Induction of CD4+ Th1 lymphocytes that recognize known and novel class II MHC restricted epitopes from the melanoma antigen gp100 by stimulation with recombinant protein

MicroRNAs as T Lymphocyte Regulators in Multiple Sclerosis

MicroRNA (miRNA) is a class of endogenous non-coding small RNA with regulatory activities, which generally regulates the expression of target genes at the post-transcriptional level. Multiple Sclerosis (MS) is thought to be an autoimmune-mediated chronic inflammatory demyelinating disease of the central nervous system (CNS) that typically affect young adults. T lymphocytes play an important role in the pathogenesis of MS, and studies have suggested that miRNAs are involved in regulating the proliferation, differentiation, and functional maintenance of T lymphocytes in MS. Dysregulated expression of miRNAs may lead to the differentiation balance and dysfunction of T lymphocytes, and they are thus involved in the occurrence and development of MS. In addition, some specific miRNAs, such as miR-155 and miR-326, may have potential diagnostic values for MS or be useful for discriminating subtypes of MS. Moreover, miRNAs may be a promising therapeutic strategy for MS by regulating T lymphocyte function. By summarizing the recent literature, we reviewed the involvement of T lymphocytes in the pathogenesis of MS, the role of miRNAs in the pathogenesis and disease progression of MS by regulating T lymphocytes, the possibility of differentially expressed miRNAs to function as biomarkers for MS diagnosis, and the therapeutic potential of miRNAs in MS by regulating T lymphocytes.

Antitumoral potency of methanolic extract from Nitraria retusa leaves via its immunomodulatory effect

Background

The purpose of this study was to assess the antitumoral effect of the methanol extract (MeOH) from Nitraria retusa leaves and to investigate its immunomodulatory activity that mediated the prevention of tumor progression in tumor-bearing mice.

Methods

Balb/c mice weighing 18–20 g were subcutaneously implanted with B16-F10 cells then injected intra-peritoneally, 7 days later with (200 mg/kg bw) of MeOH extract, for 21 days. After euthanization on day 21, the tumors were weighed. Lymphocyte proliferation, cytotoxic T lymphocyte (CTL) and NK activity were evaluated using the MTT assay. Macrophage phagocytosis was studied by measuring their lysosomal activity and nitric oxide production.

Results

The methanol extract inhibited significantly the growth of the implanted tumor, and increased remarkably splenocyte proliferation as well as NK and CTL activities, in tumor-bearing mice. It also promoted lysosomal activity of treated animal macrophages.

Conclusion

Our findings suggest that antitumoral effect of MeOH extract is related with to immunomodulatory activity.

An exhaustion-like phenotype constrains the activity of CD4+ T cells specific for a self and melanoma antigen

While the immune system has the capacity to recognize and destroy melanoma, tolerance mechanisms often hinder the development of effective anti-tumor immune responses. Since many melanoma antigens are self proteins expressed in normal melanocytes, self antigen exposure before tumor development can negatively impact the function of T cells specific for these self/tumor antigens. However, the contribution of self tolerance to anti-melanoma T cell dysfunction remains largely unexplored. We have previously described a TCR transgenic (Tg) mouse model in which T cells specific for the self/melanoma antigen, tyrosinase-related protein 1 (TRP1), develop in the presence of endogenous TRP1 expression (Ag+) and diminished antigen presentation due to the absence of gamma-interferon-inducible lysosomal thiol reductase (GILT-/-). We show that TRP1-specific T cells from these Ag+GILT-/-Tg mice do not protect from melanoma tumor growth, fail to induce autoimmune vitiligo, and undergo diminished proliferation compared to T cells from Ag-GILT+/+Tg mice. Despite an increased frequency of TRP1-specific Treg cells in Ag+GILT-/-Tg mice compared to Ag-GILT+/+Tg animals, Treg cell depletion only partially rescues the proliferative capacity of T cells from TRP1-expressing mice, suggesting the involvement of additional suppressive mechanisms. An increased percentage of melanoma-specific T cells from Ag+GILT-/-Tg animals express PD-1, an inhibitory receptor associated with the maintenance of T cell exhaustion. Antibody blockade of PD-1 partially improves the ability of TRP1-specific T cells from Ag+GILT-/-Tg mice to produce IL-2. These findings demonstrate that melanoma-specific T cells exposed to a self/melanoma antigen in healthy tissue develop an exhaustion-like phenotype characterized by PD-1-mediated immunosuppression prior to encounter with tumor.

