Ion release is an important environmental behavior of silver nanoparticles (AgNPs), and characterization of Ag(+) release is critical for understanding the environmental fate, transport, and biological impacts of AgNPs. The ion release kinetics of AgNPs with three primary diameters (20, 40, and 80 nm) were studied by dispersing them in quarter-strength Hoagland medium at two initial concentrations (300 and 600 μg/L). Ag(+) release rates were found to depend on primary particle size and concentration, when other environmental factors (e.g., dissolved oxygen and protons) were kept constant. A kinetic model was developed to describe the Ag(+) release based on the hard sphere theory using the Arrhenius equation. The model fitted the experimental data well with correlation coefficients of 0.97-0.99, and the model usefully interpreted the dependence of ion release kinetics on the primary particle size and concentration. Moreover, the effects of environmental factors (e.g., dissolved oxygen, pH, temperature, and salinity) potentially can be interpreted as well. This model provides fundamental insight into the ion release kinetics of AgNPs in aqueous environments, allowing us to better understand and predict the nanotoxicity of AgNPs.

SUMMARY Herpes Zoster (shingles) causes significant morbidity in immune compromised hosts and older adults. While a vaccine is available for prevention of shingles, its efficacy declines with age. To help to understand the mechanisms driving vaccinal responses, we constructed a multiscale, multifactorial response network (MMRN) of immunity in healthy young and older adults immunized with the live attenuated shingles vaccine Zostavax®. Vaccination induces robust antigen-specific antibody, plasmablasts and CD4+ T cells, yet limited CD8+ T cell and antiviral responses. The MMRN reveals striking associations between orthogonal datasets such as transcriptomic and metabolomics signatures, cell populations and cytokine levels, and identifies immune and metabolic correlates of vaccine immunity. Networks associated with inositol phosphate, glycerophospholipids and sterol metabolism are tightly coupled with immunity. Critically, the sterol regulatory binding protein 1 and its targets are key integrators of antibody and T follicular cell responses. Our approach is broadly applicable to study human immunity, and can help to identify predictors of efficacy as well as mechanisms controlling immunity to vaccination.

Human herpesviruses are important causes of potentially severe chronic infections for which T cells are believed to be necessary for control. In order to examine the role of virus-specific CD8 T cells against Varicella Zoster Virus (VZV), we generated a comprehensive panel of potential epitopes predicted in silico and screened for T cell responses in healthy VZV seropositive donors. We identified a dominant HLA-A*0201-restricted epitope in the VZV ribonucleotide reductase subunit 2 and used a tetramer to analyze the phenotype and function of epitope-specific CD8 T cells. Interestingly, CD8 T cells responding to this VZV epitope also recognized homologous epitopes, not only in the other α-herpesviruses, HSV-1 and HSV-2, but also the γ-herpesvirus, EBV. Responses against these epitopes did not depend on previous infection with the originating virus, thus indicating the cross-reactive nature of this T cell population. Between individuals, the cells demonstrated marked phenotypic heterogeneity. This was associated with differences in functional capacity related to increased inhibitory receptor expression (including PD-1) along with decreased expression of co-stimulatory molecules that potentially reflected their stimulation history. Vaccination with the live attenuated Zostavax vaccine did not efficiently stimulate a proliferative response in this epitope-specific population. Thus, we identified a human CD8 T cell epitope that is conserved in four clinically important herpesviruses but that was poorly boosted by the current adult VZV vaccine. We discuss the concept of a “pan-herpesvirus” vaccine that this discovery raises and the hurdles that may need to be overcome in order to achieve this.

Vaccines against mucosally invasive, intracellular pathogens must induce a myriad of immune responses in order to provide optimal mucosal and systemic protection, including CD4+ T cells, CD8+ T cells and antibody-producing B cells. In general, CD4+ T cells are known to provide important helper functions for both CD8+ T cell and B cell responses. However, the relative importance of CD4+ T cells, CD8+ T cells and B cells for mucosal protection is less clearly defined. We have studied these questions in detail using the murine model of Trypanosoma cruzi infection. Despite our initial hypothesis that mucosal antibodies would be important, we show that B cells are critical for systemic, but not mucosal, T. cruzi protective immunity. B cell deficient mice developed normal levels of CD8+ effector T cell responses early after mucosal T. cruzi infection and T. cruzi trans-sialidase vaccination. However, after highly virulent systemic challenge, T. cruzi immune mice lacking T. cruzi-specific B cells failed to control parasitemia or prevent death. Mechanistically, T. cruzi-specific CD8+ T cells generated in the absence of B cells expressed increased PD-1 and Lag-3 and became functionally exhausted after high-level T. cruzi systemic challenge. T. cruzi immune serum prevented CD8+ T cell functional exhaustion and reduced mortality in mice lacking B cells. Overall, these results demonstrate that T. cruzi-specific B cells are necessary during systemic, but not mucosal, parasite challenge.

