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Updated: Aug 8, 2025
Evaluation of Host-Pathogen Responses and Vaccine Efficacy in Mice
Published on: February 22, 2019
Intranasal immunization with outer membrane vesicles (OMV) protects against airway colonization and systemic
Sophie L Higham1, Stephen Baker2, Katie E Flight1
1Department of Infectious Disease, Imperial College London, St Marys Campus, Norfolk Place, London W2 1PG, United Kingdom.
Objectives:
The multidrug-resistant bacteria Acinetobacter baumannii is a major cause of hospital-associated infection; a vaccine could significantly reduce this burden. The aim was to develop a clinically relevant model of A. baumannii respiratory tract infection and to test the impact of different immunization routes on protective immunity provided by an outer membrane vesicle (OMV) vaccine.
Methods:
BALB/c mice were intranasally challenged with isolates of oxa23-positive global clone GC2 A. baumannii from the lungs of patients with ventilator-associated pneumonia. Mice were immunized with OMVs by the intramuscular, subcutaneous or intranasal routes; protection was determined by measuring local and systemic bacterial load.
Results:
Infection with A. baumannii clinical isolates led to a more disseminated infection than the prototype A. baumannii strain ATCC17978; with bacteria detectable in upper and lower airways and the spleen. Intramuscular immunization induced an antibody response but did not protect against bacterial infection. However, intranasal immunization significantly reduced airway colonization and prevented systemic bacterial dissemination.
Conclusions:
Use of clinically relevant isolates of A. baumannii provides stringent model for vaccine development. Intranasal immunization with OMVs was an effective route for providing protection, demonstrating that local immunity is important in preventing A. baumannii infection.
Insights
Intranasal immunization with outer membrane vesicle (OMV) vaccines effectively protects against Acinetobacter baumannii respiratory infections by reducing bacterial load. This highlights the importance of local immunity for preventing hospital-associated infections caused by this multidrug-resistant bacterium.
Area of Science:
- Infectious Diseases
- Vaccinology
- Microbiology
Background:
- Acinetobacter baumannii is a multidrug-resistant bacterium frequently causing hospital-associated infections.
- A vaccine is needed to mitigate the burden of A. baumannii infections.
Purpose of the Study:
- To establish a clinically relevant model for A. baumannii respiratory tract infection.
- To evaluate the efficacy of an outer membrane vesicle (OMV) vaccine administered via different routes.
Main Methods:
- Developed a mouse model using clinical isolates of A. baumannii from ventilator-associated pneumonia patients.
- Administered OMV vaccine via intramuscular, subcutaneous, and intranasal routes.
- Assessed protection by measuring local and systemic bacterial loads.
Main Results:
- Clinical A. baumannii isolates caused disseminated infections in the respiratory tract and spleen.
- Intramuscular immunization generated antibodies but offered no protection.
- Intranasal immunization significantly reduced airway colonization and prevented systemic spread.
Conclusions:
- Clinically relevant isolates provide a robust model for A. baumannii vaccine development.
- Intranasal OMV immunization is an effective strategy for protection.
- Local mucosal immunity plays a critical role in preventing A. baumannii infections.
