Programming Bordetella pertussis lipid A to promote adjuvanticity

Area of Science:

• Microbiology
• Immunology
• Vaccine Development

Background:

• Bordetella pertussis causes whooping cough; whole-cell vaccines are effective but reactogenic.
• Vaccine reactogenicity is linked to the lipid A component of B. pertussis lipooligosaccharide (LOS).
• Lipid A variants like monophosphoryl lipid A (MPLA) can serve as adjuvants to improve vaccine efficacy.

Purpose of the Study:

• To engineer B. pertussis strains with modified lipid A to reduce reactogenicity and enhance adjuvant properties.
• To investigate the immune activation pathways triggered by these modified lipid A variants.
• To assess the pyrogenicity and endotoxicity of the engineered B. pertussis strains.

Main Methods:

• Utilized lipid A modifying enzymes from other bacteria to engineer B. pertussis.
• Validated lipid A modifications using MALDI-TOF mass spectrometry.
• Assessed TLR4 activation, TRIF pathway signaling, IRF3 phosphorylation, and type I interferon production.
• Conducted Monocyte Activation Tests (MAT) to evaluate pyrogenicity by measuring IL-6 response in PBMCs.

Main Results:

• Created B. pertussis strains with distinct lipid A modifications, including a hexa-acylated monophosphorylated lipid A.
• Engineered lipid A variants significantly reduced human TLR4 activation but activated the TRIF pathway.
• Modified LOS promoted IRF3 phosphorylation and type I interferon production, mimicking MPLA.
• Four lipid A variants demonstrated increased adjuvanticity, reduced endotoxicity, and significantly decreased IL-6 response in pyrogenicity tests.

Conclusions:

• Developed B. pertussis lipid A variants with reduced TLR4 activation and pyrogenicity.
• These modifications enhance adjuvant properties, offering potential for less reactogenic whole-cell pertussis vaccines.
• Findings support the development of adaptable adjuvants for current pertussis vaccine formulations, improving immunization strategies.