Our approach, which crosslinks the antibody to the surface-exposed SPA, shows not only a better uptake of the targeted bacteria by the tumor (already 24 h post

intravenous injection), but is also more versatile, since it requires only a specific antibody against a cell surface-exposed ligand to specifically target the bacteria to the ligand-producing cells. Whether these bacteria will be subsequently internalized by the target cells will presumably depend on the cell receptor recognized by the antibody. A769662 Conclusions Certainly, further studies are needed to test this promising cell targeting technology for possible therapeutic applications (e.g. drug delivery to selected cells) but the experiments shown here successfully demonstrate the proof of principle of the approach. Methods Ethics Statement All animals experiments were carried out in accordance with protocols approved by the Regierung von Unterfranken, Germany. Bacterial strains, plasmids, media and growth conditions All strains and plasmids used are listed in Table 1. E.coli DH10b was used for all plasmid DNA manipulations. Competent Lm cells were Selleckchem SAHA HDAC prepared and transformed by electroporation as described by Park and Stewart [30]. All experiments were performed with Lm grown to mid-logarithmic growth phase (OD600 =

0.8) at 37°C cultivated in brain heart infusion (BHI, BD Difco, USA). In experiments indicated, addition of amberlite XAD-4 to the BHI media led to the upregulation of SPA expression Olopatadine in mid-logarithmic phase by activating PrfA and thus listeriolysin promoter P hly . Bacteria were washed twice in 0.9% NaCl (Applichem, Germany) solution, resuspended in 20% v/v glycerol (Applichem, Germany) in 0.9% NaCl solution and stored as aliquots at -80°C. Bacterial

CFUs were determined by plating serial dilutions on BHI agar plates supplemented with 5 μg/ml tetracycline (Sigma, Germany). Table 1 Bacterial strains and plasmids Strains and plasmids Relevant genotype Reference or source L. monocytogenes EGD-e ΔtrpS × pFlo-trpS wild-type T. Chakraborty (PS-341 in vitro University of Giessen, Germany [36] ΔtrpS,inlA/B × pFlo-trpS   [32] Lm-spa- ΔtrpS,aroA,inlA/B × pFlo-trpS This work Lm-spa+ ΔtrpS,aroA,inlA/B,int::Phly-spa × pFlo-trpS This work ΔtrpS × pSP0-PactA-gfp   [36] Lm-spa- × pSP0-P actA -gfp ΔtrpS,aroA,inlA/B × pSP0-PactA-gfp This work Lm-spa+,aroA+ × pSP0-P actA -gfp ΔtrpS,inlA/B,int::Phly-spa × pSP0-PactA-gfp This work Lm-spa+ × pSP0-P actA -gfp ΔtrpS,aroA,inlA/B,int::Phly-spa × pSP0-PactA-gfp This work Plasmids pFlo-trpS TcR, [36] pSP0-PactA-gfp EmR, gfp-ORF, actA-promoter [36] pLSV101intAB EmR, ORIts, mutagenesis plasmid [31] pLSV101intAB::P hly -spa spa-ORF, hly-promoter This work Plasmid and strain construction To amplify the spa gene from S.