| Mycoplasma hyorhinis(Mhr)is generally a commensal inhabitant on the mucosa of the upper respiratory tract and tonsils of swine..It is popular in the pig population and can cause multiple serositis,arthritis,pneumonia,and otitis media under certain circumstances.The occurrence of chronic inflammation leads to a decline in pig performance.At the same time,Mhr can also infect humans,which is related to the occurrence and development of gastric cancer,prostate cancer and other cancers.It is also one of the common pollutants in cell culture.In this study,we focused on the artificial pathogenesis model of Mhr and the role of glyceraldehyde 3-phosphate dehydrogenase in the pathogenesis of Mhr infection.The establishment of the challenge model is an important basis for carrying out research on pathogenic mechanisms,and development of vaccines and drugs,etc.The infection modes used in the Mhr challenge model have been reported to be different,and the tissues involved in the disease are not exactly the same.There will follow some difficulties and challenges to develop the Mhr researches.In this study,an artificial model was developed using 495 c isolate via a combination of different routes.Seven days after the infection,the experimental pigs developed clinical symptoms such as joint swelling,a slight increase in temperature,and depression.Necropsy examination was performed 21 days after the infection.Symptoms include multiple serositis and arthritis but no consolidation of the lungs.Experimental pigs can produce significant Ig M,Ig G,and s Ig A antibodies.By comparing different infection modes,we found that the symptoms of animals attacked by intraperitoneal injection,nasal drip and intravenous injection were more severe than those of animals challenged by intratracheal injection,intraperitoneal injection,intrapulmonary injection,nasal drip and intravenous injection.It suggests that the formation of systemic infection may play a key role in the pathogenesis of Mhr.Adhesion to the respiratory epithelium cells is considered the necessary prerequisite in Mhr colonization and dissemination.The second part of the study focuses on the role of glyceraldehyde-3-phosphate dehydrogenase(GAPDH)in the pathogenesis of Mhr infection.Firstly,a recombinant plasmid containing the Mhr GAPDH gene was successfully constructed and transformed into E.coli.A positive recombinant strain was successfully identified by PCR screening,and the recombinant protein,rMhr-GAPDH was induced and purified.GAPDH expression on the surface of Mhr was confirmed by flow cytometry.Indirect immunofluorescence test proved that rMhr-GAPDH protein can adhere to NCI-H292 cells.The microplate adhesion test for quantitative detection showed that rMhr-GAPDH can adhere to NCI-H292 cell membrane protein and PK cell membrane protein in a dose-dependent manner.This adhesion can be inhibited by anti-GAPDH antibody.The above results prove that GAPDH is one of the adhesion factors of Mhr.On the other hand,host fibrinolytic system is an important way for a variety of bacteria to achieve systemic infection.Based on this,the role of GAPDH in Mhr using host fibrinolytic system is further studied.Far-Western blot and ELISA showed that rMhr-GAPDH can specifically bind to plasminogen(Plg).Plg is activated to plasmin by the addition of tissue plaminogen activator(t PA).The above results show that GAPDH also functions as a plasminogen receptor(Plg R).It help Mhr utilize the host fibrinolytic system and develop systemic infections.To sum up,in this research,a model of Mhr artificial animal model was successfully established.Systemic infection was found to play an important role in pathogenesis through comparison of different infection pathways.GAPDH was identified as an adhesion factor of Mhr,and it acts as a Plg R to mediate host fibrinolytic system to promote Mhr systemic infections.The results of this study provide an important data basis for the study of the pathogenesis of Mhr. |
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