Virtual Poster 21st Lancefield International Symposium for Streptococci and Streptococcal Diseases 2022

Characterization of the third type of cholesterol-dependent cytolysins produced from Streptococcus mitis strains (#213)

Atsushi Tabata 1 2 3 , Airi Matsumoto 2 , Ai Fujimoto 2 , Takuya Ikeda 3 , Kazuto Ohkura 4 , Toshifumi Tomoyasu 1 2 3 , Ayuko Takao 5 , Hisashi Ohkuni 6 , Hideaki Nagamune 1 2 3
  1. Department of Bioengineering, Division of Bioscience and Bioindustry, Graduate School of Technology, Industrial and Social Sciences, Tokushima University Graduate School, Tokushima, Japan
  2. Department of Biological Science and Technology, Life System, Institute of Technology and Science, Tokushima University Graduate School, Tokushima, Japan
  3. Department of Bioengineering, Faculty of Bioscience and Bioindustry, Tokushima University Graduate School, Tokushima, Japan
  4. Division of Clinical Pharmacy and Pharmaceutical Sciences, Graduate School of Pharmaceutical Sciences, Suzuka University of Medical Science, Suzuka, Mie, Japan
  5. Department of Oral Microbiology, School of Dental Medicine, Tsurumi University, Yokohama, Kanagawa, Japan
  6. Health Science Research Institute East Japan, Kounosu, Saitama, Japan

[Background] Mitis group streptococci (MGS) is one of the opportunistic pathogens of human habitual in the oral cavity. Except for human pathogen Streptococcus pneumoniae, many of the species belonging to MGS are recognized as an opportunistic pathogen. One of the MGS, Streptococcus mitis, is also recognized as human opportunistic pathogen, however, recent reports showed that a part of strains of S. mitis possess the pneumococcal pathogenic factors. Cholesterol-dependent cytolysin (CDC) is one of these factors, such as a pneumolysin homolog named mitilysin and a five-domain type CDC named S. mitis-derived human platelet aggregation factor/lectinolysin. In the present study, we introduced the characteristics of the third type of CDC with five-domains structure produced by S. mitis.

[Methods] The recombinant of this CDC and its mutants were expressed in Escherichia coli system and prepared by Ni-affinity-chromatography. The functional characterization of the recombinant proteins was conducted by the assays for the hemolytic activity, erythrocyte aggregation activity, and the intercellular association activity between human culture cells.

[Results] The recombinant proteins of the third type of CDC recognized the dual-receptors, i.e., cholesterol and human CD59 and showed human erythrocyte preferential hemolysis. Moreover, this CDC expressed the N-terminal additional domain-dependent erythrocyte aggregation activity and intercellular association of human cells.

[Conclusions] This third type of CDC showed the human-preferential hemolytic activity and intercellular association/aggregation of human cells. Therefore, these characteristics are suggested to contribute to the potential pathogenicity of S. mitis strains producing this type of CDC.