Bombyx mori bidensovirus (BmBDV) has been identified as causing chronic densonucleosis in Bombyx mori specifically. The replication mechanism of BmBDV remains unknown. Its genome comprises two single stands DNA (VD1 and VD2). In order to rescue infectious virions in vitro, we obtained the total viral DNA extracted from the BmBDV-infected larvae midguts, subsequently cloned the full-length sequence of BmBDV genome fragments by PCR and constructed recombinant plasmids pMD18T-VD1 and pUC-VD2. The linear genome fragments were obtained by digesting recombinant plasmids with corresponding restriction enzymes, and then collectively transfected BmN cells by the method of liposome-embedding. We determined the replication of the virus gene by PCR with the template of demethylated total DNA extracted from the post-transfect BmN cells. Meanwhile, we collected the total proteins from the post-transfect BmN cells and the larvae midgut of feeding the post-transfect BmN cells to perform Western blotting analysis, and detected the expression of viral genes. Here we firstly confirm that infectious virions can be rescued in BmN cells by linear co-transfect method.
Animals ; Bombyx ; DNA, Viral ; Densovirus ; growth & development ; Larva ; Transfection ; Virion ; Virus Cultivation

An artificial intron consisting of the 5'-donor site (from the first intron of the human beta-globin gene) and the 3'-acceptor site (from the intron of an immunoglobulin gene heavy chain variable region) was obtained with a splice overlap extension PCR and was then inserted in frame into the coding sequence of nostructural protein NS1 gene fused to GFP gene in a recombinant mosquito densovirus plasmid p7NS1-GFP. The constructed plasmid was named as p7NS1-Intron-GFP. The plasmid p7NS1-Intron-GFP was co transfected with the helper plasmid pUCA into C6/36 cells, then the packaged recombinant and wild type viruses were purified and recovered. The second-instars of Aedes albopictus larvae were exposed to recombinant and wild type virus mixed stock. The high level GFP expression in C6/36 cells and larvae was observed under fluorescence microscope, indicating that the inserted artificial intron exerted its normal function in self-splicing both in vitro and in vivo. This study laid a foundation for application of an artificial intron in insect cells and development of new strategy for genetic engineering technology of mosqtuito and its pathogens.
Animals ; Cell Line ; Culicidae ; genetics ; virology ; Densovirus ; genetics ; Green Fluorescent Proteins ; genetics ; metabolism ; Introns ; genetics ; Polymerase Chain Reaction

To better understand the genomic structure and function of Bombyx mori bidensovirus (China isolate) VD1, the VD1 was purified and cloned into the pUC119 vector, and the complete nucleotide sequence of VD1 was determined. Sequence analysis showed that VD1 genome consisted of 6543 nts including inverted terminal repeats (ITRs) of 224 nts. In the viral genome, three major open reading frames (ORF1, ORF2 and ORF3) in the plus strand and one major ORF (ORF4) in the complementary strand were identified. Comparison of the complete genome sequence between Bombyx mori bidensovirus (China isolate) and BmDNV-2 (Yamanashi isolate) showed an identity of 98.4% in VD1, with a total number of 104 bp substitutions and 1 bp insertions found in Bombyx mori bidensovirus (China isolate), the highly variable regions were mainly located in VD1 ORF3 and VD1 ORF4. Northern blotting revealed that VD1 contained 1.1 kb and 1.5 kb transcript in the left-half 'plus' strand, and one transcript about 3.3 kb of 'minus' strand in the right-half. Sequencing of 3' and 5' ends of transcript products showed the 1.1 kb transcript started at nt 290 and ended at nt 1437, the 1.5 kb transcript was found to start nt 1423 and ended at 2931, and the 3.3 kb transcript was found to start nt 6287 and ended at nt 2922. Therefore, the 1.5 kb transcript in the left-half plus' strand and 3.3 kb transcripts of minus' strand in the right-half overlapped for 10 nts at the 3' ends. These results indicate that this virus employs a transcription strategy that is radically different from that of the other reported DNVs.
Amino Acid Sequence ; Animals ; Base Sequence ; Bombyx ; virology ; Densovirus ; genetics ; Genome, Viral ; Molecular Sequence Data ; Transcription, Genetic

OBJECTIVETo investigate arboviruses in Wenshan and Hekou county which are the Sino-Vietnam frontier regions of Wenshan, Yunnan province, China.

