Outer Membrane Vesicle-Coated Nanoparticle Vaccine Protects Against Acinetobacter baumannii Pneumonia and Sepsis

Area of Science:

• Microbiology
• Immunology
• Nanotechnology

Background:

• Acinetobacter baumannii is a highly multidrug-resistant (MDR) Gram-negative pathogen and a global health priority.
• Outer membrane vesicles (OMVs) are potential vaccine candidates but are often heterogeneous.
• An effective vaccine could protect vulnerable populations and curb antimicrobial resistance.

Purpose of the Study:

• To develop and evaluate a novel vaccine platform combining nanoparticle technology with Acinetobacter baumannii outer membrane vesicles (Ab-OMVs).
• To assess the immunogenicity and protective efficacy of the Ab-OMV-coated nanoparticle vaccine (Ab-NPs) against A. baumannii infection.

Main Methods:

• Gold nanoparticle cores were coated with immunogenic Ab-OMVs to create Ab-NPs.
• Immunogenicity was assessed by measuring IgG titers in rabbits.
• Vaccine efficacy was evaluated in mouse models of sepsis and pneumonia, analyzing immune responses including B cell recruitment, dendritic cell activation, and cytokine levels.

Main Results:

• Ab-NP vaccination in rabbits induced robust IgG titers that enhanced human neutrophil opsonophagocytic killing.
• Passive immunization with Ab-NPs protected mice against lethal A. baumannii sepsis.
• Active immunization with Ab-NPs protected mice against sepsis and pneumonia, reducing proinflammatory cytokine storm and enhancing immune cell responses.

Conclusions:

• Nanoparticles serve as an efficient and effective platform for delivering OMV vaccines.
• The Ab-NP vaccine platform shows significant promise for combating Acinetobacter baumannii infections.
• This platform may be applicable to other high-priority multidrug-resistant pathogens.