Humoral immune responses inhibit the antitumor activities mediated by salmonella enterica serovar choleraesuis

Salmonella is a powerful antitumor agent owing to its tumor-targeting potential, antitumor capability, and ability to deliver therapeutic genes. Host factors including innate and adaptive immune responses play roles in Salmonella-induced antitumor activity. An emerging realization from animal models that host immune system responses to Salmonella remains uncertain. Herein, we used naive mice and Salmonella enterica serovar choleraesuis (S. choleraesuis) immunized mice to study the role of humoral immune response in the antitumor activity of S. choleraesuis. When the anti-Salmonella antibody existed, the invasion activity and gene transfer capability of S. choleraesuis were significantly decreased. Adaptive immune response inhibited S. choleraesuis to target the tumor sites in the immunized mice after systemic administration. Tumors in naive mice treated with S. choleraesuis were significantly smaller than those treated with the control vehicle. By contrast, the treatment of S. choleraesuis was not capable of delaying tumor growth and enhancing survival in experimental metastasis models in the immunized mice. Adoptive transfer of immunized serum and knockout mice experiments demonstrated that adaptive immune responses play important roles in the antitumor activity of S. choleraesuis. These findings provide the basis for future studies aiming to modulate the immune response during bacterial therapy.