In this short review we summarize the different strategies for discovery and development of antiviral agents, including targeting virus entry into host, virus replication within cells, infant virus assembly and release from the infected cells. The progress on development of various classes of antivirus agents and their potential in virus therapy, mainly targeting human immunodeficiency virus （HIV）, was also discussed.
RNA interference has been widely used for gene therapy of various infectious diseases and malignant tumors. However, its poor stability in serum has limited further clinic application. Here, we found that stability of siRNA in serum enhanced obviously when 3′-terminus of sense strand （siRNA-pS） was conjugated with peptide, while same conjugation at 3′-terminus of antisense strand brought no such effects. And it was also found that only the peptide residue in siRNA-pS could be cut off by RNase A. All these results indicated that nucleases in serum prefer to invade siRNA duplex through the 3′-end of sense strand.
In this paper,a series of peptide-siRNA conjugates with phosphodiester unit as the linker targeting to Cdc2 gene were synthesized by solid phase stepwise strategy.The conjugation of peptides at either 3’-terminus of siCdc2 bring no change to the classical A-form of RNA duplex,but slightly compromise the thermodynamic stability.Peptide conjugation at the 3’-terminus of sense strand could improve the serum stability obviously,however,the opposite peptide conjugation at the 3’-terminus of antisense strand shows no such influence.According to the results of artificial silencing activity assay system,peptide conjugation at 3’-terminus of antisense strand slightly weakens the silencing activity of siCdc2.But sense strand peptide conjugation exhibits similar silencing activity as native siCdc2,meanwhile,it could mitigate the unwanted off-target effect of sense strand targeting to its own mRNA.
WANG XiaoFengHUANG YeLIU YangCHEN YueJIN HongWeiZHENG YiDU QuanYANG ZhenJunZHANG LiHe
In this study,a series of 5′-phosphorylated siRNAs with D-/L-isonucleotide(isoNA)or locked nucleic acid(LNA)incorporated at the 5′-terminus were synthesized.It was found that after incorporating either isoNA or LNA at the 5′-terminus of the antisense strand or sense strand,the silencing activity of modified strands has been inhibited,which cannot be recovered by phosphorylation at the 5′-terminus;however,the silencing activity of unmodified strand to its own target was increased.This work indicates that the isoNA and LNA modification at 5′-terminus can interfere with the strand selection during the RISC assembling process,and the disturbance of the 5′-phosporylation should not be the only viable mechanism.
Investigation intracellular trafficking of siRNAs following their delivery to cells is of great interest to elucidate dynamics of siRNA in cytoplasm. In this study, we present a novel confocal laser scanning microscopy （CLSM） method to evaluate a novel delivery system of 3＇-peptide-siRNA therapeutic, which was named 3＇-pAs-siRNA/CLD. This method could not only calculate the content of the intracellular 3＇-peptide-siRNA, but also quantify its co-localization with cellular substructure. We observed that 3＇-pAs-siRNA/CLD, which provided the better antitumor capability, also had a better cell uptake, endosome escape and a longer retention time in A375. This novel strategy was proved to be efficient, quantified and visualized, thus making the dynamics research of siRNA in cytoplasm clear and simplified.
Yiping DiaoJing SunMengyi YangBo XuLihe ZhangZhenjun Yang
Synthetic oligonucleotides including antisense oligonucleotides and siRNA have shown promising therapeutic potential.However,to realize the therapeutic potential of synthetic oligonucleotides,many obstacles have to be overcome,such as their poor biological stability,non-specific activity and inadequate cell membrane permeability.In this paper,the achievements by Lihe Zhang＇s group in the study of isonucleotide modified oligonucleotides and oligonucleotides conjugated with cell penetrating peptides are summarized.
Normally, cellular responses to modified siRNAs or new siRNA delivery systems have been studied in group cell behavior by PCR, western blotting and fluorescence microscopy. In this study, we present a novel high-content screening （HCS） strategy to evaluate a novel delivery system （named CLD） of siRNA therapeutics, with which both the content of intracellular siRNAs and changes in protein expressing levels have been quantified in group cells and cellular population. We also observed that with the better cell uptake, CLD provided siRNA therapeutics （siBraf） better antitumor capability. This novel strategy was proved to be with efficiency, accuracy and high competency to adherent cell lines, thus making siRNA research more simplified.
Cationic lipids have been applied to siRNA delivery for tumor therapeutics. However, the excess positive charges of these nanoplexes may lead to high cytotoxicity and nonnegligible immunogenicity both in vitro and in vivo, which limited the applications of gene drugs. We constructed multi-component lipoplex to delivery 3＇,3＂-bis-peptide-siRNA conjugate （pp-siRNA） by the treatment of melanoma. Based on the previous studies that the gemini lipid （CLD） encapsulated pp-siRNA, a novel neutral cytosin-l-yl- lipid （DNCA） was considered to replace a certain ration of CLD by hydrogen bonds and ~t-n stacking for reducing the cytotoxicity. It similarly retained in both the loading efficiency and targeted mRNA inhibition when DNCA was accounted for 40% in the lipoplex, with lower toxicity. Moreover, CLD/DNCA/pp-siRNA nanoplex could be uptake in A375 cells and internalized mainly by macropinocytosis and caveolin-mediated endocytosis. Besides, 90% CLD/DNCA/pp-siRNA nanoplexes presented the highest efficient knockdown for the mutant B-RAF mRNA （-80%）. All the results demonstrated that the mixed cationic and neutral lipids could efficiently realize the delivery of pp-siRNA and had potential application for cancer therapy.