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BackgroundImmunization of mice with the Trypanosoma cruzi trans-sialidase (TS) gene using plasmid DNA, adenoviral vector, and CpG-adjuvanted protein delivery has proven highly immunogenic and provides protection against acute lethal challenge. However, long-term protection induced by TS DNA vaccines has not been reported. The goal of the present work was to test whether the co-administration of a plasmid encoding IL-15 (pIL-15) could improve the duration of protection achieved through genetic vaccination with plasmid encoding TS (pTS) alone.MethodologyWe immunized BALB/c mice with pTS in the presence or absence of pIL-15 and studied immune responses [with TS-specific IFN-γ ELISPOT, serum IgG ELISAs, intracellular cytokine staining (IFN-γ, TNF-α, and IL-2), tetramer staining, and CFSE dilution assays] and protection against lethal systemic challenge at 1 to 6 months post vaccination. Mice receiving pTS alone developed robust TS-specific IFN-γ responses and survived a lethal challenge given within the first 3 months following immunization. The addition of pIL-15 to pTS vaccination did not significantly alter T cell responses or protection during this early post-vaccination period. However, mice vaccinated with both pTS and pIL-15 challenged 6 months post-vaccination were significantly more protected against lethal T. cruzi challenges than mice vaccinated with pTS alone (P<0.05). Improved protection correlated with significantly higher numbers of TS-specific IFN-γ producing total and CD8+ T cells detected>6 months post immunization. Also, these TS-specific T cells were better able to expand after in vitro re-stimulation.ConclusionAddition of pIL-15 during genetic vaccination greatly improved long-term T cell survival, memory T cell expansion, and long-term protection against the important human parasite, T. cruzi.

The ability to regulate ongoing inflammation using regulatory T cells (Tregs) is under intense investigation. Strategies to induce and expand Ag-specific Tregs are being developed, and whether various types of Tregs are suppressive in the inflammatory conditions associated with ongoing disease needs to be determined. In this study, we report that TGF-β–induced Tregs (iTregs) and expanded Tregs specific for a major self-Ag in autoimmune gastritis suppress inflammation and associated pathology when administered late in the process of ongoing disease. Transferred iTregs localized to the stomach, maintained Foxp3 and suppressor functions, and engaged several distinct mechanisms to alleviate disease progression. In addition to suppressing the production of inflammatory cytokines in the stomach and preventing the destruction of parietal cells, we show that iTregs secrete numerous chemokines and regulate both iTreg and effector T cell trafficking into the stomach. These data support efforts to use iTregs in therapies to treat autoimmunity and inflammatory diseases and provide novel insight into the biological mechanisms of iTreg-mediated immune suppression.

Trypanosoma cruzi is an intracellular parasite and the causative agent of Chagas disease. Previous work has shown that the chemokine receptor CCR5 plays a role in systemic T. cruzi protection. We evaluated the importance of CCR5 and CCL5 for mucosal protection against natural oral and conjunctival T. cruzi challenges. T. cruzi-immune CCR5−/− and wild-type C57BL/6 mice were generated by repeated infectious challenges with T. cruzi. CCR5−/− and WT mice developed equivalent levels of cellular, humoral and protective mucosal responses. However, CCR5−/−-immune mice produced increased levels of CCL5 in protected gastric tissues, suggesting compensatory signaling through additional receptors. Neutralization of CCL5 in CCR5−/−-immune mice resulted in decreased mucosal inflammatory responses, reduced T. cruzi-specific antibody secreting cells, and significantly less mucosal T. cruzi protection, confirming an important role for CCL5 in optimal immune control of T. cruzi replication at the point of initial mucosal invasion. To further investigate the mechanism responsible for mucosal protection mediated by CCL5-CCR5 signaling, we evaluated the effects of CCL5 on B cells. CCL5 enhanced proliferation and IgM secretion in highly purified B cells triggered by suboptimal doses of LPS. In addition, neutralization of endogenous CCL5 inhibited B cell proliferation and IgM secretion during stimulation of highly purified B cells, indicating that B cell production of CCL5 has important autocrine effects. These findings demonstrate direct effects of CCL5 on B cells, with significant implications for the development of mucosal adjuvants, and further suggest that CCL5 may be important as a general B cell co-activator.