Complete sequence of the NS1 gene (S6 RNA) of US bluetongue virus serotype 17

Oncolytic bluetongue viruses: promise, progress, and perspectives

Humans are sero-negative toward bluetongue viruses (BTVs) since BTVs do not infect normal human cells. Infection and selective degradation of several human cancer cell lines but not normal ones by five US BTV serotypes have been investigated. We determined the susceptibilities of many normal and human cancer cells to BTV infections and made comparative kinetic analyses of their cytopathic effects, survival rates, ultra-structural changes, cellular apoptosis and necrosis, cell cycle arrest, cytokine profiles, viral genome, mRNAs, and progeny titers. The wild-type US BTVs, without any genetic modifications, could preferentially infect and degrade several types of human cancer cells but not normal cells. Their selective and preferential BTV-degradation of human cancer cells is viral dose–dependent, leading to effective viral replication, and induced apoptosis. Xenograft tumors in mice were substantially reduced by a single intratumoral BTV injection in initial in vivo experiments. Thus, wild-type BTVs, without genetic modifications, have oncolytic potentials. They represent an attractive, next generation of oncolytic viral approach for potential human cancer therapy combined with current anti-cancer agents and irradiation.

A multiplex PCR for simultaneous detection and differentiation of North American serotypes of bluetongue and epizootic hemorrhagic disease viruses

In the present study, a multiplex RT-PCR-based assay for simultaneous detection and differentiation of North American serotypes of bluetongue (BT) virus (BTV) and epizootic hemorrhagic disease (EHD) virus (EHDV) in cell culture and clinical samples was developed. Two pairs of primers (B1 and B4) and (E1 and E4) were designed to hybridize to non-structural protein 1 (NS1) genomes of (BTV-11) and (EHDV-1), respectively. The multiplex PCR-based assay utilized a single tube-PCR amplification in which EHDV and BTV primers were used simultaneously in a multiplex format. The BTV primers generated a 790 base pair (bp) specific PCR product from RNA samples of North American BTV serotypes 2, 10, 11, 13 and 17; whereas EHDV serotypes 1 and 2 or total nucleic acid extract from non-infected baby hamster kidney (BHK) cells failed to demonstrate the 790bp specific BTV PCR product. Likewise, the EHDV primers produced a 387bp specific PCR product from RNA samples of EHDV serotypes 1 and 2, but not from BTV serotypes 2, 10, 11, 13, 17 or from total nucleic acid extract of BHK cell controls. Two pairs of nested primers (B2 and B3) and (E2 and E3), internal to the annealing sites of primers (B1and B4) and primers (E1 and E4), produced a 520bp specific BTV and a 224bp specific EHDV PCR product from BTV and EHDV first amplification products, respectively. These nested amplifications increased the sensitivity of the PCR assay and confirmed the specificity of the first amplified EHDV or BTV PCR products. The described multiplex RT-PCR-based assay could be used to facilitate rapid detection and differentiation of North American BTV and EHDV serotypes and to provide a valuable tool to study the epidemiology of these orbivirus infections in susceptible animal populations.

Expression of the non-structural protein NS1 of bluetongue virus in bacteria and yeast: identification of two antigenic sites at the amino terminus

cDNA transcribed from bluetongue virus serotype 1 (Australia) dsRNA 5 coding for non-structural protein NS1 was amplified in a polymerase chain reaction and ligated downstream of the T7 RNA polymerase promoter in the bacterial expression plasmid pET-5b, as a fusion protein with glutathione S-transferase using the pGEX bacterial expression system or the metallothionein promoter in the yeast expression plasmid pYELC5. The linear epitopes bound by six monoclonal antibodies to NS1 were localised to two antigenic regions at the amino terminus by Western blots using a series of carboxy-terminal truncations of the NS1 protein overexpressed in Escherichia coli. Expression of truncated NS1 genes using the pGEX expression system in E. coli enabled a more detailed map of the two epitopes to be constructed. The first epitope is thought to lie between amino acid residues 40-59, while the second is defined by the peptide sequences flanking amino acid 96.

Nucleotide sequence of the genome segment encoding nonstructural protein NS1 of bluetongue virus serotype 20 from Australia

The nucleotide sequence of the genome segment (S6) encoding the nonstructural protein NS1 of an Australian isolate of bluetongue virus serotype 20 (BTV 20) has been determined from a series of overlapping cDNA clones synthesized using two terminal 15-mer oligonucleotides as primers. The gene consists of 1769 nucleotides with an open reading frame between nucleotides 35 and 1690 encoding a protein of 552 amino acids (molecular weight 64,506 Da; net charge -2 at pH 7). Comparison of the nucleotide and deduced amino acid sequence of this genome segment with cognate segments of isolates of BTV 1 from Australia and South Africa, and BTV 10 and BTV 17 from the United States, revealed homologies of 98%, 80%, 79%, and 79%, respectively, at the nucleotide level and 98%, 90%, 89%, and 90% identity, respectively, at the amino acid level. The data indicate that the evolutionary divergence between NS1 genes of two different Australian BTV serotypes (BTV 20 and BTV 1) is less than that between isolates of the same (BTV 1) or different serotypes from different geographical locations.

Expression of a full-length nonstructural protein NS1 of bluetongue virus serotype 17 in Escherichia coli

The relative abundance of the nonstructural protein NS1 in bluetongue virus (BTV)-infected cells, the existence of NS1 in the BTV particles and the highly conserved NS1 gene among BTV serotypes indicate the diagnostic potential of using NS1 in detecting BTV infections. In this study a NS1 gene was expressed with the T7 RNA polymerase expression system to produce a full-length NS1 protein. Sheep anti-NS1 antibodies were raised with the E. coli-produced NS1 and used to show that the NS1 proteins of the five BTV serotypes in the Unites States were immunologically indistinguishable.

Expression of bluetongue virus serotype 17 NS1 protein from a cloned gene

A full-length copy of the coding region of segment 6 from bluetongue virus (BTV) serotype 17 was constructed from five overlapping cDNA clones. The gene coding for the NS1 protein was cloned into an expression plasmid under the control of a bacteriophage T7 promoter and expressed both in vitro and in Escherichia coli BL21(DE3) cells which contain a T7 RNA polymerase gene in their chromosome. Expression in both systems resulted in the synthesis of a protein comigrating with NS1 and a minor polypeptide comigrating with another viral-induced protein, NS1a, sometimes seen in BTV-infected cells. The proteins induced in E. coli were synthesized to high levels as insoluble products.