Preliminary Study On Thermotolerant Form Of Swine Enzootic Pneumonia Attenuated Vaccine

Swine Enzootic Pneumonia,also known as Mycoplasma Pneumonia of Swine,is a kind of chronic respiratory disease caused by Mycoplasma hyopneumoniae.The infection rate of SEP is extremely high regardless of the season.Generally,most infectors among fattening and adult,swine are asymptomatic while sow can suffer acute attack during latter half of gestation.Mhp can give rise to organized pneumonia with gasp as the clinical symptom after colonizing the ciliated epithelium cells.At this time,swine always possess a low FCR and can continues sends severe complications,which can lead to death and great economic losses.The eradication of SEP should focus on improving the management and implementing vaccination.Several commercial vaccines,including imported inactivated vaccine and homebred attenuated live vaccine,are available for use.However,imported inactivated vaccines are always expensive and need complex immunization schedule,while homebred attenuated live vaccines rely on a cold chain under-15? to store and transport.They are rarely used in domestic pig farms.This experiment is looking forward to produce a thermostable SEP attenuated live vaccine which can resist ambient storage.The research methods mainly used are formulation screen,technological parameter optimization and stability test.And the evaluation criterions of the vaccine are product shape,titer loss under 37? residual moisture content,physical property and shelf life.From this study,we finally produced several vaccine with qualified appearance and well heat-resistant quality,which provided a preliminary basis for the further research on live vaccine for ambient storage.Experiment I Screening of thermostable formulation for SEP attenuated live vaccine.The applying of thermostable protectant can both provide protection for antigen during drying process and improve stability of the vaccine.Firstly,we selected FD formulation D6?D8 based on previous experiment,and designed VFD formulation P1,P3,P6,P7,P8,T3,Z1,Z2,Z3,Z4,W1,W2,W3,W4 and W5 to participate in primary screen.Via calculating the titer loss of each formulation-made vaccine 10 days placing in 37? condition,we got the basic formulation D6,P7 and Z4.Then we did a single factor experiment.Formulation D6,P7,P7-3X and P7-4X stood out from 41 formulations using the same evaluation criterions of the primary screen,with each titer loss is 0.50LgCCU50/1.0mL,0.75LgCCU50/1.0mL,0 and 0.5 LgCCU50/1.0mL.Experiment ? Technological parameter optimization of SEP attenuated live vaccine manufacturing technologyBefore parameter optimization,we found that the activity of Mhp is more influenced by vitrification-built damage of VFD rather than FD and high permeable pressure.Then we improved vaccine shape by primary drying parameter optimization,and promoted vaccine thermal endurance properties by stability drying parameter optimization.After parameter optimization,D6 formulation vaccine got no drying loss and a thermostable loss of 0.375 LgCCU50/1.0mL after 10 days placing in 37? condition.P7-3X formulation vaccine got a drying loss of 0.5 LgCCU50/1.0mL and no thermostable loss after 30 days placing in 37?condition.Experiment ? Stability test of thermostable SEP attenuated live vaccinePhysical property tests were done on D6?P7 formulation vaccine by DSC,XRD and SEM.The results showed that vaccines were in a stable amorphous state with high Tg.Then we tested the repeatability of this research and the shelf life of our products.Results show,D6 formulation vaccine possesses ?20days shelf life under 37?,12 days under 45 ?.P7 formulation vaccine produced by basic procedure possesses>15days shelf life under 37?,?9 days under 45?,and no titer loss under 15? over 59days.The best thermostable vaccine was using procedure SDIV with P7-3X formulation.It only has a insignificant loss as 1.0LgCCU50/1.0mL,under 37? over 59 days.These results have a remarkable superiority compared with commercial vaccine——ZhiBining.