Pierre Langlade-Demoyen

H-2 class I knockout, HLA-A2.1-transgenic mice: a versatile animal model for preclinical evaluation of antitumor immunotherapeutic strategies.

H‐2 class I‐negative, HLA‐A2.1‐transgenic HHD mice were used for a comparative evaluation of the immunogenicity of HLA‐A2.1‐restricted human tumor‐associated cytotoxic T lymphocyte (CTL) epitopes. A hierarchy was established among these peptides injected into mice in incomplete Freunds adjuvant which correlates globally with their capacity to bind and stabilize HLA‐A2.1 molecules. Co‐injection of a helper peptide enhanced most CTL responses. In contrast, classical HLA class I‐transgenic mice which still express their own class I molecules did not, in most cases, develop HLA‐A2.1‐restricted CTL responses under the same experimental conditions. Different monoepitope immunization strategies of acceptable clinical usage were compared in HHD mice. Recombinant Ty‐virus‐like particles, or DNA encoding epitopes fused to the hepatitis B virus middle envelope protein gave the best results. Using this latter approach and a melanoma‐based polyepitope construct, CTL responses against five distinct epitopes could be elicited simultaneously in a single animal. Thus, HHD mice provide a versatile animal model for preclinical evaluation of peptide‐based cancer immunotherapy.

Identification of a human telomerase reverse transcriptase peptide of low affinity for HLA A2.1 that induces cytotoxic T lymphocytes and mediates lysis of tumor cells

Telomerase reverse transcriptase (TRT) is a tumor-associated antigen expressed in the vast majority of human tumors and is presently one of the most promising target candidates for a therapeutic cancer vaccine. TRT is also expressed at low level in selected tissues and should be considered a self antigen. In the present study we sought to develop cytotoxic T lymphocytes (CTL) responses directed against human (h)TRT peptides with low relative affinity for which the available repertoire is to be preferentially spared from tolerance. This was accomplished by using analogue peptides of hTRT whose relative affinity for the MHC was increased by a targeted (→Tyr) substitution in position one. By immunizing HLA A2.1 transgenic mice with these analogue peptides, we identified one such low relative affinity peptide (p572) that is endogenously processed and presented by HLA A2.1 in tumor cells, and is recognized by specific CTL. We used the highly immunogenic analogue peptide to successfully induce TRT-specific CTL in cancer patients and normal donors. CTL against p572-lysed human and mouse tumor cells but not activated autologous B cells. This peptide represents, therefore, an important candidate component of a cancer vaccine based on a TRT substrate and validates the strategy of targeting peptides with low affinity for the MHC for cancer immunotherapy.

Retrovirus antigens recognized by cytolytic T lymphocytes activate tumor rejection in vivo

We have initiated the molecular definition of the antigens recognized by Gross MuLV-specific cytolytic T lymphocytes on the surface of Gross MuLV-induced tumor cells. A panel of target cells was obtained by the double transfection and expression of a retrovirus gene and a foreign H-2 gene in recipient mouse fibroblasts. Our results show that class I H-2 transplantation antigens have a directive influence in determining the antigenicity of proteins encoded by the gag and env MuLV genes. Genes not linked to H-2 influence the intensity and the specificity of the cytolytic T lymphocyte response to Gross MuLV-induced tumors. Finally, MuLV-induced antigens expressed by transfected fibroblasts induce tumor immunity and lead to accelerated tumor rejection in vivo.

Identification of cryptic MHC I-restricted epitopes encoded by HIV-1 alternative reading frames.

Human immunodeficiency virus (HIV) 1 major histocompatibility complex (MHC) I–restricted epitopes are widely believed to be derived from viral proteins encoded by primary open reading frames. However, the HIV-1 genome contains alternative reading frames (ARFs) potentially encoding small polypeptides. We have identified a panel of epitopes encoded by ARFs within the gag, pol, and env genes. The corresponding epitopic peptides were immunogenic in mice humanized for MHC-I molecules. In addition, cytotoxic T lymphocytes recognizing these epitopes were found in HIV-infected patients. These results reveal the existence of atypical mechanisms of HIV-1 epitope generation. They indicate that the repertoire of epitopes recognized by the cellular anti–HIV-1 immune response is broader than initially thought. This should be taken into account when designing vaccine strategies aimed at activating these responses.

