Synthesis And Antiviral Evaluation Of 2′,3′-Secothymidine Analogs of ddT and AZT

Abstract

2′,3′-Secothymidine derivatives related to AZT and ddT have been synthesized and evaluated for their activity against HIV-1 and various DNA and RNA viruses. These acyclic nucleosides exhibited no antiviral activities.     

人免疫缺陷病毒I型抗AZT抗药株的体外研究

人免疫缺陷病毒Ⅰ型（ＨＩＶ－１）抗３＇─叠氮─３＇─脱氧胸腺嘧啶（ＡＺＴ）抗药株经体外感染Ｃ８１６６淋巴细胞在高浓度ＡＺＴ条件下筛选获得,并暂命名为ＨＩＶ─１─Ｒ株。该抗药株与ＨＴＬＶ─ⅢＢ株相比,在同一感染复数（Ｍ０１）病毒量感染Ｃ８１６６细胞,经不同浓度的ＡＺＴ处理后,其复制的病毒量和对ＡＺＴ的敏感性有显著的差异,抗药株感染Ｃ８１６６细胞,加ＡＺＴ处理后,分离细胞ＤＮＡ作ＰＣＲ扩增后分析,特异性病毒的ＤＮＡ量比敏感株高１００倍以上,显示其抗药性作用点在病毒逆转录ＤＮＡ前。     

Antiviral Nucleoside Drug Delivery via Amino Acid Phosphoramidates

Abstract

Stable and water soluble amino acid phosphomonoester amidates of AZT were synthesized and shown to have potent anti-HIV-1 activity. Intracellular and cell extract metabolism studies revealed that these compounds are likely to be enzymatically converted to the corresponding monophosphates. In addition, we have shown that the half life and tissue distribution of a phosphoramidate of AZT is 5 and 10-fold greater, respectively, than AZT.     

Synthesis of 1′,2′-Seco-nucleoside Analogues of AZT

Abstract

1′,2′-Seco-AZT (3) and its 3′R,4′S diastereomer (19) were prepared and evaluated as antiviral agents. The chiral, acyclic side chains of these thymine acyclonuleosides were derived from D-isoascorbic acid. The two AZT analogues, 3 and 19, were screened against HIV, other RNA viruses, and two DNA viruses and they were found to be inactive.     

Expression of an extracellular ribonuclease gene increases resistance to Cucumber mosaic virus in tobacco

Background

The apoplast plays an important role in plant defense against pathogens. Some extracellular PR-4 proteins possess ribonuclease activity and may directly inhibit the growth of pathogenic fungi. It is likely that extracellular RNases can also protect plants against some viruses with RNA genomes. However, many plant RNases are multifunctional and the direct link between their ribonucleolytic activity and antiviral defense still needs to be clarified. In this study, we evaluated the resistance of Nicotiana tabacum plants expressing a non-plant single-strand-specific extracellular RNase against Cucumber mosaic virus.

Results

Severe mosaic symptoms and shrinkage were observed in the control non-transgenic plants 10 days after inoculation with Cucumber mosaic virus (CMV), whereas such disease symptoms were suppressed in the transgenic plants expressing the RNase gene. In a Western blot analysis, viral proliferation was observed in the uninoculated upper leaves of control plants, whereas virus levels were very low in those of transgenic plants. These results suggest that resistance against CMV was increased by the expression of the heterologous RNase gene.

Conclusion

We have previously shown that tobacco plants expressing heterologous RNases are characterized by high resistance to Tobacco mosaic virus. In this study, we demonstrated that elevated levels of extracellular RNase activity resulted in increased resistance to a virus with a different genome organization and life cycle. Thus, we conclude that the pathogen-induced expression of plant apoplastic RNases may increase non-specific resistance against viruses with RNA genomes.

     

Synthesis,Anti-Hiv Activity,and Biological Properties of 2′,3′-Didehydro-2′,3′-Dideoxythwidine (d4T)

Abstract

D4T is a thymidine analogue with an in vitro potency against HIV comparable to that of AZT but is less toxic to a variety of cell lines including human hemopoietic progenitor cells.     

Synthetic and Antiviral Studies of Certain Acyclic 3′-Azido-3′-Deoxythymidine (AZT) Analogues

Abstract

A direct alkylation of trimethylsilylated pyrimidines and azapyrimidines with 1-azido-3-benzyloxy-2-chloromethoxypropane gave acyclic analogues of AZT in a good overall yield. None of the compounds exhibited significant antiviral activity against human immunodeficiency virus and herpes simplex virus.     

Mechanism of antiviral drug resistance of vaccinia virus: identification of residues in the viral DNA polymerase conferring differential resistance to antipoxvirus drugs

The acyclic nucleoside phosphonate (ANP) family of drugs shows promise as therapeutics for treating poxvirus infections. However, it has been questioned whether the utility of these compounds could be compromised through the intentional genetic modification of viral sequences by bioterrorists or the selection of drug resistance viruses during the course of antiviral therapy. To address these concerns, vaccinia virus (strain Lederle) was passaged 40 times in medium containing an escalating dose of (S)-1-[3-hydroxy-2-(phosphonomethoxypropyl)-2,6-diaminopurine [(S)-HPMPDAP], which selected for mutant viruses exhibiting a ~15-fold-increased resistance to the drug. (S)-HPMPDAP-resistant viruses were generated because this compound was shown to be one of the most highly selective and effective ANPs for the treatment of poxvirus infections. DNA sequence analysis revealed that these viruses encoded mutations in the E9L (DNA polymerase) gene, and marker rescue studies showed that the phenotype was produced by a combination of two (A684V and S851Y) substitution mutations. The effects of these mutations on drug resistance were tested against various ANPs, both separately and collectively, and compared with E9L A314T and A684V mutations previously isolated using selection for resistance to cidofovir, i.e., (S)-1-[3-hydroxy-2-(phosphonomethoxypropyl)cytosine]. These studies demonstrated a complex pattern of resistance, although as a general rule, the double-mutant viruses exhibited greater resistance to the deoxyadenosine than to deoxycytidine nucleotide analogs. The S851Y mutant virus exhibited a low level of resistance to dCMP analogues but high-level resistance to dAMP analogues and to 6-[3-hydroxy-2-(phosphonomethoxy)propoxy]-2,4-diaminopyrimidine, which is considered to mimic the purine ring system. Notably, (S)-9-[3-hydroxy-2-(phosphonomethoxy)propyl]-3-deazaadenine retained marked activity against most of these mutant viruses. In vitro studies showed that the A684V mutation partially suppressed a virus growth defect and mutator phenotype created by the S851Y mutation, but all of the mutant viruses still exhibited a variable degree of reduced virulence in a mouse intranasal challenge model. Infections caused by these drug-resistant viruses in mice were still treatable with higher concentrations of the ANPs. These studies have identified a novel mechanism for the development of mutator DNA polymerases and provide further evidence that antipoxviral therapeutic strategies would not readily be undermined by selection for resistance to ANP drugs.