ACTIVE IMMUNIZATION OF HUMAN OVARIAN-CANCER PATIENTS AGAINST A COMMON CARCINOMA (THOMSEN-FRIEDENREICH) DETERMINANT USING A SYNTHETIC CARBOHYDRATE ANTIGEN

In a phase I study, ten ovarian cancer patients with extensive metastatic disease despite chemotherapy were immunized three to eight times subcutaneously with the synthetic form of the immunodominant disaccharide (beta-Gal1 --> 3-alpha-GalNAc) of the Thomsen-Friedenreich antigen conjugated to KLH (TF-alpha-KLH) plus DETOX adjuvant. Six patients were given a "low" dose of TF-alpha-KLH (100-mu-g/injection) and four patients were given a "high" dose (500-mu-g/injection). All patients received a single low-dose cyclophosphamide treatment (200 mg/m2 i.v.) 3 days prior to commencement of the series of immunizations. Immunizations were 2 weeks apart. Little or no toxicity was noted. As expected, all patients (prior to immunization) had naturally occurring IgM antibodies against the synthetic TF-alpha hapten. None of the patients had detectable pre-existing IgG or IgA antibodies against synthetic TF-alpha hapten. Nine of the ten ovarian cancer patients showed a significant increase in IgM titer above pre-existing levels following immunizations with TF-alpha-KLH plus DETOX adjuvant. These same patients also produced IgG anti-TF-alpha and eight of these also produced IgA anti-TF-alpha, although the IgA responses were weaker. Most of the IgG responses followed the IgM responses by 2-4 weeks. Two patients produced a vigorous IgG response after their first TF-alpha-KLH injection, suggesting a recall response. Both direct ELISAs on various solid-phase synthetic carbohydrate antigens and hapten inhibition experiments confirmed the TF-alpha hapten specificity of the antibodies. IgM and IgG anti-TF-alpha-specific antibodies reacted with natural TF antigen, by ELISA and FACS analysis, although the titers were generally lower than the titers against the immunizing TF-alpha hapten. Increased levels of cytotoxic antibodies against TF-expressing tumor cell targets were detected in eight of the ten patients following immunization. One patient who had no detectable cytotoxic antibodies prior to immunization developed increasingly strong cytotoxic antibodies as a function of the number of immunizations. The low antigen dose patients showed as good or better humoral immune responses than the high antigen dose patients. All four high-dose and four of six low-dose patients developed moderate to strong DTH reactions at the vaccination sites. Our results demonstrate that KLH is an acceptable carrier for carbohydrate haptens in humans and that DETOX is an appropriate nontoxic adjuvant for the generation of high-titer specific anticarbohydrate responses in human cancer patients. To our knowledge, this is the first demonstration that synthetic carbohydrate antigens can be used to generate an immune response in humans against a clinically relevant cancer-associated antigen.