| Since 2010,the TMUV has wide spread in China and caused a huge economic loss of duck industry.The TMUV route of transmission is widely,mainly includes mosquito,sparrow,and the virus could infect many kinds of animals,not only ducks,geese,chicken and mouse could also get infection.According to study,TMUV could infect mouse,and epidemiological investigation of duck industry workers in Shandong China result show that 71.9% of 132 serum samples had antibodies and 47.7% of oral swabs were positive for viral RNA,indicating possible infection in humans,TMUV pose a threat to human health.Therefore,prevention and control TMUV spread is very urgent.Not only by propagate mosquito,the TMUV also can propagate by sparrow and some birds.Because of the widely route of transmission and fast speed of transmission,it is hard to prevention and control.The TMUV has been named SDS strain was isolated from ducks and passaged serially in chicken embryo and duck embryo alternately.Passaging the virulent strain after the 61 th,after SDS-61 generation just infection the embryo but unable to cause the embryo death.In order to choose a better vaccine strain,we screen for 70 th,80th,90 th and 100 th four generations about efficacy study.Final the 70 th generation has been confirm as the vaccine strain and named SDS-70.The SDS-70 virulence is 2.46log10 median embryo infective dose(EID50)and do not contain any other viruses,bacteria or mycoplasma.In 1m L doses infect ducks,it did not induce clinical symptoms and the duck produced the high antibody and gent a good protection.After passaged five generations by ducks,it also did not induce clinical symptoms.According to the pathological results,it can be seen that most tissues and organs have no pathological changes.Only the spleen medulla appear slight haemorrhage and lighten after the time of immunity.Upon testing,the SDS-70 vaccine was pure and avirulent in 1 to 6-week-old ducks.Through immune the SDS-70 vaccine,the duck induced better immune effect to protect the ducks against the virulent SDS-10 virulent strain.The TMUV include pre M/M,E,NS1,NS2,NS2 B,NS3,NS4 A,NS4B and NS5 of nine structural proteins.Among the structural proteins,E protein play an important role in the host-specific adaption and attenuation of virus,since E protein mediated the essential functions of attachment to,and fusion with,host cell membranes.Besides,glycosylation sites play an important role in protein structure and function.Sequenced of 20/40/60/80/100 generations of whole genome,and compare with the first generation of strains.In the 80 th generation,in 154 amino acid site of E gene has a mutation from N to H.This mutation has led to a glycosylation sites disappeared in consequence of NYSA change to HYSA.The disappeared of glycosylation sites may change the construction of the virus and change the virulence of the virus.In sum,we have developed a live attenuated vaccine candidate has a good effect against duck TMUV and security for duck.In the future,we should study whether the vaccine can infect mammals. |
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