Immunogenic HLA-B*0702-Restricted Epitopes Derived from Human Telomerase Reverse Transcriptase That Elicit Antitumor Cytotoxic T-Cell Responses

Purpose: The human telomerase reverse transcriptase (hTERT) is considered as a potential target for cancer immunotherapy because it is preferentially expressed in tumor cells. To increase the applicability of hTERT-based immunotherapy, we set out to identify CTL epitopes in hTERT restricted by HLA-B*0702 molecule, a common MHC class I allele. Experimental Design: HLA-B*0702-restricted peptides from hTERT were selected by using a method of epitope prediction and tested for their immunogenicity in human (in vitro) and HLA-B*0702 transgenic mice (in vivo). Results: All the six hTERT peptides that were predicted to bind to HLA-B*0702 molecule were found to induce primary human CTL responses in vitro. The peptide-specific CD8+ CTL lines were tested against various hTERT+ tumor cells. Although differences were observed according to the tumor origin, only three CTL lines specific for p277, p342, and p351 peptides exhibited cytotoxicity against tumor cells in a HLA-B*0702-restricted manner. In addition, this cytotoxicity was inhibited by the addition of peptide-loaded cold target cells and indicated that these epitopes are naturally processed and presented on the tumor cells. Further, in vivo studies using humanized HLA-B*0702 transgenic mice showed that all the candidate peptides were able to induce CTL responses after peptide immunization. Furthermore, vaccination with a plasmid DNA encoding full-length hTERT elicited peptide-specific CTL responses, indicating that these epitopes are efficiently processed in vivo. Conclusions: Together with previously reported hTERT epitopes, the identification of new CTL epitopes presented by HLA-B*0702 increases the applicability of hTERT-based immunotherapy to treating cancer.

Analysis of Spontaneous Tumor-Specific CD4 T-cell Immunity in Lung Cancer Using Promiscuous HLA-DR Telomerase-Derived Epitopes: Potential Synergistic Effect with Chemotherapy Response

Purpose: To investigate the presence and impact of spontaneous telomerase-specific CD4 T-cell responses in cancer patients. Experimental Design: A multistep approach was used to design novel pan-HLA-DR–restricted peptides from telomerase. T-cell clones isolated from cancer patients were used to characterize the polarization of telomerase-specific CD4 response. The presence of spontaneous CD4 T-cell response against telomerase was monitored in 84 metastatic non–small cell lung cancer (NSCLC) patients before first-line chemotherapy (CT) using IFN-γ ELISPOT assay. Then we analyzed the impact of the pretherapeutic telomerase-specific CD4 T immunity on clinical outcome in patients according to their respective response to CT. Results: We described four novel telomerase-derived CD4 epitopes referred as universal cancer peptides (UCP) that effectively bind to most commonly found human MHC class II alleles. UCP-specific CD4 T-cell repertoire is present in human and UCP-specific CD4 T-cell clones generated from cancer patients exhibited high avidity and are Th1 polarized. Significant frequency (38%) of naturally occurring UCP-specific T-cell responses were detected before CT in advanced NSCLC but not in healthy volunteers. This response was shown to significantly increase overall survival (OS) of patients responding to CT (Median OS: 53 vs. 40 weeks, P = 0.034). Conclusions: These results show for the first time a potential synergistic effect of telomerase-specific CD4 T-cell response with CT response in NSCLC and underline the potential role of tumor-specific CD4 T-cell response on the efficiency of conventional anticancer therapy. Clin Cancer Res; 18(10); 2943–53. ©2012 AACR.

