A novel proteoliposomal vaccine elicits potent antitumor immunity in mice.

Therapeutic vaccination against idiotype is a promising strategy for immunotherapy of B-cell malignancies. Its feasibility, however, is limited by the requirement for a patient-specific product. Here we describe a novel vaccine formulation prepared by simply extracting cell-membrane proteins from lymphoma cells and incorporating them together with IL-2 into proteoliposomes. The vaccine was produced in 24 hours, compared with more labor-intensive and time-consuming hybridoma or recombinant DNA methods. The vaccine elicited T-cell immunity in vivo, as demonstrated by secretion of type 1 cytokines. It protected against tumor challenge at doses of tumor antigen 50 to 100 times lower than that previously observed using either liposomes formulated with IL-2 and secreted lymphoma immunoglobulin or a prototype vaccine consisting of lymphoma immunoglobulin conjugated to keyhole limpet hemocyanin. The increased potency justifies testing similar patient-specific human vaccines prepared using extracts from primary tumor samples.

Vaccine-induced tumor-specific immunity despite severe B-cell depletion in mantle cell lymphoma.

The role of B cells in T-cell priming is unclear, and the effects of B-cell depletion on immune responses to cancer vaccines are unknown. Although results from some mouse models suggest that B cells may inhibit induction of T cell-dependent immunity by competing with antigen-presenting cells for antigens, skewing T helper response toward a T helper 2 profile and/or inducing T-cell tolerance, results from others suggest that B cells are necessary for priming as well as generation of T-cell memory. We assessed immune responses to a well-characterized idiotype vaccine in individuals with severe B-cell depletion but normal T cells after CD20-specific antibody-based chemotherapy of mantle cell lymphoma in first remission. Humoral antigen- and tumor-specific responses were detectable but delayed, and they correlated with peripheral blood B-cell recovery. In contrast, vigorous CD4(+) and CD8(+) antitumor type I T-cell cytokine responses were induced in most individuals in the absence of circulating B cells. Analysis of relapsing tumors showed no mutations or change in expression of target antigen to explain escape from therapy. These results show that severe B-cell depletion does not impair T-cell priming in humans. Based on these results, it is justifiable to administer vaccines in the setting of B-cell depletion; however, vaccine boosts after B-cell recovery may be necessary for optimal humoral responses.

Human autologous tumor-specific T-cell responses induced by liposomal delivery of a lymphoma antigen.

PURPOSE: The idiotype (Id) of the immunoglobulin on a given B-cell malignancy is a clonal marker that can serve as a tumor-specific antigen. We developed a novel vaccine formulation by incorporating Id protein with liposomal lymphokine that was more potent than a prototype, carrier-conjugated Id protein vaccine in preclinical studies. In the present study, we evaluated the safety and immunogenicity of this vaccine in follicular lymphoma patients. EXPERIMENTAL DESIGN: Ten patients with advanced-stage follicular lymphoma were treated with five doses of this second generation vaccine after chemotherapy-induced clinical remission. All patients were evaluated for cellular and humoral immune responses. RESULTS: Autologous tumor and Id-specific type I cytokine responses were induced by vaccination in 10 and 9 patients, respectively. Antitumor immune responses were mediated by both CD4+ and CD8+ T cells, were human lymphocyte antigen class I and II associated, and persisted 18 months beyond the completion of vaccination. Specific anti-Id antibody responses were detected in four patients. After a median follow-up of 50 months, 6 of the 10 patients remain in continuous first complete remission. CONCLUSIONS: This first clinical report of a liposomal cancer vaccine demonstrates that liposomal delivery is safe, induces sustained tumor-specific CD4+ and CD8+ T-cell responses in lymphoma patients, and may serve as a model for vaccine development against other human cancers and infectious pathogens.