[A comparative study on the properties of trichosanthin before and after site-directed PEGylation].

An Qun-xing, Lei Ying-feng, Mu Shi-jie, Zhang Xian-qing, Chen Rui, Xia Ai-jun, Chen Chen, Yi Jing, Wu Yuan-ru, Yu Rui, Xu Zhi-kai

Department of Blood Transfusion, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China.

Zhonghua Yi Xue Za Zhi. 2008 May 27;88(20):1433-6.

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).