The success of adoptive cell transfer in the treatment of metastatic cancer in humans is dependent on the selection of highly active tumor-specific cytotoxic T cells. We report here that CTLs capture membrane fragments from their targets while exerting cytotoxic activity and thus gain a detectable functional signature by which they can be identified. Fluorochrome labeling or biotinylation was used to tag tumor cells. CD8 + T cells were coincubated with the tagged targets, sorted, and functionally evaluated. Our results show that membrane capture by CD8 + lymphocytes is T-cell receptor dependent, epitope specific, and preferentially associated with highly cytotoxic clonal subsets. CTLs that captured membranes from unmodified melanoma exhibited enhanced cytotoxic activity against tumor cell lines and autologous melanoma. In a human melanoma in vivo model, adoptive transfer of membrane-capturing, peptide-specific T cells, but not noncapturing or bulk CD8 + T cells, inhibits tumor progression. Membrane capture is therefore a signature of antigenspecific CTLs endowed with high functional avidity and may have direct relevance in the clinical application of adoptive immunotherapy.

No abstract

In this study, we tested the efficacy of amphotericin B (AmB)-arabinogalactan (AmB-AG) conjugates for the treatment of experimental leishmaniasis. Chemical conjugation of AmB to a water-soluble, biodegradable, and biocompatible polymer could present many advantages over presently available AmB formulations. Two conjugates were tested, a reduced (rAmB-AG) form and an unreduced (uAmB-AG) form. In vitro, the drug concentrations which lower the values of parasites (for promastigotes) or infected macrophages (for amastigotes) to 50% of the untreated values (ED50s) of uAmB-AG and rAmB-AG were 0.19 and 0.34 μg/ml, respectively, forLeishmania major promastigotes and 0.17 and 0.31 μg/ml, respectively, for amastigotes. The effect on Leishmania infantum-infected macrophages was more marked, with ED50s of 0.035 μg/ml for rAmB-AG and 0.027 μg/ml for uAmB-AG. In in vivo experiments, BALB/c mice injected with L. major were treated from day 2 onwards on alternate days for 2 weeks. Both conjugates, as well as liposomal AmB (all at 6 mg/kg of body weight) and Fungizone (1 mg/kg), significantly delayed the appearance of lesions compared to that in untreated mice. In addition, both conjugates, but not liposomal AmB, were significantly more effective than Fungizone. Subcutaneous injection of the conjugates (6 mg/kg) was significantly more effective than liposomal AmB in delaying the appearance of lesions. Higher AmB concentrations of up to 12 mg/kg could be administered by this route. When an established infection was treated, uAmB-AG was somewhat more effective than liposomal AmB. In summary, water-soluble polymeric AmB derivatives were found effective and safe for the treatment of leishmanial infections. The conjugates, which are stable and can be produced relatively cheaply (compared to lipid formulations), can be used in the future for the treatment of leishmaniasis infections.

No abstract

No abstract