Prior TLR5 induction in human T cells results in a transient potentiation of subsequent TCR-induced cytokine production

Enhancement of immune response against Bordetella spp. by disrupting immunomodulation

Well-adapted pathogens must evade clearance by the host immune system and the study of how they do this has revealed myriad complex strategies and mechanisms. Classical bordetellae are very closely related subspecies that are known to modulate adaptive immunity in a variety of ways, permitting them to either persist for life or repeatedly infect the same host. Exploring the hypothesis that exposure to immune cells would cause bordetellae to induce expression of important immunomodulatory mechanisms, we identified a putative regulator of an immunomodulatory pathway. The deletion of btrS in B. bronchiseptica did not affect colonization or initial growth in the respiratory tract of mice, its natural host, but did increase activation of the inflammasome pathway, and recruitment of inflammatory cells. The mutant lacking btrS recruited many more B and T cells into the lungs, where they rapidly formed highly organized and distinctive Bronchial Associated Lymphoid Tissue (BALT) not induced by any wild type Bordetella species, and a much more rapid and strong antibody response than observed with any of these species. Immunity induced by the mutant was measurably more robust in all respiratory organs, providing completely sterilizing immunity that protected against challenge infections for many months. Moreover, the mutant induced sterilizing immunity against infection with other classical bordetellae, including B. pertussis and B. parapertussis, something the current vaccines do not provide. These findings reveal profound immunomodulation by bordetellae and demonstrate that by disrupting it much more robust protective immunity can be generated, providing a pathway to greatly improve vaccines and preventive treatments against these important pathogens.

Immunomodulation as a Novel Strategy for Prevention and Treatment of Bordetella spp. Infections

Well-adapted pathogens have evolved to survive the many challenges of a robust immune response. Defending against all host antimicrobials simultaneously would be exceedingly difficult, if not impossible, so many co-evolved organisms utilize immunomodulatory tools to subvert, distract, and/or evade the host immune response. Bordetella spp. present many examples of the diversity of immunomodulators and an exceptional experimental system in which to study them. Recent advances in this experimental system suggest strategies for interventions that tweak immunity to disrupt bacterial immunomodulation, engaging more effective host immunity to better prevent and treat infections. Here we review advances in the understanding of respiratory pathogens, with special focus on Bordetella spp., and prospects for the use of immune-stimulatory interventions in the prevention and treatment of infection.

Cooperation between T cell receptor and Toll-like receptor 5 signaling for CD4+ T cell activation

CD4⁺ T cells recognize antigens through their T cell receptors (TCRs); however, additional signals involving costimulatory receptors, for example, CD28, are required for proper T cell activation. Alternative costimulatory receptors have been proposed, including members of the Toll-like receptor (TLR) family, such as TLR5 and TLR2. To understand the molecular mechanism underlying a potential costimulatory role for TLR5, we generated detailed molecular maps and logical models for the TCR and TLR5 signaling pathways and a merged model for cross-interactions between the two pathways. Furthermore, we validated the resulting model by analyzing how T cells responded to the activation of these pathways alone or in combination, in terms of the activation of the transcriptional regulators CREB, AP-1 (c-Jun), and NF-κB (p65). Our merged model accurately predicted the experimental results, showing that the activation of TLR5 can play a similar role to that of CD28 activation with respect to AP-1, CREB, and NF-κB activation, thereby providing insights regarding the cross-regulation of these pathways in CD4⁺ T cells.

