Gram-negative bacterial infections account for more than half a million severe sepsis cases every year in the United States, where a major pathogenic factor is lipopolysaccharides (LPS) and their corresponding toxic component, lipid A. Minimizing serum lipid A level was expected to be an effective therapy for managing severe sepsis. This hypothesis has been validated in clinical studies. For instance, hemoperfusion methods using immobilized polymyxin B (PB) to remove circulating LPS have proven beneficial. However, common LPS- neutralizing agents, such as PB, are highly toxic, therefore have rather restricted therapeutic applications. In addition, the repertoire of LPS-binding agents is limited by their naturally occurring precursors. On the other hand, due to the difficulties in targeting the lipid A moiety, de novo discovery of LPS-neutralizing compounds remains challenging. Herein, a modular screening approach will be implemented to identify lipid A-specific binders form cyclic peptide libraries. A rhodamine-phenylboronic acid conjugate will be used to stain the polysaccharide part in LPS, which allows differentiating polysaccharide-specific binders from lipid A-specific ones. Three orthogonal methods will be employed to validate the affinity and specificity of identified peptides. Further in vitro validations will be performed on bone marrow-derived macrophages and human peripheral blood mononuclear cells to test the bioactivity. These cells will be challenged with LPS in conjunction with the peptides and their cytokine production will be evaluated. Lower cytokine levels indicate better LPS neutralization effects. Ultimately, the goal is to identify pan-LPS reactive peptides that exhibit high LPS-neutralization capability as well as low cytotoxicity.

Public Health Relevance

Gram-negative bacteria infections cause more than half a million sever sepsis cases annually in the US, where lipopolysaccharides are the most pathogenic factor. Effective agents for neutralizing those circulating lipopolysaccharides in septic patients are greatly underdeveloped. We plan to implement a modular high throughput screening strategy to identify cyclic peptides that can effectively neutralize those lipopolysaccharides, which will provide novel drug leads for further medicinal developments.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Small Research Grants (R03)
Project #
1R03AI139916-01A1
Application #
9824087
Study Section
Special Emphasis Panel (ZRG1)
Program Officer
Xu, Zuoyu
Project Start
2019-05-10
Project End
2021-04-30
Budget Start
2019-05-10
Budget End
2020-04-30
Support Year
1
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of California Riverside
Department
Chemistry
Type
Earth Sciences/Resources
DUNS #
627797426
City
Riverside
State
CA
Country
United States
Zip Code
92521