Sonochemical decomposition effects of nickelocene aiming for low-temperature and dispersant-free synthesis of nickel fine particle.

Sonochemical decomposition effects of nickelocene, which sublimates easily were investigated to synthesize dispersant-free nickel fine particles at low temperature. In a hydrazine monohydrate and 2-propanol mixed solvent, the reduction of nickelocene was promoted by ultrasound irradiation, and nickel fine particles were synthesized while precluding the sublimation of nickelocene. Unlike the common hydrazine reduction of nickel salts, which requires multiple-step reactions, nickelocene was reduced directly without forming intermediates. The effect of the water-bath temperature (20-60 °C) was investigated, where larger fine particles were synthesized using a higher water-bath temperature (60 °C). When irradiated at 20 °C, the reduction rate of nickelocene was low, leading to the formation of nickel fine particles and organic nanoparticles via the reduction and decomposition of nickelocene. The ultrasound frequency was also investigated, where fine nickel particles were synthesized using low-frequency ultrasound irradiation. The formation of high-temperature hotspots led to the diffusion and growth of nickel on the surface of the nickel fine particles; therefore, raspberry-like nickel fine particles were synthesized. In this study, the difficult-to-handle nature of nickelocene, owing to its sublimation properties, was easily overcome by ultrasound irradiation. Instantaneous and localized reactions at hotspots contributed to inhibiting particle growth. Furthermore, Ni fine particles were synthesized via a direct reduction pathway, which differs from previous reactions. This method represents a new, dispersant-free, low-temperature process for synthesizing Ni fine particles.

Persistence of neutralizing antibody and its protective efficacy induced by a live attenuated tetravalent dengue vaccine, KD-382, in cynomolgus monkeys.

An effective dengue vaccine should induce a long-lasting immune response against all four serotypes simultaneously with a minimum number of immunizations. Our live attenuated tetravalent dengue vaccine candidate, KD-382, was developed using a classical host range mutation strategy (no addition of artificial genetic modification). In our previous study, cynomolgus monkeys immunized with a single dose of KD-382 seroconverted to all four serotypes. However, it is important to determine if neutralizing antibodies (NAbs) induced by KD-382 can work as a long-lasting immune response to prevent dengue. In this study, a single dose of KD-382 induced a strong NAb response against all four serotypes in cynomolgus monkeys. We also confirmed that NAb titers against all four serotypes persist for at least five years, indicating its high potential as a dengue vaccine candidate. Next, we evaluated the effect of pre-existing dengue immunity on NAb responses induced by KD-382. We administered KD-382 to cynomolgus monkeys pre-administered one of the monovalent parental wild-type strains 60 days before vaccination. Regardless of the pre-immunized serotype, all the monkeys showed sufficient tetravalent NAb responses, which lasted for over two years. All the KD-382 vaccinated monkeys were then challenged with different parental wild-type viruses than that used for pre-administration; viral RNA in the serum was less than the lower limit of quantification, indicating complete protection against secondary heterologous dengue infection without any harmful disease enhancement. Consequently, KD-382 successfully induced a long-lasting and protective tetravalent NAb response in monkeys, suggesting that KD-382 is a promising vaccine candidate usable for both dengue seronegative and seropositive individuals.

Invariant chain p41 mediates production of soluble MHC class II molecules.

Major histocompatibility complex class II (MHC II) molecules are mainly expressed on antigen presentation cells and play an important role in immune response. It has been reported that MHC II molecules are also detected in serum as a soluble form (sMHC II molecules), and they are considered to be involved in the maintenance of self-tolerance. However, the mechanism by which sMHC II molecules are produced remains unclear. Invariant chain (Ii), also called CD74, plays an important role in antigen presentation of MHC II molecules. In the present study, we analyzed the role of Ii on the production of sMHC II molecules. We found that the amount of sMHC II molecules in serum was decreased in Ii-deficient mice compared to wild-type mice. sMHC II molecules were secreted from cells transfected with MHC II molecules and Ii but not from cells transfected with MHC II molecules alone. Moreover, isoform p41 of Ii-transfected cells induced more sMHC II molecules compared to isoform p31-transfected cells. The molecular weight of sMHC II molecules from MHC II and Ii p41-transfected cells was approximately 60 kDa, indicating that sMHC II molecules are a single heterodimer of α and ß chains that is not associated with micro-vesicles. From the analysis of Ii-deletion mutants, we found that the luminal domain of Ii p41 is crucial for the production of sMHC II molecules. These results suggested that Ii has an important role in production of sMHC II molecules.

EpsinR, a target for pyrenocine B, role in endogenous MHC-II-restricted antigen presentation.

While the presentation mechanism of antigenic peptides derived from exogenous proteins by MHC class II molecules is well understood, relatively little is known about the presentation mechanism of endogenous MHC class II-restricted antigens. We therefore screened a chemical library of 200 compounds derived from natural products to identify inhibitors of the presentation of endogenous MHC class II-restricted antigens. We found that pyrenocine B, a compound derived from the fungus Pyrenochaeta terrestris, inhibits presentation of endogenous MHC class II-restricted minor histocompatibility antigen IL-4 inducible gene 1 (IL4I1) by primary dendritic cells (DCs). Phage display screening and surface plasmon resonance (SPR) analysis were used to investigate the mechanism of suppressive action by pyrenocine B. EpsinR, a target molecule for pyrenocine B, mediates endosomal trafficking through binding of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). Lentiviral-mediated short hairpin (sh) RNA downregulation of EpsinR expression in DCs resulted in a decrease in the responsiveness of CD4+ T cells. Our data thus suggest that EpsinR plays a role in antigen presentation, which provides insight into the mechanism of presentation pathway of endogenous MHC class II-restricted antigen.