Atsuo Ito

Stimulation of In Vivo Antitumor Immunity with Hollow Mesoporous Silica Nanospheres

The use of appropriate adjuvants that support the generation of robust and long-lasting antitumor immune responses is crucial for tumor immunotherapy owing to the immunosuppressive environment of the growing tumor. However, the most commonly used adjuvant, aluminum hydroxide, is ineffective for generating such immune responses and therefore not suitable for cancer immunotherapy. It is now shown that plain hollow mesoporous silica nanospheres markedly improve the antitumor immunity, the Th1 and Th2 immunity, and the CD4(+) and CD8(+) effector memory Tu2005cell population in bone marrow inu2005vivo and may thus be used as immunoadjuvants to treat cancer in humans.

Particle-size-dependent toxicity and immunogenic activity of mesoporous silica-based adjuvants for tumor immunotherapy

Conventionally used adjuvants alone are insufficient for triggering cell-mediated immunity, although they have been successfully developed to elicit protective antibody responses in some vaccines. Here, with the aim of eliciting cell-mediated immunity, pathogen-associated molecular patterns (PAMPs) were immobilized with apatite within the pores and on the surface of mesoporous silica (MS) with particle sizes from 30 to 200nm to prepare novel MS-Ap-PAMP adjuvants, which showed cell-mediated anti-tumor immunity that was markedly improved compared to commercial alum adjuvant in vitro and in vivo. The toxicity and antitumor immunity of the MS-Ap-PAMP adjuvants were evaluated in vitro and in vivo. MS with a particle size of 200nm showed minimum in vitro cytotoxicity to NIH3T3 cells, particularly at concentrations no higher than 100μgml(-1). In particular, apatite precipitation within the pores and on the surface of MS decreased the in vitro cytotoxicity of MS particles. The MS-Ap-PAMP adjuvants showed the maximum in vitro immunogenic activity among original culture medium, PAMP and alum-PAMP. Moreover, injection of the MS-Ap-PAMP adjuvant in combination with liquid-nitrogen-treated tumor tissue (derived from Lewis lung carcinoma cells) into C57BL/6 mice markedly inhibited in vivo tumor recurrence and the development of rechallenged tumor compared to those with commercial alum adjuvant. The MS-Ap-PAMP adjuvant contributed to the elicitation of a potent systemic antitumor immunity without obvious toxicity in vivo.

Mesoporous Silica-Calcium Phosphate-Tuberculin Purified Protein Derivative Composites as an Effective Adjuvant for Cancer Immunotherapy

The synthesis of mesoporous silica/calcium phosphate composite loaded with the immunopotentiator tuberculin purified protein derivative (PPD-MS/CaP) as an effective adjuvant for cancer immunotherapy is reported here. The PPD-MS/CaP adjuvant is prepared by immersing mesoporous silica in a supersaturated calcium phosphate solution supplemented with the immunopotentiator PPD for 24 h. PPD is coprecipitated with calcium phosphate inside and on the surface of mesoporous silica. By loading the immunopotentiator PPD in the PPD-MS/CaP adjuvant, an enhanced activation of antigen-presenting cells, such as GM-CSF secretion by THP-1 differentiated macrophages, is obtained probably due to sustained PPD release and an efficient cellular uptake of PPD. The PPD-MS/CaP adjuvant mixed with liquid-N2 -treated tumor tissue effectively triggers anti-tumor immune response and markedly inhibits in vivo tumor growth. The PPD-MS/CaP adjuvant is a promising alternative for cancer immune therapy.

Hollow Structure Improved Anti-Cancer Immunity of Mesoporous Silica Nanospheres In Vivo.

Hollow and non-hollow mesoporous silica nanospheres are synthesized and used for cancer vaccine adjuvants. The hollow structure of mesoporous silica nanospheres significantly promote cellular uptake of a model cancer antigen by macrophage-like cells in vitro, improve anti-cancer immunity, CD4(+) and CD8(+) T cell populations in splenocytes of mice in vivo.

Pore size-dependent immunogenic activity of mesoporous silica-based adjuvants in cancer immunotherapy

Commonly used aluminum hydroxide (Alum) adjuvant provokes a strong type 2 helper T cell (Th2) response for mediating antibody production but is rather ineffective for disease prevention that requires type 1 helper T cell (Th1) response for mediating cellular immunity in human vaccination. Here, for the purpose of inducing Th1 antitumor immunity, a mesoporous silica (MS)-based adjuvant is prepared. Three kinds of MS particles with nearly identical particle size and surface area but different pore sizes of 4, 7 and 10 nm were prepared. No serious in vitro cytotoxicity was observed for the MS particles at 5, 20, 50, and 100 μg/mL. Pathogen-associated molecular patterns (PAMPs) were immobilized with apatite (Ap) on MS to prepare the MS-based and PAMP-loaded adjuvants (MS-Ap-PAMP adjuvants). Macrophage-like cells cultured in the presence of MS-Ap-PAMP adjuvant with a MS pore size of 10 nm showed the maximum in vitro immunogenic activity. Injection of the MS-Ap-PAMP adjuvant with a MS pore size of 10 nm in combination with liquid nitrogen-treated tumor tissue (derived from Lewis lung carcinoma cells) to C57BL/6 mice markedly inhibited the development of rechallenged tumor in vivo, while no such antitumor immunity was induced in injection of Alum mixed with PAMP in combination with liquid nitrogen-treated tumor tissue. The MS-Ap-PAMP adjuvant contributed to the elicitation of a potent systemic Th1 antitumor immunity in vivo.

