Streptococcus suis enolase functions as a protective antigen displayed on the bacterial cell surface.
BACKGROUND
Streptococcus suis serotype 2 (SS2) has evolved into a highly infectious entity, posing a great threat to public health. Screening for and identification of protective antigens plays an important role in developing therapies against SS2 infections.


METHODS
Multiple strategies were used to investigate a new surface protein that has the potential to be a protective antigen. These strategies included molecular cloning, biochemical and biophysical analyses, enzymatic assay, immunological approaches (eg, immunoelectron microscopy), and experimental infections of animals.


RESULTS
We identified an enolase gene from SS2 and systematically characterized its protein product, enolase. Biophysical data indicated that S. suis enolase is an octameric protein. Enzymatic assays verified its ability to catalyze the dehydration of 2-phospho-D-glycerate to phosphoenolpyruvate. In consideration of the strong antigenicity of enolase, an efficient enolase-based method was established for monitoring SS2 infections. Combined evidence strongly indicated that SS2 enolase can localize on the bacterial cell surface and facilitate bacterial adherence. Additionally, we found that enolase can confer complete protection against SS2 infection to mice, which suggests that enolase has potential as a vaccine candidate.


CONCLUSIONS
We conclude that S. suis enolase functions as a protective antigen displayed on the bacterial cell surface and that it can be used to develop new strategies to combat SS2 infections.
Department of Epidemiology, Research Institute for Medicine of Nanjing Command, Nanjing Normal University, Nanjing, China.
Youjun
Y
Feng
Xiuzhen
X
Pan
Wen
W
Sun
Changjun
C
Wang
Huimin
H
Zhang
Xianfu
X
Li
Ying
Y
Ma
Zhuqing
Z
Shao
Junchao
J
Ge
Feng
F
Zheng
George F
GF
Gao
Jiaqi
J
Tang
D018829:Adhesins, Bacterial / Q000737:chemistry / Q000235:genetics; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000235:genetics; D021821:Communicable Diseases, Emerging / Q000382:microbiology; D006801:Humans; D051379:Mice; D010751:Phosphopyruvate Hydratase / Q000737:chemistry* / Q000235:genetics / Q000276:immunology; D013290:Streptococcal Infections / Q000201:enzymology*; D017011:Streptococcus suis / Q000201:enzymology*; D034421:Sus scrofa; D013553:Swine Diseases / Q000382:microbiology*; D014611:Vaccination; D037521:Virulence Factors; D015047:Zoonoses / Q000382:microbiology
D018829:Adhesins, Bacterial; D000942:Antigens, Bacterial; D037521:Virulence Factors; D010751:Phosphopyruvate Hydratase