Langerhans cell-like dendritic cells stimulated with an adjuvant direct the development of Th1 and Th2 cells in vivo

Adjuvant activity of cordycepin, a natural derivative of adenosine from Cordyceps militaris, on an inactivated rabies vaccine in an animal model

Vaccination is the most feasible way of preventing rabies, an ancient zoonosis that remains a major public health concern globally. However, administration of inactivated rabies vaccination without adjuvants is always inefficient and necessitates four to five injections. In the current study, we explored the adjuvant characteristics of cordycepin, a major bioactive component of Cordyceps militaris, to boost immune responses against a commercially available rabies vaccine. We found that cordycepin could stimulate stronger phenotypic and functional maturation of dendritic cells (DCs). For animal experiments, mice were immunized 3 times with rabies vaccine in the presence or absence of cordycepin at 1-week interval. Analysis of T cell differentiation and serum antibody isotypes showed that humoral immunity was dominant with a Th2 biased immune response. These results were also supported by the raised ratio of follicular helper T cells (TFH) and germinal center B cells (GCB). Thus, titer of rabies virus neutralizing antibody (RVNAb) and rabies virus-specific memory B cells were both raised as a result. Furthermore, administration of cordycepin did not cause pathological phenomena or body weight loss. The findings indicate that cordycepin could be used as a promising adjuvant for rabies vaccines to get a higher range of protection without any side effects.

Toll-like Receptor-4 (TLR4) Agonist-Based Intranasal Nanovaccine Delivery System for Inducing Systemic and Mucosal Immunity

Eliciting a robust immune response at mucosal sites is critical in preventing the entry of mucosal pathogens such as influenza and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). This task is challenging to achieve without the inclusion of a strong and safe mucosal adjuvant. Previously, inulin acetate (InAc), a plant-based polymer, is shown to activate toll-like receptor-4 (TLR4) and elicit a robust systemic immune response as a vaccine adjuvant. This study investigates the potential of nanoparticles prepared with InAc (InAc-NPs) as an intranasal vaccine delivery system to generate both mucosal and systemic immune responses. InAc-NPs (∼250 nm in diameter) activated wild-type (WT) macrophages but failed to activate macrophages from TLR4 knockout mice or WT macrophages when pretreated with a TLR4 antagonist (lipopolysaccharide-RS (LPS-RS)), which indicates the selective nature of a InAc-based nanodelivery system as a TLR4 agonist. Intranasal immunization using antigen-loaded InAc-NPs generated ∼65-fold and 19-fold higher serum IgG1 and IgG2a titers against the antigen, respectively, as compared to PLGA-NPs as a delivery system. InAc-NPs have also stimulated the secretion of sIgA at various mucosal sites, including nasal-associated lymphoid tissues (NALTs), lungs, and intestine, and produced a strong memory response indicative of both humoral and cellular immune activation. Overall, by stimulating both systemic and mucosal immunity, InAc-NPs laid a basis for a potential intranasal delivery system for mucosal vaccination.

The role of Langerhans cells in pathologies of the skin

Langerhans cells (LCs) are epidermal immune cells of myeloid origin. Although these cells were primarily thought to play a defensive role in the skin, evidence now indicates a diverse range of LC-mediated effects including the relay of viral antigens in herpes simplex infection, recruitment of eosinophils in atopic dermatitis and promotion of a Th17 response in Candida infection. LCs may have a protective or suppressive function in pathologies of the skin, with differing functions being driven by the skin milieu. Understanding LC function will help guide the development of interventions that modulate these cells for therapeutic benefit.

