# Generation and Evaluation of a Multi-Epitope Vaccine Against Acinetobacter baumannii, a Nosocomial Bacterial Pathogen

## TL;DR

This paper presents a new multi-epitope vaccine against Acinetobacter baumannii, a drug-resistant hospital infection, showing promising protection in mice.

## Contribution

The novel contribution is the design and evaluation of multi-epitope vaccines using immunoinformatics and experimental validation in mice.

## Key findings

- AMEV1 and AMEV2 conferred 60% and 80% protection against Acinetobacter baumannii in mice.
- AMEV5 achieved 90% survival in mice after lethal infection challenge.
- Vaccination activated antigen-specific T and B cells, indicating strong immune response.

## Abstract

Background/Objectives: Multidrug-resistant (MDR) Acinetobacter baumannii (Ab) has emerged as a significant bacterial pathogen responsible for nosocomial infections. The most common clinical manifestations of Ab infection include ventilator-associated pneumonia and catheter-related bloodstream/urinary infections. Given the extensive MDR phenotype of Ab, preventive vaccination strategies are crucial for protecting susceptible populations. Methods: We utilized immunoinformatics to identify candidate peptides containing both putative B- and T-cell epitopes from proteins associated with Ab pathogenesis. Subsequently, we designed novel Acinetobacter Multi-Epitope Vaccines (AMEVs), each comprising an Ab thioredoxin A (TrxA) leader protein, five to seven of the identified peptide antigens, and a C-terminal His(6x)-tag to facilitate protein purification. Results: Subcutaneous vaccination of C57BL/6 mice with AMEV1 or AMEV2, formulated with TiterMax adjuvant, conferred 60% and 80% protection, respectively, against intraperitoneal Ab challenge. AMEV vaccination induced a robust antibody response to each corresponding whole protein and most of its component peptides. We then constructed an improved vaccine, AMEV5, which included the Ab TrxA protein and seven confirmed B-cell epitope peptides. Subcutaneous immunization of BALB/c mice (n = 10 per group) with rAMEV5 emulsified in Adda03 adjuvant activated antigen-specific IL-5-secreting T cells and antibody-producing B cells. Evaluation of vaccine efficacy demonstrated that AMEV2- and AMEV5-immunized mice were protected from a lethal intraperitoneal Ab challenge, with survival rates of 70% and 90%, respectively. Conclusions: These study results provide insights into the application of reverse vaccinology to combat the rise of MDR Acinetobacter infection.