Sequential Vaccination With Heterologous Acinetobacter baumannii Strains Induces Broadly Reactive Antibody Responses

Area of Science:

• Microbiology
• Immunology
• Infectious Diseases

Background:

• Multi-drug resistant (MDR) Acinetobacter baumannii poses a significant threat.
• Existing treatments are limited, necessitating novel therapeutic strategies.
• Capsular serotypes of A. baumannii complicate universal treatment approaches.

Purpose of the Study:

• To investigate the potential of antibody therapy targeting conserved protein antigens of A. baumannii.
• To assess cross-protective immunity induced by antibodies against diverse clinical isolates.
• To evaluate the efficacy of targeting protein antigens over capsular polysaccharides.

Main Methods:

• Mice were immunized with single or multiple A. baumannii strains.
• Antibody responses to protein antigens were induced and measured.
• Flow cytometry IgG binding assays and immunoblots assessed bacterial recognition.
• Neutrophil phagocytosis assays and a mouse infection model were employed.

Main Results:

• Immunization with multiple strains elicited broader antibody responses to protein antigens.
• Sera from multi-strain immunized mice showed enhanced recognition of diverse A. baumannii strains.
• Antibodies targeting protein antigens promoted neutrophil phagocytosis and reduced bacterial load in vivo.
• Bacterial capsule partially hindered IgG recognition and phagocytosis.

Conclusions:

• Antibodies targeting conserved protein antigens offer a viable strategy for A. baumannii infections.
• Multi-strain immunization enhances cross-protective immunity against diverse A. baumannii.
• Antibody-based therapies targeting protein antigens are a promising alternative for MDR A. baumannii infections.