Langerhans cell-like dendritic cells treated with ginsenoside Rh2 regulate the differentiation of Th1 and Th2 cells in vivo

Ginsenoside Rh2 is one of the rare ginsenosides extracted from Panax ginseng C. A. Mey. The anti-allergic activity of ginsenoside Rh2 has been documented in some literature. In this work, an anti-allergic mechanism of ginsenoside Rh2 was investigated by focusing on the differentiation of T cells through Langerhans cells (LCs). Langerhans cell-like dendritic cells (LDCs) were generated in vitro and were used as substitute for LCs.In vivo the mRNA expression for IFN-γ and CXCR3 of T cells was increased after being injected with ginsenoside Rh2-treated LDCs thereby increasing the concentration of IFN-γ in the culture supernatants of CD3+/CD28+ T lymphocytes. However,in vitro, the expression of mRNA for CD40 and CD80 on ginsenoside Rh2-treated LDCs was up-regulated significantly and the endocytic activity of LDCs was down-regulated slightly. These findings indicate that T cells differentiation could be regulated by ginsenoside Rh2 through LDCs in vivo by altering the antigen presenting capacity, maturation and phagocytosis of LDCs.

Anti-pruritic and anti-inflammatory effects of oxymatrine in a mouse model of allergic contact dermatitis

BACKGROUND

Allergic contact dermatitis (ACD) is a highly prevalent inflammatory disease of the skin. As a result of the complex etiology in ACD, therapeutic compounds targeting refractory pruritus in ACD lack efficacy and lead to numerous side effects.

OBJECTIVE

In this study, we investigated the anti-pruritic effects of oxymatrine (OMT) and explored its mechanism of action in a mouse model of ACD.

METHOD

72 male SPF C57BL/6 mice were randomly divided into control group, ACD model group, dexamethasone positive control group (0.08 mg kg-1) and 3 OMT groups (80, 40, 20 mg kg-1). OMT was administrated by intraperitoneal injection 1 h before video recording on day 10, 24 h after 2nd challenge with SADBE. Cheek skin fold thickness was measured before treatment and after recording. H&E staining was used for pathological observation. RT-qPCR, Immunohistochemistry and LEGENDplexTM assay were used to detect cytokines levels. The population of Treg cells in peripheral blood were detected via flow cytometry.

RESULTS

OMT treatment significantly decreases the skin inflammation and scratching bouts. It rescues defects in epidermal keratinization and inflammatory cell infiltration in ACD mice. Administration of OMT significantly reduced levels of IFN-γ, IL-13, IL-17A, TNF-α, IL-22 and mRNA expression of TNF-α and IL-1β. Furthermore, it increased the percentage of Treg cells in peripheral blood of ACD mice.

CONCLUSION

We have demonstrated that OMT exhibits anti-pruritic and anti-inflammatory effects in ACD mice by regulating inflammatory mediators. OMT might emerge as a potential drug for the treatment of pruritus and skin inflammation in the setting of ACD.

Betamethasone, but Not Tacrolimus, Suppresses the Development of Th2 Cells Mediated by Langerhans Cell-Like Dendritic Cells

It is well known that Langerhans cells (LCs) work as the primary orchestrators in the polarization of the immune milieu towards a T helper type 1 (Th1) or T helper type 2 (Th2) response. In this study, we investigated the effects of tacrolimus and betamethasone, each used as topical applications in atopic dermatitis (AD), on Th2 cell development mediated by LCs. LC-like dendritic cells (LDCs) were generated from mouse bone marrow cells and used as substitutes for LCs. Mice were primed with ovalbumin (OVA) peptide-pulsed LDCs, which had been treated with tacrolimus or betamethasone, via the hind footpad. After 5 d, the cytokine response in the popliteal lymph nodes was investigated by enzyme-linked immunosorbent assay. The expression of cell surface molecules on LDCs was investigated via reverse transcriptase polymerase chain reaction. Administration of OVA peptide-pulsed LDCs, which had been treated with betamethasone, inhibited Th2 cell development, as represented by the down-regulation of interleukin-4 production, and also inhibited Th1 cell development, represented by the down-regulation of interferon-γ production. However, tacrolimus-treated LDCs did not induce such inhibition of the development of Th1 and Th2 cells. The inhibition of Th1 and Th2 cell development was associated with the suppression of CD40 and T-cell immunoglobulin, and mucin domain-containing protein (TIM)-4 expression, respectively, in LDCs. These results suggest that the topical application of betamethasone to skin lesions of patients with AD acts on epidermal LCs, and may inhibit the development of Th2 cells, thus being of benefit for the control of AD.