Immunogenicity of the truncated NDV F protein surface-displayed on Lactobacillus casei / 生物工程学报

To evaluate immune efficacy of the recombinant Lactobacillus casei, we constructed pLA-Newcastle disease virus (NDV)-F/L. casei and obtained the expression products. PCR amplified the NDV F gene carrying part of the major epitopes. The target gene was inserted to the shuttle plasmid pLA, and then transformed into Escherichia coli BL21 (DE3) in order to screen positive recombinant plasmid. The positive recombinant plasmid was transformed into L. casei by electroporation to construct pLA-NDV-F/L. casei. The positive strains were identified by PCR. The reactivity of the recombinant bacteria was identified by Western blotting and the protein expression was detected by indirect immunofluorescence, flow cytometry and laser confocal microscopy. The 14-day-old chickens in each group were vaccinated by oral plus nose drops. The pLA-NDV-F/L. casei twice immunization group and three times immunization group, the commercial vaccine group, the pLA/L. casei group, the unchallenge PBS and the challenge PBS group were established. IgG in serum and sIgA in the lavage fluid of intestinal, nasal and lung were detected by ELISA. The protection rate of chickens was evaluated. The results showed that 94.10% of the recombinant bacteria expressed the F protein. The recombinant protein was highly expressed on the surface of L. casei with a protein size of 62 kDa, which specifically bound to anti-NDV serum. The levels of anti-F IgG and sIgA antibodies in each test group were significantly higher than those in the control groups. The duration of antibody in the pLA-NDV-F/L. casei three-time immunization group lasted 28 days longer than that in the twice immunized group, and there was no significant difference between antibody peak values. The attack protection rates in each group of immunized pLA-NDV-F/L. casei three times, twice, attenuated vaccine, pLA/L. casei and PBS were 80%, 80%, 90%, 0% and 0%, respectively. Therefore, the antigenic protein of NDV F was successfully expressed by L. casei expression system, which has of reactogenicity and immunogenicity, and could induce protective immune responses in chickens.

Establishment and evaluation of DAS-ELISA for detecting bovine respiratory syncytial virus / 中国人兽共患病学报

In order to develop a double antibody sandwich assay (DAS-ELISA) for detecting bovine respiratory syncytial virus (BRSV),New Zealand white rabbits and BALB/c mice were immunized with the purified G protein as an antigen to prepare anti-G protein polyclonal and monoclonal antibodies.The antibody concentration and reaction conditions of DAS-ELISA were optimized by square titration,and its sensitivity,specificity,and coincidence rate were validated.Five hybridoma were stably secreting Mab which subclass belonged to IgG1κ.Western blot and IFA test showed that PcAb and Mab could react specifically with G protein and BRSV.The PcAb and Mab as the capture antibody and detection antibody respectively,and their optimal working concentrations were determined to be 2.5 μg/mL and 10μg/mL,the critical value 0.22 and the detection limit of 1.43 μg/mL,batch,inter-assay coefficient of variation less than 10 ％.The DAS-ELISA had no cross-reaction with several pathogens which often caused bovine respiratory disease.When 45 nasal swabs of clinical samples were simultaneously detected by the DAS-ELISA and RT-PCR,the sensitivity,specificity and coincidence rate were 92.0 ％,100 ％,95.6 ％,respectively.It' s indicated that the established DAS-ELISA detection method can be used to detect a large number of clinical samples.It was the foundation of monitoring and quick diagnosis for BRSV.

Immunogenicity of recombinant Lactobacillus casei expressing VP2 protein of infectious bursal disease virus in chickens / 生物工程学报

In order to determine immunogenicity and protective effect in chickens, we used the IBDV (Infectious bursal disease virus)-Vp2/Lactobacillus casei as antigen transfer system. First, the immunized and control chickens were challenged by IBDV/DQ at lethal dose to determine the protective ratio. Second, chickens were orallyand intranasally vaccinated twice with 10(9) CFU/mL pLA-VP2/L. casei, pLA/L. casei and PBS as negativecontrol and commercial vaccine as positive control. The bursa injury and the lesion score wererecorded post challenge. The level of specific IgG and sIgA in pLA-VP2/L. casei and positive control groups was significantly higher than that in negativecontrol groups. The protection efficacy in pLA-VP2/L. casei oral group was higher than that inintranasal group. The SI. of pLA-VP2/L. casei oral group was significant higher than other groups. The lesion score indicated the pLA-VP2/L. casei was safer than commercial vaccine for bursa. Collectively, the pLA-VP2/L. casei could be a vaccine candidate for IBDV.