B Subunit of Shiga Toxin-Based Vaccines Synergize with α-Galactosylceramide to Break Tolerance against Self Antigen and Elicit Antiviral Immunity

The nontoxic B subunit of Shiga toxin (STxB) targets in vivo Ag to dendritic cells that preferentially express the glycolipid Gb3 receptor. After administration of STxB chemically coupled to OVA (STxB-OVA) or E7, a polypeptide derived from HPV, in mice, we showed that the addition of α-galactosylceramide (α-GalCer) resulted in a dramatic improvement of the STxB Ag delivery system, as reflected by the more powerful and longer lasting CD8+ T cell response observed even at very low dose of immunogen (50 ng). This synergy was not found with other adjuvants (CpG, poly(I:C), IFN-α) also known to promote dendritic cell maturation. With respect to the possible mechanism explaining this synergy, mice immunized with α-GalCer presented in vivo the OVA257–264/Kb complex more significantly and for longer period than mice vaccinated with STxB alone or mixed with other adjuvants. To test whether this vaccine could break tolerance against self Ag, OVA transgenic mice were immunized with STxB-OVA alone or mixed with α-GalCer. Although no CTL induction was observed after immunization of OVA transgenic mice with STxB-OVA, tetramer assay clearly detected specific anti-OVA CD8+ T cells in 8 of 11 mice immunized with STxB-OVA combined with α-GalCer. In addition, vaccination with STxB-OVA and α-GalCer conferred strong protection against a challenge with vaccinia virus encoding OVA with virus titers in the ovaries reduced by 5 log compared with nonimmunized mice. STxB combined with α-GalCer therefore appears as a promising vaccine strategy to more successfully establish protective CD8+ T cell memory against intracellular pathogens and tumors.

Role of T cell help and endoplasmic reticulum targeting in protective CTL response against influenza virus.

We report on the induction of primary and long‐term memory cytotoxic T lymphocyte (CTL) responses against the nucleoprotein of the influenza virus A/PR8/34 in mice immunized with plasmid DNA targeted to B lymphocytes in the spleen. We found that the magnitude of the CTL response and the size of the pool of memory CTL was greater when the CTL response was induced in presence of T cell help. Interestingly, immunization with a signal sequence‐competent transgene was markedly superior to immunization with a transgene lacking the endoplasmic reticulum (ER) targeting sequence, in inducing CTL. We also found a correlation between in vivo protection from lethal virus challenge and (1) the availability of T cell help and (2) ER targeting. Immunization of dendritic cell‐deficient mice suggests that B lymphocytes function as antigen‐presenting cells in this model of immunization. Collectively, the results suggest that somatic transgene immunization is a conceptually new approach to induce effective anti‐viral CTL responses and to assess the parameters critical for long‐lasting and protective CTL responses in vivo.

Immunogenicity and tolerance following HIV-1/HBV plant-based oral vaccine administration

Transgenic tobacco plants expressing a HIV-1 polyepitope associated with hepatitis B (HBV) virus-like particles (VLPs) were previously described. It is demonstrated here that oral administration of these transgenic plants to humanized HSB mice to boost DNA-priming can elicit anti-HIV-1 specific CD8+ T cell activation detectable in mesenteric lymph nodes. Nevertheless, a significant regulatory T cell activation was induced in vivo by the vaccination protocols. The balance between tolerance and immunogenicity remains the main concern in the proof of concept of plant-based vaccine.

Analysis of T-cell defects in the specific immune response against acute lymphoblastic leukemia cells

We previously showed that a specific antileukemia T-cytotoxic response is spontaneously elicited in acute lymphoblastic leukemia (ALL) patients and might contribute to host antileukemia defense, even though it is insufficient for tumor growth control. In this study, we report that multifactorial factors account for some of the acquired immune defects seen in ALL patients. In bone marrow of ALL patients, T cells do not express CD40L and CD25 markers, their apoptosis rate is increased, and a predominance of a CD4 cell subset expressing a Th2 phenotype is detected. A lack of expression of B7-1 molecules and other activation molecules is observed on all ALL blasts. These different parameters combined lead to in vivo dysfunction of T-cell proliferative and cytotoxic activity.