Inhibition of interactions betweenAcanthamoeba culbertsoni trophozoites and bacteria by antibodies to a mannose-binding protein

Abstract

Introduction and Aim:Acanthamoebaacts as a reservoir for a variety of bacterial pathogens including Escherichia coli K1, Legionella pneumophila,etc., Inthis study, it was analyzed whether a polyclonal serum and a monoclonal antibody to Acanthamoeba culbertsonimannose-binding protein (MBP) could inhibit its interactions such as bacterial association, invasion and survival. Materials and Methods: In our findings, the amoeba was highly associated with E. coliO157:H7 by about 97%, but a non-pathogenic strain of E. coliDH5? was associated three-times lower than the pathogenic E. coliO157:H7. On the other hand, the association of Staphylococcus aureusand Bacillus subtiliswith the amoeba was about 60% and 65%, respectively. The polyclonal serum to MBP inhibited amoebial association with the four above said bacteria by about 35% to 40% except for non-pathogenic E. coliDH5? which had a 28% decrease as compared with untreated E. coliDH5?. On the other hand, monoclonal antibody to MBP also decreased the amoebial inhibition with bacteria, but its inhibitory effect was not as high as the polyclonal serum. After bacteria associate with the amoeba, they can be ingested or invaded into the amoeba. S. aureus and B. subtiliswere not higher than E. coliO157:H7 but 18% of the bacteria invaded the amoeba. When the polyclonal serum was preincubated with the amoeba, it inhibited the bacterial invasion of about 19% in E.coliO157:H7. On the other hand, S. aureus and B. subtiliswere inhibited by 12% and 10% by the polyclonal serum, respectively. The inhibitory effect of the monoclonal antibody was not as high as the polyclonal serum, but E. coliO157:H7 invasion was inhibited by about 13% as compared with untreated E. coliO157:H7. The invaded bacteria were subsequently incubated for one hour for survival within amoeba cytoplasm. Results: Surviving bacteria were decreasedas compared with invasion results and the decrease percentage of survived E. coliO157:H7 was about 21% as compared with invaded bacteria. However, the other two bacteria, S. aureus and B. subtilis, showed less decrease than the invaded bacteria. On the other hand, the polyclonal and monoclonal antibody showed similar decreasing patterns. Conclusion: Therefore, MBP was one of the mediators for crosstalk between A. culbertsoni trophozoites and bacteria. This study will be helpful for understanding interactions between the amoeba and bacteria via lectins, e.g., MBP. Furthermore, with characteristics of A. culbertsoni to phagocytose bacteria, MBP could be one of the very important factors for crosstalk and the understanding of pathophysiology. Keywords: Mannose-binding protein; bacteria; Acanthamoeba.