Sub-compartmentalization of the gastrointestinal (GI) immune system determined with microbeads that differ in release properties

Oral vaccines: directed safe passage to the front line of defense

Oral vaccines are safe and easy to administer and convenient for all ages. They have been successfully developed to protect from many infectious diseases acquired through oral transmission. We recently found in animal models that formulation of oral vaccines in a nanoparticle-releasing microparticle delivery system is a viable approach for selectively inducing large intestinal protective immunity against infections at rectal and genital mucosae. These large-intestine targeted oral vaccines are a potential substitute for the intracolorectal immunization, which has been found to be effective against rectogenital infections but is not feasible for mass vaccination. Moreover, the newly developed delivery system can be modified to selectively target either the small or large intestine for immunization and accordingly revealed a regionalized immune system in the gut. Future applications and research endeavors suggested by the findings are discussed.

Large intestine-targeted, nanoparticle-releasing oral vaccine to control genitorectal viral infection

Both rectal and vaginal mucosal surfaces serve as transmission routes for pathogenic microorganisms. Vaccination through large intestinal mucosa, previously proven protective for both of these mucosal sites in animal studies, can be achieved successfully by direct intracolorectal (i.c.r.) administration, but this route is clinically impractical. Oral vaccine delivery seems preferable but runs the risk of the vaccine's destruction in the upper gastrointestinal tract. Therefore, we designed a large intestine-targeted oral delivery with pH-dependent microparticles containing vaccine nanoparticles, which induced colorectal immunity in mice comparably to colorectal vaccination and protected against rectal and vaginal viral challenge. Conversely, vaccine targeted to the small intestine induced only small intestinal immunity and provided no rectal or vaginal protection, demonstrating functional compartmentalization within the gut mucosal immune system. Therefore, using this oral vaccine delivery system to target the large intestine, but not the small intestine, may represent a feasible new strategy for immune protection of rectal and vaginal mucosa.

Gastrointestinal infection with Mexican TcI Trypanosoma cruzi strains: different degrees of colonization and diverse immune responses

Mexican Ninoa and Queretaro (Qro) TcI strains of Trypanosoma cruzi have shown different degrees of virulence, and the two strains produce heterogeneous immune responses in the hearts of infected mice. This work shows that the same strains can invade the intestine by an intraperitoneal route and establish an infection, mainly in the colon. The three segments of the small intestine (duodenum, jejunum and ileum) were infected to a lesser degree than the colon. Despite the fact that parasites were predominantly found in the colon, an obvious inflammatory reaction was observed in the submucosal layer along the entire intestinal tract, with the virulent Qro strain causing significantly more areas of higher immune infiltration. A clear recruitment of CD4⁺ and CD8⁺ T lymphocytes to the mesenteric ganglia was observed during infection with the virulent strain. Macrophages were also differentially distributed in the gastrointestinal tract. These later cells infiltrated fewer amastigote nests in the mice infected with the Qro strain than in the mice infected with the Ninoa strain. When IFN-γ, TNF-α, and IL-4 levels were measured, an increase in these cytokines was observed compared with the uninfected mice. The role of these inflammatory reactions in the pathogenesis of Chagas enteropathy is also discussed in this paper.

Bioadhesive capacity and immunoadjuvant properties of thiamine-coated nanoparticles

The general aim of this work was to develop polymeric nanoparticle carriers with bioadhesive properties, and to evaluate its adjuvant potential for oral vaccination. Thiamine was used as specific ligand-nanoparticle conjugate (TNP) to target specific sites within the gastrointestinal tract, enterocytes and Peyer's patches. The affinity of nanoparticles to the gut mucosa was studied in orally inoculated rats. In contrast to conventional non-coated nanoparticles (NP), higher levels of TNP were found in the ileum tissue, showing a strong capacity to be captured by Peyer's patches. TNP were characterized by an AUCadh which was found to be three times higher than for control NP. To investigate the adjuvant capacity of TNP, ovalbumin (OVA) was used as standard antigen. Oral immunization of BALB/c mice with OVA-TNP induced stronger serum titers of specific IgG2a and IgG1 and mucosal IgA compared to OVA-NP. This mucosal immune response (IgA) was about 4-titers higher than that elicited by OVA-NP. These results suggest the use of thiamine-coated nanoparticles as particle vectors for oral vaccine and immunotherapy delivery strategies.

Mucosally restricted antigens as novel immunological targets for antitumor therapy

Colorectal cancer is the third most common malignancy and the second most common cause of cancer-related mortality worldwide. While surgery remains the mainstay of therapy, approximately 50% of persons who undergo resection develop parenchymal metastatic disease. Unfortunately, current therapeutic regimens offer little improvement in survival. Using immunotherapy to fill this therapeutic gap has enjoyed limited success, reflecting a paucity of tumor-associated antigens. In that context, there is a significant unrealized opportunity to exploit structural and functional immune system compartmentalization to generate a therapeutic immune response against metastatic colorectal tumors employing biomarkers whose expression is normally confined to intestinal epithelial cells and their derivative malignancies. This novel class of biomarkers, here termed cancer mucosa antigens, may fill the unmet therapeutic need for colorectal cancer-associated immune targets. As a concrete example, guanylyl cyclase C is an intestinal mucosa-specific biomarker ideally suited to test this hypothesis and serve as the first cancer mucosa antigen for colorectal cancer immunotherapy. Here, we discuss colorectal cancer immunity, immune compartmentalization and preliminary results targeting guanylyl cyclase C in mouse models of colorectal cancer, as well as the potential paradigm shift to employing cancer mucosa antigens in immunotherapy of colorectal cancer.