High expression of the classical swine fever virus (CSFV) envelope protein E2 by a single amino acid mutation and its embedded in the pseudorabies virus (PRV) vector for immunization.

Pseudorabies (PR) and classical swine fever (CSF) are economically important infectious diseases in pigs. Most pig farms in China are vaccinated against these two diseases. Gene-deleted pseudorabies virus (PRV) can be used to develop promising and economical multivalent live attenuated viral vector vaccines. It has been reported that recombinant PRV can express a truncated E2 protein (1-338 aa), but it has not been reported that recombinant PRV can express a full-length E2 protein. We constructed nine groups of E2 proteins with different expression forms and found that the E2 protein could be expressed in vitro only when the transmembrane region of E2 was removed and the signal peptide was added. Analysis of the transmembrane region of E2 revealed that the high hydrophobicity of the E2 transmembrane region was the main reason for its inability to express. By mutating an amino acid to reduce the hydrophobicity of the transmembrane region, it was found that the full-length mutant of E2 (E2FL-muta3 or E2FL-muta4) could be expressed. The expressed full-length mutant E2 could also localize to the cell membrane. Mice immunized with a PRV vector vaccine expressing E2FL-muta3 or E2FL-muta4 developed specific cellular immunity to the E2 protein and stimulated higher levels of E2 antibody than mice immunized with a PRV vector expressing truncated E2. After immunizing the rabbits, the lethal challenge by PRV-ZJ2013 and the febrile response elicited by CSFV were simultaneously prevented. These results suggest that rPRV-dTK/gE-E2FL-muta4 is a promising bivalent vaccine against CSFV and PRV infections.

Recombinant pseudorabies virus (PRV) expressing stabilized E2 of classical swine fever virus (CSFV) protects against both PRV and CSFV.

Pseudorabies (PR) and classical swine fever (CSF) are economically important infectious diseases of pigs. Most pig farms in China are immunized against these two diseases. Here, we describe a stabilized E2 protein as an immunogen inserted into the PRV genome as a bivalent live virus-vectored vaccine. The E2 protein has 48 variant sites, there are 2-5 candidate amino acids per variant site, and the relative energy contribution of each amino acid to E2 energy was calculated. Combined substitutions of amino acids at the neighbor variant site (neighbor substitution) were performed to obtain the E2 protein sequence with the lowest energy (stabilized E2). Multiple amino acid substitutions at 48 variant sites were performed, and the results were consistent with neighbor substitutions. The stabilized E2 sequence was obtained, and its energy decreased by 22 Rosetta Energy Units (REUs) compared with the original sequence. After the recombinant PRV expressing stabilized E2 of CSFV was constructed, the secretion efficiency of stabilized E2 was increased by 2.97 times, and the thermal stability was increased by 10.5 times. Immunization of mice resulted in a 2-fold increase in antibody production, and a balanced antibody level against subtype 1.1 and subtype 2.1d E2 was achieved. In rabbits immunized, the lethal challenge of PRV-ZJ and the fever response induced by CSFV could be prevented simultaneously. These findings suggest that rPRV-muta/287aaE2 is a promising bivalent vaccine against CSFV and PRV infections.

[Construction of an infectious clone of pseudorabies virus strain ZJ genome maintained as a bacterial artificial chromosome].

pHA2 plasmid sequence,with Bacterial Artificial Chromosome(BAC) vector and the GFP expression cassette, was introduced into the UL23(TK) gene of Pseudorabies virus(PRV)strain ZJ by homologous recombination,and the recombinant PRV (rPRV-HA2) was confirmed and isolated by plaque purification. The circular genome of rPRV-HA2 was electroporated into Escherichia coli strain DH10B and then the PRV BAC (pPRV) was recovered. The transfection of pPRV into VeroE6 cells resulted in productive infection. The rescued virus isolated following transfection was indistinguishable from rPRV-HA2 in cytopathic effects (CPE) and replication curve in vitro. The growth kinetics of the viruses indicated that partial deletion of TK gene and BAC vector insertion had no effect on the viral titre and plaque size in vitro. The PRV BAC system will enable quick and reliable manipulation of the viral genome for the functional investigation on the PRV genes and the development of PRV vector in vaccine.

[Effects of Fuzheng Huayu recipe on MMP-2 activity and type IV collagen expression at fibrotic lung].

