Comparison between bacillus Calmette-Guérin and the A60 mycobacterial antigen complex used as cancer-preventive immunotherapies

Preparations of live or lysates of Mycobacterium bovis strain Calmette-Guerin (BCG) have long been used as treatments for a variety of cancer types, especially those involving the urinary tract, with varying success. This study was conducted to compare the antitumoral activity of BCG and the thermostable macromolecular antigen complex of BCG (A6O) when used as preventive treatments, in conjunction with or without tumor antigens, against growth and dissemination of the EMT6 murine tumor cell line. It was demonstrated that tumor antigens alone did not significantly alter the oncological indexes, although a slight increase in both T lymphocyte and macrophage activations was found. It was further demonstrated that A6O induces a protective activity up to 40% greater than that of live BCG and that this protection was not accompanied by any of the adverse effects sometimes observed during BCG immunotherapy.