Mapping codon usage of the translation initiation region in porcine reproductive and respiratory syndrome virus genome.

BACKGROUND: Porcine reproductive and respitatory syndrome virus (PRRSV) is a recently emerged pathogen and severely affects swine populations worldwide. The replication of PRRSV is tightly controlled by viral gene expression and the codon usage of translation initiation region within each gene could potentially regulate the translation rate. Therefore, a better understanding of the codon usage pattern of the initiation translation region would shed light on the regulation of PRRSV gene expression. RESULTS: In this study, the codon usage in the translation initiation region and in the whole coding sequence was compared in PRRSV ORF1a and ORFs2-7. To investigate the potential role of codon usage in affecting the translation initiation rate, we established a codon usage model for PRRSV translation initiation region. We observed that some non-preferential codons are preferentially used in the translation initiation region in particular ORFs. Although some positions vary with codons, they intend to use codons with negative CUB. Furthermore, our model of codon usage showed that the conserved pattern of CUB is not directly consensus with the conserved sequence, but shaped under the translation selection. CONCLUSIONS: The non-variation pattern with negative CUB in the PRRSV translation initiation region scanned by ribosomes is considered the rate-limiting step in the translation process.

[Construction and sequencing of full-length cDNA of peste des petits ruminants virus].

To develop a reverse genetics system of Peste des petits ruminants virus(PPRV), five pairs of oligonucleotide primers were designed on the basis of the full-length genomic sequence of PPRV Nigeria 75/ 1 strain. Using RT-PCR technique, five over-lapping cDNA fragments, designated as JF1, JF2, JF3, JF4 and JF5, respectively, were amplified, followed by cloning into pcDNA3.1(+)vector. An AscI restriction enzyme site and a T7 promoter sequence were introduced immediately upstream of 5'-end, while a PacI restriction enzyme site was engineered downstream of 3'-end. Using pok12 as a plasmid vector, the full-length cDNA clone pok12-PPRV of Nigeria 75/1 was assembled by connecting the five cDNA fragments via the unique restriction endonuclease site of PPRV genome. The resultant nucleotide sequence of the PPRV Nigeria 75/1 strain in the study was compared with other members of genus morbillivirus, and phylogenetic analysis was used to examine the evolutionary relationships. The results showed that PPRV Nigeria 75/ 1 was antigenically closely related to Rinderpest virus and Measles virus. Successful construction of full-length cDNA clone of PPRV Nigeria 75/1 strain lays the basis rescuing PPRV effectively and enables further research of PPRV at molecular level.

[Combined expression of TSO45W-4BX from Taenia solium and porcine CD58 in Escherichia coli].

OBJECTIVE: To express the TSO45W-4BX of Taenia solium in combination with CD58 as a molecular adjuvant for improving the protective efficacy of the TSO45W-4BX recombinant vaccine. METHODS: TSO45W-4BX and porcine CD58 genes were amplified by PCR, using recombinant plasmids pGEM-4B and pGEM-CD58 as template respectively. The CD58 fragment was inserted into the recombinant plasmid pGEX-4T-1 with directly ligated TSO45W-4BX. The transformant was induced with IPTG and followed by identifying the integrity of the recombinant containing TS045W-4BX and porcine CD58 with PCR and sequencing. The products were analyzed by SDS-PAGE and Western blotting. RESULTS: The expression products of Mr 69,000 GST-4BX/CD58 and Mr 41,000 GST-4BX were present mainly in the form of inclusion bodies and soluble substance respectively, and both were recognized by sera of cysticercosis patients. CONCLUSIONS: The TSO45W-4BX co-expressed with porcine CD58 conserves its immune reactivity.

[Adjuvant effect of CpG DNA recombinant plasmid on antigen of Cysticercus cellulosae].

In order to prove the adjuvant effect of CpG DNA recombinant plasmid, the total antibodies and their IgG2a subtype induced by antigen of Cysticercus cellulosae, and content of IL-4 and IFN-gamma secreted from splenic cell of mouse immunized were measured. The recombinant plasmids showed an adjuvant effect, and CpG2 was the best adjuvant among the plasmids. It is proved that the CpG DNA possesses a synergistic effect with AI(OH)3 and 206 adjuvant, and is an effective Th1 type adjuvant in mice.

[Screening of cDNA clone for putative RNA polymerase subunit of Cysticercus cellulosae].

OBJECTIVE: To obtain related genes of Cysticercus cellulosae from spliced leader (SL) cDNA library. METHODS: Spliced leader library of Cysticercus cellulosae was constructed using SL specific primer and oligo (dT) 15 with M13M4 primer, and positive clones were then screened randomly, identified with enzyme restriction, followed by sequencing and homologous analysis. RESULTS: The amino acid sequence, encoded by the positive clone with a poly (A)22 tail and a complete open reading frame (ORF), was with homology of RNA polymerase subunit genes of human, B. napus, fission yeast, A. thaliana, C. elegans and fruit fly up to 71.6%. CONCLUSION: The protein, RNA polymerase subunit encoded putatively by the clone, is high conservative in different species.

[Expression of phosphoprotein P2 of Cysticercus cellulosae in Pichia pastoris and its application].

Cysticercosis is caused by the metacestode form of Taenia solium-Cysticercus cellulosae and it causes great economic losses and threatens the people's health. There are some problems on how to control cysticercosis, in order to resolve the key problem that the native antigen to diagnose and prevent cysticercosis is very limited and is not satisfied, Pichia pastoris Expression System was used to express recombinant P2 protein. The interested P2 gene was got by digesting the pGEM - P2 vector using restriction endonuclease, then it was inserted into the secretory pPIC9K Pichia pastoris expression vector and transformed into E. coli. Positive recombinant plasmids were selected sequenced and named pPIC9K-P2 and it was linearized by Sal I and Bgl II, then the linear DNA transfored into Pichia pastoris GS115 by electroporation. The recombinant expression vector pPIC9K - P2 integrated into GS115 via homologous recombination between the transforming DNA and regions of homology within the genome. The transformants were screened for multicopy recombinants using G418 and were distinguished for Mut phenotypes by MD and MM. Two different phenotypes were generated-HIS+ MUT+ (Methanol utilization plus) and HIS+ MUT(S) (Methanol utilization slow). PCR analysis of the multicopy recombinants indicated that the P2 gene was integrated within the genome of pichia Pastoris. The multicopy recombinants were named GS115/pPIC9K - P2HIS+ MUT+ and GS115/pPIC9K-P2HIS+ MUT(S), both HIS+ MUT+ and HIS+ MUT(S) were induced with methanol. The results of SDS-PAGE and Western blot demonstrated that the culture supernatant of the induced Pichia pastoris contained P2 protein which was accumulated up to 33 % of total proteins in the culture supernant and its molecular weight is 12.6kD. The results of the clinical study indicated that the expression P2 protein could be used to diagnose human cysticercosis and swine cysticercosis as diagnosis antigen.