Synthetic Pseudaminic-Acid-Based Antibacterial Vaccine Confers Effective Protection against Acinetobacter baumannii Infection

[Image: see text] Acinetobacter baumannii exhibits resistance to most first-line antibiotics; thus, development of new antibacterial agents is urgently required. Pseudaminic acid exists as the surface glycan of A. baumannii. In this study, we chemically synthesized pseudaminic acid, conjugated it to carrier protein CRM197 using the OPA (ortho-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 A. baumannii. 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) A. baumannii, for which current treatment options are extremely limited.