Pitfalls of vaccinations with WT1-, Proteinase3- and MUC1-derived peptides in combination with MontanideISA51 and CpG7909

Abstract

T cells with specificity for antigens derived from Wilms Tumor gene (WT1), Proteinase3 (Pr3), and mucin1 (MUC1) have been demonstrated to lyse acute myeloid leukemia (AML) blasts and multiple-myeloma (MM) cells, and strategies to enhance or induce such tumor-specific T cells by vaccination are currently being explored in multiple clinical trials. To test safety and immunogenicity of a vaccine composed of WT1-, Pr3-, and MUC1-derived Class I-restricted peptides and the pan HLA-DR T helper cell epitope (PADRE) or MUC1-helper epitopes in combination with CpG7909 and MontanideISA51, four patients with AML and five with MM were repetitively vaccinated. No clinical responses were observed. Neither pre-existing nor naive WT1-/Pr3-/MUC1-specific CD8+ T cells expanded in vivo by vaccination. In contrast, a significant decline in vaccine-specific CD8+ T cells was observed. An increase in PADRE-specific CD4+ T helper cells was observed after vaccination but these appeared unable to produce IL2, and CD4+ T cells with a regulatory phenotype increased. Taken into considerations that multiple clinical trials with identical antigens but different adjuvants induced vaccine-specific T cell responses, our data caution that a vaccination with leukemia-associated antigens can be detrimental when combined with MontanideISA51 and CpG7909. Reflecting the time-consuming efforts of clinical trials and the fact that 1/3 of ongoing peptide vaccination trails use CpG and/or Montanide, our data need to be taken into consideration.

Fig. 1

a Vaccine composition, b patient characteristics, and clinical responses after vaccination. CTCAE grading of side effects is indicated. Clinical responses were evaluated at the end of study (day 84). DTH delayed type hypersensitivity reaction, SD stable disease, PD progressive disease, n.d. not determined, Pretreatment treatment prior study entry

Fig. 2

Decrease in vaccine-specific T cells (VST) and increase in regulatory CD4⁺ T cells after vaccination. a Pentamer-positive CD8⁺ T cells before (day −7) and after (days 14–84) vaccination in all patients (n = 9). CMV sero-positive (CMVpos) group n = 6, sero-negative (CMVneg) group n = 3, VST before vaccination group (VST) n = 5, no VST before vaccination group (NoVST) n = 4, HIV-reverse-transcriptase-peptide (HIVRT). b Pentamer-positive CD8⁺ T cells were gated and percentages of pentamer-positive effector memory/effector T cells (CD27⁻/CCR7⁻) calculated before vaccination and at day 42 after vaccination. c Percent cytokine producing PADRE-specific CD4⁺ T cells as measured by ICC. d Flow cytometry analysis of patient-derived PBMC samples collected prior to vaccination and at day 42 and 84. Cells were incubated with anti-CD3, anti-CD8, anti-CD4, anti-CD25, anti-CD127, and anti-FoxP3. Regulatory phenotype is defined as: CD25⁺CD127^lowFoxP3⁺ CD4⁺ T cells. The dotted line represents the threshold of a more then twofold increase of CD25⁺CD127^lowFoxP3⁺ CD4⁺ T cells after vaccination. n.p. not possible