Peptide-pulsed Peripheral Blood Mononuclear Cells plus IL-12 as a Melanoma Vaccine
Peptide-pulsed Peripheral Blood Mononuclear Cells plus IL-12 as a Melanoma Vaccine
ABSTRACT & COMMENTARY
Synopsis: Peptides from MAGE-3 and MelanA that bind to HLA-A2 and stimulate in vitro T-cell responses have been identified. A phase 1 study of immunization with MAGE-3 or MelanA peptide-pulsed peripheral blood mononuclear cells (PBMCs) coadministered with various doses of recombinant human interleukin (IL)-12 was performed in HLA-A2+ melanoma patients to determine toxicity and T-cell responses of this immunization strategy. Specific CD8+ T-cell responses, low toxicity, and some limited antitumor activity following vaccination were reported. This immunization approach is clinically feasible and warrants additional clinical evaluation.
Source: Gajewski T, et al. Clin Cancer Res. 2001; 7(3 Suppl):895s-901s.
The stimulation of selective recognition and destruc- tion of melanoma cells by components of the immune system is a central goal of many melanoma treatment strategies.1-3 Achieving this goal requires that melanomas express antigens that can elicit immune responses. In addition, the immune response specific for a melanoma antigen must be able to mediate a protective and/or therapeutic effect. Extensive in vitro cellular and molecular analyses have identified melanoma-associated antigens that can stimulate T-cell responses, and many clinical trials are now in progress to determine whether effective in vivo T-cell mediated antimelanoma activity can be obtained against these melanoma-associated antigens. These antigens include the products of nonmutated genes expressed in melanoma cells and in the testis, such as the MAGE antigens, as well as differentiation antigens such as MelanA that have differential expression on melanoma cells compared with normal tissue.4 While the optimal strategy to vaccinate patients with these antigens remains unknown, the role of IL-12 has been suggested as an important cytokine for stimulation of antigen-specific immunity.5
This phase 1 study by Gajewski and colleagues evaluated HLA-A2+ melanoma patients to determine the toxicity and immunologic activity of vaccination with MAGE-3 or MelanA peptide-pulsed autologous PBMCs plus various doses of recombinant IL-12. Patients were required to have metastatic disease, a tumor biopsy demonstrating expression of either MAGE-3 or MelanA by RT-PCR, and no requirement for immunosuppressive medications. The vaccine was available by obtaining 100-150 mL of heparinized blood prior to treatment and isolating PBMCs by centrifugation over a density gradient. The PBMCs were incubated with either MelanA (27-35) peptide (AAGIGILTV; 50 mL) or MAGE-3 (271-279) peptide (FLWGPRALV; 20 mL) for 1 hour, followed by irradiation (2000 rads) of the pulsed cells (~ 108 total). The vaccine was administered as a subcutaneous (SC) injection, and IL-12 at the assigned dose level (0, 30, 100, or 300 ng/kg/dose) was injected SC adjacent to a vaccine site on days 1, 3, and 5 of each cycle. Cycles were repeated every 3 weeks, and disease status was assessed every 3 cycles. An aliquot of the PBMCs was obtained at the time of vaccine preparation to fractionate CD8+ and CD8- T-cell populations for cryopreservation and subsequent immunologic assays.
A total of 15 patients were enrolled into the study and received MAGE-3 (7 patients) or MelanA (8 patients) either alone (4 patients) or together with IL-12 (either 30, 100, or 300 ng/kg/dose; 3, 4, and 4 patients, respectively). The overall clinical outcome included 1 complete response, 1 partial response, 4 mixed responses, 1 stable disease, and 8 patients with progressive disease. Toxicity was minimal and consisted primarily of grade 1 fatigue and fever in the cohorts of patients receiving IL-12 dose levels of 0, 30, or 100 ng/kg/dose. Toxicity was more severe in the IL-12 dose level of 300 ng/kg/dose with all patients experiencing grade 2-3 fatigue or myelosuppression. Specific T-cell reactivity against the immunizing peptide (either MAGE-3 or MelanA) was assessed by measuring peptide-specific interferon-gamma production by purified CD8+ T-cells prior to each immunization and after the third treatment. Increases in interferon-gamma producing CD8+ T-cells were seen following vaccination in several patients: 1 receiving no IL-12; 3 receiving 30 ng/kg/dose; 3 receiving 100 ng/kg/dose; and 1 receiving 300 ng/kg/dose at each of the IL-12 dose levels. In 2 patients with progressively growing tumors following vaccination, biopsies of the growing tumors were analyzed and shown by RT-PCR to be negative for the antigen used in the vaccine. Gajewski et al concluded that vaccination with peptide-pulsed PBMCs plus IL-12 induces specific immunity and has clinical activity. The development of polyepitope vaccines was suggested for future evaluation.
Comment by Mark R. Albertini, MD
The use of defined antigen vaccines for melanoma immunotherapy offers several potential advantages over the use of melanoma cell vaccine approaches. A defined peptide or gene therapy vaccine would be specific and only contain the "relevant" antigen as a melanoma vaccine. Thus, additional "irrelevant" antigens that are present in intact melanoma cells would not be part of the vaccine. Potentially immunosuppressive cytokines produced by intact melanoma cells would likewise not be part of the vaccine. A defined vaccine preparation for a given patient, perhaps dependent on the HLA type of the patient, could also make this type of vaccine a practical option for melanoma patients. Several clinical studies have reported antitumor activity and/or T-cell immunity in melanoma patients receiving defined antigen vaccine approaches.6,7 Thus, significant enthusiasm is present for the clinical testing of defined antigen approaches for melanoma patients.
The current report by Gajewski et al demonstrates the clinical feasibility of a vaccine strategy using peptide-pulsed autologous peripheral blood mononuclear cells plus IL-12. The demonstration of some clinical activity in this small phase 1 study is encouraging. While increases in peptide-specific T-cell responses were seen in patients following immunization, the assay for peptide specific responses required an initial period of in vitro stimulation prior to the analysis for peptide-specific responses. Additional assays, such as assays for intracellular cytokine production, may allow for analysis for peptide-specific responses without requiring significant additional in vitro culture of the T-cells.8 The magnitude of the T-cell stimulation with this approach will require further analysis with a greater number of patients being treated with a similar vaccine dose.
In conclusion, vaccination with peptide-pulsed PBMCs plus IL-12 induced peptide-specific T-cell responses in some melanoma patients. The dose of IL-12 required for this vaccine has low toxicity, and the peptide-pulsed PBMC vaccine can be easily prepared. Further testing in melanoma patients is needed to better define the activity of this approach.
References
1. Moingeon P. Vaccine. 2001;19:1305-1326.
2. Sznol M. PPO Updates. 1999;13(7):1-14.
3. Pardoll D. Nature. 1998;4(Suppl):525-531.
4. Kawakami Y, et al. PPO Updates. 1996;10(12):1-20.
5. Trinchieri G. Annu Rev Immunol. 1995;13:251-276.
6. Lee P, et al. Nature. 1999;5(6):677-685.
7. Rosenberg S, et al. Nature. 1998;4(3):321-327.
8. Holden T, et al. Clin Cancer Res. 2001;7(Suppl): 902S-908S.
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