| Streptococcus suis serotype 2（S. suis 2） is an important zoonotic pathogen, which can cause swine and human meningitis, endocarditis, sepsis and toxic shock ayndrome（STSS） and other symptoms, and even death by the wound infection. It not only causes great economic losses in the pig industry worldwide, but also threat severely to the health of human. To study its pathogenic mechanism has important guiding significance for the effective prevention and control of streptococcus disease.It is found that there are two metalloproteinases including SsPepO and HP2082 in S. suis 2, which are respectively coded by gene SSU050153 and SSU052082. Earlier stage work of our laboratory had shown that SsPepO played an important role in the pathogenic process of S. suis 2, but whether HP2082 associated with its virulence remains to be seen. Bioinformatics analysis showed that SsPepO and HP2082 have 28% and 69% homology respectively with Streptococcus pneumoniae endopeptidase PepO, and the PepO in Streptococcus pneumoniae could combine the host complement protein C1 q, adjusting the immune attack mediated by complement and promoting the adhesion and invasion of Streptococcus pneumoniae to the host cell. It is presumed that the two metalloproteinases in S. suis 2 also have similar effect in the immuno-evasion process of S. suis 2. Therefore, this project takes the two metalloproteinases as the research objects, aiming to clarify their interaction with the complement protein C1 q, the role in the immuno-evasion process and the influence to the pathogenic process of S. suis 2.The experiment is studied from two aspects. On the one hand, research the effect of HP2082 on the virulence of S. suis 2 from the overall level. The results found that the growth characteristics, hemolysis activity, survival ability in blood, adhesion ability to cell and mice infected ability of the mutant strain △SSU052082 had no significant differences compared with wild strain SC19, showing that HP2082 had little influence on the virulence of S. suis 2 in mouse model. On the other hand, study the role of SsPepO and HP2082 in the immuno-evasion process of S. suis 2 from the cellular and molecular level. Through a series of interaction experiment of the two metalloproteinases with complement protein C1 q, such as complement activation, whole blood of sterilization, direct combination, cells infection and so on, the results showd SsPepO and HP2082 could activate the classical complement pathway effectively, and could combine the complement protein C1 q to promote adhesion and invasion of S. suis 2 to the host cell. |
