Degree Type

Thesis

Date of Award

1-1-1997

Degree Name

Master of Science

Department

Veterinary Microbiology and Preventive Medicine

Major

Veterinary Microbiology

Abstract

The ORF 3 and 3.1 genes of PRCV isolate NVSL 5170 were intact with only 2 nucleotide differences in this region when compared to TGEV isolate VMRI 5170. However, the first different nucleotide in the 3.1 gene of NVSL 5170 created a stop codon which may have resulted in a truncated 3.1 protein. In conclusion, TGEV isolate VMRI 5170 and PRCV isolate NVSL 5170 are closely related to each other in both antigenic and genetic properties as well as biological characteristics. In addition, Phylogenetic analysis of the sequences demonstrated a very close relationship among these two isolates and presented strong evidence that PRCV isolate NVSL 5170 emerged from TGEV isolate VMRI 5170 by a single deletion. This deletion could possibly be the cause of the smaller S glycoprotein and the smaller plaque size of PRCV isolate, NVSL 5170.The S gene of the TGEV isolate VMRI 5170 showed a 96-97% homology with the published sequences of TGEV, with 120-169 nucleotide differences. The identity between the S gene sequence of the PRCV isolate NVSL 5170 and that of other PRCV isolates was also 96-97%. The PRCV isolate NVSL 5170 had a truncated S gene with a 714 nucleotide deletion. This is the largest deletion detected thus far in PRCV isolates. Without accounting for the deletion, TGEV isolate VMRI 5170 and PRCV isolate NVSL 5170 showed a very high level of homology in the S gene with only 6 nucleotide differences between all 4353 nucleotides. At the amino acid level, the difference was only 4 amino acids. The protein profiles of these isolates by radioimmunoprecipitation assay also confirmed that the M and N proteins of TGEV isolate VMRI 5170 and PRCV isolate NVSL 5170 were similar in size but the S glycoprotein of PRCV isolate NVSL 5170 was smaller.A TGEV isolate, VMRI 5170, and a PRCV isolate, NVSL 5170, originating from a TGE outbreak on a swine farm in 1995, were characterized biologically, antigenically and genetically. Their growth characteristics were compared with the standard Miller strain of TGEV. The growth curves for the three viruses were similar. However, the average plaque size of the PRCV isolate NVSL 5170 (0.99 +/- 0.31 mm) was smaller than that for the TGEV isolate VMRI 5170 (2.33 +/- 0.56 mm) and the TGEV isolate Miller (2.47 +/- 0.50 mm). These isolates reacted in virus neutralization tests with both hyperimmune sera raised against the Miller strain of TGEV and the MAbs against the conserved epitopes on the S glycoprotein of TGEV. For genetic characterization of these isolates, the S and 3/3.1 genes were sequenced and compared with known sequences of TGEV and PRCV isolates.

Copyright Owner

None None

Language

en

OCLC Number

38850001

File Format

application/pdf

File Size

88 pages

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