Comprehensive Mechanism Analysis of Mesoporous-Silica-Nanoparticle-Induced Cancer Immunotherapy

A plain mesoporous silica nanoparticle without any immunomodulatory molecules significantly enhances anticancer immunity in vivo. Comprehensive mechanism of mesoporous-silica-nanoparticle-induced cancer immunotherapy is analyzed in this paper. The mesoporous silica nanoparticle promotes both Th1 and Th2 immune responses, as it accelerates lymphocytes proliferation, stimulates IFN-γ, IL-2, IL-4, and IL-10 cytokine secretion by lymphocytes ex vivo, and increases IgG, IgG1, IgG2a, IgM, and IgA antibody titers in mice serum compared with those of alum and adjuvant-free groups. Moreover, the mesoporous silica nanoparticle enhances effector memory CD4(+) and CD8(+) T cell populations in three most important immune organs (bone marrow, lymph node, and spleen) of mice compared with those of alum and adjuvant-free groups three months after adjuvant injection. The present study paves the way for the application of mesoporous silica nanoparticle as immunoadjuvant for cancer immunotherapy.

Simple synthesis route of mesoporous AlOOH nanofibers to enhance immune responses

A facile method to synthesize mesoporous AlOOH nanofibers using inorganic aluminum salts as the aluminum source and urea as the pore-forming and precipitating agent is reported. The uptake of AlOOH by macrophage-like cells is about 2 times of commercial Alum. The AlOOH adjuvant markedly stimulates the immune responses compared to the commercial Alum adjuvant.

Rod-shaped and substituted hydroxyapatite nanoparticles stimulating type 1 and 2 cytokine secretion.

A Th1 immune response is required for modern vaccines as the most commonly used alum adjuvant has weak capacity for inducing Th1 immune response. Herein, rod-shaped hydroxyapatite (HA), magnesium-substituted HA (MgHA) and zinc-substituted HA (ZnHA) nanoparticles with irregular nanopores were synthesized and used as immunoadjuvants. Magnesium and zinc substitution in HA showed no influence on morphology, particle size, zeta potential and surface area of the nanoparticles. The rod-shaped MgHA and ZnHA nanoparticles promoted the cellular uptake of a molecular immunopotentiator, stimulated both type 1 and 2 cytokine secretion in vitro that relate to Th1 and Th2 immunity of bone marrow dentritic cells, respectively. The MgHA and ZnHA nanoparticles may be useful as immunoadjuvants for human.

Signal Molecule-Calcium Phosphate Composites: Novel Approaches to Controlling Cellular and/or Biological Reactions and Functions

Signal molecule-calcium phosphate (CaP) composites are formed in supersaturated CaP solutions containing signal molecules. The molecules coprecipitate with CaPs in the form of coating layers or particulates and are immobilized in the CaP matrix forming a nanocomposite of the molecule and CaP. Various substrates are used for the coprecipitation. The molecules thus immobilized include laminin, fibronectin, bone morphogenic protein-2 (BMP-2), fibroblast growth factor-2 (FGF-2), antibiotics, DNA, α-amylase, and immunogenic molecules. Solution chemistry, CaP phase, morphology, and molecule content affect biological activity of signal molecule-CaP composites. Depending on the choice of molecule, signal molecule-CaP composites have various applications including tissue regeneration, gene delivery, and cancer immunotherapy. For tissue regeneration, immobilization of signal molecules with CaP on a substrate can achieve a sustained regulation activity of the signal molecules and is applied to promote bone regeneration and soft tissue regeneration. DNA-CaP composite layers are surface-mediated gene delivery system that has gene delivery efficiency as high as that of a commercial lipid-based system. The efficiency has been improved further by the incorporation of cell adhesion molecules and lipids in the layers. Gene delivery systems using CaP composite layers are effective in enhancing cell differentiation and bone tissue regeneration in vitro and in vivo. Substituted tricalcium phosphate and mesoporous silica loaded with pathogen-associated molecular patterns using coprecipitation with CaP are used as an adjuvant for cancer immunotherapy. The composite adjuvants mixed with liquid-nitrogen-treated tumor tissue effectively triggered antitumor immune response and markedly inhibited the growth of rechallenged tumor cells (tumor recurrence model) in vivo.

Novel Apatite-Pathogen-Associated Molecular Patterns Adjuvants for Cancer Immune Therapy

An apatite-pathogen-associated molecular patterns (PAMPs) adjuvant was prepared by coprecipitation of apatite and PAMPs using a supersaturated calcium phosphate solution supplemented with PAMPs. In this study, we used a hydrothermal extract of human tubercle bacillus (HTB) as PAMPs. The effects of coprecipitation conditions on immunogenic activity were studied. The adjuvants prepared using extract of at 10 and 20 μg/mL showed higher in vitro immunogenic activity than that at 2 μg/mL. The adjuvants prepared under stir at speed of 300 rpm showed better in vitro immunogenic activity than those under still. The adjuvants prepared using 10 μg/mL of extract of HTB under stir at speed of 300 rpm may be promising for cancer immune therapy.