Detection of bovine viral diarrhea virus by spot hybridization with probes prepared from cloned cDNA sequences

Department of Pathobiology, College of Veterinary Medicine, University of Tennessee, Knoxville 37901-1071.

A cytopathic strain of bovine viral diarrhea virus (BVDV) was purified from infected cell culture fluids by isopycnic density-gradient centrifugation. Genomic RNA was extracted and tailed with adenine residues at the 3' end with poly-A polymerase. Double-stranded complementary DNA (cDNA) was synthesized, using the poly-A-tailed RNA as a template and oligo-dT as a primer, and then cloned into the pUC9 plasmid. Virus-specific cDNA sequences, varying in length from 0.5 to 2.5 kilobases (kb), were obtained. One BVDV-specific sequence of cloned cDNA, 1.1 kb in length and with an internal Pst I restriction endonuclease cleavage site, was selected for use as a probe. The cloned cDNA insert was removed from the plasmid either with or without flanking plasmid sequences and labeled with 32P-nucleotides by nick translation for use as hybridization probes for BVDV. The performance of probes of smaller fragments of the insert was compared to that of the intact sequence in hybridization assays. In addition, 2 methods of specimen preparation were compared to establish optimum parameters for hybridization. The hybridization assay was 10-100 times more sensitive than infectivity assays for BVDV in infected cell cultures. Freezing of specimens reduced by 10-fold the sensitivity of hybridization for BVDV target sequences. The probes prepared from the cloned cDNA hybridized with all cytopathic and noncytopathic BVDV strains tested but not with uninfected cell cultures, cellular ribosomal RNA, bovine coronavirus, bluetongue virus, or bovine adenovirus 3. Probes prepared with native plasmid DNA did not hybridize with BVDV or uninfected cell cultures.(ABSTRACT TRUNCATED AT 250 WORDS)