Synthetic Poly(L-Glutamic Acid)-conjugated CpG Exhibits Antitumor Efficacy With Increased Retention in Tumor and Draining Lymph Nodes After Intratumoral Injection in a Mouse Model of Melanoma.

There is an urgent need for new clinically applicable drug-delivery methods to enhance accumulation of immune-activating drugs in tumors. We synthesized a poly(L-glutamic acid)-CpG ODN2216 conjugate (PG-CpG) and injected it intratumorally into C57BL/6 mice bearing subcutaneous B16-ovalbumin melanoma. PG-CpG elicited the same potent antitumoral activity as CpG with respect to reducing tumor growth and triggering antigen-specific CD8 T-cell responses in this well-established solid tumor model. Moreover, PG-CpG was retained significantly longer in both tumor and draining lymph nodes than was free CpG after intratumoral injection. Specifically, 48 hours after injection, 26.5%±16.9% of the injected PG-CpG dose versus 4.72%±2.61% of free CpG remained at the tumor, and 1.53%±1.22% of the injected PG-CpG versus 0.37%±0.33% of free CpG was retained in the draining inguinal lymph nodes. These findings indicate that PG is an effective synthetic polymeric carrier for delivery of immunostimulatory agents to tumors and lymph nodes.

Sublingual injection of microparticles containing glycolipid ligands for NKT cells and subunit vaccines induces antibody responses in oral cavity.

Natural Killer T (NKT) cells are a unique type of innate immune cells which exert paradoxical roles in animal models through producing either Th1 or Th2 cytokines and activating dendritic cells. Alpha-galactosylceramide (αGalCer), a synthetic antigen for NKT cells, was found to be safe and immune stimulatory in cancer and hepatitis patients. We recently developed microparticle-formulated αGalCer, which is selectively presented by dendritic cells and macrophages, but not B cells, and thus can avoid the anergy of NKT cells. In this study, we have examined the immunogenicity of microparticles containing αGalCer and protein vaccine components through sublingual injection in mice. The results showed that sublingual injection of microparticles containing αGalCer and ovalbumin triggered IgG responses in serum (titer >1:100,000), which persisted for more than 3months. Microparticles containing ovalbumin alone also induced comparable level of IgG responses. However, immunoglobulin subclass analysis showed that sublingually injected microparticles containing αGalCer and ovalbumin induced 20 fold higher Th1 biased antibody (IgG2c) than microparticles containing OVA alone (1:20,000 as compared to 1:1000 titer). Sublingual injection of microparticles containing αGalCer and ovalbumin induced secretion of both IgG (titer >1:1000) and IgA (titer=1:80) in saliva secretion, while microparticles containing ovalbumin alone only induced secretion of IgG in saliva. Our results suggest that sublingual injection of microparticles and their subsequent trafficking to draining lymph nodes may induce adaptive immune responses in mucosal compartments. Ongoing studies are focused on the mechanism of antigen presentation and lymphocyte biology in the oral cavity, as well as the toxicity and efficacy of these candidate microparticles for future applications.

MUC1 glycopeptide epitopes predicted by computational glycomics.

Bioinformatic tools and databases for glycobiology and glycomics research are playing increasingly important roles in functional studies. However, to verify hypotheses generated by computational glycomics with empirical functional assays is only an emerging field. In this study, we predicted glycan epitopes expressed by a cancer-derived mucin, MUC1, by computational glycomics. MUC1 is expressed by tumor cells with a deficiency in glycosylation. Although numerous diagnostic reagents and cancer vaccines have been designed based on abnormally glycosylated MUC1 sequences, the glycan and peptide sequences responsible for immune responses in vivo are poorly understood. The immunogenicity of synthetic MUC1 glycopeptides bearing Tn or sialyl-Tn antigens have been studied in mouse models, while authentic glyco-epitopes expressed by tumor cells remain unclear. To examine the immunogenicity of authentic cancer derived MUC1 glyco-epitopes, we expressed membrane bound forms of MUC1 tandem repeats in Jurkat, a mutant cancer cell line deficient of mucin-type core-1 ß1-3 galactosyltransferase activity, and immunized mice with cancer cells expressing authentic MUC1 glyco-epitopes. Antibody responses to individual glyco-epitopes were determined by chemically synthesized candidate MUC1 glycopeptides predicted through computational glycomics. Monoclonal antibodies can be generated toward chemically synthesized glycopeptide sequences. With RPAPGS(Tn)TAPPAHG as an example, a monoclonal antibody 16A, showed 25-fold higher binding to glycosylated peptide (EC50=9.278±1.059 ng/ml) compared to its non-glycosylated form (EC(50)=247.3±16.29 ng/ml) as measured by ELISA experiments with plate-bound peptides. A library of monoclonal antibodies toward authentic MUC1 glycopeptide epitopes may be a valuable tool for studying glycan and peptide sequences in cancer, as well as reagents for diagnosis and therapy.

