الفهرس 
Chapter I : IntroductionOnly 14 pages are availabe for public view
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Abstract
6. Bovine respiratory syncytial virus (BRSV) has been established as an important viral component in the bovine respiratory disease complex (BRDC). It has an important and serious impact on livestock industry.
Prevention of the BRSV infection as part of a herd health programme is therefore important so different approaches have been followed to develop safe and efficacious BRSV vaccines, but there are little published data regarding the efficacy of BRSV vaccination.
In the present study we have attempted to apply alternative methods for evaluation of live attenuated vaccine of BRSV to be more effective, cheaper, faster and easily applied method for evaluation the efficacy of live attenuated BRSV vaccine.
We carried out the evaluation of BRSV vaccine by the following methods:
Sterility test. 2- Identity test. 3- Safety test. 4- Potency test.
The evaluated vaccines were proven sterile and free from bacterial and fungal contamination. Safety of the prepared vaccines was detected in mice, guinea pigs and calves. The identity test was carried out to all evaluated batches by ٍVNT and RT-PCR which give positive amplification of 700 pb fragment indicating presence of BRSV, In application of potency test we applied in vitro and in vivo potency tests:
1- In vitro: (titration on T.C and IFAT).
2- In vivo: (serological tests: SNT and ELISA).
The Titration of BRSV vaccine batches in cell culture using indirect fluorescent antibody technique ( IFAT), shows different titers for 6 batches, The results of humoral immune response of 6 vaccine batches was evaluated in calves after inoculation with two doses of the vaccine with two weeks interval. Evaluation of the humoral immune response depending on the antibody titers against the virus in sera of vaccinated calves was measured using SNT and ELISA at 0, 1, 2, 3, 4, 6, 8, 12, 14, 16, 18, 20, and 24 weeks intervals post vaccination.
The obtained results showed the following:
The results of titration of 6 evaluated batches were 105.3, 105.2 ,105,104 , 104.3 and 104.6 respectively.
The humeral immune response to 1st ,2nd and 3rd BRSV vaccine batches in vaccinated calves showed that protective neutralizing serum antibody titer (0.6) started from 2nd week post vaccination, reached the highest level by 10th week post vaccination and persisted in protective level until 18 weeks post vaccination using SNT, while ELISA confirmed the results of SNT showing that positive titer started from the first week post vaccination, reached the highest level of positive titer 8th week post vaccination and persisted in high level until 24 weeks post vaccination.
The humeral immune response to 4th, 5th and 6th batches of live attenuated BRSV vaccine in vaccinated calves using SNT showed that un protective neutralizing serum antibody titer less than (0.6) till the 4th week, also ELISA showed that negative titer less than (1000) till the 4th week.
from the above studies results we can conclude that the evaluation of BRSV can be carried out via vitro techniques beside identification test and safety test, which are more economic, rapid and safe.