title: Site-directed PEGylation of trichosanthin retained its anti-HIV activity with reduced potency in vitro.
abstract: 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.
authors.affiliation: Laboratory of Molecular Immunopharmacology, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, PR China.
authors.forename: Jian-Hua
authors.initials: JH
authors.lastname: Wang
authors.forename: Siu-Cheung
authors.initials: SC
authors.lastname: Tam
authors.forename: Hai
authors.initials: H
authors.lastname: Huang
authors.forename: Dong-Yun
authors.initials: DY
authors.lastname: Ouyang
authors.forename: Yuan-Yuan
authors.initials: YY
authors.lastname: Wang
authors.forename: Yong-Tang
authors.initials: YT
authors.lastname: Zheng
mesh_terms: D000818:Animals; D019380:Anti-HIV Agents / Q000737:chemistry* / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D016655:HIV Core Protein p24 / Q000096:biosynthesis; D015497:HIV-1 / Q000187:drug effects; D006801:Humans; D016297:Mutagenesis, Site-Directed; D011092:Polyethylene Glycols / Q000737:chemistry* / Q000494:pharmacology; D011817:Rabbits; D012270:Ribosomes / Q000187:drug effects; D013329:Structure-Activity Relationship; D013601:T-Lymphocytes / Q000821:virology; D015978:Trichosanthin / Q000031:analogs & derivatives* / Q000235:genetics / Q000494:pharmacology*
chemical_list: D019380:Anti-HIV Agents; D016655:HIV Core Protein p24; D011092:Polyethylene Glycols; D015978:Trichosanthin