Objective: To construct PEGylated trichosanthin (TCS) mutein and analyze its bioactivities, immunogenicity, acute toxicity, and pharmacokinetics.
Methods: The potential antigenic determinant site YFF81-83 in the molecule of TCS was selected to undergo site-directed mutagenesis. Thus, a TCS mutein named TCS(YFF81-83ACS) was constructed and expressed in Escherichia coli of the line BL21 (DE3). Wild TCS (wTCS), TCSY(FF81-83ACS), and PEGylated TCS(YFF81-83ACS) (PEG- TCS(YFF81-83ACS)) of different concentrations were incubated with the supercoiled plasmid pUC19 to detect the DNAse activity, mixed with rabbit reticulocyte lysate to detect the ribosome inactivation activity, subcutaneously injected into 6 mice respectively to measure the serum IgG and IgE levels, intravenously injected into mice to observe the toxicity, and intravenously injected into SD rats to observe its -plasma half-life.
Results: The DNAse activity of the PEG-TCS(YFF81-83ACS) was similar to that of the wTCS. The ribosome inactivation activity of the PEG-TCS(YFF81-83ACS) was 1/9-1/8 of that of the wTCS (P < 0.05). The serum IgE and IgG levels of the PEG-TCS(YFF81-83ACS) were both significantly lower than those of the wTCS (both P < 0.05). The LD50 of the PEG-TCS(YFF81-83ACS) was 1.8 times that of the wTCS (P < 0.05). The mean residence time and plasma half-life of the PEG-TCS(YFF81-83ACS) were significantly increased and its plasma clearance was significantly decreased (all P < 0.05).
Conclusion: Site-directed mutagenesis and PEGylation of TCS provide a new approach for reconstructing TCS.