High-dose RHAMM-R3 peptide vaccination for patients with acute myeloid leukemia, myelodysplastic syndrome and multiple myeloma

Abstract

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 microg 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 microg 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.

Figure 1.

Immunological responses of patient #8 (see Table 1) with multiple myeloma during the course of RHAMM-R3 peptide vaccination. ELISpot assays for the release of interferon gamma (Panel A) and granzyme B (Panel B) were performed after stimulation with RHAMM-R3 peptide. Stimulation with an influenza matrix protein (IMP)-derived peptide served as a positive control, no peptide stimulation as a negative control. Peptide-specific T-cell activity was measured by interferon release, whereas granzyme B secretion indicated the lytic potential of the T-cells. An increase of RHAMM-R3 specific T-cell activity could be noted.

Figure 2.

Change in frequency of RHAMM specific CD8⁺ T cells and CD4⁺ CD25hiFoxP3⁺ regulatory T cells in the peripheral blood from patient #7 (see Table 1) with multiple myeloma during the course of RHAMM-R3 peptide vaccination. While the frequency of CD8⁺ T lymphocytes specifically recognizing RHAMM-R3 as demonstrated by tetramer binding increased, the frequency of regulatory T cells decreased.

Figure 3.

Immune responses by RHAMM-R3 specific CD8⁺ T cells and regulatory T cells of patient # 3 (see Table 1) with MDS in the course of RHAMM-R3 peptide vaccination. ELISpot assays for the release of interferon gamma (Panel A) and granzyme B (Panel B) were performed after stimulation with RHAMM-R3 peptide. Stimulation with an influenza matrix protein (IMP)-derived peptide served as a positive control, no peptide stimulation as a negative control. Peptide-specific T-cell activity was measured by interferon release, whereas granzyme B secretion indicated the lytic potential of the T cells. In this particular patient, no increase of RHAMM-R3 specific T-cell activity could be noted. In contrast, the frequency of regulatory T cells as measured by flow cytometry (Panel C) for this patient showed a relevant increase.

Figure 4.

Changes in the peripheral blood count of patient # 2 (see Table 1) with MDS during the course of RHAMM-R3 peptide vaccination. The three different lineages are marked by different symbols as indicated in the inlay box; please note also the three different scales for the y-axis. During RHAMM-R3 peptide vaccination the peripheral blood counts normalized. However, a certain decrease could be noted after cessation of vaccination therapy.