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Subject: Veterinary Microbiology × Author: DEEPTHI, B × Start date: 2005 ×
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    ThesisItemOpen Access
    STUDIES ON THE ANTIGENIC RELATIONSHIP BETWEEN BTV-2, 9 & 15 IDENTIFIED IN ANDHRA PRADESH
    (SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA, 2008-11) DEEPTHI, B; SREENIVASULU, D(MAJOR); SATYANARAYANA CHETTY, M; ESWARA PRASAD, P
    ABSTRACT : The presence of multiple serotypes of the midge-borne bluetongue virus and lack of effective vaccine are the major impediments in controlling bluetongue in sheep. Attempts are being made to develop the vaccine employing the available serotypes to control the disease in the state. Hence, it is essential to identify the antigenic relationship among the serotypes to identify the candidate vaccine strains to be incorporated in the preparation of vaccine. Further, interference phenomenon was also reported among the serotypes. To understand the antigenic relationship between BTV-2, 9 and 15 serotypes, the viruses were propagated in BHK21 cell lines which showed 90% of the CPE by 72 hrs. Purification of the BTV serotypes by polyethylene glycol precipitation revealed a single light scattering zone at 50-60% sucrose interface. Presence of BTV in the purified samples was confirmed by RNA extraction and observed the segmented nature of the nucleic acid. The purified virus samples of the BTV serotypes 2, 9 and 15 were used to raise hyper immune serum in rabbits. Neutralizing antibodies for the BTV serotypes were detected by day 21 PI and the titres persisted up to day 60 PI, the period under study. Maximum titres induced against BTV-2, 9 and 15 were 1:320, 1:256 and 1:640 respectively. Reciprocal cross neutralization test was employed to find out the R% values between BTV-2, 9 and 15 which indicated the extent of antigenic relationship between the serotypes. R% value between BTV-2 and BTV-9 was recorded as 2.8. R% value of 3.53 and 2.8 were observed between BTV-2 & 15 and BTV-9 & 15 respectively. The R% values recorded in the present study revealed a weak antigenic relationship between the BTV serotypes. The extent of antigenic relationship between the BTV serotypes was also determined by multiple sequence alignment of the nucleotide and amino acid sequences of the reference BTV serotypes 2, 9 and 15. The sequence analysis of the VP2 gene revealed a homology of 47-53% and 29-41% at the nucleotide and amino acid levels respectively. R% values obtained using reciprocal cross neutralization test with the BTV-2, 9 and 15 serotypes isolated in native sheep of Andhra Pradesh and the genomic analysis of the reference serotypes of BTV-2, 9 and 15 revealed very weak antigenic relationship and were highly divergent.