Antigen Processing and Presentation by Epidermal Langerhans Cells: Induction of Immunity or Unresponsiveness

Identification of osteoporosis markers through bioinformatic functional analysis of serum proteome

Osteoporosis is a severe chronic skeletal disorder that increases the risks of disability and mortality; however, the mechanism of this disease and the protein markers for prognosis of osteoporosis have not been well characterized. This study aims to characterize the imbalanced serum proteostasis, the disturbed pathways, and potential serum markers in osteoporosis by using a set of bioinformatic analyses. In the present study, the large-scale proteomics datasets (PXD006464) were adopted from the Proteome Xchange database and processed with MaxQuant. The differentially expressed serum proteins were identified. The biological process and molecular function were analyzed. The protein-protein interactions and subnetwork modules were constructed. The signaling pathways were enriched. We identified 209 upregulated and 230 downregulated serum proteins. The bioinformatic analyses revealed a highly overlapped functional protein classification and the gene ontology terms between the upregulated and downregulated protein groups. Protein-protein interactions and pathway analyses showed a high enrichment in protein synthesis, inflammation, and immune response in the upregulated proteins, and cell adhesion and cytoskeleton regulation in the downregulated proteins. Our findings greatly expand the current view of the roles of serum proteins in osteoporosis and shed light on the understanding of its underlying mechanisms and the discovery of serum proteins as potential markers for the prognosis of osteoporosis.

Heat shock proteins HSP27 and HSP70 are present in the skin and are important mediators of allergic contact hypersensitivity

Proteomic analysis of murine skin has shown that a variety of heat shock proteins (HSPs) are constitutively expressed in the skin. Using murine allergic contact hypersensitivity as a model, we investigated the role of two heat shock proteins, HSP27 and HSP70, in the induction of cutaneous cell-mediated immune responses. Immunohistochemical examination of skin specimens showed that HSP27 was present in the epidermis and HSP70 was present in both the epidermis and dermis. Inhibition of HSP27 and HSP70 produced a reduction in the 1-fluoro-2,4-dinitrobenzene contact hypersensitivity response and resulted in the induction of Ag-specific unresponsiveness. Treatment of dendritic cell cultures with recombinant HSP27 caused in the up-regulation of IL-1beta, TNF-alpha, IL-6, IL-12p70, and IL-12p40 but not IL-23p19, which was inhibited when Abs to HSP27 were added. The 1-fluoro-2,4-dinitrobenzene-conjugated dendritic cells that had been treated with HSP27 had an increased capacity to initiate contact hypersensitivity responses compared with control dendritic cells. This augmented capacity required TLR4 signaling because neither cytokine production by dendritic cells nor the increased induction of contact hypersensitivity responses occurred in TLR4-deficient C3H/HeJ mice. Our findings indicate that a cascade of events occurs following initial interaction of hapten with the skin that includes increased activity of HSPs, their interaction with TLR4, and, in turn, increased production of cytokines that are known to enhance Ag presentation by T cells. The results suggest that HSPs form a link between adaptive and innate immunity during the early stages of contact hypersensitivity.

Tetanus toxoid-loaded transfersomes for topical immunization

Topical immunization is a novel immunization strategy by which antigens and adjuvants are applied topically to intact skin to induce potent antibody and cell-mediated responses. Among various approaches for topical immunization, the vesicular approach is gaining wide attention. Proteineous antigen alone or in combination with conventional bioactive carriers could not penetrate through the intact skin. Hence, specially designed, deformable lipid vesicles called transfersomes were used in this study for the non-invasive delivery of tetanus toxoid (TT). Transfersomes were prepared and characterized for shape, size, entrapment efficiency and deformability index. Fluorescence microscopy was used to investigate the mechanism of vesicle penetration through the skin. The immune stimulating activity of these vesicles was studied by measuring the serum anti-tetanus toxoid IgG titre following topical immunization. The immune response was compared with the same dose of alum adsorbed tetanus toxoid (AATT) given intramuscularly, topically administered plain tetanus toxoid solution, and a physical mixture of tetanus toxoid and transfersomes again given topically. The results indicated that the optimal transfersomal formulation had a soya phosphatidylcholine and sodium deoxycholate ratio of 85:15%, w/w. This formulation showed maximum entrapment efficiency (87.34 +/- 3.81%) and deformability index (121.5 +/- 4.21). An in-vivo study revealed that topically administered tetanus toxoid-loaded transfersomes, after secondary immunization, elicited an immune response (anti-TT-IgG) comparable with that produced by intramuscular AATT. Fluorescence microscopy revealed the penetration of transfersomes through the skin to deliver the antigen to the immunocompetent Langerhans cells.

