Antiviral Chemistry and Chemotherapy

We have shown that the K65R resistance mutation in HIV type-1 (HIV-1) reverse transcriptase (RT) is selected more rapidly in subtype C than subtype B HIV-1 in biochemical, cell culture and clinical studies. Template-usage experiments demonstrated that subtype C nucleotide coding sequences caused RT to preferentially pause, leading to K65R acquisition. This new study now further establishes the basis for differential occurrence of both K65R and thymidine analogue mutations (TAMs) between subtypes.

Gel-based nucleotide extension assays were used to study the homopolymeric sequence surrounding K65.

When positive double-stranded DNA synthesis was evaluated from a negative single-stranded DNA template, pausing at the 67 region, which is linked to occurrence of TAMs, was alleviated with both subtype B and C templates at high dCTP concentrations, but this alleviation was more pronounced with the subtype C template. By contrast, pausing at the 65 region on the subtype C but not subtype B template always occurred and was not alleviated at high levels of nucleotide triphosphates or by other means. Furthermore, templates containing repeats of the homopolymeric sequence spanning codons 64–66 of pol showed corresponding pausing repeats at the 65 region with the subtype C template only. Inverted RNA and DNA templates both displayed pausing at position K65 for the subtype C template and a ladder of pausing events culminating at codon 67 for the subtype B templates.

These results further establish a mechanistic basis for the exclusion of both K65R and TAMs on single templates as well as the preferential acquisition of K65R in subtype C viruses.

Olomoucine II, the most recent derivative of roscovitine, is an exceptionally potent pharmacological inhibitor of cyclin-dependent kinase activities. Here, we report that olomoucine II is also an effective antiviral agent.

Antiviral activities of olomoucine II were tested on a range of human viruses in in vitro assays that evaluated viral growth and replication.

Olomoucine II inhibited replication of a broad range of wild-type human viruses, including herpes simplex virus, human adenovirus type-4 and human cytomegalovirus. Olomoucine II also inhibited replication of vaccinia virus and herpes simplex virus mutants resistant to conventional acyclovir treatment. This report is the first demonstration of a poxvirus being sensitive to a cyclin-dependent kinase inhibitor. The antiviral effects of olomoucine II could be observed at lower concentrations than with roscovitine, although both were short-term. A remarkable observation was that olomoucine II, when used in combination with the DNA polymerase inhibitor cidofovir, was able to almost completely eliminate the spread of infectious adenovirus type-4 progeny from infected cells.

Our results show that when targeting two complementary antiviral mechanisms, strongly additive effects could be observed.

The development of antiviral drugs has provided crucial new means to mitigate or relieve the debilitating effects of many viral pathogens. New classes of inhibitors are essential to combat swine influenza viral infection.

A series of isatine-sulfadimidine derivatives were screened for antiviral activity against swine influenza A/California/07/2009 (H1N1) virus in Madin–Darby canine kidney (MDCK) cell culture. Cytotoxicity of the synthesized compounds was also tested in uninfected MDCK cells.

All the compounds inhibit the influenza A (H1N1) in MDCK cells. The most active compounds, SPIII-5Br and SPIII-5H, inhibited virus-induced cytopathology by 50% at 27 and 30 μM, respectively, with 50% cytotoxicity occurring at a much higher dose (975–1,000 μM). The positive control compound ribavirin inhibits the replication of the virus at 18 μM and cytotoxic concentration was found to be >1,000 μM.

SPIII-5Br and SPIII-5H exhibited potency in the same range as ribavirin and are suitable candidate molecules for further investigation.