Modulating endotoxin activity by combinatorial bioengineering of meningococcal lipopolysaccharide

Area of Science:

• Microbiology
• Immunology
• Biochemistry

Background:

• Neisseria meningitidis lipopolysaccharide (LPS) is highly toxic, limiting its therapeutic applications.
• Modifying LPS lipid A acylation and phosphorylation can alter its endotoxic activity.
• Understanding LPS structure-activity relationships is crucial for developing safe immunomodulators.

Purpose of the Study:

• To engineer novel Neisseria meningitidis LPS mutants with reduced toxicity.
• To investigate the impact of specific lipid A modifications on LPS endotoxic activity.
• To explore the potential of engineered LPS derivatives as vaccine adjuvants or TLR4-based therapeutics.

Main Methods:

• Systematic molecular bioengineering of meningococcal LPS by deleting biosynthetic enzymes and inducing modifying enzymes.
• Mass spectrometry for detailed compositional analysis of LPS molecular species.
• Immune cell stimulation assays to correlate LPS structure with endotoxic activity and cytokine induction.

Main Results:

• Deletion of lptA (removing phosphethanolamine) reduced activity in both hexa- and penta-acylated LPS.
• PagL deacylase expression in a penta-acylated mutant unexpectedly increased LPS activity.
• Temperature-sensitive LpxP expression allowed controlled modification of LPS acylation levels.
• Engineered LPS derivatives exhibited a spectrum of Toll-like receptor 4 (TLR4) activity and differential cytokine profiles.

Conclusions:

• Molecular bioengineering can generate Neisseria meningitidis LPS mutants with tunable endotoxic activity.
• Specific lipid A modifications, including acylation and phosphorylation, significantly impact LPS immunogenicity.
• These novel LPS derivatives offer potential for developing safer vaccine adjuvants and TLR4-targeted therapies.