Evaluation of prime/boost regimens using recombinant poxvirus/tyrosinase vaccines for the treatment of patients with metastatic melanoma.

PURPOSE: Two clinical trials were conducted to evaluate the clinical efficacy and immunologic impact of vaccination against the tyrosinase protein plus systemic interleukin 2 (IL-2) administration in patients with advanced metastatic melanoma. EXPERIMENTAL DESIGN: Full-length tyrosinase was employed as an immunogen to induce diverse immunologic responses against a commonly expressed melanoma antigen. Heterologous prime/boost vaccination with recombinant vaccinia and fowlpox vectors encoding tyrosinase was first explored in a randomized three-arm phase II trial, in which vaccines were administered alone or concurrently with low-dose or high-dose IL-2. In a subsequent single cohort phase II trial, all patients received the same vaccines and high-dose IL-2 sequentially rather than concurrently. RESULTS: Among a total of 64 patients treated on these trials, 8 objective partial responses (12.5%) were observed, all in patients receiving high-dose IL-2. Additional patients showed evidence of lesional regression (mixed tumor response) or overall regression that did not achieve partial response status (minor response). In vitro evidence of enhanced immunity against tyrosinase following protocol treatments was documented in 3 of 49 (6%) patients tested serologically, 3 of 23 (13%) patients tested for T-cell recognition of individual tyrosinase peptides, and 4 of 16 (25%) patients tested for T-cell recognition of full-length tyrosinase protein with real-time reverse transcription-PCR techniques. CONCLUSIONS: Whereas prime/boost immunization with recombinant vaccinia and fowlpox viruses enhanced antityrosinase immunity in some patients with metastatic melanoma, it was ineffective alone in mediating clinical benefit, and in combination with IL-2 did not mediate clinical benefit significantly different from that expected from treatment with IL-2 alone.

Quantitative real-time RT-PCR as a method for monitoring T lymphocyte reactivity to full-length tyrosinase protein in vaccinated melanoma patients.

The major goal of therapeutic cancer vaccine trials is to mediate tumor regression. However, it is critically important to devise in vitro immunological assays that correlate with clinical outcome, for use as surrogate markers of vaccine efficacy. To date, clinical emphasis has been placed on peptide vaccines, but trends towards the use of more complex immunogens such as whole proteins require the development of efficient and sensitive methods for monitoring their immunological effects. In the context of a vaccination trial using full-length tyrosinase (Ty) to immunize patients with metastatic melanoma, a monitoring technique was developed in which autologous dendritic cells (DC) infected with a recombinant adenovirus encoding the Ty protein were used to assess the Ty-specific reactivity of fresh peripheral blood lymphocytes (PBL) collected from patients at different intervals during therapy. Quantitative real-time RT-PCR (qRT-PCR) was used to measure the production of cytokine mRNA by T cells following a 2.5-h incubation with Ty-expressing DC. Two out of ten patients studied demonstrated Ty protein-specific reactivity that increased during and after the period of vaccination. While one of these patients also reacted to an HLA-A1-compatible Ty peptide, the second did not recognize any of the known Ty epitopes, highlighting the importance of this technique for monitoring the effects of complex vaccines.