Complete Genomic Sequence of Bluetongue Virus Serotype 1 from China

Abstract

We report here the complete genomic sequence of the Chinese bluetongue virus serotype 1 (BTV1) strain SZ97/1. This work is the first to document the complete genomic sequence of a BTV1 strain from China and represents the second complete sequence of BTV1 in the world. The sequence information provided here will help determine the geographic origin of Chinese BTV1 and provide data to facilitate future analyses of the genetic diversity and phylogenetic relationships of BTV strains.

GENOME ANNOUNCEMENT

Bluetongue virus (BTV) is the type species of the genus Orbivirus, within the family Reoviridae (6). The genome of BTV consists of 10 linear double-stranded RNA segments encoding the seven structural proteins (VP1 to VP7) and three nonstructural proteins (NS1, NS2, and NS3/NS3a) (4, 5, 7, 8, 10). Twenty-four BTV serotypes have thus far been recognized in the world, and a putative 25th serotype has recently been proposed (BTV25) (1). Since 1979, seven BTV serotypes (BTV1, BTV2, BTV3, BTV4, BTV12, BTV15, and BTV16) have been isolated in China (2, 9, 12). BTV serotypes 1 and 16 are the two most prevalent serotypes in China, and each serotype causes a disease with obvious clinical signs in infected sheep. To date, only one full genomic sequence of a BTV1 strain has been reported (3). There have been no reports, however, describing the full genomic sequence of BTV1 strains isolated from China or other locations. It is necessary to acquire and analyze additional complete genomic sequences of BTV1 strains to study the molecular features of BTV1 strains and establish phylogenic relationships among BTV serotypes.

In the present study, we report the full genomic sequence (including noncoding regions) of the serotype 1 BTV strain SZ97/1, which was isolated from the blood of a sheep that showed obvious signs of bluetongue disease in Yunnan Province of China in 1997. Viral double-stranded RNA (dsRNA) preparation, full-length cDNA synthesis, PCR amplification, cloning, and sequencing of SZ97/1 were performed according to the protocol described by Yang et al. (11).

The nucleotide sequences of the 10 SZ97/1 segments were determined. The nucleotide length of SZ97/1 segments 1 through 10 are as follows: segment 1, 3,944 bp; segment 2, 2,940 bp; segment 3, 2,772 bp; segment 4, 1,981 bp; segment 5, 1,772 bp; segment 6, 1,635 bp; segment 7, 1,156 bp; segment 8, 1,125 bp; segment 9, 1,049 bp; and segment 10, 822 bp. The lengths of the 10 proteins of SZ97/1 are as follows: VP1, 1,302 amino acids (aa); VP2, 961 aa; VP3, 901 aa; VP4, 644 aa; VP5, 526 aa; VP6, 329 aa; VP7, 349 aa; NS1, 552 aa; NS2, 354 aa; NS3/NS3a, 229/216 aa. We compared the SZ97/1 sequence with the genomic sequence of the only previously published report of a BTV1 strain (GenBank accession numbers FJ969719 to FJ969728), which was determined from a virus isolated in South Africa (3). The SZ97/1 BTV1 strain differed from the South African BTV1 isolate at 10 nucleotide positions which encoded only four amino acid changes, suggesting that the Chinese BTV1 is closely related to South African BTV1.

The data presented here are the first to report the complete sequence of a BTV1 strain isolated in China and represent only the second complete sequence of BTV1 in the world. These data will facilitate future investigations of the molecular characteristics and geographic origins of BTV1 strains from China as well as other countries.

Nucleotide sequence accession numbers.

The full genomic sequence of the BTV1 strain SZ97/1 was deposited in GenBank. The accession numbers JN848759 to JN848768 correspond to SZ97/1 segments 1 through 10, respectively.