Guy Warnier

IL-22 Is Required for Imiquimod-Induced Psoriasiform Skin Inflammation in Mice

Psoriasis is a common chronic autoimmune skin disease of unknown cause that involves dysregulated interplay between immune cells and keratinocytes. IL-22 is a cytokine produced by the TH1, TH17, and TH22 subsets that are functionally implicated in the psoriatic pathology. We assessed the role of IL-22 in a mouse model where psoriasiform skin inflammation is triggered by topical application of the TLR7/8 agonist imiquimod. At the macroscopic level, scaly skin lesions induced by daily applications of imiquimod in wild-type mice were almost totally absent in IL-22–deficient mice or in mice treated with a blocking anti–IL-22 Ab. At the microscopic level, IL-22–deficient mice showed a dramatic decrease in the development of pustules and a partial decrease in acanthosis. At the molecular level, the absence or inhibition of IL-22 strongly decreased the expression of chemotactic factors such as CCL3 and CXCL3 and of biomarkers such as S100A8, S100A7, and keratin 14, which reflect the antimicrobial and hyperproliferative responses of keratinocytes. IL-22 also played a major role in neutrophil infiltration after imiquimod treatment. IL-23 was required for IL-22 production, and γδ TCR lymphocytes represented the major source of IL-22 in lymph nodes from imiquimod-treated mice. However, T cells were not absolutely required for IL-22 production because imiquimod-induced IL-22 expression in the skin is still preserved in Rag2−/− mice. Taken together, our data show that IL-22 is required for psoriasis-like lesions in the mouse imiquimod model and is produced by both T cells and innate immune cells.

The Production of a New MAGE-3 Peptide Presented to Cytolytic T Lymphocytes by HLA-B40 Requires the Immunoproteasome

By stimulating human CD8+ T lymphocytes with autologous dendritic cells infected with an adenovirus encoding MAGE-3, we obtained a cytotoxic T lymphocyte (CTL) clone that recognized a new MAGE-3 antigenic peptide, AELVHFLLL, which is presented by HLA-B40. This peptide is also encoded by MAGE-12. The CTL clone recognized MAGE-3–expressing tumor cells only when they were first treated with IFN-γ. Since this treatment is known to induce the exchange of the three catalytic subunits of the proteasome to form the immunoproteasome, this result suggested that the processing of this MAGE-3 peptide required the immunoproteasome. Transfection experiments showed that the substitution of β5i (LMP7) for β5 is necessary and sufficient for producing the peptide, whereas a mutated form of β5i (LMP7) lacking the catalytically active site was ineffective. Mass spectrometric analyses of in vitro digestions of a long precursor peptide with either proteasome type showed that the immunoproteasome produced the antigenic peptide more efficiently, whereas the standard proteasome more efficiently introduced cleavages destroying the antigenic peptide. This is the first example of a tumor-specific antigen exclusively presented by tumor cells expressing the immunoproteasome.

IL-13 Mediates In Vivo IL-9 Activities on Lung Epithelial Cells but Not on Hematopoietic Cells

Increased IL-9 expression, either systemically or under the control of lung-specific promoter, induces an asthma-like phenotype, including mucus overproduction, mastocytosis, lung eosinophilia, and airway hyperresponsiveness. These activities correlate with increased production of other Th2 cytokines such as IL-4, IL-5, and IL-13 in IL-9 Tg mice. To determine the exact role of IL-13 in this phenotype, mice overexpressing IL-9 were crossed with IL-13-deficient mice. In these animals, IL-9 could still induce mastocytosis and B lymphocyte infiltration of the lungs. Although IL-9-induced eosinophilia in the peritoneal cavity was not diminished in the absence of IL-13, IL-13 was required for IL-9 to increase eotaxin expression and lung eosinophilia. Mucus production and up-regulation of lung epithelial genes upon IL-9 overexpression were completely abolished in the absence of IL-13. Using hemopoietic cell transfer experiments with recipients that overexpressed IL-9 but were deficient in the IL-9 receptor (IL-9R), we could demonstrate that the effect of IL-9 on lung epithelial cells is indirect and could be fully restored by transfer of hemopoietic cells expressing IL-9R. Mucus production by lung epithelial cells was only up-regulated when hemopoietic cells simultaneously expressed functional IL-9R and IL-13 genes, indicating that IL-13 is not a cofactor but a direct mediator of the effect of IL-9 on lung epithelial cells. Taken together, these data indicate that IL-9 can promote asthma through IL-13-independent pathways via expansion of mast cells, eosinophils, and B cells, and through induction of IL-13 production by hemopoietic cells for mucus production and recruitment of eosinophils by lung epithelial cells.

