The Dynamic Distribution And Gene Immunization Of Streptococcus Suis Type 2 In Guinea Pig Model

An animal model of Streptococcus suis type 2 causing meningitis and septicaemia was established with guinea-pigs. The dynamic distribution of the bactera in guinea pigs model was investigated. The mm gene coding muraminidase-released protein (MRP) of Streptococcus suis type 2 was inserted into the plasmid pcDNA3.1(-)MycHisC to construct eukaryotic expression plasmid. The immune effect of the DNA vaccine to guinea- pigs and the function of MRP were evaluated. 1 Guinea-pig was established as an animal model, which was induced meningitis and septicaemia experimentally with isolate HA980 1 of Streptoco- ccus suEs type 2. The results showed that young guinea-pigs before weaning were susceptible. The optimum route of inoculation was determined to be hyodermic inoculation. Clinical signs and pathological changes of an acute meningitis were observed. LD50 of HA9801 to guinea-pigs had been determined. The organisms could be reisolated from the brain, cerebrospinal fluid and other organs. All of the above was same as that of piglets infected naturally. Guinea-pig model could be useful for further research on Streptococcus suis type 2 infection. 3 E~k*~ M眫i~ 2 The dynamic distribution of Jiangsu isolate HA9801 of Streptococcus suEs type 2 in guinea pigs model was investigated by the hyodermic and intranasal infections. The results showed the organisms could be reisolated from heart blood at 28 hours after hyodermic inoculation. The bacteria could be reisolated from lung, spleen and tonsil at 32 hours afler inoculation, too. Between 32?6 hours, the organisms could transmit to liver, kidney, cerebrospinal fluid and the brain. The guinea pigs suffered obvious nervous signs and were rapidly to death. It showed the reisolation positive rates of heart blood and tonsil were 61.5% and 69.2% at 120 hours. After intranasal inoculation, 50% of guinea pigs were found to have positive nasal swab at the 4th day after inoculation, 100% at the 8th day. Heart blood samples of guinea pigs were 50% positive at the 9th day, and 700/o positive at the l2th條8th day. The organisms could be reisolated from the cerebrospinal fluids and brains of the guinea-pigs which showed clinical nervous signs and death. 3 The plasmid pMRI 1 harbouring mrp gene of Streptococcus suis type 2 was transformed into E.coli and expressed protein of 136 KD. The expressed protein was used as antigen by broken E. co/i with ultrasonic disintegrator and immunized animal model guinea pigs. Immunoblotting and PPA-ELISA were used to detect specific anti-MRP antibody and the titers of anti-serum, respectively. The expressed protein could protect partly guinea pigs against Streptococcus suis type 2 infection. 4 Muraminidase-released protein gene (mrp) and extraclluar protein factor gene (epf) of Streptococcus stiEs type 2 were labeled with DIG-dUTP, respectively. Both of the probes had specificity and sensitivity. DNAs of 24 Streptococcal strains were detected by dot-blot using these probes. The results showed that the positive rates of mrp/mrp* and epf/epf?were same of 58.33% (14/24) . It showed that dot-blotting with DNA probes labled by DIG-dUTP could be used to investigate the molecular epidemiology of Streptococcus suEs type 2. 5 The mrp gene coding MRP of Streptococcus suis type 2 was inserted into the plasmid pcDNA3.1(-)MycHisC, under the cytom...