“…The beneficial effect of tumor immunotherapy by intralesional injection of transplanted intradennal tumors in guinea pigs is related to virulence, since the viable organism must grow long enough to establish a granulomatous reaction in the tumor and in regional lymph nodes, with the infection eventually being abolished (19,20). However, in experimental animals other than guinea pigs (i.e., mice, rats, and hamsters), typical BCG infection is usually progressive (17,21,22), and in these systems enhancement of malignancies has been frequently detected (9-1 1).…”