A prospective open-label study of sirolimus for the treatment of anti-Hu associated paraneoplastic neurological syndromes

BACKGROUND

Several lines of evidence suggest a T cell-mediated immune response in paraneoplastic neurological syndromes with anti-Hu antibodies (Hu-PNS). In order to investigate whether suppression of T cell-mediated immune responses in Hu-PNS patients improved their neurological outcome, we performed a prospective open-label, single-arm study on sirolimus.

METHODS

Seventeen progressive Hu-PNS patients were treated with sirolimus with an intended treatment duration of 8 weeks. Primary outcome measures were (i) functional improvement, defined as a decrease of one or more points on the modified Rankin Scale (mRS), and (ii) improvement of neurological impairment, defined as an increase of one or more points on the Edinburgh Functional Impairment Tests (EFIT).

RESULTS

One patient showed improvement on both clinical scales (mRS and EFIT). This patient presented with limbic encephalitis and improved dramatically from an mRS score of 3 to mRS 1. Another patient, with subacute sensory neuronopathy, remained stable at mRS 2 and improved one point on the EFIT scale. The other patients showed no improvement on the primary outcome measures. Median survival was 21 months.

CONCLUSION

We conclude that treatment of Hu-PNS patients with sirolimus may improve or stabilize their functional disabilities and neurological impairments. However, the effects of this T cell-targeted therapy were not better than reported in trials on other immunotherapies for Hu-PNS. Trial Registration https://www.clinicaltrialsregister.eu/ctr-search/trial/2008-000793-20/NL.

Identification of a potential physiological precursor of aberrant cells in refractory coeliac disease type II

OBJECTIVE

Refractory coeliac disease type II (RCDII) is a severe complication of coeliac disease (CD) characterised by aberrant intraepithelial lymphocytes (IELs) of unknown origin that display an atypical CD3(-)CD7(+)icCD3(+) phenotype. In approximately 40% of patients with RCDII these lymphocytes develop into an invasive lymphoma. In the current study we aimed to identify the physiological counterpart of these cells.

DESIGN

RCDII cell lines were compared with T-cell receptor positive (TCR(+)) IEL (T-IEL) lines by microarray analysis, real-time quantitative PCR and flow cytometry. This information was used to identify cells with an RCDII-associated phenotype in duodenal biopsies from non-refractory individuals by multicolour flow cytometry.

RESULTS

RCDII lines were transcriptionally distinct from T-IEL lines and expressed higher levels of multiple natural killer (NK) cell receptors. In addition to the CD3(-)CD7(+)icCD3(+) phenotype, the RCDII lines were distinguishable from other lymphocyte subsets by the absence of CD56, CD127 and CD34. Cells matching this surface lineage-negative (Lin(-)) CD7(+)CD127(-)CD34(-) phenotype expressed a functional interleukin-15 (IL-15) receptor and constituted a significant proportion of IELs in duodenal specimens of patients without CD, particularly children, and were also found in the thymus. In patients without CD, the Lin(-)CD7(+)CD127(-)CD34(-) subset was one of four subsets within the CD3(-)CD7(+)icCD3(+) population that could be distinguished on the basis of differential expression of CD56 and/or CD127.

CONCLUSION

Our studies indicate that the CD3(-)CD7(+)icCD3(+) population is heterogeneous and reveal the existence of a Lin(-) subset that is distinct from T, B, NK and lymphoid tissue inducer cells. We speculate that this IL-15 responsive population represents the physiological counterpart of aberrant cells expanded in RCDII and transformed in RCDII-associated lymphoma.

Oral DNA vaccination: antigen uptake and presentation by dendritic cells elicits protective immunity

Melanoma differentiation antigens, such as glycoprotein 100 (gp100), have been shown to induce both cellular and humoral immune responses against melanoma in mouse and man. They are therefore considered as potential targets for melanoma immunotherapy. In this study, we have used the attenuated auxotrophic mutant strain SL7207 of Salmonella typhimurium as vehicle for a human gp100 (hgp100) DNA vaccine against melanoma. In vitro studies indicate that Salmonella/pCMV-hgp100 is efficiently scavenged by dendritic cells, resulting in the expression of the hgp100 transcription unit in the DC. In addition, oral administration of Salmonella/pCMV-hgp100 results in the expression of hgp100 RNA and protein by cells exhibiting DC-morphology in mesenteric lymph nodes as soon as 3 days after vaccination. Analysis of the efficacy of the Salmonella/pCMV-hgp100 vaccine in the B16/hgp100 model demonstrated the induction of strong anti-hgp100 CTL responses and protective immunity in 70% of the vaccinated mice, but not in control mice. Based on these data, we consider S. typhimurium as a useful vehicle for the design of recombinant DNA based anti-cancer vaccines.

