Nonisotopic assays of viral polymerases and related proteins

C6-structural optimizations of 2-aryl-1H-pyrazole-S-DABOs: From anti-HIV to anti-DENV activity

Both HIV and DENV are serious threats to human life, health and social economy today. So far, no vaccine for either HIV or DENV has been developed successfully. The research on anti-HIV or DENV drugs is still of great significance. In this study we developed a series of novel 2-Aryl-1H-pyrazole-S-DABOs with C6-strucutral optimizations as potent NNRTIs, among which, 8 compounds had low cytotoxicity and EC₅₀ values in the range of 0.0508 ∼ 0.0966 μM, and their selectivity index was SI > 1415 ∼ 3940. In particular, two compounds 4a and 4b were identified to have good inhibitory effects on DENV of four serotypes. The EC₅₀ of compound 4a and 4b against DENV-II (13.2 μM and 9.23 μM, respectively) were better than that of the positive control ribavirin (EC₅₀ = 40.78 μM). In addition, the effect of C-6 substituents on the anti-HIV or anti-DENV activity of these compounds was also discussed.

Design, synthesis and anti-HIV evaluation of 5-alkyl- 6-(benzo[d][1,3]dioxol-5-alkyl)-2-mercaptopyrimidin-4(3H)-ones as potent HIV-1 NNRTIs

In order to discover and develop the new HIV-1 NNRTIs, a series of 5-alkyl-6-(benzo[d][1,3]dioxol-5-ylalkyl)-2-mercaptopyrimidin-4(3H)-ones was synthesized and screened for their in vitro cytotoxicity against HIV-1. Most of the compounds we synthetized showed high activity against wild-type HIV-1 strain (IIIB) while IC₅₀ values are in the range of 0.06-12.95 μM. Among them, the most active HIV-1 inhibitor was compound 6-(benzo[d][1,3]dioxol-5-ylmethyl)-5-ethyl-2-((2-(4-hydroxyphenyl)-2-oxoethyl)thio)pyrimidin-4(3H)-one (5b), which exhibited similar HIV-1 inhibitory potency (IC₅₀ = 0.06 μM, CC₅₀ = 96.23 μM) compared with nevirapine (IC₅₀ = 0.04 μM, CC₅₀ >200 μM) and most of compounds exhibited submicromolar IC₅₀ values indicating they were specific RT inhibitors. The compounds 5b, 6-(benzo[d] [1,3]dioxol-5-yl)-5-ethyl-2-((2-(4-hydroxyphenyl)-2-oxoethyl)thio)pyrimidin-4(3H)-one (5c) and 4-(2-((4-(benzo[d][1,3]dioxol-5-ylmethyl)-5-ethyl-6-oxo-1,6-dihydropyrimidin-2-yl)thio)acetyl)phenylbenzo[d][1,3]dioxole-5-carboxylate (5r) were selected for further study. It was found that all of them had little toxicity to peripheral blood mononuclear cell (PBMC), and had a good inhibitory effect on the replication of HIV-1 protease inhibitor resistant strains, fusion inhibitor resistant strains and nucleosides reverse transcriptase inhibitor resistant strains, as well as on clinical isolates. Besides, compound 5b and 5c showed inhibition of HIV-1 RT RNA-dependent DNA polymerization activity and DNA-dependent DNA polymerization activity, while compound 5r only showed inhibition of HIV DNA-dependent DNA polymerization activity, which was different from classical reverse transcriptase inhibitors. Our study which offered the preliminary structure-activity relationships and modeling studies of these new compounds has provided the valuable avenues for future molecular optimization.

Synthesis and biological evaluation of a series of 2-(((5-akly/aryl-1H-pyrazol-3-yl)methyl)thio)-5-alkyl-6-(cyclohexylmethyl)-pyrimidin-4(3H)-ones as potential HIV-1 inhibitors

