STUDY OF ASSOCIATION TO THP-1 CELLS OF POTENTIALLY PROBIOTIC STRAINS OF Bifidobacterium

MINNAARD, JESSICA; ROLNY, IVANNA S; ASSAD, SABRINA; PEREZ, PABLO F

Congreso; X CONGRESO ARGENTINO DE MICROBIOLOGIA GENERAL SAMIGE; 2014

Bifidobacterium are potentially probiotic microorganisms that colonized the new born intestine and they are also present in children and adult intestine where they lead to immunomodulatory effects. Since macrophages are key players in the immune response, the aim of the present study was to gain insight on the interaction between Bifidobacterium and human monocytic THP-1 cells. According to the surface properties and their ability to adhere onto cultured enterocytes, two strains were selected: B. bifidum CIDCA 5310 (high surface hydrophobicity and adhesion) and B. adolescentis CIDCA 5317 (low surface hydrophobicity and adhesion). Bifidobacteria were cultured in anaerobic conditions and the planktonic or whole (planktonic + sessile) population were used in experiments. Monocytic THP1 cells were differentiated with phorbol myristate acetate (PMA) 200 nm for 3 days. Co-incubations (THP1 cells-bacteria) were performed for 1h or 2h at 37°C at different bacteria/monocyte ratios (multiplicity of infection, MOI). Cells associated to FITC-labeled bacteria were determined by flow cytometry (FL1+ cells) and plate counts on MRS agar (Samples were treated with gentamicin to assess bacteria internalization). Flow cytometry was also used to evaluated necrosis (propidium iodide staining; FL2+ cells). Microscopy analysis revealed different interaction patterns for the two strains. Whereas strain CIDCA 5310 lead to large clusters around the phagocytic cells, strain CIDCA 5317 lead to a more diffuse interaction. Flow cytometry analysis of THP1 cells incubated 1 h with the planktonic population of bacteria (MOI=20) showed 90.10 ± 1.56 % of cells associated to strain CIDCA 5310 and 57.15 ± 0.35 % associated to strain CIDCA 5317. Results for the whole population (sessile + planktonic) microorganisms were 92.30 ± 4.80 and 12.60 ± 3.80 of cells associated (FL1 + events) to strain CIDCA 5310 and strain CIDCA 5317, respectively. For strain CIDCA 5310, MOI of 50 or higher lead to around 70 % necrosis whereas values remains similar to controls (20 %) for strain CIDCA 5317. The ratio of invading/associated bacteria was: 0.16 ± 0.10 (1 h of incubation) and 0.20 ± 0.02 (2 h incubation) for strain CIDCA 5310, whereas for strain CIDCA 5317 values were 0.15 ± 0.03 irrespectively of the timepoints considered. The results demonstrated that the interaction of bifidobacteria with THP-1 cells is strain-dependent. These findings correlate with the different surface properties previously reported for the strains under study. The strain-dependent effect of probiotic microorganisms has been demonstrated in several scientific reports. In this context, the differential interaction of microorganisms with professional phagocytic cells could be a key mechanism to shape the immune response triggered by selected strains of potentially probiotic bifidobacteria.