Dendritic cells break tolerance and induce protective immunity against a melanocyte differentiation antigen in an autologous melanoma model

Tyrosinase-related protein (TRP) 2 belongs to the melanocyte differentiation antigens and has been implicated as a target for immunotherapy of human as well as murine melanoma. In the current report, we explored the efficacy of nonmutated epitopes with differential binding affinity for MHC class I, derived from mouse TRP2 to induce CTL-mediated, tumor-reactive immunity in vivo within the established B16 melanoma model of C57BL/6 mice. The use of nonmutated TRP2-derived epitopes for vaccination provides a mouse model that closely mimics human melanoma without introduction of xenogeneic or otherwise foreign antigen. The results demonstrate that vaccination with TRP2 peptide-loaded bone marrow-derived dendritic cells (DCs) results in activation of high avidity TRP2-specific CTLs, displaying lytic activity against both B16 melanoma cells and normal melanocytes in vitro. In vivo, protective antitumor immunity against a lethal s.c. B16 challenge was observed upon DC-based vaccination in this fully autologous tumor model. The level of protective immunity positively correlated with the MHC class I binding capacity of the peptides used for vaccination. In contrast, within this autologous model, vaccination with TRP2 peptide in Freund's adjuvant or TRP2-encoding plasmid DNA did not result in protective immunity against B16. Strikingly, despite the observed CTL-mediated melanocyte destruction in vitro, melanocyte destruction in vivo was sporadic and primarily restricted to minor depigmentation of the vaccination site. These results emphasize the potency of DC-based vaccines to induce immunity against autologous tumor-associated antigen and indicate that CTL-mediated antitumor immunity can proceed without development of adverse autoimmunity against normal tissue.

Dendritic cell-based vaccines: from mouse models to clinical cancer immunotherapy

B and T lymphocytes are the effectors of specific immunity. However, their function is critically dependent on dendritic cells (DC). DC are professional antigen presenting cells that both initiate and modulate the immune response. The recent breakthrough in the generation of DC from their progenitors has stimulated research on DC in both fundamental and clinical immunology. Objective immune response induction has now been reported in clinical studies using DC. In this review we discuss the development and potential of DC-based vaccines to induce antitumor immunity.

Heterogeneous expression of the SSX cancer/testis antigens in human melanoma lesions and cell lines

The SSX genes, located on the X chromosome, encode a family of highly homologous nuclear proteins. The SSX1 and SSX2 genes were initially identified as fusion partners of the SYT gene in t(X;18)-positive synovial sarcomas. Recently, however, it was found that these two genes, as well as the highly homologous SSX4 and SSX5 genes, are aberrantly expressed in different types of cancers, including melanomas. Because normal SSX expression has been detected only in the testis and, at very low levels, the thyroid, these proteins are considered as new members of the still growing family of cancer/testis antigens. These antigens are presently considered as targets for the development of cancer immunotherapy protocols. In the present study, we developed a monoclonal antibody found to recognize SSX2, SSX3, and SSX4 proteins expressed in formaldehyde-fixed and paraffin-embedded tissues. This antibody was used to investigate SSX expression in normal testis and thyroid, benign melanocytic lesions, melanoma lesions, and melanoma cell lines. SSX nuclear expression in the testis was found to be restricted to spermatogenic cells, mainly spermatogonia. Of 18 melanoma cell lines analyzed, 9 showed SSX RNA and protein expression, although heterogeneously and at variable levels. Treatment of an SSX-negative cell line with 5-aza-2'-deoxycytidine, a demethylating agent, led to SSX RNA and protein expression, indicating a role for methylation in transcription regulation. Thirty-four of 101 primary and metastatic melanoma cases and 2 of 24 common nevocellular and atypical nevus cases showed SSX nuclear staining. Again, SSX expression was heterogeneous, ranging from widespread to scarce. Our findings stress the importance of assessing the a priori SSX expression status of melanoma cases that may be selected for immunotherapeutic trials.

The renal cell carcinoma-associated antigen G250 encodes a human leukocyte antigen (HLA)-A2.1-restricted epitope recognized by cytotoxic T lymphocytes