IL-9 Promotes IL-13-Dependent Paneth Cell Hyperplasia and Up-Regulation of Innate Immunity Mediators in Intestinal Mucosa

IL-9 contributes to lung inflammatory processes such as asthma, by promoting mast cell differentiation, B cell activation, eosinophilia, and mucus production by lung epithelial cells. The observation that IL-9 overexpressing mice show increased mast cell numbers in the intestinal mucosa suggests that this cytokine might also play a role in intestinal inflammation. In colons from IL-9 transgenic mice, the expression of Muc2, a major intestinal mucin gene, was up-regulated, together with that of CLCA3 chloride channel and resistin like α, which are goblet cell-associated genes. Additional IL-9 up-regulated genes were identified and included innate immunity genes such as angiogenin 4 and the PLA2g2a phospholipase A2, which are typical Paneth cell markers. Histochemical staining of Paneth cells by phloxine/tartrazine showed that IL-9 induces Paneth cell hyperplasia in Lieberkühn glands of the small intestine, and in the colonic mucosa, where this cell type is normally absent. Expression of Paneth cell markers, including angiogenin 4, PLA2g2a, and cryptdins, was induced in the colon of wild-type mice after two to four daily administrations of IL-9. By crossing IL-9 transgenic mice with IL-13−/− mice, or by injecting IL-9 into IL-4R−/− mice, we showed that IL-13 was required for the up-regulation of these Paneth cell-specific genes by IL-9. Taken together, our data indicate that Paneth cell hyperplasia and expression of their various antimicrobial products contribute to the immune response driven by TH2 cytokines, such as IL-9 and IL-13 in the intestinal mucosa.

The expression of mouse gene P1A in testis does not prevent safe induction of cytolytic T cells against a P1A‐encoded tumor antigen

Tumor antigen P815AB is recognized by cytolytic T lymphocytes (CTL) on mouse mastocytoma P815. This antigen is encoded by P1A, a gene activated in several tumors but silent in normal tissues except for testis and placenta. Notwithstanding the expression of P1A in testis, we found that male mice mounted P815AB‐specific CTL responses as efficiently as females. The responding males remained fertile and no autoimmune lesions were observed in their testes. By immunohistochemistry with a rabbit antiserum directed against the P1A protein, we identified spermatogonia as the testicular cells expressing P1A. The absence of MHC class‐1 molecules on spermatogonia could be one of the mechanisms of protection against testicular autoimmunity, as the antigenic peptide should not be displayed at the cell surface. Human genes MAGE, BAGE and GAGE, which also code for tumor antigens recognized by autologous CTL, are not expressed in normal tissues other than testis. The results obtained in mice with antigen P815AB suggest that immunization of human males with such antigens will not generate autoimmune side‐effects. Although P1A is strongly expressed in placenta, we also found that gestation did not prevent generation of CTL responses against antigen P815AB, and that such CTL responses did not affect gestation outcome. We identified labyrinthine trophoblasts as the placental cells expressing P1A. Again, the absence of MHC class‐1 molecules on these cells provides a plausible explanation for placental protection, although other mechanisms may also play a role. Int. J. Cancer, 70:349–356, 1997.

Induction of a cytolytic T-cell response in mice with a recombinant adenovirus coding for tumor antigen P815A

We investigated the efficacy of a recombinant adenovirus in inducing a cytolytic T‐lymphocyte (CTL) response in mice against tumor antigen P815A, which is present on mouse mastocytoma P815. The recombinant adenoviral vector (Adeno.PIA) contained the sequence coding for the antigenic nonapeptide which binds to the H‐2.Ld molecule to form antigen P815A. We verified that murine cells infected in vitro with Adeno.PIA were lysed by an anti‐P815A CTL clone. Mice then received a single intradermal injection of Adeno.PIA, and after a few weeks their spleen cells were stimulated in vitro with tumor cells expressing antigen P815A. An anti‐P815A CTL response was observed with the spleen lymphocytes of nearly all the mice, providing the lymphocytes were re‐stimulated in vitro with cells expressing both P815A and co‐stimulatory molecule B7.1. When the stimulatory cells did not express B7.1, a specific CTL response was observed in only 45% of the mice, and it was less intense. The Adeno.PIA viral vector was unable to raise an anti‐P815A response in mice that had been previously infected with a recombinant adenovirus carrying the β‐galactosidase gene or with a defective adenovirus. We conclude that adenoviral vectors may be very useful for the priming of cytolytic T‐cell responses directed against human tumor antigens. Other modes of immunization may be necessary to boost the responses induced with adenoviral vectors.

