dominant component of the neisserial outer
membrane, can bind Opa proteins on adjacent bacteria, and that changes in LOS structure can affect bacterial
opacity, Opa expression, Opa-CCM interactions, and Neisseria survival. For these reasons, I hypothesize that
lipooligosaccharide is an important factor in Neisseria for maintenance of Opa loop structure, for facilitating
Opa-CCM complex formation and for triggering engulfment of Neisseria via Opa-CCM interaction, and may be
an essential molecular piece we have been missing in our previous experimental characterization.
 I propose to build upon the lab’s expertise with Opa and CCM proteins to (i) determine the role of LOS
on the Opa protein and the structural assembly of Opa’s characteristic dynamic and hypervariable loops (Aim
1) and (ii) to assess the effect of LOS on the affinity of the Opa-CCM complex formation and its ability to trigger
engulfment in human cells in a CCM-dependent manner. I will take a biophysical approach to Aim 1, utilizing
spectroscopic techniques to characterize any change in Opa’s conformational heterogeneity or secondary
structure in the presence of LOS, which will be a large part of my training. In a world-class environment, I will
be trained in electron paramagnetic resonance (EPR) spectroscopic techniques, circular dichroism and nuclear
magnetic resonance (NMR) spectroscopy. In Aim 2, I will combine biochemical and cell-based approaches to
characterize the effect of LOS on Opa-CCM protein complex formation and cellular uptake. This experimental
approach will supplement my biophysical training and help me become a well-rounded scientist who can tackle
complex biological questions with an arsenal of techniques. By describing the molecular basis for Opa-CCM
interaction, we will provide a more solid foundation for the development of novel vaccines and antibiotics to the
broader community studying Neisseria infection.

## Key facts

- **NIH application ID:** 10333374
- **Project number:** 5F32GM136076-03
- **Recipient organization:** UNIVERSITY OF VIRGINIA
- **Principal Investigator:** Meagan Leigh Belcher Dufrisne
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $70,360
- **Award type:** 5
- **Project period:** 2020-02-01 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10333374

## Citation

> US National Institutes of Health, RePORTER application 10333374, Determining the role of lipooligosaccharide on the Opa structural ensemble and the formation of an Opa-CEACAM complex (5F32GM136076-03). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10333374. Licensed CC0.

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