The end of twentieth century has introduced some changes into T helper (Th) cells division. The identification of the new subpopulation of T helper cells producing IL-17 modified model of Th1–Th2 paradigm and it was named Th17. High abilities to stimulate acute and chronic inflammation made these cells ideal candidate for crucial player in development of autoimmune disorders. Numerous publications based on animal and human models confirmed their pivotal role in pathogenesis of human systemic and organ-specific autoimmune diseases. These findings made Th17 cells and pathways regulating their development and function a good target for therapy. Therapies based on inhibition of Th17-dependent pathways are associated with clinical benefits, but on the other hand are frequently inducing adverse effects. In this review, we attempt to summarize researches focused on the importance of Th17 cells in development of human autoimmune diseases as well as effectiveness of targeting IL-17 and its pathways in pre-clinical and clinical studies.

The receptor for hyaluronic acid–mediated motility (RHAMM) is an antigen eliciting both humoral and cellular immune responses in patients with acute myeloid leukemia (AML), myelodysplastic syndrome (MDS), and multiple myeloma (MM). We initiated a phase 1 clinical trial vaccinating 10 patients with R3 (ILSLELMKL), a highly immunogenic CD8⁺ T-cell epitope peptide derived from RHAMM. In 7 of 10 patients, we detected an increase of CD8⁺/HLA-A2/RHAMM R3 tetramer⁺/CD45RA⁺/CCR7⁻/CD27⁻/CD28⁻ effector T cells in accordance with an increase of R3-specific CD8⁺ T cells in enzyme linked immunospot (ELISpot) assays. In chromium release assays, a specific lysis of RHAMM-positive leukemic blasts was shown. Three of 6 patients with myeloid disorders (1/3 AML, 2/3 MDS) achieved clinical responses: one patient with AML and one with MDS showed a significant reduction of blasts in the bone marrow after the last vaccination. One patient with MDS no longer needed erythrocyte transfusions after 4 vaccinations. Two of 4 patients with MM showed a reduction of free light chain serum levels. Taken together, RHAMM-R3 peptide vaccination induced both immunologic and clinical responses, and therefore RHAMM constitutes a promising target for further immunotherapeutic approaches. This study is registered at http://ISRCTN.org as ISRCTN32763606 and is registered with EudraCT as 2005-001706-37.

The expression of tumor-associated antigens (TAAs) might play a critical role in the control of minimal residual disease (MRD) in acute myeloid leukemia (AML), and therefore might be associated with clinical outcome in AML. In a DNA microarray analysis of 116 AML samples, we found a significant correlation between high mRNA levels of G250/CA9 and longer overall survival (P = .022), a similar trend with high mRNA levels of PRAME (P = .103), and a hint for RHAMM/HMMR. In contrast, for other TAAs like WT1, TERT, PRTN3, BCL2, and LAMR1, we found no correlation with clinical outcome. High expression of at least 1 of the 3 TAAs, RHAMM/HMMR, PRAME, or G250/CA9, provided the strongest favorable prognostic effect (P = .005). Specific T-cell responses were detected in 8 (47%) of 17 patients with AML in complete remission for RHAMM/HMMR-R3 peptide, in 7 (70%) of 10 for PRAME-P3 peptide, and in 6 (60%) of 10 for newly characterized G250/CA9-G2 peptide, a significant increased immune response compared with patients with AML patients who had refractory disease (P < .001). Furthermore, we could demonstrate specific lysis of T2 cells presenting these epitope peptides. In conclusion, expression of the TAAs RHAMM/HMMR, PRAME, and G250/CA9 can induce strong antileukemic immune responses, possibly enabling MRD control. Thus, these TAAs represent interesting targets for polyvalent immunotherapeutic approaches in AML.

The interpretation of the results obtained from immunomonitoring of clinical trials is a difficult task due to the variety of methods and protocols available to detect vaccine-specific T-cell responses. This heterogeneity as well as the lack of standards has led to significant scepticism towards published results. In February 2005, a working group was therefore founded under the aegis of the Association for Immunotherapy of Cancer (“CIMT”) in order to compare techniques and protocols applied for the enumeration of antigen-specific T-cell responses. Here we present the results from two consecutive phases of an international inter-laboratory testing project referred to as the “CIMT monitoring panel”. A total of 13 centers from six European countries participated in the study in which pre-tested PBMC samples, synthetic peptides and PE-conjugated HLA-tetramers were prepared centrally and distributed to participants. All were asked to determine the number of antigen-specific T-cells in each sample using tetramer staining and one functional assay. The results of the first testing round revealed that the total number of cells analyzed was the most important determinant for the sensitive detection of antigen-specific CD8⁺ T-cells by tetramer staining. Analysis by ELISPOT was influenced by a combination of cell number and a resting phase after thawing of peripheral blood mononuclear cells. Therefore, the experiments were repeated in a second phase but now the participants were asked to change their protocols according to the new guidelines distilled from the results of the first phase. The recommendations improved the number of antigen-specific T-cell responses that were detected and decreased the variability between the laboratories. We conclude that a two-step approach in inter-laboratory testing allows the identification of distinct variables that influence the sensitivity of different T-cell assays and to formally show that a defined correction to the protocols successfully increases the sensitivity and reduces the inter-center variability. Such “two-step” inter-laboratory projects could define rational bases for accepted international guidelines and thereby lead to the harmonization of the techniques used for immune monitoring.

Background Recently, we demonstrated immunological and clinical responses to a RHAMM-R3 peptide vaccine in patients with acute myeloid leukemia, myelodysplastic syndrome and multiple myeloma. To improve the outcome of the vaccine, a second cohort was vaccinated with a higher dose of 1,000 μg peptide. Design and Methods Nine patients received four vaccinations subcutaneously at a biweekly interval. Immunomonitoring of cytotoxic CD8⁺ as well as regulatory CD4⁺ T cells was performed by flow cytometry as well as by enzyme-linked immunospot (ELISpot) assays. Parameters of clinical response were assessed. Results In 4 of 9 patients (44%) we detected positive immunological responses. These patients showed an increase of CD8⁺RHAMM-R3_tetramer⁺/CD45RA⁺/CCR7⁻/CD27⁻/CD28⁻ effector T cells and an increase of R3-specific CD8+ T cells. Two of these patients showed a significant decrease of regulatory T cells (Tregs). In one patient without response Tregs frequency increased from 5 to 16%. Three patients showed clinical effects: one patient with myelodysplastic syndrome RAEB-1 showed a reduction of leukemic blasts in the bone marrow, another myelodysplastic syndrome patient an improvement of peripheral blood counts and one patient with multiple myeloma a reduction of free light chains. Clinical and immunological reactions were lower in this cohort than in the 300 μg cohort. Conclusions High-dose RHAMM-R3 peptide vaccination induced immunological responses and positive clinical effects. Therefore, RHAMM constitutes a promising structure for further targeted immunotherapies in patients with different hematologic malignancies. However, higher doses of peptide did not improve the frequency and intensity of immune responses in this trial. (This study is registered at http://ISRCTN.org as ISRCTN32763606)

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