Heterologous Display of PmpD Passenger at the Surface of OMVs.

is the bacterial pathogen that causes most cases of sexually transmitted diseases annually. To combat the global spread of asymptomatic infection, development of effective (mucosal) vaccines that offer both systemic and local immune responses is considered a high priority. In this study, we explored the expression of full-length (FL) PmpD, as well as truncated PmpD passenger constructs fused to a "display" autotransporter (AT) hemoglobin protease (HbpD) and studied their inclusion into outer membrane vesicles (OMVs) of and Typhimurium. OMVs are considered safe vaccine vectors well-suited for mucosal delivery. By using AT HbpD-fusions of chimeric constructs we improved surface display and successfully generated OMVs decorated with a secreted and immunogenic PmpD passenger fragment (aa68-629) to 13% of the total protein content. Next, we investigated whether a similar chimeric surface display strategy could be applied to other AT antigens, i.e., secreted fragments of Prn (aa35-350) of and VacA (aa65-377) of . The data provided information on the complexity of heterologous expression of AT antigens at the OMV surface and suggested that optimal expression strategies should be developed on an antigen-to-antigen basis.