Role of suilysin in pathogenesis of Streptococcus suis capsular serotype 2

• Published in: Microbial pathogenesis Vol. 34; no. 1; pp. 27 - 37
• Main Authors: Lun, Shichun, Perez-Casal, Jose, Connor, Wayne, Willson, P.J
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier India Pvt Ltd 2003; Elsevier
• Subjects: Aerosol challenge; Aerosols; Amino Acid Sequence; Animals; Antibodies, Bacterial - blood; Arthritis, Infectious - immunology; Arthritis, Infectious - microbiology; Arthritis, Infectious - veterinary; Bacterial Capsules - immunology; Bactericidal test; Bacteriology; Biological and medical sciences; Blood Bactericidal Activity; Cell Line - metabolism; Cell Line - microbiology; Cloning, Molecular; Cytokine production; Fundamental and applied biological sciences. Psychology; Gene Targeting; Hemolysin Proteins - genetics; Hemolysin Proteins - physiology; Humans; Male; Meningitis, Bacterial - immunology; Meningitis, Bacterial - microbiology; Meningitis, Bacterial - veterinary; Microbiology; Molecular Sequence Data; Monocytes - metabolism; Monocytes - microbiology; Organ Specificity; Organic Chemicals; Pathogenicity, virulence, toxins, bacteriocins, pyrogens, host-bacteria relations, miscellaneous strains; Pericarditis - immunology; Pericarditis - microbiology; Pericarditis - veterinary; Pharynx; Pig model; Pleurisy - immunology; Pleurisy - microbiology; Pleurisy - veterinary; Sepsis - immunology; Sepsis - microbiology; Sepsis - veterinary; Serotyping; Streptococcal Infections - immunology; Streptococcal Infections - microbiology; Streptococcal Infections - veterinary; Streptococcus suis; Streptococcus suis - classification; Streptococcus suis - genetics; Streptococcus suis - immunology; Streptococcus suis - pathogenicity; Suilysin; Swine; Swine Diseases - immunology; Swine Diseases - microbiology; Tumor Necrosis Factor-alpha - biosynthesis; Virulence; Pig model; Cytokine production; Suilysin; Aerosol challenge; Bactericidal test; Streptococcus suis; Cytolysin; Pathogenesis; Virulence; Cytokine; Natural immunity; Pig; Microorganism capsule; Streptococcaceae; Vertebrata; Mammalia; Bacteria; Micrococcales; Artiodactyla; Serotype; Ungulata
• ISSN: 0882-4010; 1096-1208
• DOI: 10.1016/S0882-4010(02)00192-4

Three suilysin (SLY) knockout mutant strains of Streptococcus suis serotype 2 were generated by allelic replacement from one North American and two European wild type strains. The mutants were characterized by Southern blot, Western blot and phenotyping. In vitro bactericidal testing showed that both wild type and SLY mutants were resistant to bactericidal factors in whole pig blood. To demonstrate the role of SLY during S. suis infection, four animal trials were carried out using young pigs. Either high dose (4×10 6 CFU/ml/pig) or low dose (0.5×10 6 CFU/ml/pig) live cell aerosol was applied to the pharynx. In one trial, a low challenge dose of North American strain SX332 and its isogenic sly − mutant strain (SX932) resulted in acute disease in 3/5 of pigs exposed to the wild type strain, while 5/5 of pigs exposed to the mutant strain survived the trial. In the repeat trial, 1/8 of pigs in wild type group and 6/8 of pigs in mutant group developed disease. The high dose trial with 332/932 pair showed that 4/8 pigs challenged with wild type and 5/8 of pigs challenged with mutant strain developed disease respectively. The third low dose trial, using European strain 31533 and its isogenic sly − mutant strain SX911, showed that 1/8 of pigs challenged with the wild type strain and 4/8 of pigs challenged with the corresponding mutant strain developed disease. All the diseased pigs showed fever, clinical signs and developed septicemia. S. suis was isolated from tissue samples such as brain, submandibular lymph node, lung, spleen, liver, heart or joint. Serum antibody titer against cell surface proteins changed little while the antibody titer against SLY increased only in the wild type group after challenge. sly gene was cloned and expressed in E. coli. The recombinant SLY (rSLY) protein showed 800 hemolysin units per μg protein. In vitro study showed that rSLY triggered TNFα production by human monocytes and IL-6 production by pig pulmonary alveolar macrophages and monocytes. Thus, the results of this study suggest that SLY does not seem to be a critical virulence factor for S. suis serotype 2 respiratory infection, but by stimulating cytokine release it may play a role in innate immunity.