The adjuvant G3 promotes a Th1 polarizing innate immune response in equine PBMC

The immunomodulatory effect of a new particulate adjuvant, G3, alone or in combination with agonists to TLR2/1 or TLR5 was evaluated in cultures of equine PBMC. Exposure to the G3 adjuvant up-regulated genes encoding IFN-γ, IL-1β, IL-6, IL-8, IL-12p40 and IL-23p19 in the majority of the horses tested, indicating that the G3 adjuvant induced a pro-inflammatory and Th1 dominated profile. In accordance, genes encoding IL-13, IL-4, IL-10 and TGF-β remained unaffected and genes encoding IFN-α, IL-17A and TNF-α were only occasionally and weakly induced. The two TLR agonists Pam3CSK4 (TLR2/1) and FliC (TLR5) induced cytokine profiles characterized by a clear induction of IL-10 as well as up-regulation of the genes encoding IL-1β, IL-6 and IL-8. The presence of G3 modified this response, in particular by reducing the FliC and Pam3CSK4 induced production of IL-10. Furthermore, G3 acted in synergy with Pam3CSK4 in enhancing the production of IFN-γ whereas G3 combined with FliC increased the gene expression of IL-8. Thus, the G3 adjuvant seems to have the capacity to promote a Th1 polarizing innate immune response in eqPBMC, both by favouring IFN-γ production and by reducing production of IL-10 induced by co-delivered molecules. These features make G3 an interesting candidate to further evaluate for its potential as an adjuvant in equine vaccines.

Pretreatment of activated human CD8 T cells with IL-12 leads to enhanced TCR-induced signaling and cytokine production

During the immune response to pathogens and autoantigens, CD8T cells are exposed to numerous inflammatory agents including the cytokine IL-12. Previous studies have focused on how IL-12 regulates T cell functions when present during or after the activation of the T cell receptor (TCR). However, recent studies suggest that prior exposure to IL-12 also alters the TCR responsiveness of murine T cells. Whether similar phenomena occur in human activated CD8T cells and the mechanisms mediating these effects remain unexplored. In this study, we observed that pretreatment of human activated CD8T cells with IL-12 results in increased cytokine mRNA and protein production following subsequent TCR challenge. The potentiation of TCR-mediated cytokine release was transient and required low doses of IL-12 for at least 24h. Mechanistically, prior exposure to IL-12 increased the TCR induced activation of select MAPKs and AKT without altering the activation of more proximal TCR signaling molecules, suggesting that the IL-12 mediated changes in TCR signaling are responsible for the increased production of cytokines. Our data suggest that prior treatment with IL-12 potentiates human CD8T cell responses at sites of infection and inflammation, expanding our understanding of the function of this clinically important cytokine.

Exposure of Human CD4 T Cells to IL-12 Results in Enhanced TCR-Induced Cytokine Production, Altered TCR Signaling, and Increased Oxidative Metabolism

Human CD4 T cells are constantly exposed to IL-12 during infections and certain autoimmune disorders. The current paradigm is that IL-12 promotes the differentiation of naïve CD4 T cells into Th1 cells, but recent studies suggest IL-12 may play a more complex role in T cell biology. We examined if exposure to IL-12 alters human CD4 T cell responses to subsequent TCR stimulation. We found that IL-12 pretreatment increased TCR-induced IFN-γ, TNF-α, IL-13, IL-4 and IL-10 production. This suggests that prior exposure to IL-12 potentiates the TCR-induced release of a range of cytokines. We observed that IL-12 mediated its effects through both transcriptional and post-transcriptional mechanisms. IL-12 pretreatment increased the phosphorylation of AKT, p38 and LCK following TCR stimulation without altering other TCR signaling molecules, potentially mediating the increase in transcription of cytokines. In addition, the IL-12-mediated enhancement of cytokines that are not transcriptionally regulated was partially driven by increased oxidative metabolism. Our data uncover a novel function of IL-12 in human CD4 T cells; specifically, it enhances the release of a range of cytokines potentially by altering TCR signaling pathways and by enhancing oxidative metabolism.

Re-examination of the rainbow trout (Oncorhynchus mykiss) immune response to flagellin: Yersinia ruckeri flagellin is a potent activator of acute phase proteins, anti-microbial peptides and pro-inflammatory cytokines in vitro

Flagellin is the principal component of bacterial flagellum and a major target of the host immune system. To provide new insights into the role of flagellin in fish immune responses to flagellated microorganisms, a recombinant flagellin from Yersinia ruckeri (rYRF) was produced and its bioactivity investigated in the trout macrophage cell line RTS-11 and head kidney cells. rYRF is a potent activator of pro-inflammatory cytokines, acute phase proteins, antimicrobial peptides and subunits of the IL-12 cytokine family. This and the synergy seen with IFN-γ to enhance further expression of specific IL-12 and TNF-α isoforms may suggest that flagellin could be a useful immune stimulant or adjuvant for use in aquaculture. Gene paralogues were often differentially modulated, highlighting the need to study all of the paralogues of immune genes in fish to gain a full understanding of the effects of PAMPs or other stimulants, and the potential immune responses elicited.