Comparative Prime-Boost Vaccinations Using Semliki Forest Virus, Adenovirus, and ALVAC Vectors Demonstrate Differences in the Generation of a Protective Central Memory CTL Response against the P815 Tumor

Tumor-specific Ags are potential target molecules in the therapeutic treatment of cancer. One way to elicit potent immune responses against these Ags is to use recombinant viruses, which activate both the innate and the adaptive arms of the immune system. In this study, we have compared Semliki Forest virus (SFV), adenovirus, and ALVAC (poxvirus) vectors for their capacity to induce CD8+ T cell responses against the P1A tumor Ag and to elicit protection against subsequent challenge injection of P1A-expressing P815 tumor cells in DBA/2 mice. Both homologous and heterologous prime-boost regimens were studied. In most cases, both higher CD8+ T cell responses and better tumor protections were observed in mice immunized with heterologous prime-boost regimens, suggesting that the combination of different viral vectors is beneficial for the induction of an effective immune response. However, homologous immunization with SFV provided potent tumor protection despite a rather moderate primary CD8+ T cell response as compared with mice immunized with recombinant adenovirus. SFV-immunized mice showed a rapid and more extensive expansion of P1A-specific CD8+ T cells in the tumor-draining lymph node after tumor challenge and had a higher frequency of CD62L+ P1A-specific T cells in the blood, spleen, and lymph nodes as compared with adenoimmunized mice. Our results indicate that not only the magnitude but in particular the quality of the CD8+ T cell response correlates with tumor protection.

AhR modulates the IL-22-producing cell proliferation/recruitment in imiquimod-induced psoriasis mouse model

IL‐22 has a detrimental role in skin inflammatory processes, for example in psoriasis. As transcription factor, AhR controls the IL‐22 production by several cell types (i.e. Th17 cells). Here, we analyzed the role of Ahr in IL‐22 production by immune cells in the inflamed skin, using an imiquimod‐induced psoriasis mouse model. Our results indicate that IL‐22 is expressed in the ear of imiquimod‐treated Ahr−/− mice but less than in wild‐type mice. We then studied the role of AhR on three cell populations known to produce IL‐22 in the skin: γδ T cells, Th17 cells, and ILC3, and a novel IL‐22‐producing cell type identified in this setting: CD4−CD8−TCRβ+ T cells. We showed that AhR is required for IL‐22 production by Th17, but not by the three other cell types, in the imiquimod‐treated ears. Moreover, AhR has a role in the recruitment of γδ T cells, ILC3, and CD4−CD8−TCRβ+ T cells into the inflamed skin or in their local proliferation. Taken together, AhR has a direct role in IL‐22 production by Th17 cells in the mouse ear skin, but not by γδ T cells, CD4−CD8−TCRβ+ T cells and ILCs.

Induction of cytolytic T lymphocytes by immunization of mice with an adenovirus containing a mouse homolog of the human MAGE-A genes.

Abstract The genes of the MAGE-A family code for antigens that are strictly tumor-specific and are shared by many human tumors. Melanoma patients have been immunized against these antigens and some tumor regressions have been observed. However, no unequivocal evidence of cytolytic T cell responses has been obtained by analyzing the blood lymphocytes of these patients. Hence it was considered worthwhile to examine in mouse systems whether or not immunization against antigens derived from the mouse Mage homologs can produce cytolytic T cell responses. We have identified an antigenic peptide encoded by mouse gene Mage-a2, and here we show that immunization of DBA/2 mice with a recombinant adenovirus containing either just the sequence encoding this peptide or a large part of the Mage-a2 coding sequence produces strong cytolytic T cell responses. The Mage-a2 system should prove useful for the comparison of vaccination modalities that could be applied to human patients in therapeutic vaccination trials with MAGE antigens.

Dual TCR Expression Biases Lung Inflammation in DO11.10 Transgenic Mice and Promotes Neutrophilia via Microbiota-Induced Th17 Differentiation

A commonly used mouse model of asthma is based on i.p. sensitization to OVA together with aluminum hydroxide (alum). In wild-type BALB/c mice, subsequent aerosol challenge using this protein generates an eosinophilic inflammation associated with Th2 cytokine expression. By constrast, in DO11.10 mice, which are transgenic for an OVA-specific TCR, the same treatment fails to induce eosinophilia, but instead promotes lung neutrophilia. In this study, we show that this neutrophilic infiltration results from increased IL-17A and IL-17F production, whereas the eosinophilic response could be restored upon blockade of IFN-γ, independently of the Th17 response. In addition, we identified a CD4+ cell population specifically present in DO11.10 mice that mediates the same inflammatory response upon transfer into RAG2−/− mice. This population contained a significant proportion of cells expressing an additional endogenous TCR α-chain and was not present in RAG2−/− DO11.10 mice, suggesting dual antigenic specificities. This particular cell population expressed markers of memory cells, secreted high levels of IL-17A, and other cytokines after short-term restimulation in vitro, and triggered a neutrophilic response in vivo upon OVA aerosol challenge. The relative numbers of these dual TCR lymphocytes increased with the age of the animals, and IL-17 production was abolished if mice were treated with large-spectrum antibiotics, suggesting that their differentiation depends on foreign Ags provided by gut microflora. Taken together, our data indicate that dual TCR expression biases the OVA-specific response in DO11.10 mice by inhibiting eosinophilic responses via IFN-γ and promoting a neutrophilic inflammation via microbiota-induced Th17 differentiation.