Evidence has accumulated that the immune system can play a significant role in the defense against tumors in humans. Especially melanoma and renal cell carcinoma (RCC) are considered immunogenic tumors. In contrast to melanoma, hardly any RCC-associated antigens have been identified as targets for RCC-reactive T cells. Here, we report the identification of a human leukocyte antigen (HLA)-A2.1-restricted T-cell epitope within the G250 antigen. This antigen is expressed in 85% of RCCs but not by neighboring normal kidney tissue and has recently been molecularly defined and shown to be identical to MN/CA IX. Computer-aided motif prediction revealed the presence of 60 potential HLA-A2.1-binding peptides within the G250 antigen. Subsequent binding analysis showed that 13 of these peptides bound to HLA-A2.1 with high-to-intermediate affinity. Analysis of their immunogenicity in HLA-A2.1Kb transgenic mice indicated that 4 of the 13 peptides gave rise to cytotoxic T lymphocytes (CTLs) capable of lysing peptide-loaded target cells. However, only the G250 peptide 254-262 induced CTLs that recognized target cells that endogenously expressed the G250 antigen. Similarly, we were also able to raise human CTLs against the G250 peptide 254-262, which lysed target cells that endogenously expressed the G250 antigen. These findings and the high prevalence of this antigen in RCC patients makes G250 a potential target for anti-RCC immunotherapy.

Generation and functional characterization of mouse monocyte-derived dendritic cells

Dendritic cells (DC) are potent antigen-presenting cells with the unique capacity to initiate primary immune responses. As a result, DC are currently used in clinical studies to induce immunity against infectious disease and malignant cells. However, multiple DC subsets exist and it has been suggested that the type of DC may affect the immune response induced. The vast majority of DC used in experimental mouse tumor models is derived from bone marrow progenitors. In contrast, most in vitro as well as in vivo human studies involve the use of DC generated from adherent peripheral blood-derived monocytes in the presence of GM-CSF and IL-4. In the current report, we describe for the first time the generation and characterization of mouse monocyte-derived DC (MODC). The results indicate that mouse MODC display similar morphology, phenotype and immunostimulatory activity as compared to bone marrow-derived DC. Both DC subsets were able to efficiently take up and subsequently cross-present protein antigen to cytotoxic T cells. Moreover, we demonstrate that vaccination with peptide-loaded MODC mediates induction of tumor-reactive immunity in vivo. The isolation and characterization of mouse MODC will provide a valuable research tool to investigate fundamental aspects of DC biology and which DC subsets are most suitable to induce anti-tumor immunity.

Biodistribution and vaccine efficiency of murine dendritic cells are dependent on the route of administration

Dendritic cells (DCs) are professional antigen-presenting cells, well equipped to initiate an immune response. Currently, tumor antigen-derived peptide loaded DCs are used in clinical vaccination in cancer patients. However, the optimal dose and route of administration of a DC vaccine still remain to be determined. Using indium-111-labeled DCs, we investigated whether the route of administration does affect the biodistribution of DCs in lymphoid organs and whether it influences the outcome of DC vaccination in the B16 mouse melanoma tumor model. The results demonstrate that i.v. injected DCs mainly accumulate in the spleen, whereas s.c. injected DCs preferentially home to the T-cell areas of the draining lymph nodes. Using tyrosinase-related protein-2-derived peptide-loaded DC vaccination in a fully autologous B16 melanoma tumor model, we observed a delay in tumor growth, improved survival as well as increased antitumor cytotoxic T-cell reactivity after s.c. vaccination as compared to i.v. vaccination. These data demonstrate that optimal induction of antitumor reactivity against the autologous melanocyte differentiation antigen tyrosinase-related protein-2-derived peptide occurs after s.c. vaccination and correlates with the preferential accumulation of DCs in the T-cell areas of lymph nodes.

Genetic vaccination against the melanocyte lineage-specific antigen gp100 induces cytotoxic T lymphocyte-mediated tumor protection

Melanocyte lineage-specific antigens, such as gp100, have been shown to induce both cellular and humoral immune responses against melanoma. Therefore, these antigens are potential targets for specific antimelanoma immunotherapy. A novel approach to induce both cellular and humoral immunity is genetic vaccination, the injection of antigen-encoding naked plasmid DNA. In a mouse model, we investigated whether genetic vaccination against the human gp100 antigen results in specific antitumor immunity. The results demonstrate that vaccinated mice were protected against a lethal challenge with syngeneic B16 melanoma-expressing human gp100, but not control-transfected B16. Both cytotoxic T cells and IgG specific for human gp100 could be detected in human gp100-vaccinated mice. However, only adoptive transfer of spleen-derived lymphocytes, not of the serum, isolated from protected mice was able to transfer antitumor immunity to nonvaccinated recipients, indicating that CTLs are the predominant effector cells. CTI, lines generated from human gp100-vaccinated mice specifically recognized human gp100. Interestingly, one of the CTL lines cross-reacted between human and mouse gp100, indicating the recognition of a conserved epitope. However, these CTLs did not appear to be involved in the observed tumor protection. Collectively, our results indicate that genetic vaccination can result in a potent antitumor response in vivo and constitutes a potential immunotherapeutic strategy to fight cancer.

