The tetraspanin CD37 is widely expressed in B-cell malignancies and represents an attractive target for immunotherapy with mAbs. We have chimerized a high-affinity mouse Ab to CD37 and engineered the CH2 domain for improved binding to human

We performed a phase I trial to evaluate the safety and tolerability of repeated skin injections of IL-2-transfected autologous melanoma cells into patients with advanced disease. Cell suspensions, propagated from excised metastases, were IL-2 gene transfected by adenovirus-enhanced transferrinfection and X-irradiated prior to injection. Vaccine production was successful in 54% of the patients. Fifteen patients (37%) received two to eight skin vaccinations of either 3 x 10(6) (intradermal) or 1 x 10(7) (half intradermal, half subcutaneous) transfected melanoma cells per vaccination (secreting 140-17,060 biological response modifier program units of IL-2/10(6) cells/24 hr). Analyses of safety and efficacy were carried out in 15 and 14 patients, respectively. Overall, the vaccine was well tolerated. All patients displayed modest local reactions (erythema, induration, and pruritus) and some experienced flu-like symptoms. Apart from newly appearing (4 of 14) and increasing (5 of 14) anti-adenovirus and newly detectable anti-nuclear antibody titers (1 of 15), recipients developed de novo or exhibited increased melanoma cell-specific delayed-type hypersensitivity (DTH) reactions (8 of 15) and vitiligo (3 of 15) and showed signs of tumor regression (3 of 15). This supports the idea of a vaccine-induced or -amplified anti-cancer immune response. None of the patients exhibited complete or partial regressions, but five of them experienced periods of disease stabilization. Three of these individuals received more than the four planned vaccinations and their mean survival time was 15.7 +/- 3.5 months as compared to 7.8 +/- 4.6 months for the entire patient cohort. These data indicate that IL-2-producing, autologous cancer cells can be safely administered to stage IV melanoma patients and could conceivably be of benefit to patients with less advanced disease.

Prolonged presence of mIFNgamma at the site of antigen presentation is crucial for the generation of systemic immune responses in the B16 melanoma model. These studies show that liposomal encapsulation of cytokines is an attractive strategy for paracrine cytokine delivery in tumor vaccine development.

Vaccination using well-characterized allogeneic tumor cell lines expressing standardized doses of immunostimulatory cytokines is an attractive alternative for autologous gene-transfected tumor cell vaccines. In the present study, we show that vaccination with irradiated allogeneic K1735 (H-2 k ) or B16F10 (H-2 b ) melanoma cells induces a moderate degree of cross-protection against the M-3 melanoma (H-2 d ) in DBA/2 mice. Cross-protection against the syngeneic tumor was markedly improved when the allogeneic vaccines were transfected with the interleukin-2 (IL-2) gene. The IL-2 gene-modified allogeneic vaccines were effective for prophylactic vaccination against subsequent tumor challenge and for therapeutic vaccination against pre-existing tumor deposits, with efficacies that were comparable with that of the IL-2 gene-modified syngeneic vaccines. Cross-protection correlated with the cytotoxic activity of splenocytes against M-3 targets. Allogeneic vaccination was not effective in another model, against the B16F10 melanoma in C57BL/6 mice, irrespective of genetic modification with the IL-2 or granulocyte-macrophage colony-stimulating factor genes. Cancer Gene Therapy (2000) 7, 870 -878

We sought to define the molecular setup of an antigen‐presenting cell that elicits antigen‐specific T cell responses in vitro using insect cells that were infected with recombinant baculoviruses. Expression of single‐chain HLA was complemented step‐by‐step with costimulatory molecules, including CD54 and CD80, by co‐infection with the relevant viruses. Role of CD8 was assessed by introducing hybrid class I molecules where the alpha‐3 domain of the HLA heavy chain molecule was replaced by its murine Kb counterpart. Circulating T cells that respond to the EBV‐derived HLA‐A2‐restricted peptide GLGCTLVAML were previously shown to bear hallmarks of memory cells. We found that the HLA+peptide complex alone displayed on the surface of insect cells was sufficient toelicit IFN‐γ secretion from these freshly isolated CD8+ T cells in ELISpot assays. Binding of CD8 was absolutely required, but coexpression of costimulatory molecules resulted only in minimal increase in the number of spots. Tumor antigen‐specific CTL clones also reacted in a strictly antigen‐specific manner, but required CD54 for quantitative responses. The amount of IFN‐γ produced by the individual reactive T cells was evaluated as spot size, and was also influenced by the costimulatory molecules: CD54 increased also the response magnitude of cultured CTL lines, while CD80 enhanced cytokine release from freshly isolated CD8+ T cells. Understanding the stimulatory requirements of functionally competent effector/memory T cells and their exact enumeration will be helpful for increasing the efficacy of vaccines.