Intradermal delivery of Shigella IpaB and IpaD type III secretion proteins: Kinetics of cell recruitment and antigen uptake mucosal and systemic immunity and protection across serotypes

摘要

Shigella is one of the leading pathogens contributing to the vast pediatric diarrheal disease burden in low-income countries. No licensed vaccine is available and the existing candidates are only partially effective and serotype-specific. Shigella type III secretion system proteins IpaB and IpaD, which are conserved across Shigella spp., are candidates for a broadly protective, subunit-based vaccine. Herein, we investigated the immunogenicity and protective efficacy of IpaB and IpaD administered intradermally (i.d.) with a double-mutant of the E. coli heat-labile enterotoxin (dmLT) adjuvant using microneedles. Different dosage levels of IpaB and IpaD with or without dmLT were tested in mice. Vaccine delivery into the dermis, recruitment of neutrophils, macrophages, dendritic cells (DC) and Langerhans cells (LC), and colocalization of vaccine antigens within skin-activated antigen presenting cells (APC) was demonstrated through histology and immunofluorescence microscopy. Ag-loaded neutrophils, macrophages, DC and LC remained in the tissue at least one week. IpaB, IpaD and dmLT-specific serum IgG and IgG secreting cells were produced following i.d. immunization. The protective efficacy was 70% against S. flexneri and 50% against S. sonnei. Similar results were obtained when the vaccine was administered intranasally, with the i.d. route requiring 25-40 times lower doses. Distinctively, IgG was detected in mucosal secretions; sIgA as well as mucosal and systemic IgA antibody secreting cells (ASC) were seemingly absent. Vaccine-induced T cells produced IFN-γ, IL-2, TNF-α, IL-17, IL-4, IL-5 and IL-10. These results demonstrate the potential of i.d. vaccination with IpaB and IpaD to prevent Shigella infection and support further studies in humans.