紫锥菊根末对猪PRRSV抗体的影响

对紫锥菊根末对猪繁殖与呼吸综合征病毒(PRRSV)感染后抗体水平的影响及其潜在机理进行了深入的研究。发现紫锥菊根末可能直接抑制病毒的复制和侵染,从而对抗体水平产生影响,实验研究发现紫锥菊根末可能具有增强机体对病毒的抵抗能力,从而促进抗体产生的作用。综合认为紫锥菊根末对猪PRRSV感染后抗体水平的影响可能与其免疫调节作用有关。由此,为开发紫锥菊根末的临床应用价值提供了一定的借鉴。研究发现紫锥菊根末能调节免疫调节因子的产生和作用,从而对免疫反应的调节和抗体产生的途径起到一定的促进作用。对进一步深入研究紫锥菊根末在猪PRRSV感染防控中的应用具有重要的意义,同时也为研究免疫调节机理提供新的参考。

Construction and Immunogenicity of Associated DNA Vaccine of PRRS and PCV-2 Disease

[ Objective ] The aim of the study was to construct associated DNA vaccine of PRRS （Porcine reproductive and respiratory syndrome） and PCV-2 （Porcine circovirus type 2） disease and study its immunogenicity. [ Method] In_ this study, the ORF5 gene of PRRSV isolated in Liaoning was cloned into plRES-neo expression vector, and the neo gene of plRES-neo expression vector was substituted by the ORF2 gene of the PCV-2 Mongolia strain to construct the recombinant expression vector. The expression in BHK cells was detected through Western blot and IFA. Then the ELISA antibody level and the number of spleen T lymphocytes were detected after Balb/c mice were immunized with this DNA vaccine. E Result] The recombinant plasmid plRES-ORF2-ORF5 was constructed successfully and could express the target proteins in BHK cells, as indicated by Western blot and IFA. There was no significant difference in ELISA antibody between plRES-ORF2-ORF5 immunized group and inactived vaccine immunized groups, while the number of spleen T lymphocytes induced by DNA vaccine was higher than that induced by inactived vaccine. [ Conclusion] The recombinant plasmid plRES-ORF2-ORF5 should induce good humoral immune response and cellular immune response in mice, providing the conditions for better prevention and control of PRRS and PCV-2 disease.

Review for Porcine Reproductive and Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome （PRRS） is the severest disease of pigs worldwide, caused by a highly genetically diverse RNA virus, called Porcine reproductive and respiratory syndrome virus （PRRSV）. The research summarized the genome characteristics of PRRSV particles and the most updated knowledge of structure protein function, and introduced the intellectual of PRRSV transmission and host immune response, which is very important for prevention and control for PRRS. A report showed that mass vaccination can stabilize the immunity of the entire herd, and this is the first required step for a PRRS eradication plan. However, the attenuated live vaccines may not achieve a valid prevention. The final goal of the EU project is to develop new generation, efficacious and safe maker vaccines that can be adapted to temporary changes and geographical differences.Robinson reported that broadly antibodies could neutralize all rapidly evolving type Ⅰ and type Ⅱ viruses, while further studies are expected to elucidate mechanisms of neutralizing antibody production and maturation and to investigate conserved epitope targets of cross-neutralization in this rapidly evolving virus.

An Attenuated Highly Pathogenic Chinese PRRS Viral Vaccine Confers Cross Protection to Pigs against Challenge with the Emerging PRRSV NADC30-Like Strain

A novel PRRSV strain was isolated in China that was genetically similar to the NADC30 strain which is reported to have spread throughout China. The objective of the present study was to evaluate the cross-protective efficacy of the live vaccine TJM-F92 in young pigs against challenge with a NADC30-like strain, HN201605. Twenty-five PRRSV-and antibody-free pigs were randomly divided into the following five groups: Vac/ChA, Unvac/ChA, Vac/ChB, Unvac/ChB and the mock.The pigs in groups Vac/ChA and Vac/ChB were inoculated intramuscularly with 1 mL TJM-F92(10^(5.0) TCID_(50)/mL). At28 days post vaccination(0 days post challenge), groups Vac/ChA and Unvac/ChA were inoculated intranasally with 10^(4.5) TCID_(50)/mL PRRSV strain TJ F3(2 mL/pig), while groups Vac/ChB and Unvac/Ch B were inoculated, using the same route, with the same dose of the NADC30-like strain HN201605 F3. Protective effects of the PRRSV strain were observed in all pigs in the Vac/ChA and Vac/ChB groups. Neither high fever nor signs of clinical disease were observed through the experiment in these groups, whereas pigs in Unvac/ChA group exhibited serious clinical symptoms, pathological lesions,and weight loss. In Unvac/ChB group, pigs developed milder clinical symptoms, which demonstrated that the NADC30-like strain HN201605 had moderate pathogenicity. The results suggest that the MLV vaccine strain TJM-F92 is an effective and safe vaccine candidate for use in China.

Mutational analysis of the SDD sequence motif of a PRRSV RNA-dependent RNA polymerase

The subgenomic mRNA transcription and genomic replication of the porcine reproductive and respiratory syndrome virus (PRRSV) are directed by the viral replicase. The replicase is expressed in the form of two polyproteins and is subsequently processed into smaller nonstructural proteins (nsps). nsp9, containing the viral replicase, has characteristic sequence motifs conserved among the RNA-dependent RNA polymerases (RdRp) of positive-strand (PS) RNA viruses. To test whether the conserved SDD motif can tolerate other conserved motifs of RNA viruses and the influence of every residue on RdRp catalytic activity, many amino acids substitutions were introduced into it. Only one nsp9 substitution, of serine by glycine (S3050G), could rescue mutant viruses. The rescued virus was genetically stable. Alteration of either aspartate residue was not tolerated, destroyed the polymerase activity, and abolished virus transcription, but did not eliminate virus replication. We also found that the SDD motif was essentially invariant for the signature sequence of PRRSV RdRp. It could not accommodate other conserved motifs found in other RNA viral polymerases, except the GDD motif, which is conserved in all the other PS RNA viruses. These findings indicated that nidoviruses are evolutionarily related to other PS RNA viruses. Our studies support the idea that the two aspartate residues of the SDD motif are critical and essential for PRRSV transcription and represent a sequence variant of the GDD motif in PS RNA viruses.