Cloning, expression and tissue distribution of the murine homologue of the melanocyte lineage-specific antigen gp100

Melanocyte lineage-specific antigens, like gp100, have been shown to be recognized by tumour-infiltrating lymphocytes isolated from melanoma patients. Therefore these antigens might be used as targets for specific anti-melanoma immunotherapy. To investigate this potential in syngeneic mouse models, we cloned and characterized the murine homologue of gp100 from a B16 murine melanoma cDNA library. The isolated cDNA clone encodes a protein of 626 amino acids, sharing 79.7% sequence homology with human gp100. Expression of murine gp100 was restricted to cells of the melanocyte lineage, as determined by Northern and Western analysis. However, like human gp100, reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed low levels of transcription of the murine gp100 gene in all the cell lines and normal tissues tested. In contrast, murine tyrosinase, another melanocyte differentiation antigen, mimics human tyrosinase expression and did show absolute melanocyte lineage-specific expression. The characterization of murine gp100 will allow investigation of anti-gp100 immune responses in C57BL/6 mice using the syngeneic B16 tumour model and the possible adverse effects of such immunity on normal melanocytes.

Transcription of the gene encoding melanoma-associated antigen gp100 in tissues and cell lines other than those of the melanocytic lineage

The expression of the gp100 antigen is generally thought to be confined to cells of the melanocytic lineage, which makes the protein a suitable melanoma-specific marker. Strikingly, after screening a panel of normal tissues, tumour samples and cell lines of non-melanocytic origin, we found transcripts encoding gp100 in virtually every tissue and cell line tested. In contrast, tyrosinase and MART-1/MelanA transcripts were detected only in cells of the melanocytic lineage. However, no gp100 protein could be detected by either Western blotting or cytotoxicity assays. Therefore, at the protein level, gp100 remains exclusive for cells of melanocytic origin despite its transcription in many cell types. The major implication of this finding is that screening of patient material for gp100 expression should preferrably be performed by antibody staining. Reverse transcriptase polymerase chain reaction (RT-PCR) can be employed, provided that it is performed in a tightly controlled, semiquantitative setting.

Identification of a novel peptide derived from the melanocyte-specific gp100 antigen as the dominant epitope recognized by an HLA-A2.1-restricted anti-melanoma CTL line

Cytotoxic T lymphocytes (CTL) reactive with human melanoma tumor cells occasionally display cross-reactivity with normal melanocytes. Previously, we identified the melanocyte lineage-specific antigen gp 100 that is expressed by both melanoma cells and normal melanocytes, as a target antigen for tumor-infiltrating lymphocytes derived from a melanoma patient (TIL 1200). Here, we demonstrate that the oligoclonal HLA-A2.1-restricted TIL 1200 line is reactive with 2 distinct peptides derived from the gp 100 protein. Apart from the peptide corresponding to gp 100 amino acids 457-466, we identified the gp 100 peptide 154-162 as a second epitope recognized by TIL 1200. A 100-fold lower concentration of this novel gp 100 peptide was required for target-cell sensitization compared to peptide 457-466, indicating that the 154-162 peptide is the dominant gp 100 epitope for TIL 1200. Together with the recently described gp 100 280-288 epitope, 3 distinct CTL epitopes have now been identified in gp 100, all presented in the context of HLA-A2.1. Therefore, gp 100 is an attractive target antigen in the development of immuno-therapeutic protocols against melanoma.

Melanocyte lineage-specific antigen gp100 is recognized by melanoma-derived tumor-infiltrating lymphocytes

We recently isolated a cDNA clone that encodes the melanocyte lineage-specific antigen glycoprotein (gp)100. Antibodies directed against gp100 are an important tool in the diagnosis of human melanoma. Since the gp100 antigen is highly expressed in melanocytic cells, we investigated whether this antigen might serve as a target for antimelanoma cytotoxic T lymphocytes (CTL). Here, we demonstrate that cytotoxic tumor-infiltrating lymphocytes (TIL) derived from a melanoma patient (TIL 1200) are directed against gp100. HLA-A2.1+ melanoma cells are lysed by TIL from this patient. In addition, murine double transfectants, expressing both HLA-A2.1 and gp100, are lysed by TIL 1200, whereas transfectants expressing only HLA-A2.1 are not susceptible to lysis. Furthermore, the HLA-A2.1+ melanoma cell line BLM, which lacks gp100 expression and is resistant to lysis, becomes susceptible after transfection of gp100 cDNA. Finally, HLA-A2.1+ normal melanocytes are lysed by TIL 1200. These data demonstrate that the melanocyte differentiation antigen gp100 can be recognized in the context of HLA-A2.1 by CTL from a melanoma patient. Gp100 may therefore constitute a useful target for specific immunotherapy against melanoma, provided that no unacceptable cytotoxicity towards normal tissue is observed.