Nuclease activity of the recombinant plancitoxin-1-like proteins with mutations in the active site from Trichinella spiralis / 生物工程学报

Although there are 125 predicted DNase Ⅱ-like family genes in the Trichinella spiralis genome, plancitoxin-1-like (Ts-Pt) contains the HKD motif, a typical conserved region of DNase Ⅱ, in N- and C-terminal. It is generally believed that histidine is the active site in DNase Ⅱ. To study the nuclease activity of recombinant Ts-Pt with mutations in the active site from T. spiralis, different fragments of the mutated Ts-Pt genes were cloned using overlap PCR technique and inserted into the expressing vector pET-28a(+), and transformed into Escherichia coli Rosseta (DE3). The fusion proteins were purified by Ni-NTA affinity chromatography and SDS-PAGE. Nuclease activity of the recombinant proteins was detected by agarose gel electrophoresis and nuclease-zymography. The recombinant plasmids harboring the mutated Ts-Pt genes were constructed and expressed as inclusive body in a prokaryotic expression system. After renaturation in vitro, the recombinant proteins had no nuclease activity according to agarose gel electrophoresis. However, the expressed proteins as inclusive body displayed the ability to degrade DNA after renaturation in gel. And the nuclease activity was not affected after subjected to mutation of active site in N- and C-termini of Ts-Pt. These results provide the basis to study the relationship between DNase Ⅱ-like protein family and infection of T. spiralis.

Expression and adjuvant effects of the fusion peptide TBP5 / 生物工程学报

Thymopentin (TP5) and bursopentin (BP5) are both immunopotentiators. To explore whether the TP5-BP5 fusion peptide (TBP5) has adjuvant activity or not, we cloned the TBP5 gene and confirmed that the TBP5 gene in a recombinant prokaryotic expression plasmid was successfully expressed in Escherichia coli BL21. TBP5 significantly promoted the proliferation of thymic and splenic lymphocytes of mice. The potential adjuvant activity of the TBP5 was examined in mice by coinjecting TBP5 and H9N2 avian influenza virus (AIV) inactivated vaccine. HI antibody titers, HA antibodies and cytokines levels (IL-4 and IFN-γ) were determined. We found that TBP5 markedly elevated serum HI titers and HA antibody levels, induced the secretion of both IL-4 and IFN-γ cytokines. Furthermore, virus challenge experiments confirmed that TBP5 contributed to inhibition replication of the virus [H9N2 AIV (A/chicken/Jiangsu/NJ07/05)] from mouse lungs. Altogether, these findings suggest that TBP5 may be an effective adjuvant for avian vaccine and that this study provides a reference for further research on new vaccine adjuvants.