Existence and characterization of allelic variants of Sao, a newly identified surface protein from Streptococcus suis.
Surface antigen one (Sao) is a newly identified protein from the major zoonotic pathogen, Streptococcus suis. In search of functional proteins related to the pathogenesis of Chinese S. suis 2 (SS2), unexpectedly, a variant of Sao protein was obtained. To test its prevalence in S. suis, PCR assay was adopted to address the coding genes systematically. It was found that there are three allelic variants of sao gene, namely sao-S, sao-M, and sao-L based on the different lengths of the genes (approximately 1.5, approximately 1.7, and approximately 2.0 kb, respectively). These differences were determined to be caused by heterogeneity within the number of C-terminal repeat sequences (R), which had been seen as a pathogenicity-related domain in the plant pathogen, Xanthomonas oryzae. Two variants (sao-M and sao-L) were only found in SS2. All three variant proteins were prepared in vitro and their biochemical and biophysical properties were characterized. A soluble form of Sao-M protein was then used as a capture antigen to develop an enzyme-linked immunosorbent assay method to detect antibodies against SS2 in convalescent pig sera. Taken together, the results exhibit the properties of Sao proteins and provide an efficient Sao-M-based method for monitoring SS2 infection.
Feng
Youjun
Y
Center for Molecular Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
Zheng
Feng
F
Pan
Xiuzhen
X
Sun
Wen
W
Wang
Changjun
C
Dong
Yaqing
Y
Ju
Ai-ping
AP
Ge
Junchao
J
Liu
Di
D
Liu
Cuihua
C
Yan
Jinghua
J
Tang
Jiaqi
J
Gao
George F
GF
D000483:Alleles; D000595:Amino Acid Sequence; D000942:Antigens, Bacterial / Q000032:analysis* / Q000737:chemistry / Q000235:genetics*; D000954:Antigens, Surface / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D005798:Genes, Bacterial; D014644:Genetic Variation; D008565:Membrane Proteins / Q000032:analysis* / Q000737:chemistry / Q000235:genetics*; D008969:Molecular Sequence Data; D017011:Streptococcus suis / Q000235:genetics / Q000276:immunology*
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D008565:Membrane Proteins