Abstract
M-cells (microfold cells) are thought to be a primary conduit of intestinal antigen trafficking. Using an established neutralizing anti-RANKL (Receptor Activator of NF-κB Ligand) antibody treatment to transiently deplete M-cells in vivo, we sought to determine whether intestinal M-cells were required for the effective induction of protective immunity following oral vaccination with ΔiglB (a defined live attenuated Francisella novicida mutant). M-cell depleted, ΔiglB-vaccinated mice exhibited increased (but not significant) morbidity and mortality following a subsequent homotypic or heterotypic pulmonary F. tularensis challenge. No significant differences in splenic IFN-γ, IL-2, or IL-17 or serum antibody (IgG1, IgG2a, IgA) production were observed compared to non-depleted, ΔiglB-vaccinated animals suggesting complementary mechanisms for ΔiglB entry. Thus, we examined other possible routes of gastrointestinal antigen sampling following oral vaccination and found that ΔiglB co-localized to villus goblet cells and enterocytes. These results provide insight into the role of M-cells and complementary pathways in intestinal antigen trafficking that may be involved in the generation of optimal immunity following oral vaccination.
Highlights
Oral vaccination serves as an efficacious mechanism to induce potent systemic and mucosal immunity
Additional flow cytometry imaging analysis (Fig 4D) confirmed the internalization of mCherry-ΔiglB by goblet cells (GCs) 90 minutes post-vaccination. These results demonstrate that GCs may serve as a novel host cell for F. tularensis and a potential mechanism for soluble and particulate antigens to enter from the intestinal lumen
Antigen trafficking within the intestine has been primarily attributed to M-cells [34,35,36], and previous studies have shown that in the absence of M-cells, infections with Yersinia enterocolitica [37], prions [38], and retrovirus [39] were abrogated, and antigen-specific T-cell responses to oral infection with Salmonella typhimurium was impaired [23, 40]
Summary
Oral vaccination serves as an efficacious mechanism to induce potent systemic and mucosal immunity. This route targets the largest immune organ in the body, the gut and its associated lymphoid tissue, which contains 80% of the body's activated B cells [1] and up to 70% of the body’s immunocytes [2]. Role of M-Cells in Oral Tularemia Vaccine had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript
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