Site-directed PEGylation of trichosanthin retained its anti-HIV activity with reduced potency in vitro |
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Authors: | Wang Jian-Hua Tam Siu-Cheung Huang Hai Ouyang Dong-Yun Wang Yuan-Yuan Zheng Yong-Tang |
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Institution: | a Laboratory of Molecular Immunopharmacology, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650223, PR China b Department of Physiology, The Chinese University of Hong Kong, Shatin, N.T., Hong Kong, PR China c Graduate School of the Chinese Academy of Sciences, Beijing 100039, PR China |
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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 20 kDa (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. |
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Keywords: | Trichosanthin Ribosome inactivating protein HIV-1 Polyethylene glycol Antiviral activity |
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