Extraction, Isolaion And Preliminary Structural Characrerixation Of Different Serotype Capsular Polysaccharides From Streptococcus Suis

Streptococcus suis is a facultative anaerobic Gram-positive bacteria, which can cause a variety of pig and human diseases. Capsular polysaccharides have anti-phagocytic activity and play an important role in the pathogenesis of Streptococcus suis. Therefore, many scholars are trying to explore ways to prevent these diseases. The capsular polysaccharide-based vaccine development work is ongoing. In this paper, three serotypes of immune activity of pure capsular polysaccharides T₁, T_1/2 and T₁₄, were extracted from Streptococcus suis serotypes 1, 1/2 and 14 capsular polysaccharides by a variety of extraction and separation techniques and immunological detection methods. And physical and chemical properties of each component (sugar content, protein content, sialic acid content, monosaccharide composition, molecular weight, etc.) were analyzed. Through used a variety of chemical analysis and modern instrumental analysis techniques, preliminarily determined Streptococcus suis serotypes 1/2 and 14 capsular polysaccharide chemical structure.Different enzymolysis and step precipitation of calcium methods followed by static culture of Streptococcus suis serotypes 1, 1/2 and 14 were extracted, and the extracted capsular polysaccharide fractions CPS₁, CPS_1/2 and CPS₁₄ were carried out preliminary analysis of the physical and chemical properties respectively. CPS₁, CPS_1/2 and CPS₁₄ were further purified by Q sepharose F.F. and Sephacryl S-300, and T₁, T_1/2, T₁₄ were proved to be Streptococcus suis serotypes 1, 1/2 and 14 capsular polysaccharides by Dot-ELISA, respectively. Their molecular weights were estimated as 262.5 kD, 512.7 kD and 487.4 kD, respectively. Sugar content was 29.3%, 96.6% and 53.5%, respectively. Protein content was 3.1%, 4.3% and 0.5%, respectively. The sialic acid content ratio of T₁, T_1/2 and T₁₄ was 1:2.67:0.19. The method of PMP-HPLC and TLC analysis showed that, The molar ratio of T₁ monosaccharide composition is Gal:GlcN:Glc:Rha:GalN=1:1.46:0.79:2.13:0.27. The molar ratio of T_1/2 monosaccharide composition is Gal:GlcN:Glc:Rha:GalN=1:0.63:0.6:0.43:0.56. The molar ratio of T₁₄ monosaccharide composition is Gal:GlcN:Glc:Rha =1:0.46:0.34:0.08. A more systematic study of chemical structure of T_1/2, T₁₄ and its corresponding product (named DT_1/2, DT₁₄) after removal of sialic acid were elucida- ted by chemical analysis methods and modern spectroscopic techniques, such as IR,NMR and GC-MS. The results showed that T_1/2 is mainly composed of four structural units, namely→3,4)Gal-(1→, Gal-(1→,→3,4)Rha-(1→,→3)Glc-(1→, and containing little→2,3)Rha-(1→,→4)Rha-(1→branches. T₁₄ is mainly composed of three structural units, namely Gal-(1→,→3,6)Gal-(1→,→3)Glc-(1→,and containing little→2,4)Rha-(1→branches. In addition, this study also received T₁-1, T_1/2-B, T₁₄-B and T₁₄-C polysaccharide, and physical and chemical properties of each component (sugar content, protein content, sialic acid content, monosaccharide composition, molecular weight, etc.) were analyzed.The research of the Streptococcus suis capsular polysaccharide is focused on serotype 2, and the same pathogenic Streptococcus suis serotypes 1,1/2 and 14 are less reported, especially for its purification and structural analysis. In this paper, Streptoc- occus suis serotypes 1, 1/2 and 14 capsular polysaccharides (T₁, T_1/2 and T₁₄) and their associated non-immunogenicity of polysaccharides (T₁-B, T_1/2-B, T₁₄-B and T₁₄-C) were conducted a preliminary study, through the systematic research of Streptococcus suis serotypes 1/2 and 14 capsular polysaccharide chemical structures, so as to provide more clues and evidence for the capsular polysaccharide-based vaccine, thus promoting the future development of multivalent vaccines and conjugate vaccines.