Mice were administered attenuated Salmonella typhimurium with (SalpIL2) and without a gene for human interleukin 2 (Sal-NG) 7 days before challenge with 2 × 105 OS cells via tail vein. Three weeks after injection, mice were harvested for splenic lymphocytes and tumor enumeration.
Prophylaxis with attenuated SalpIL2 significantly reduces pulmonary metastases in number and volume (P < .0001 and P < .0001) with respect to saline controls. Furthermore, splenic natural killer cell populations were increased 396 % with SalpIL2 (P < .0007) and 426 % with Sal-NG (P < .0003) compared to nontreated groups.
Host natural killer response is greatly amplified and maybe partially responsible for the effective immune response against the formation of pulmonary metastases. A single oral dose of SalpIL2 may be a novel form of adjuvant therapy for patients after early detection of primary OS.