Influenza vaccine powder formulation development: spray-freeze-drying and stability evaluation

The purpose of this study was to develop a spray-freeze-drying (SFD) process for preparing an influenza vaccine dry powder formulation suitable for epidermal powder immunization. After preformulation of two types of flu vaccines, their dry-powder formulations were prepared by SFD. Powder properties and physical stability were determined using particle size analysis, tap density measurement, scanning electron microscopy, optical microscopy, and moisture content analysis. Chemical and biochemical stability of vaccine antigens was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, single radial immunodiffusion assay, and in vivo immunogenicity in a mouse model. We demonstrated that SFD could produce high-density particles-a critical parameter for effective skin penetration. From the stability perspective, the stress posed by SFD was mild because the antigen in the dry powder retained its stability, potency, and immunogenicity. Among several formulations screened, we noted that formulation composition has a significant role in the powder's long-term physical and biochemical stability. One formulation, in particular, containing sub-unit vaccine (45 microg of antigen in 1 mg of powder) with a tertiary mixture of trehalose, mannitol, and dextran, exhibited excellent overall stability, including acceptable biochemical stability after being exposed to a highly humid environment. After all, we have not only demonstrated the suitability of SFD to prepare powders for epidermal powder immunization but also developed a systematic formulation development strategy that allowed the optimization of an influenza vaccine dry powder formulation. More important, this study led to the selection of a formulation system that had been successfully tested in a human clinical study.

Epidermal powder immunization against influenza

Epidermal powder immunization (EPI) can efficiently deliver powdered protein vaccines to the epidermis. A phase I clinical trial was conducted to evaluate powdered trivalent influenza vaccine delivered using the PowderJect ND5.2 delivery system. Subjects received either Fluvirin IM injection (15 microg of each influenza strain), a single EPI vaccination (15 microg of each influenza strain) or two adjacent EPI (total of 30 microg of each influenza strain). Systemic reactogenicity was similar between control and EPI vaccines. Site reactions following EPI were primarily mild and self-limiting. Seroconversions, titer increases and geometric mean titers to all strains were equivalent or higher in EPI-immunized groups than in controls. Powdered influenza vaccine delivered by EPI is safe and elicits humoral immune responses in humans.

Epidermal powder immunization: cellular and molecular mechanisms for enhancing vaccine immunogenicity

Epidermal powder immunization (EPI) of mice with an influenza vaccine elicited consistently a higher hemagglutination inhibition (HI) antibody titers than intramuscular (IM) injection using the same dose of vaccine. The epidermal Langerhans cells (LCs) at the site of EPI were found to play an important role in the immune responses. Indeed, depletion of LCs from the immunization site prior to EPI caused a significant reduction in the antibody response. Transfer of LCs isolated from the EPI sites to naive mice induced a robust antigen-specific antibody response. Cytokines produced by target site cells appear to be important for the augmented immune responses induced by EPI. LTR72, a genetically detoxified heat-labile toxin from Escherichia coli with a strong adjuvant effect in EPI, was found to bind the keratinocytes of the epidermis, but not the LCs, and caused the production of elevated TNF-alpha and IL-12 cytokines in emigrating epidermal cells. These results have important implications for the development of a more efficacious human influenza vaccine.

Viral warts in organ transplant recipients: new aspects in therapy

The long-term success of organ transplantation depends on the prevention of allograft rejection and improvement in quality of life for the patients. This has been achieved through better immunosuppressive regimens with lower dosages and a new generation of immunosuppressive drugs. However, these immunosuppressive agents not only impair the patient's reactivity to the graft, but also to infectious organisms, thereby making them more susceptible to opportunistic pathogens. Because of this, organ transplant recipients are predisposed to epithelial malignancies and infections. The majority of transplant recipients will develop warts induced by human papillomavirus (HPV). Some of these viral warts may present with atypical histological features and may progress into squamous cell carcinomas. The risk for cutaneous cancers after transplantation is much higher than in the immunocompetent population. Current therapies for HPV-associated skin tumours mainly depend on the destruction of affected skin areas. These treatment modalities are of limited efficacy and are usually painful for the patients. A promising novel therapeutic agent is imiquimod, an immune response modifier. Clinical efficacy of imiquimod has been observed for different skin lesions, including viral warts in both immunocompetent and immunosuppressed patients.

Targeting epidermal Langerhans cells by epidermal powder immunization

Immune reactions to foreign or self-antigens lead to protective immunity and, sometimes, immune disorders such as allergies and autoimmune diseases. Antigen presenting cells (APC) including epidermal Langerhans cells (LCs) play an important role in the course and outcome of the immune reactions. Epidermal powder immunization (EPI) is a technology that offers a tool to manipulate the LCs and the potential to harness the immune reactions towards prevention and treatment of infectious diseases and immune disorders.

