Surface (S) Layer Proteins of Lactobacillus acidophilus Block Virus Infection via DC-SIGN Interaction

We describe the unexpected binding of S-layer to cells devoid of DC-SIGN but also confirm that the presence of DC-SIGN was essential for S-layer’s antiviral activity. S-layer protein exerted its antiviral effect with different kinetics than mannan, a known viral inhibitor that also acts on DC-SIGN (Yu et al., 2017). Together our results suggest that inhibition of viral entry by S-layer occurs via a novel S-layer/DC-SIGN interaction. Materials and Methods Isolation of S-Layer Proteins S-layer proteins were extracted from overnight cultures of L. acidophilus ATCC 4356 cells grown in MRS medium at 37°C by using 6 M LiCl. The protein was extensively dialyzed against distilled water overnight at 4°C and after centrifugation (10,000 × g 20 min), it was suspended in sterile H2O and stored at 20°C (Beveridge et al., 1997). Purity was evaluated by SDS-PAGE, which showed a single band after Coomassie blue staining. Cell Lines and Viruses Vero cells, 3T3 cells, and 3T3 cells stably expressing human DC-SIGN (3T3 DC-SIGN) were cultured at 37°C in Dulbecco’s modified Eagle’s medium containing 10% fetal bovine serum, 100 U penicillin/ml, and 100 μg streptomycin/ml. 3T3 parental and 3T3 DC-SIGN-expressing cells were a kind gift from Vineet N. Kewal Ramani, HIV Drug Resistance Program, NCI. SFV was a well-characterized plaque-purified isolate (Glomb-Reinmund and Kielian, 1998), CHIKV was the vaccine strain 181/25, obtained fr...
Source: Frontiers in Microbiology - Category: Microbiology Source Type: research