Preparation and anti-tumor efficiency evaluation of bacterial magnetosome-anti-4-1BB antibody complex: Bacterial magnetosome as antibody carriers isolated from Magnetospirillum gryphiswaldense.

Bacterial magnetosomes (BMs) are used as carriers for antibodies, enzymes, and nucleic acids. This study aimed to demonstrate the clinical utility of BMs derived from Magnetospirillum gryphiswaldense for use in anti-tumor immunotherapy. Bis(sulfosuccinimidyl) suberate (BS3) was used to prepare BM-anti-4-1BB antibody complexes. We used syngeneic TC-1 mouse models of cancer to investigate whether BMs combined with an anti-4-1BB agonistic antibodies could enhance the therapeutic effects of anti-4-1BB antibodies in localized disease settings. Anti-4-1BB antibodies were combined with purified BMs at a concentration of 168 mg antibody per milligram BM (mg IgG/mg BM) using BS3. The anti-4-1BB antibody-coupled BMs (BM-Ab complexes) and control BMs displayed similar morphologies and measurements when examined by transmission electron microscope (TEM). In a mouse tumor model, intravenous injection of BM-Abs combined with magnetic treatment resulted in greater tumor protection than did other treatment methods (P < 0.05). These results demonstrate the in vivo anti-tumor properties of BM-Abs complexes. The coupling of anti-4-1BB antibodies to magnetosomes may have potential for clinical application to antitumor antibody therapy.