Biological Response Modifier in Cancer Immunotherapy

Biological response modifiers (BRMs) emerge as a lay of new compounds or approaches used in improving cancer immunotherapy. Evidences highlight that cytokines, Toll-like receptor (TLR) signaling, and noncoding RNAs are of crucial roles in modulating antitumor immune response and cancer-related chronic inflammation, and BRMs based on them have been explored. In particular, besides some cytokines like IFN-α and IL-2, several Toll-like receptor (TLR) agonists like BCG, MPL, and imiquimod are also licensed to be used in patients with several malignancies nowadays, and the first artificial small noncoding RNA (microRNA) mimic, MXR34, has entered phase I clinical study against liver cancer, implying their potential application in cancer therapy. According to amounts of original data, this chapter will review the regulatory roles of TLR signaling, some noncoding RNAs, and several key cytokines in cancer and cancer-related immune response, as well as the clinical cases in cancer therapy based on them.

In vivo Toll-like receptor 5 (TLR5) imaging with radiolabeled anti-TLR5 monoclonal antibody in rapamycin-treated mouse allogeneic skin transplantation model

BACKGROUND

In organ transplantation, increasing evidence, both in experimental and human studies, indicates that Toll-like receptor (TLR) activation is involved in the innate immune recognition of allograft. TLR5, the only protein recognition receptor of TLRs, is indicated potentially to be the immune regulation target. This study was designed to determine whether TLR5 could be a biomarker for in vivo allograft visualization, after immunosuppressant rapamycin treatment, using radiolabeled sodium iodide ((131) I)-anti-TLR5 monoclonal antibody (mAb).

METHODS

BALB/c mice were transplanted with C57BL/6 skin, with/without rapamycin treatment (the rapamycin-treated group and the phosphate buffered saline [PBS]-rejection group, respectively). In vivo dynamic whole-body phosphor-autoradiography and ex vivo biodistribution studies were conducted after (131) I-anti-TLR5 mAb injection.

RESULTS

Dynamic phosphor-autoradiography imaging showed clear graft localization from 12 h onward. At 72 h after injection, graft uptake quantified from images was higher for the rapamycin-treated group (26,448 ± 904 digital light units [DLU]/mm(2) ), compared with the PBS-treated allo-rejection group (9176 ± 576 DLU/mm(2) ). Treatment with anti-TLR5 mAb inhibited graft uptake. Organ biodistribution study reflected the same tendency, and (131) I-anti-TLR5 mAb uptake reached a maximum of 12.05 ± 1.86 %ID/g (percent injected dose per gram) at 1 h, and graft-to-native skin ratio reached 8.10 ± 0.10 %ID/g at 72 h after injection in rapamycin-treated grafts.

CONCLUSION

Radiolabeled anti-TLR5 mAb showed higher uptake in allo-treated grafts compared with allo-rejection grafts, which was proved by non-invasive dynamic phosphor-autoradiography imaging, and invasive ex vivo biodistribution. Radiolabeled anti-TLR5 mAb is a new tracer for non-invasive in vivo imaging of TLR5 in rapamycin-treated allograft.

TCR-mediated functions are enhanced in activated peripheral blood T cells isolated from leucocyte reduction systems

Buffy coats are the most common method for the acquisition of activated primary human T cells for research or clinical applications, but recently leukocyte reduction system (LRS) cones have emerged as a viable source for these cells. In this study, we determined if activated human T cells derived from buffy coats or LRS cones had different functionality. No changes in the expression of surface receptors were observed except for a significant increase in CD44 expression on T cells isolated from LRS cones. LRS cone-derived T cells trended towards higher receptor-mediated cytokine production and had significantly increased donor-to-donor variability in IFN-γ production. TCR-induced ERK1/ERK2 and AKT phosphorylation was also increased in T cells isolated from LRS cones. In conclusion, LRS cones are an excellent source of T cells for clinical and research applications, but these cells have subtle functional differences from T cells isolated using standard buffy coats.