Antigen Unnecessary For Antitumor Activity Of ALVAC-CEA B7.1 Vaccine.(Brief Article)

2001 JUN 13 - (NewsRx.com & NewsRx.net) --

by N.R. Saltmarsh, staff medical writer - An adjuvant that was proposed to enhance the efficacy of a canarypox virus vaccine for metastatic cancer has failed to pass muster.

Nevertheless, the ALVAC-CEA B7.1 vaccine, which encodes the gene for the tumor-associated antigen carcinoembryonic antigen (CEA) and for a T-cell co-stimulatory molecule, B7.1, can extend the stable disease period up to 13 months on its own, M. von Mehren and colleagues at the Fox Chase Cancer Center, Philadelphia, Pennsylvania, and the U.S. National Cancer Institute found.

The researchers tested ALVAC-CEA B7.1 with or without granulocyte macrophage colony-stimulating factor (GM-CSF) in two groups of patients with advanced CEA-expressing tumors. They had hoped that GM-CSF, which has been shown to be an effective vaccine adjuvant, would boost the activity of ALVAC-CEA B7.1.

von Mehren and coworkers vaccinated 30 patients intradermally with 4.5x10(8) plaque-forming units of ALVAC-CEA B7.1 every other week for eight weeks and 30 with an identical regimen of ALVAC-CEA B7.1 plus GM-CSF given subcutaneously for five days starting two days before each vaccination.

Biopsies of vaccine sites obtained 48 hours following vaccination revealed that the patients who received GM-CSF had a greater number of leukocytic infiltrate cells but were less likely to have a predominant lymphocytic infiltrate compared with patients who received vaccine alone.

An ELISPOT assay for the production of interferon-gamma showed that after four vaccinations, CEA-specific T-cell precursors were statistically increased from baseline measurements in HLA-A2-positive patients who received vaccine alone, while patients who received vaccine plus adjuvant had no such increase.