GILT modulates CD4+ T-cell tolerance to the melanocyte differentiation antigen tyrosinase-related protein 1

Gamma-IFN-inducible lysosomal thiol reductase (GILT) facilitates major histocompatibility complex class II-restricted processing through endocytic reduction of protein disulfide bonds and is necessary for efficient class II-restricted processing of melanocyte differentiation antigen, tyrosinase-related protein 1 (TRP1). Using class II-restricted, TRP1-specific T-cell receptor transgenic mice, we identify a role, to our knowledge, previously unreported, for GILT in the maintenance of tolerance to TRP1. TRP1-specific thymocytes are centrally deleted in the presence of GILT and TRP1. In contrast, CD4 single-positive thymocytes and peripheral T cells develop in the absence of GILT or TRP1, demonstrating that GILT is required for negative selection of TRP1-specific thymocytes. Although TRP1-specific T cells escape thymic deletion in the absence of GILT, they are tolerant to TRP1 and do not induce vilitigo. TRP1-specific T cells that develop in the absence of GILT have diminished IL-2 and IFN-γ production. Furthermore, GILT-deficient mice have a 4-fold increase in the percentage of TRP1-specific regulatory T (Treg) cells compared with TRP1-deficient mice, and depletion of Treg cells partially restores the ability of GILT-deficient TRP1-specific CD4(+) T cells to induce vitiligo. Thus, GILT has a critical role in regulating CD4(+) T-cell tolerance to an endogenous skin-restricted antigen relevant to controlling autoimmunity and generating effective immunotherapy for melanoma.

Stress and allergic diseases

Allergy describes a constellation of clinical diseases that affect up to 30% of the world's population. It is characterized by production of allergen-specific IgE, which binds to mast cells and initiates a cascade of molecular and cellular events that affect the respiratory tract (rhinitis and asthma), skin (dermatitis, urticaria), and multiple systems (anaphylaxis) in response to a variety of allergens including pollens, mold spores, animal danders, insect stings, foods, and drugs. The underlying pathophysiology involves immunoregulatory dysfunctions similar to those noted in highly stressed populations. The relationships in terms of potential for intervention are discussed.

GILT accelerates autoimmunity to the melanoma antigen tyrosinase-related protein 1

Melanocyte differentiation Ags, including tyrosinase-related protein (TRP) 1, are relevant to both autoimmune skin depigmentation (vitiligo) and tumor immunity, because they are expressed by both benign melanocytes and many malignant melanomas. Melanoma patients generate CD4(+) T cells that specifically recognize these proteins. TRP1 contains internal disulfide bonds and is presented by MHC class II molecules. Gamma-IFN-inducible lysosomal thiol reductase (GILT) facilitates the generation of class II-binding peptides by the endocytic reduction of protein disulfide bonds. We show in this study that GILT is required for efficient MHC class II-restricted processing of a TRP1 epitope in vitro and accelerates the onset of vitiligo in TRP1-specific TCR transgenic mice. The presence of GILT confers a small increase in the percentage of autoreactive T cells with an effector memory phenotype that may contribute to earlier disease onset. The onset of vitiligo is associated with a greater increase in the percentage of autoreactive T cells with an effector memory phenotype. Given that many self and tumor Ags have disulfide bonds and are presented on MHC class II, GILT is likely to be important in the pathogenesis of other CD4(+) T cell-mediated autoimmune diseases and for the development of effective cancer immunotherapy.

A mycoplasma peptide elicits heteroclitic CD4+ T cell responses against tumor antigen MAGE-A6

PURPOSE

Although T-helper (Th) epitopes have been previously reported for many tumor antigens, including MAGE-A6, the relevant HLA-DR alleles that present these peptides are expressed by only a minority of patients. The identification of tumor antigenic epitopes presented promiscuously by many HLA-DR alleles would extend the clinical utility of these peptides in vaccines and for the immunomonitoring of cancer patients.

EXPERIMENTAL DESIGN

A neural network algorithm and in vitro sensitization assays were employed to screen candidate peptides for their immunogenicity.