Vaccine-induced immunity against Helicobacter pylori in the absence of IL-17A.

BACKGROUND: Helicobacter pylori (H. pylori) is a gram negative bacterium that can cause diseases such as peptic ulcers and gastric cancer. IL-17A, a proinflammatory cytokine that can induce the production of CXC chemokines for neutrophil recruitment, has recently been shown to be elevated in both H. pylori-infected patients and mice. Furthermore, studies in mouse models of vaccination have reported levels significantly increased over infected, unimmunized mice and blocking of IL-17A during the challenge phase in immunized mice reduces protective immunity. Because many aspects of immunity had redundant or compensatory mechanisms, we investigated whether mice could be protectively immunized when IL-17A function is absent during the entire immune response using IL-17A and IL-17A receptor knockout (KO) mice immunized against H. pylori. MATERIALS AND METHODS: Gastric biopsies were harvested from naïve, unimmunized/challenged, and immunized/challenged wild type (WT) and KO mice and analyzed for inflammation, neutrophil, and bacterial levels. Groups of IL-17A KO mice were also treated with anti-IFNγ or control antibodies. RESULTS: Surprisingly, all groups of immunized KO mice reduced their bacterial loads comparably to WT mice. The gastric neutrophil counts did not vary significantly between IL-17A KO and WT mice, whereas IL-17RA KO mice had on average a four-fold decrease compared to WT. Additionally, we performed an immunization study with CXCR2 KO mice and observed significant gastric neutrophils and reduction in bacterial load. CONCLUSION: These data suggest that there are compensatory mechanisms for protection against H. pylori and for neutrophil recruitment in the absence of an IL-17A-CXC chemokine pathway.

Vaccination of mice against H pylori induces a strong Th-17 response and immunity that is neutrophil dependent.

BACKGROUND & AIMS: Vaccine efficacy against gastric Helicobacter pylori infection has been shown in mice, but little is known about the mechanisms of bacterial clearance. Our aim was to investigate a possible T-cell/neutrophil pathway of vaccine-induced protection. METHODS: Nonimmune and immunized mice were compared for their response to H pylori challenge. T-cell responses were assessed by recall assays. Interleukin (IL)-17-induced chemokine production was evaluated by cytokine enzyme-linked immunosorbent assay. In a kinetic study, biopsy specimens were collected at multiple time points postchallenge and assessed for bacterial load and inflammation. Relative levels of T cells, IL-17, interferon gamma, MIP-2, KC, and LIX were determined by quantitative polymerase chain reaction. The role of neutrophils was evaluated by antibody-mediated depletion of neutrophils following challenge. RESULTS: Immunization induced strong interferon gamma- and IL-17-producing T-cell responses, and IL-17 was capable of inducing significant amounts of KC and MIP-2 from dendritic cells, macrophages, fibroblasts, and gastric epithelial cells. Challenge of immunized mice induced significantly greater gastritis than that of infected mice, preceding significantly lower bacterial loads by day 7. In immune mice, T-cell recruitment to the gastric mucosa correlated with a continuous rise in IL-17 and interferon gamma levels, followed by KC, MIP-2, and LIX production and the recruitment of significant numbers of neutrophils by day 5. Antibody-mediated depletion of neutrophils abrogated vaccine efficacy. CONCLUSIONS: Vaccination of mice against H pylori results in a significant Th-17 cell recall response associated with increases in chemokines that attract neutrophils to the stomach, which are important for eradication of H pylori.