Photoimmunology of lupus erythematosus and dermatomyositis: a speculative review

David Norris has proposed a four step model for the pathogenesis of LESSD (1): (1) exposure to UV light induces the release of proinflammaotry epidermal and dermal mediators such as IL-1 and TNF-alpha; (2) these mediators induce changes in epidermal and dermal cells including the induction of adhesion molecules and promotion of the translocation of normally intracellular autoantigen such as Ro/SS-A to the surface of epidermal cells; (3) autoantibody from the circulation binds to autoantigens such as Ro/SS-A that have been translocated to the surface of epidermal keratinocytes and (4) keratinocyte cytotoxicity ensues as the results of lymphoid cells that have been recruited from the circulation recognizing and responding to the Fc domains of autoantibody molecules bound to autoantigen expressed on the surface of keratinocytes (i.e. antibody-dependent cell-mediated cytotoxicity). Although this remains among the most attractive of hypotheses for the explanation of Ro/SS-A antibody-associated forms of LESSD such as SCLE and neonatal LE, it does not address the pathogenesis of other forms of LESSD such as DLE, which are not associated with high-level Ro/SS-A antibody production or other known autoantibody specificities (low-level Ro/SS-A autoantibody production has been noted recently in DLE patients (155)). In addition, this hypothesis implies that the fundamental abnormality in SCLE and neonatal LE is the production of high levels of Ro/SS-A autoantibody; however, equally high levels of Ro/SS-A antibodies having similar molecular specificities are frequently encountered in other conditions such as Sjögren's syndrome in which LESSD is seen only infrequently. Also, a nude mouse model of anti-Ro/SS-A autoantibody in deposition grafted human skin has been developed; however, no inflammation or epidermal injury occurs in these animals (83). Most work has indicated that the action spectrum for Ro/SS-A autoantigen modulation in human epidermal keratinocytes is limited to the UVB spectrum; however, recent studies have suggested that UVA is involved in the elicitation of certain forms of photosensitive cutaneous LE such as SCLE. The hypothesis that CD4+ T cells that are specific for autoantigens in the skin whose expression is altered by UVR exposure might play a role in the expression of LESSD needs to be explored further. Because LE is thought to be a polygenic autoimmune disease, it is possible that polymorphism of genes that govern the skin's response to UVR might be involved in the pathogenesis of photosensitive LESSD. Candidate genes would include: The Ro/SS-A autoantigenic polypeptides and h-YRNA; cytokines, cytokine receptors and adhesion molecules induced on epidermal keratinocytes and dermal endothelial cells by UVR; molecules involved in DNA repair; components of pathways leading to the generation and quenching of oxygen free radicals and components of the UVR-induced apoptosis cascade. Unfortunately, so little is known about DM photosensitivity that it is difficult to even speculate about pathogenetic mechanisms that might be involved other than to extrapolate from the observations and currents of thought relating to photosensitive cutaneous LE. A truly limiting aspect of our understanding in this area has been the absence of working models of the patterns of inflammation seen in LESSD and cutaneous DM. Until such models become available, considering the limitations of human studies, alone it is highly likely that reviews of this subject will continue to be based on much in speculation as observation.

Histologic features of foreign body reactions in patients infected with human immunodeficiency virus type 1. The Military Medical Consortium for Applied Retroviral Research

BACKGROUND

Within a large population of patients seropositive for human immunodeficiency virus type 1 (HIV-1), seven had biopsy specimens that showed foreign body reactions with histologic features different from those seen in non-HIV-1-positive patients.

OBJECTIVE

These cases were reviewed to determine whether there was a specific pattern of response to foreign bodies in HIV-1 infection and whether this pattern was related to the stage of disease.

METHODS

Biopsy specimens were reviewed to identify ruptured epidermal cysts. These were studied in routine hematoxylin-and-eosin-stained sections and with immunohistochemical stains to characterize the inflammatory infiltrate.

RESULTS

The lesions in HIV-1-infected patients contained abundant macrophages with evidence of decreased function and a lack of giant cells.

CONCLUSION

These histologic features suggest an early functional deficit before there is a significant decrease in the number of T4 lymphocytes.

Role of Langerhans cells and other dendritic cells in viral diseases

Langerhans cells are part of a vast system of potent antigen-presenting cells known under the name of dendritic cells. During the last decade, much has been learned on dendritic cell involvement in the immune response to infectious diseases. This review briefly summarizes our current understanding of the role played by Langerhans cells and other dendritic cells in the pathogenesis of DNA and RNA virus infections. These data may form the basis for the development of innovative approaches in the diagnosis, prevention, and treatment of viral diseases.

Ultraviolet B-irradiated antigen-presenting cells display altered accessory signaling for T-cell activation: relevance to immune responses initiated in skin

A principal mechanism by which ultraviolet (UV) B radiation exerts its selective and antigen-specific suppressive influence on immune responses is through its effects on the capacity of antigen-presenting cells (APC) in skin, primarily Langerhans cells (LC), to differentially activate T-cell subsets. Recent evidence has indicated that LC, following UVB radiation, lose the capacity to stimulate proliferation of CD4+ Th1, but not of Th2, clones. Additional work has shown this acquired unresponsiveness of Th1 cells to represent a long-lasting form of clonal anergy that results from a block in their ability to produce IL-2. Although not completely delineated, these defects appear to be the result of preserved delivery of the primary signal transduced by interaction of the MHC/antigen complex on APC with the T-cell receptor complex, in the absence of a viable second signal normally delivered by interaction of a co-stimulatory factor from APC with its appropriate ligand on the T cells. These findings support the notion that the outcome of certain immune responses depends greatly upon conditions that are brought to bear on APC and T cells during the time of antigen presentation.