ABSTRACT
Objective:In order to develop a safer vaccine strain exploit Salmonella typhimurium vaccine strain .A ΔsipB mutant of Salmonella typhimurium SL 1344 strain was constructed.Methods: Firstly, the recombinant suicide plasmid containing the missing 585 bp sipB ( PREΔsipB ) was built by homologous recombination , and screenned by two-step method.Results: PCR and sequencing results showed that SL 1344ΔsipB was successfully constructed.It was no significant changes compared with SL 1344.But compared with the parent strains SL 1344 , the mutant strain had obvious change in its virulence , oral challenge of bacteria in mice revealed that LD50 of the mutant strain was 1.70 ×108 CFU,the toxicity reduced about 1.4%.The protection rate induced by the sipB mutant was 50%,and the serum antibody peaked 14 d post-immunization.Conclusion:The SL1344ΔsipB mutant was constructed suc-cessfully,and genetic stability ,significantly reduced virulence.The study provides a new approach for further study of the relationship between the gene and pathogenicity of Salmonella typhimurium.It is likely that the ΔsipB mutant could be adapted to develope attenuated Salmonella vaccine.
ABSTRACT
Objective:To discuss the effects of recombinant IFN-α-IL-18 fusion protein on chicken lymphocyte transformation and the chicken nuclear factor kappa B ( NF-κB ) activity.Methods: The recombinant plasmids pPICZ-IFN-α, pPICZ-IL-18 and pPICZ-IFN-α-IL-18 were constructed,and transformed into P.Pastoris X-33 strain by electroporation.The recombinant proteins were ex-pressed under the induction of 1% methanol,and detected by SDS-PAGE and Western blot.The biological activities of the expressed products were detected by the lymphocyte transformation test,the NF-κB concentration in chicken lymphocyte and lymphocytic nucleus were detected at different times with ELISA.Results:SDS-PAGE and Western blot showed that the expressed products existed in super-natant,and the molecular weights were about 22 kD,23 kD and 43 kD,respectively.The expressed products IL-18 and IFN-α-IL-18 could stimulate chicken lymphocyte transformation (P0.05).Compared with the control group,the total NF-κB concentration in chicken lymphocyte induced by IL-18 and IFN-α-IL-18 were increased (P0.05),but the NF-κB in lymphocytic nucleus showed the remarkable increase ( P<0.05 ) .Conclusion: IFN-α-IL-18 and IL-18 can promote lymphocyte transformation significantly, the activity of IFN-αinduced lymphocyte transformation is imperfect.The biological activity of stimulating lymphocyte transformation is associated with the NF-κB expression,activation and nucleo-cytoplasmic transport.The study built foundation for the function of IFN-α-IL-18 fusion protein and the exploration of the role of controlling epidemic diseases.