New generation of oral mucosal vaccines targeting dendritic cells

Abstract

As most infectious organisms gain entry at mucosal surfaces, there is a great deal of interest in developing vaccines that elicit effective mucosal immune responses against pathogen challenge. Targeted vaccination is one of the most effective methods available to prevent and control infectious diseases. Mucosal vaccines can offer lower costs, better accessibility, needle free delivery, and a higher capacity for mass immunizations during pandemics. Both local mucosal immunity and robust systemic responses can be achieved through mucosal vaccination. Recent progress in understanding the molecular and cellular components of the mucosal immune system have allowed for the development of a novel mucosal vaccine platform utilizing specific dendritic cell-targeting peptides and orally administered lactobacilli to elicit efficient antigen specific immune responses against infections, including Bacillus anthracis in experimental models of disease.

Figure 1. The intestinal immune system

Pathogens or bacterial gene products can be captured by DC subsets situated within the epithelial layer or residing beneath the epithelial dome. These cells can either activate T and B cells directly or migrate into the mesenteric lymph nodes to present processed immunogens to T and B cells. Activated T and B cells can migrate into the periphery, poised to induce specific immunity against pathogen challenge.

Figure 2

a. Identifying 12-mer peptides that specifically bind to DCs. The Ph.D.™-12 Phage Display Peptide Library with a complexity of 10¹¹ independent 12-mer peptide sequences fused to pIII was first incubated with non-dendritic cells including, B cells, T cells, monocytes, and macrophages. The non-bound phages were then panned with human DCs. These phage peptide selections were repeated at least four times. The enriched DC-specific phage peptide library was then amplified, and the DNA isolated to identify peptide sequences. b. The ability to bind targeting peptides by DCs across different species. Identified 12-mer peptides were biotinylated to be screened for their binding to DCs derived from peripheral blood samples from various species, including avian, canine, equine, and feline DCs, and analyzed by a Fortessa cytometer. Experiments were repeated at least three times.

Figure 2

a. Identifying 12-mer peptides that specifically bind to DCs. The Ph.D.™-12 Phage Display Peptide Library with a complexity of 10¹¹ independent 12-mer peptide sequences fused to pIII was first incubated with non-dendritic cells including, B cells, T cells, monocytes, and macrophages. The non-bound phages were then panned with human DCs. These phage peptide selections were repeated at least four times. The enriched DC-specific phage peptide library was then amplified, and the DNA isolated to identify peptide sequences. b. The ability to bind targeting peptides by DCs across different species. Identified 12-mer peptides were biotinylated to be screened for their binding to DCs derived from peripheral blood samples from various species, including avian, canine, equine, and feline DCs, and analyzed by a Fortessa cytometer. Experiments were repeated at least three times.

Figure 3. Induction of intestinal and systemic immune responses against B. anthracis infection by L. gasseri expressing the targeted PA-DCpep vaccine against B. anthracis

The vaccine subunit PA of B. anthracis can be targeted by a 12-mer DC binding peptide (DCpep) expressed by L. gasseri. Mice orally treated with L. gasseri expressing the fusion protein targeted vaccine demonstrated the induction of local mucosal, as well as systemic immunity against B. anthracis infection.