Prokaryotic expression of the nucleocapsid protein gene in bovine coronavirus and its preliminary application / 中国人兽共患病学报

To obtain and analyze the sequence of the nucleocapsid gene from bovine coronavirus, and to produce the fusion protein of the N gene in E.coli in order to use this recombinant protein for the study of bovine coronavirus. The N gene of BCV-DQ strain was amplified by RT-PCR, in which the primers were designed on the basis of N gene sequence of BCV-Mebus strain. The PCR products of 1 347 bp in length were cloned and sequenced, and then inserted into the prokaryotic vector pET30a. The recombinant plasmids were then transformed into Escherichia coli BL21 and identified by SDS-PAGE and Western blot assay. ELISA assay was optimized of N protein as the coating antigen to detect the viruses in the clinical samples. In comparison with 6 BCV strains in GenBank, the sequence identity was proved to be more than 98.3%. Result in SDS-PAGE showed that the fusion protein had a molecular weight of 60 ku, and could be specifically recognized by mouse serum against BCV. The indirect ELISA was used to test 256 serum samples collected from Heilongjiang province and 65.23% samples were positive. On testing field samples, an overall agreement of 95.31% was generated between the the neutralization test of viruses (VN) and indirect ELISA. It is apparent that the N gene was highly conservative and is expressed in E. coli in high level,also the prokaryotic expression products of this gene show a fine reactiongenicity in immune responses. It was also suggested that the N protein may be a useful antigen for sero-diagnosis and epidemiological investigation of BCV.

Survival properties of ETEC surface-displayed K88ac-LT(B) on Lactobacillus casei / 生物工程学报

K88ac-LT(B) gene derived from pQE30-K88ac-LT(B) was cloned into the expression vector pLA and then the recombinant vector was transformed into the competent cells Lactobacillus casei 525. The recombinant bacteria were grown at 37 degrees C, in MRS broth. Western blotting analysis with rabbit-anti-K88ac-LT(B) polyclonal serum indicated that the recombinant protein reacted with the specific antibodies. The results showed that the molecular weight of the recombinant protein was about 71.2 kD. The K88ac-LT(B) fusion protein on the cell surface was confirmed by immunofluorescence mciroscopy and flow cytometric analysis. In addition, the survival of recombinant Lactobacillus casei 525 was studied in imitative gastrointestinal environments such as artificial gastro fluid (pH 1.5-5.5), artificial intestinal fluid, bile(0.3-3.0 g/L). The results indicated that the recombinant strain survived well in artificial gastric fluids at pH 2.5-4.5 in 5 h. The recombinant Lactobacillus casei 525 could slowly grow in the artificial intestinal fluid for different time, and could survive in 0.3% bile.

Distribution of trkA in cerebral cortex and diencephalon of the mongolian gerbil after birth

TrkA is essential components of the high-affinity NGF receptor necessary to mediate biological effects of the neurotrophins NGF. Here we report on the expression of trkA in the cerebral cortex and diencephalon of mongolian gerbils during postnatal development. The expression of trkA was identified by immunohistochemical method. In parietal cortex and piriform cortex, higher levels of trkA-IR (immunoreactivity) were detected at 3 days postnatal (P3) and at P9. Although trkA was not expressed till P3 in the parietal cortex, it was detectable at birth in the piriform cortex. Several regions, such as Layers I, IV & VI, did not show much expression. Layer I showed especially weak labeling. In the hippocampus, thalamus, and hypothalamus, higher levels of trkA-IR were detected at P6 and P12 than earlier days. But trkA was not expressed at birth in the hippocampus, at P3 in the reticular thalamic nucleus (Rt), or neonatally in the dorsomedial hypothalamic nucleus (DM). This data shows that expression of trkA is developmentally regulated and suggests that high affinity neurotrophin-receptors mediate a transient response to neurotrophines in the cerebral cortex and diencephalon during mongolian gerbil brain ontogeny.