Klebsiella pneumoniae bioconjugate vaccine functional durability in mice.

Klebsiella pneumoniae is a leading cause of hospital-acquired infections as well as the leading cause of neonatal sepsis worldwide. Further, increasing antibiotic resistance in this pathogen makes K. pneumoniae troublesome to treat. Despite its clinical importance, there is not yet an approved K. pneumoniae vaccine available. Here we tested antibody durability and long-term functionality of two previously reported bioconjugate vaccines targeting the K. pneumoniae capsular type K2 and O-antigen type O1v1. We demonstrate that both antibodies are durable in mice for up to six months with significant IgG titers. However, only the K2 antibodies exhibit functionality out to six months as evidenced by serum bactericidal activity and survival in a murine bacteremia challenge model. These results are another promising step towards demonstrating the clinical capacity of bioconjugate vaccines and their induction of durable antibody responses.