RESULTS

The MAGE-A6(140-170), MAGE-A6(172-187), and MAGE-A6(280-302) epitopes were recognized by CD4+ T cells isolated from the majority of normal donors and melanoma patients evaluated. Peptide-specific CD4+ T cells also recognized autologous antigen-presenting cell pulsed with recombinant MAGE-A6 (rMAGE) protein, supporting the natural processing and MHC presentation of these epitopes. Given the strong primary in vitro sensitization of normal donor CD4+ T cells by the MAGEA6(172-187) epitope, suggestive of potential cross-reactivity against an environmental stimulus, we identified a highly homologous peptide within the Mycoplasma penetrans HF-2 permease (MPHF2) protein. MPHF2 peptide-primed CD4+ T cells cross-reacted against autologous APC pulsed with the MAGE-A6(172-187) peptide or rMAGE protein and recognized HLA-matched MAGE-A6+ melanoma cell lines. These responses seemed heteroclitic in nature because the functional avidity of MPHF2 peptide-primed CD4+ T cells for the MAGE-A6(172-187) peptide was approximately 1,000 times greater than that of CD4+ T cells primed with the corresponding MAGE-A6 peptide.

CONCLUSIONS

We believe that these novel "promiscuous" MAGE-A6/MPHF2 Th epitopes may prove clinically useful in the treatment and/or monitoring of a high proportion of cancer patients.

Presentation of tumor antigens by dendritic cells genetically modified with viral and nonviral vectors

Genetic modification of dendritic cells (DCs) with recombinant vectors encoding tumor antigens may aid in developing new immunotherapeutic treatments for patients with cancer. Here, we characterized antigen presentation by human DCs genetically modified with plasmid cDNAs, RNAs, adenoviruses, or retroviruses, encoding the melanoma antigen gp100 or the tumor-testis antigen NY-ESO-1. Monocyte-derived DCs were electroporated with cDNAs or RNAs, or transduced with adenoviruses. CD34+ hematopoietic stem cell-derived DCs were used for retroviral transduction. Genetically modified DCs were coincubated with CD8+ and CD4+ T cells that recognized major histocompatibility complex class I- and class II-restricted epitopes from gp100 and NY-ESO-1, and specific recognition was evaluated by interferongamma secretion. Cytokine release by both CD8+ and CD4+ T cells was consistently higher in response to DCs modified with adenoviruses than cDNAs or RNAs, and maturation of DCs after genetic modification did not consistently alter patterns of recognition. Also, retrovirally transduced DCs encoding gp100 were well recognized by both CD8+ and CD4+ T cells. These data suggest that DCs transduced with viral vectors may be more efficient than DCs transfected with cDNAs or RNAs for the induction of tumor reactive CD8+ and CD4+ T cells in vitro and in human vaccination trials.

Presentation of tumor antigens by dendritic cells genetically modified with viral and nonviral vectors

Genetic modification of dendritic cells (DCs) with recombinant vectors encoding tumor antigens may aid in developing new immunotherapeutic treatments for patients with cancer. Here, we characterized antigen presentation by human DCs genetically modified with plasmid cDNAs, RNAs, adenoviruses, or retroviruses, encoding the melanoma antigen gp100 or the tumor-testis antigen NY-ESO-1. Monocyte-derived DCs were electroporated with cDNAs or RNAs, or transduced with adenoviruses. CD34+ hematopoietic stem cell-derived DCs were used for retroviral transduction. Genetically modified DCs were coincubated with CD8+ and CD4+ T cells that recognized major histocompatibility complex class I- and class II-restricted epitopes from gp100 and NY-ESO-1, and specific recognition was evaluated by interferongamma secretion. Cytokine release by both CD8+ and CD4+ T cells was consistently higher in response to DCs modified with adenoviruses than cDNAs or RNAs, and maturation of DCs after genetic modification did not consistently alter patterns of recognition. Also, retrovirally transduced DCs encoding gp100 were well recognized by both CD8+ and CD4+ T cells. These data suggest that DCs transduced with viral vectors may be more efficient than DCs transfected with cDNAs or RNAs for the induction of tumor reactive CD8+ and CD4+ T cells in vitro and in human vaccination trials.