METHODSIn September 2007, 6091 Culicines, 1334 Anophelines, 848 Aedes vexans and 53 Armigeres obturbans were collected from 5 field sites. Mosquitoes were collected and stored in liquid nitrogen after classification. The mosquito pools were homogenized, and centrifuged, then the supematant was inoculated onto C6/36 and BHK-21 cells, and the viral isolates were identified by serological and molecular biological methods.Sequence alignment and phylogenetic analysis on the viral isolates were carried out using Clustal X 1.85, GENEDOC and MEGA4 software.

RESULTSA total of 4 pairs of virus isolated with C6/36 cells cytopathic effect were observed, and other mosquito species have not cytopathic effect.Strain WS0704-2 was Banna virus which identified by antibody response and PCR. Strain WS0704-1, WS0708-1, WS0708-2 were Culex pipens pallens densovirus (CppDNV) which identified by PCR. The phylogenetic analysis the 12th segment showed significant difference between the new Banna virus and other strains isolated in China.

CONCLUSIONThere are many mosquito vectors in frontier regions (China and Vietnam) of Wenshan in Yunnan province of China, and mosquito-borne arbovirus, such as BAV were isolated here.

Animals ; Arboviruses ; classification ; genetics ; isolation & purification ; China ; Culicidae ; virology ; Densovirus ; genetics ; isolation & purification ; Phylogeny ; Sequence Alignment ; Sequence Analysis, DNA

The invertebrate parvovirus Bombyx mori Densonucleosis Virus type 3(Zhenjiang isolate), named BmDNV-3, is a kind of bidensovirus. The most obvious characteristic in the genome of BmDNV-3 is that it has 2 sets of DNA molecular (VD1, VD2),and each of them is encapsidated respectively in the form of single-stranded liner DNA ( + VD1, - VD1, + VD2, - VD2) in equal percentage. So the BmDNV-3 has 4 kinds of virions. Furthermore the sequence of BmDNV-3 is able to encode DNA polymerase itself. Some strains of silkworm revealed complete resistance to BmDNV-3, so they didn' t fall sick. To investigate the difference in the process of infection and replication between the 2 virions ( VD1, VD2) of this bidensovirus, and the difference of the increment in the resistant or susceptible host, the 5th instar larvae of the susceptible silkworm strain (HUABA 35) and the resistant silkworm strain(QIUFENG d) were inoculated determinate dose of BmDNV-3 by oral ingestion. Then the midgut were collected at 9 timepoints. The silkworm cytoplasm actin A3 was used to be normalized gene, so the number of cells in collected tissue could be determined. The result shows that whatever in the susceptible silkworm strain or in the resistant one, the copies of VD1 and VD2 in the genome of BmDNV-3 collected at the different timepoint were almost at the equal level respectively, so that the VD1 and VD2 were replicated with synchronization. The process of infection in the susceptible silkworm strain was devided into 3 partitions, latent period( 2 - 12 hours post inoculation), exponential phase (12 - 36 hours post inoculation)and stationary phase (36- 96 hours post inoculation and there are about 2 x 10(5) copies per cell) . In the resistant silkworm strain, the virus were replicated at a very low level, that was from 6 - 10 copies 2 hours post inoculation to 150 - 200 copies 96 hours post inoculation (about 20 times) . So we predict that the resistance in some of the silkworm strains from BmDNV-3 was a kind of chronic representation that the host carried virus without being caused flacherie.
Animals ; Bombyx ; genetics ; virology ; DNA, Viral ; genetics ; Densovirus ; genetics ; physiology ; Female ; Genome, Viral ; genetics ; Host-Pathogen Interactions ; Male ; Polymerase Chain Reaction ; methods ; Time Factors ; Virion ; genetics ; physiology ; Virus Replication ; genetics