Inhibition of vaccinia virus growth and virus-specific RNA synthesis by 3'-O-methyl adenosine and 3'-O-methyl guanosine

A practical and scalable synthesis of several base modified 3'-O-methyl ribonucleosides

An easy and efficient large-scale synthesis of 1, 2,-di-O-acetyl-5-O-benzoyl-3-O-methyl-d-ribofuranose (8) was accomplished from commercial 1,2:5,6-di-O-isopropylidene-α-d-allofuranose in 7-steps and 30 % overall yield. The utility of protected 8 was demonstrated via synthesis of 9-(3'-O-methyl-β-d-ribofuranosyl)-6-chloropurine (21) and six other nucleoside analogues in good yields. A library of five novel base modified nucleosides were generated starting from purine nucleoside 21 via functional group manipulations. The 3'-O-modified nucleosides are known to act as chain terminator exerting antiviral activity. The synthesis strategy described herein offers direct access to 3'-O-alkylated nucleosides with wide range of applications, including cap analogues for mRNA vaccine production. This protocol provides a route to exclusive synthesis of 3'-O-alkylated nucleosides, devoid of isomeric 2'-O-alkylated products essential for both therapeutic and biological research.

Anti-cowpox virus activities of certain adenosine analogs, arabinofuranosyl nucleosides, and 2'-fluoro-arabinofuranosyl nucleosides

Nucleoside analogs were investigated for their potential to inhibit cowpox virus (a surrogate for variola and monkeypox viruses) in cell culture and in lethal respiratory infections in mice. Cell culture antiviral activity was determined by plaque reduction assays, with cytotoxicity determined by cell proliferation assays. Selectivity indices (SI's, 50% cytotoxic concentration divided by 50% virus-inhibitory concentration) were determined for 15 compounds. Three arabinofuranosyl (Ara) nucleosides showed activity in mouse mammary tumor (C127I) cells: guanine (Ara-G), thymine (Ara-T), and adenine (Ara-A) with SI's of 113, 61, and 95, respectively. The 2'-fluoro-Ara nucleosides of 5-F-cytosine (FIAC), 5-methyluracil (FMAU), and 5-iodouracil (FIAU) exhibited SI's of 148, 77, and 29, respectively. Other potent compounds included cidofovir (a positive control) and 3'-O-methyladenosine, with SI values of 164 and 56, respectively. In general, assays performed in African green monkey kidney (Vero) cells produced lower SI's than in C127I cells, except for 5-iodo-2'-deoxyuridine (IDU) which had an SI of > 71 in Vero cells and 3.1 in C127I cells. Intranasal infection of mice with cowpox virus was followed a day later by twice daily intraperitoneal treatment with compounds for 5 days. Ara-A was active at 300 mg/kg/day (40% survival), FMAU at 100 mg/kg/day (70% survival), and cidofovir (given for 1 day only) at 100 mg/kg (80-100% survival). None of the other compounds, including IDU, prevented death nor delayed the time to death. Cidofovir had the best potential for treating orthopoxvirus infections of those tested.

Antiviral activity and inhibition of topoisomerase by ofloxacin, a new quinolone derivative

The antiviral activity of ofloxacin, a new quinolone derivative, against vaccinia virus (VV), herpes simplex virus (HSV) and influenza virus (InfV) was evaluated in both in vitro and in vivo experiments. As a result, ofloxacin showed inhibitory activity against VV in cultured mammalian cells, and prevented formation of pox tail lesions in VV-infected mice. However, it was less effective against HSV and InfV than VV. The antiviral activity of ofloxacin assessed by VV tail-lesion test was strongest when administered to mice through the oral route daily for five consecutive days post-infection. Nalidixic acid and novobiocin, well-known gyrase inhibitors, showed only weak antiviral activity in both in vitro and in vivo tests against VV. It was also demonstrated that ofloxacin inhibited virus-specific DNA and RNA syntheses. It was more inhibitory to VV topoisomerase than cellular topoisomerases. Thus, ofloxacin has selectivity for VV.

Mechanism of inhibition of herpesvirus growth by 2'-5'-linked trimer of 9-beta-D-xylofuranosyladenine

The 2'-5'-linked trimer of 9-beta-D-xylofuranosyladenine (XyloA)3 is an extremely potent inhibitor of growth of herpes simplex viruses 1 and 2. Evidence is presented that in spite of its increased stability in cell-free extracts (D.A. Eppstein, Y.V. Marsh, B.B. Schryver, M.A. Larsen, J.W. Barnett, J.P.H. Verheyden, and E.J. Prisbe, J. Biol. Chem. 257, 13390-13397, 1982), intact (XyloA)3 was not detected in Vero cells, but instead was rapidly degraded in the medium to monomeric 9-beta-D-xylofuranosyladenine (XyloA). The XyloA thus formed was rapidly taken up by cells, phosphorylated to its triphosphate, and produced inhibition of RNA synthesis. The observed inhibition of DNA synthesis (D.A. Eppstein, Y.V. Marsh, B.B. Schryver, M.A. Larsen, J.W. Barnett, J.P.H. Verheyden, and E.J. Prisbe, J. Biol. Chem. 257, 13390-13397, 1982) and herpesvirus growth by (XyloA)3 (D.A. Eppstein, J.W. Barnett, Y.V. Marsh, G. Gosselin, and J.L. Imbach, Nature (London) 302, 723, 724, 1983) is most likely the result of inhibition of RNA synthesis by its degradation product XyloA.