Gram negative bacteria secrete outer membrane vesicles (OMVs), which deliver a wide array of biomacromolecules, including toxins and virulence factors to host cells. Aggregatibacter actinomycetemcomitans (Aa) OMVs are enriched in leukotoxin (LtxA) and have been observed to contain lipids that are not found in the bacterial outer membrane (OM). The mechanism leading to LtxA enrichment in OMVs has not yet been identified. We have observed that LtxA has a strong affinity for lipopolysaccharide (LPS), the primary component of the outer leaflet of the OM. In several organisms, variations in the LPS structure within the OMVs has been found to differ from that of the OM. We therefore hypothesize that, in Aa, the OMV-specific lipids are LPS variants and that the differential affinity of LtxA for these variants regulates the toxin's enrichment in the OMV. To study this process, we will determine the LPS and LtxA composition of both the OMV and OM of Aa. We will conduct this series of experiments using OMVs purified from Aa that has been grown under a variety of conditions to obtain a better picture of LtxA enrichment in LPS under biologically relevant conditions. We will then purify the LPS from Aa OMVs and OM and quantify the affinity of LtxA for each type of LPS to relate affinity of the toxin for LPS to its observed enrichment. We anticipate that the research will result in a more complete understanding of the role of OMVs in periodontitis. In addition, the results of the work may be more broadly applicable to the general understanding of protein enrichment in or exclusion from OMVs.

Public Health Relevance

Bacteria actively produce small vesicles during infection that contain a variety of proteins, including toxins. The inclusion/enrichment of specific toxins in these vesicles has been reported but the mechanism of this process is not yet understood. This project will investigate the enrichment of a specific toxin with vesicles produced by a periodontal pathogen to obtain a detailed understanding of the delivery of toxins via vesicles.

Agency
National Institute of Health (NIH)
Institute
National Institute of Dental & Craniofacial Research (NIDCR)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21DE027769-01
Application #
9508346
Study Section
Oral, Dental and Craniofacial Sciences Study Section (ODCS)
Program Officer
Lunsford, Dwayne
Project Start
2018-09-01
Project End
2020-08-31
Budget Start
2018-09-01
Budget End
2019-08-31
Support Year
1
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Lehigh University
Department
Engineering (All Types)
Type
Biomed Engr/Col Engr/Engr Sta
DUNS #
808264444
City
Bethlehem
State
PA
Country
United States
Zip Code
18015