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Silver nanoparticle (Ag NP)/chitosan (Ch) composites with antiviral activity against H1N1 influenza A virus were prepared. The Ag NP/Ch composites were obtained as yellow or brown floc-like powders following reaction at room temperature in aqueous medium. Ag NPs (3.5, 6.5, and 12.9 nm average diameters) were embedded into the chitosan matrix without aggregation or size alternation. The antiviral activity of the Ag NP/Ch composites was evaluated by comparing the TCID50 ratio of viral suspensions treated with the composites to untreated suspensions. For all sizes of Ag NPs tested, antiviral activity against H1N1 influenza A virus increased as the concentration of Ag NPs increased; chitosan alone exhibited no antiviral activity. Size dependence of the Ag NPs on antiviral activity was also observed: antiviral activity was generally stronger with smaller Ag NPs in the composites. These results indicate that Ag NP/Ch composites interacting with viruses exhibit antiviral activity.

Infection of inbred mouse strains with Leishmania major is a well characterized model for analysis of T helper (Th)1 and Th2 cell development in vivo. In this study, to address the role of costimulatory molecules CD27, CD30, 4-1BB, and OX40, which belong to the tumor necrosis factor receptor superfamily, in the development of Th1 and Th2 cells in vivo, we administered monoclonal antibody (mAb) against their ligands, CD70, CD30 ligand (L), 4-1BBL, and OX40L, to mice infected with L. major. Whereas anti-CD70, anti-CD30L, and anti–4-1BBL mAb exhibited no effect in either susceptible BALB/c or resistant C57BL/6 mice, the administration of anti-OX40L mAb abrogated progressive disease in BALB/c mice. Flow cytometric analysis indicated that OX40 was expressed on CD4+ T cells and OX40L was expressed on CD11c+ dendritic cells in the popliteal lymph nodes of L. major–infected BALB/c mice. In vitro stimulation of these CD4+ T cells showed that anti-OX40L mAb treatment resulted in substantially reduced production of Th2 cytokines. Moreover, this change in cytokine levels was associated with reduced levels of anti–L. major immunoglobulin (Ig)G1 and serum IgE. These results indicate that anti-OX40L mAb abrogated progressive leishmaniasis in BALB/c mice by suppressing the development of Th2 responses, substantiating a critical role of OX40–OX40L interaction in Th2 development in vivo.

Extensive studies on protective immunity to rodent malaria provided the basis for the current experiments in which mice were immunized with recombinant (re) inf luenza and vaccinia viruses expressing selected sequences of the circumsporozoite (CS) protein of the human malaria parasite Plasmodium falciparum.

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We tested the immunogenicity of two

BackgroundChitin nanofibers sheets (CNFSs) with nanoscale fiber-like surface structures are nontoxic and biodegradable biomaterials with large surface-to-mass ratio. CNFSs are widely applied as biomedical materials such as a functional wound dressing. This study aimed to develop antimicrobial biomaterials made up of CNFS-immobilized silver nanoparticles (CNFS/Ag NPs).Materials and methodsCNFSs were immersed in suspensions of Ag NPs (5.17 ± 1.9 nm in diameter; mean ± SD) for 30 min at room temperature to produce CNFS/Ag NPs. CNFS/Ag NPs were characterized by transmission electron microscopy (TEM) and then tested for antimicrobial activities against Escherichia (E.) coli, Pseudomonas (P.) aeruginosa, and H1N1 influenza A virus, three pathogens that represent the most widespread infectious bacteria and viruses. Ultrathin sectioning of bacterial cells also was carried out to observe the bactericidal mechanism of Ag NPs.ResultsThe TEM images indicated that the Ag NPs are dispersed and tightly adsorbed onto CNFSs. Although CNFSs alone have only weak antimicrobial activity, CNFS/Ag NPs showed much stronger antimicrobial properties against E. coli, P. aeruginosa, and influenza A virus, with the amount of immobilized Ag NPs onto CNFSs.ConclusionsOur results suggest that CNFS/Ag NPs interacting with those microbes exhibit stronger antimicrobial activities, and that it is possible to apply CNFS/Ag NPs as anti-virus sheets as well as anti-infectious wound dressings.

Innate immunity as a first defense is indispensable for host survival against infectious agents. We examined the roles of natural killer (NK) T cells in defense against Trypanosoma cruzi infection. The T. cruzi parasitemia and survival of CD1d-deficient mice exhibited no differences compared to wild-type littermates. NK T-cell activation induced by administering ␣-galactosylceramide (␣-GalCer) to T. cruzi-infected mice significantly changed the parasitemia only in the late phase of infection and slightly improved survival when mice were infected intraperitoneally. The combined usage of ␣-GalCer and benznidazole, a commercially available drug for Chagas' disease, did not enhance the therapeutic efficacy of benznidazole. These results suggest that NK T cells do not play a pivotal role in resistance to T. cruzi infection. In addition, we found that the coadministration of ␣-GalCer with DNA vaccine impaired the induction of epitope-specific CD8 ؉ T cells and undermined the DNA vaccine-induced protective immunity against T. cruzi. Our results, in contrast to previous reports demonstrating the protective roles of NK T cells against other infectious agents, suggest that these cells might even exhibit adverse effects on vaccine-mediated protective immunity.