Synthetic Pseudaminic-Acid-Based Antibacterial Vaccine Confers Effective Protection against <i>Acinetobacter baumannii</i> Infection

Abstract

<i>Acinetobacter baumannii</i> exhibits resistance to most first-line antibiotics; thus, development of new antibacterial agents is urgently required. Pseudaminic acid exists as the surface glycan of <i>A. baumannii</i>. In this study, we chemically synthesized pseudaminic acid, conjugated it to carrier protein CRM197 using the OPA (<i>ortho</i>-phthalaldehyde) chemistry, and obtained three Pse-CRM197 conjugates with different Pse loadings. These Pse-CRM197 conjugates were found to stimulate high immune responses in mice, which protected the vaccinated mice from infections caused by Pse-producing <i>A. baumannii</i>. Our data indicate that chemically synthesized Pse-CRM197 conjugates can be developed into vaccines against Pse-bearing pathogens, thus offering a feasible alternative for the control of clinical infections caused by multidrug-resistant (MDR) <i>A. baumannii</i>, for which current treatment options are extremely limited.