OBJECTIVE: To study the mechanism of Fuzheng Huayu (FZHY) recipe against pulmonary fibrosis relating to MMP-2 activity and type IV collagen expression at lung tissue. METHOD: The pulmonary fibrosis model was induced by intratracheal instillation with bleomycin once in rats. The models were divided into 3 groups: model control, FZHY recipe treated, and methylprednisolone (Solu-Medrol) treated group, each group was of 14 model rats. Normal control group with 10 rats was intoxicated with the same amount of saline. From the second day of intoxication, FZHY recipe treated group orally took FZHY recipe at the dosage of 4.6 g x kg(-1) rat wt, methylprednisolone treated group received intraperitoneal injection with 15 mg x kg(-1) rat wt of methylprednisolone, while model and normal controls took the same volume of saline, 1 time each day and lasting for 4 weeks. Lung and body weights were weighed and the lung/body ratio was calculated. Collagens deposition was check with Masson stain, and lung hydroxyproline (Hyp) content was assayed with Jamall's method. Protein expressions of MMP-2/9 and type IV collagen at lung tissue were analyzed with Western blot and of MMP-2/9 activities by gelatin zymography. RESULT: Compared to normal rats, the model control rats had a high lung/body ratio, remarkable collagen deposition, increased Hyp content and the expressions of type IV collagen, MMP-2 and MMP-9 protein at lung tissue, increased MMP-2 activity, in particular active MMP-2 activity, but decreased MMP-9 activity. Compared to model control, FZHY recipe and methylprednisolone obviously attenuated pulmonary collagen deposition, decreased lung/body ratio and Hyp content, downregulated MMP-2 protein expression and activity, in particular active MMP-2 activity, and FZHU recipe had some better actions than methylprednisolone on lung/body ratio, type IV collagen expression and active MMP-2 activity. But both drug groups had no influence on MMP-9 protein expression and activity. CONCLUSION: FZHY recipe has a good action against experimental pulmonary fibrosis and its mechanisms are associated with the inhibition of MMP-2 protein and activity, and with the inhibition of over expression of type IV collagen at lung tissue.

[Feature changes of MMP-2/9 activities and TIMP-1/2 protein expressions during the progression of pulmonary fibrosis in rats].

OBJECTIVE: To investigate the dynamic trends of activities of matrix metalloproteinase (MMP)-2/9 and protein expressions of their inhibitors-tissue inhibitor of matrix metalloproteinase (TIMP)-1/2 during the progression of pulmonary fibrosis in rats so as to get insight of the roles played by MMP-2/9 in lung injury and fibrogenesis. METHODS: Forty-eight SD rats were randomly divided into normal control group (n=18) and bleomycin (BLM)-treated group (n=30). The pulmonary fibrosis was induced by intratracheal injection of BLM once. At the consecutive time of 1 day, 3 days, 1 week, 2, 3, and 4 weeks after intoxication, the lung-to-body weight ratio was calculated and the inflammation and collagen deposition in lung tissue were checked by HE and Masson stainings respectively. Meanwhile, the content of hypdroxyproline (Hyp) in lung tissue was assayed with Jamall's method, the protein expressions of MMP-2/9, TIMP-1/2 were examined by Western blotting, and the activities of MMP-2/9 were detected by gelatin zymography. RESULTS: The histopathological changes in lung tissue in the BLM-treated group from 1 day to 2 weeks after intoxication presented local lesions, broadened alveolar wall and septum, infiltration with lots of inflammatory cells and few of fibroblasts inside alveolar space and septum. At this early stage in the BLM-treated group, the lung-to-body weight ratio was increased significantly, the protein expressions and activities of MMP-2/9 were obviously increased especially for activity of active MMP-2, and the protein expressions of TIMP-1/2 were also increased gradually, as compared with those in the normal control group. From 3 to 4 weeks after intoxication in the BLM-treated group, the alveolar structure was damaged, parts of the alveolar space collapsed and replaced by collagens and fibroblasts, and the alveolar wall and septum obviously widened with remarkable fibrotic characteristics, as compared with those in the normal control group. Meanwhile, the lung-to-body weight ratio and the activities of MMP-2/9 were decreased in the BLM-treated group as compared with those in the same group at 2 weeks after intoxication, but the content of Hyp and the protein expressions of TIMP-1/2 were both increased dramatically, especially at 4 weeks after intoxication. CONCLUSIONS: During the lung fibrogenesis induced by BLM in rats, the alveolar inflammation is the most important alteration with enhanced MMP-2/9 activities in the early stage. While in the late stage, the main change is displayed as pulmonary fibrosis, characterized by increased TIMP-1/2 and declined MMP-2/9 activities.