Dengue Type 4 Virus Isolates Of New And Attenuated Strains Of Dengue JE Study On The Characteristics And Study On The Construction Of Chimeric Viruses

Whether a dengue virus can be a candidate attenuated vaccine strain should be determined on serials of experiments. Firstly, some of the in vitro markers of the virus should be clarified, such as plaque's property and temperature sensitivity and so on. Secondly, the virulence and immunity of the virus should be tested in laboratory animal. If the results are good, then the monkey's experiments can be done. If the results are also good, this virus can be considered as an available candidate attenuated vaccine strain. But whether this candidate attenuated vaccine strain can be used as vaccine or not should be dependent on the results of clinical trials.The purpose of this work is to study the biological and molecular characteristics of the two viruses, parental Ban18 strain and it's attenuated strain Ban18-30. The Ban18 strain was isolated from the mosquitoes in Xishuangbanan of Yunnan province and then it was propagated serially in primary hamster kidney cells (HKC). Ban18-30 strain is the 30^th passage virus of the parental Ban18.The neutralization assays of the two viruses were performed using the anti-DENV-4 ascites tested in BHK21 cells. The results showed that the both viruses were well neutralized by the antibody, neutralization index≥1000, indicating the both viruses were DEN-4.The plaque sizes of the two vaccines were performed using plaque assay method in BHK21 cells. The results showed that sizes of attenuated Ban18-30 virus was smaller than the parent virus Ban18.Neurovirulence of the Ban18-30 attenuated virus tested in sukling mice showed that the ic LD₅₀ of Ban18-30 was 1.71og lower than its parental virus Ban18. when tested in 9～11g mice, the results indicated that the Ban18-30 virus didn't kill any mouse by intracerebral inoculation whereas the parental Ban18 virus induced mice with high morbidity, 4.31ogLD₅₀. This result revealed that Ban18-30 virus was highly attenuated for mice.The immunogenicity of th e Ban18-30 attenuated virus was tested in 7～9g mice by a single intraperitoneal vaccination and a challenge after 14 days with the Ban18...