Durable carcinoembryonic antigen (CEA)-specific humoral and cellular immune responses in colorectal carcinoma patients vaccinated with recombinant CEA and granulocyte/macrophage colony-stimulating factor

Abstract

Purpose: Previous studies have indicated that carcinoembryonic antigen (CEA) might be a suitable immunotherapeutic target in colorectal carcinoma (CRC). The aim of the present study was to analyze the immunological and clinical effects of vaccination with CEA together with the adjuvant granulocyte/macrophage colony-stimulating factor (GM-CSF).

Experimental design: Twenty-four resected CRC patients without macroscopic disease were immunized seven times with recombinant CEA at four different dose levels over a 12-month period. Half of the patients received GM-CSF (80 microg/day for 4 consecutive days) at each immunization. Patients were monitored immunologically for 36 months and clinically for 76 months. T-cell response was evaluated by a [(3)H]thymidine incorporation assay, and IgG response was determined by ELISA.

Results: Minor local side effects were common. All 12 patients (100%) in the GM-CSF group developed a CEA-specific T-cell as well as an IgG response. The corresponding figures in the CEA alone group were 9 of 12 (75%) and 8 of 12 (66%), respectively. GM-CSF significantly augmented the amplitude of the T-cell response and the IgG titers. No dose-response relationship was noted. The immune responses at 12 months persisted 24 months after the last vaccination. Anti-CEA IgG titers were associated with increased survival (P < 0.05), whereas standard prognostic factors had no relationship, with the exception of serum CEA value.

Conclusions: Vaccination with recombinant CEA and GM-CSF appears to be a nontoxic regimen inducing potent and durable antigen-specific IgG and T-cell response. The results of this study justify more extensive trials with recombinant CEA protein for immunotherapy of CRC.