Site-directed PEGylation of trichosanthin retained its anti-HIV activity with reduced potency in vitro

Biochem Biophys Res Commun. 2004 May 14;317(4):965-71. doi: 10.1016/j.bbrc.2004.03.139.


Trichosanthin (TCS) was the first ribosome inactivating protein found to possess anti-HIV-1 activity. Phase I/II clinical trial of this compound had been done. Antigenicity and short plasma half-life were the major side effects preventing further clinical trial. Modification of TCS is therefore necessary to revive the interest to develop this compound as an anti-HIV agent. Three potential antigenic sites (Ser-7, Lys-173, and Gln-219) were identified by computer modeling. Through site-directed mutagenesis, these three antigenic amino acids were mutated to a cysteine residue resulting in 3 TCS mutants, namely S7C, K173C, and Q219C. These mutants were further coupled to polyethylene glycol with a molecular size of 20kDa (PEG) via the cysteine residue. This produced another three TCS derivatives, namely PEG20k-S7C, PEG20k-K173C, and PEG20k-Q219C. PEGylation had been widely used recently to decrease immunogenicity by masking the antigenic sites and prolong plasma half-life by expanding the molecular size. The in vitro anti-HIV-1 activity of these mutants and derivatives was tested. Results showed that the anti-HIV-1 activity of S7C, K173C, and Q219C was decreased by about 1.5- to 5.5-fold with slightly lower cytotoxicity. On the other hand, PEGylation produced larger decrease (20- to 30-fold) in anti-HIV activity. Cytotoxicity was, however, weakened only slightly by about 3-fold. The in vitro study showed that the anti-HIV activity of PEGylated TCS was retained with reduced potency. The in vivo activity is expected to have only slightly changed due to other beneficial effects like prolonged half-life.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Anti-HIV Agents / chemistry*
  • Anti-HIV Agents / pharmacology*
  • Cell Line
  • Cell Survival / drug effects
  • HIV Core Protein p24 / biosynthesis
  • HIV-1 / drug effects
  • Humans
  • Mutagenesis, Site-Directed
  • Polyethylene Glycols / chemistry*
  • Polyethylene Glycols / pharmacology
  • Rabbits
  • Ribosomes / drug effects
  • Structure-Activity Relationship
  • T-Lymphocytes / virology
  • Trichosanthin / analogs & derivatives*
  • Trichosanthin / genetics
  • Trichosanthin / pharmacology*


  • Anti-HIV Agents
  • HIV Core Protein p24
  • Polyethylene Glycols
  • Trichosanthin