Synthesis and in Vitro Characterization of Antigen-Conjugated Polysaccharide as a CpG DNA Carrier

Nanodelivery systems for enhancing the immunostimulatory effect of CpG oligodeoxynucleotides

Synthetic oligodeoxynucleotides containing immunostimulatory CpG motif mimic bacterial DNA and are potent activator of innate and adaptive immune responses. Therefore, CpG ODNs have significant potentials as immunotherapeutic agent for treatment of infectious diseases, allergy and cancer. Many clinical trials involving CpG ODNs either used alone or as adjuvant have been initiated. However, delivery of CpG ODNs to target sites still remains a great challenge due to their extreme susceptibility to nuclease degradation in serum and poor cellular uptake. Chemical modification of CpG ODNs backbone can protect them against degradation by nucleases, but have raised concern regarding several severe side effects. Development of efficient CpG ODNs delivery systems to address these issues and enhance their immunostimulatory effect are highly desirable. In recent years, the emergence of nanotechnology has provided unprecedented opportunities to encapsulate CpG ODN into various nanocarriers or synthesize CpG ODNs nanostructures. This review provides an overview of the delivery systems based on nanomaterials and nanostructures newly developed for enhancing the immunostimulatory effect of CpG ODNs, together with a brief discussion on perspectives for future studies in this field.

Plasmacytoid dendritic cells delineate immunogenicity of influenza vaccine subtypes

A variety of different vaccine types are available for H1N1 influenza A virus infections; however, their immunological mechanisms of action remain unclear. Here, we show that plasmacytoid dendritic cells (pDCs) and type I interferon (IFN)-mediated signaling delineate the immunogenicity of live attenuated virus, inactivated whole-virus (WV), and split-virus vaccines. Although Toll-like receptor 7 acted as the adjuvant receptor for the immunogenicity of both live virus and WV vaccines, the requirement for type I IFN production by pDCs for the immunogenicity of the vaccines was restricted to WV. A split vaccine commonly used in humans failed to immunize naïve mice, but a pDC-activating adjuvant could restore immunogenicity. In blood from human adults, however, split vaccine alone could recall memory T cell responses, underscoring the importance of this adjuvant pathway for primary, but not secondary, vaccination.

Complex formation between cationic beta-1,3-glucan and hetero-sequence oligodeoxynucleotide and its delivery into macrophage-like cells to induce cytokine secretion

A cationic polysaccharide bearing a beta-1,3-glucan main-chain structure (CUR-N(+)) forms a complex with a hetero-sequence oligonucleotide, that is, a CpG ODN, and facilitates the transportation of the resultant complex into a murine macrophage-like cell J774.A1, which induces an efficient secretion of a cytokine (IL-12) as compared with that induced by conventional carriers such as poly(ethyleneimine) (PEI) and poly(L-lysine) (PLL).

Ternary complex consisting of DNA, polycation, and a natural polysaccharide of schizophyllan to induce cellular uptake by antigen presenting cells

A natural polysaccharide called schizophyllan (SPG) can form a complex with polynucleotides, and the complex has been shown to deliver biofunctional short DNAs such as antisense DNAs and CpG-DNAs. Although it is a novel and efficient method, there is a drawback: attachment of homo-polynucleotide tails [for example, poly(dA) or poly(C)] to the end of DNA is necessary to stabilize the complex, because DNA heterosequences cannot bind to SPG. The aim of this paper is to present an alternative method in which SPG/DNA complexes can be made without using the tails. The basic strategy is as follows: since SPG can form hydrophobic domains in aqueous solutions, hydrophobic objects should be encapsulated by this domain. DNA alone is highly hydrophilic; however, once DNA/polycation complexes are made, they should be included by the SPG hydrophobic domain. The aim of this paper is to prove the formation of the polycation/DNA/SPG ternary complex. Gel electrophoresis showed that presence of SPG influenced the migration pattern of polycation+DNA mixtures. With increasing the SPG ratio, the zeta potential (zeta) of the polycation+DNA+SPG mixture decreased drastically to reach almost zeta = 0 and the particle size distributions were altered due to the ternary complex formation. Confocal laser scanning microscopy revealed that the polycation/DNA/SPG ternary complexes showed high uptake efficiency when the complexes were exposed to macrophage-like cells (J774.A1). IL-12 secretion was enhanced when CpG-DNA was added as the ternary complex. These features can be ascribed to the fact that J774.A1 has a SPG recognition site called Dectin-1 on the cellular surface and the ternary complex can be ingested by this pathway.