A series of 2-(((5-akly/aryl-1H-pyrazol-3-yl)methyl)thio)-5-alkyl-6-(cyclohexylmethyl)-pyrimidin-4(3H)-ones were synthesized and their anti-HIV-1 activities were evaluated. Most of these compounds were highly active against wild-type (WT) HIV-1 strain (IIIB) with EC₅₀ values in the range of 0.0038–0.4759 μmol/L. Among those compounds, I-11 had an EC₅₀ value of 3.8 nmol/L and SI (selectivity index) of up to 25,468 indicating excellent activity against WT HIV-1. In vitro anti-HIV-1 activity and resistance profile studies suggested that compounds I-11 and I-12 displayed potential anti-HIV-1 activity against laboratory adapted strains and primary isolated strains including different subtypes and tropism strains (EC₅₀s range from 4.3 to 63.6 nmol/L and 18.9–219.3 nmol/L, respectively). On the other hand, it was observed that those two compounds were less effective with EC₅₀ values of 2.77 and 4.87 μmol/L for HIV-1A₁₇ (K103N + Y181C). The activity against reverse transcriptase (RT) was also evaluated for those compounds. Both I-11 and I-12 obtained sub-micromolar IC₅₀ values showing their potential in RT inhibition. The pharmacokinetics examination in rats indicated that compound I-11 has acceptable pharmacokinetic properties and bioavailability. Preliminary structure–activity relationships and molecular modeling studies were also discussed.

Synthetic routes and structure-activity relationships (SAR) of anti-HIV agents: A key review

The worldwide increase of AIDS, an epidemic infection in constant development has an essential and still requires potent antiretroviral chemotherapeutic agents for reducing the integer of deaths caused by HIV. Thus, there is an urgent need for new anti-HIV drug candidates with increased strength, new targets, superior pharmacokinetic properties, and compact side effects. From this viewpoint, we first review present strategies of anti-HIV drug innovation and the synthesis of heterocyclic or natural compound as anti-HIV agents for facilitating the development of more influential and successful anti-HIV agents.

Design, synthesis and anti-HIV-1 RT evaluation of 2-(benzyl(4-chlorophenyl)amino)-1-(piperazin-1-yl)ethanone derivatives

In this study, using molecular hybridization approach, fourteen novel 2-(benzyl(4-chlorophenyl)amino)-1-(piperazin-1-yl)ethanone derivatives (7a-n) were designed as inhibitor of HIV-1 RT. The binding affinity of the designed compounds with HIV-1 RT as well as their drug-likeness behavior was predicted using in-silico studies. All the designed compounds were synthesized, characterized and in-vitro evaluated for HIV-1 RT inhibitory activity, in which tested compounds displayed significant to weak potency against the selected target. Moreover, best active compounds of the series, 7k and 7m inhibited the activity of RT with IC₅₀ values 14.18 and 12.26μM respectively. Structure Activity Relationship (SAR) studies were also performed in order to predict the influence of substitution pattern on the RT inhibitory potency. Anti-HIV-1 and cytotoxicity studies of best five RT inhibitor (7a, 7d, 7k, 7L and 7m) revealed that, except compound 7d other compounds retained significant anti-HIV-1 potency with good safety index. Best scoring pose of compound 7m was analysed in order to predict its putative binding mode with wild HIV-1 RT.

Synthesis, biological properties and anti-HIV-1 activity of new pyrimidine P1,P2-dinucleotides

New homo- and hetero-P(1),P(2)-dinucleotides were prepared with the use of multistep procedures starting from the monophosphates of 3'-fluoro-2-thiothymidine, 3'-fluoro-4-thiothymidine, AZT and 1-[(2-hydroxyethoxy)-methyl-5-propyl-6-phenylselenenyl]uracil. Anti-HIV properties of the synthesized P(1),P(2)-dinucleotides were evaluated against laboratory syncytia inducing strain HIV-1 in CEM-T4 cells. Anti-HIV activities were in the range of 5-45 nM, and therapeutic indexes were higher than 4666-14000. Interactions of the above mentioned compounds with recombinant HIV-1 reverse transcriptase were also investigated. The obtained results point to reverse transcriptase inhibition, with somewhat lower inhibitory activity than that of their parental nucleoside-5'-triphosphates. Compound 6 may be regarded as a potent anti-HIV/AIDS drug.

A simple and rapid reverse transcriptase assay for the detection of retroviruses in cell cultures

Reverse transcriptase (RT) is a good diagnostic tool for the detection of retroviruses. We have developed a simple and rapid assay for RT activity in culture supernatants. A 370-base RNA sequence from the tetracycline-resistance gene in pBR322 plasmid DNA was used as a template for RT-mediated cDNA synthesis. To detect the resultant cDNA, we used the nested polymerase chain reaction. A sensitivity test using purified recombinant RT of human immunodeficiency virus type 1 demonstrated that the detection limit of this method was 10-7-10-8 units of RT activity in 20 mul of a test sample (2 x 10-9-2 x 10-10 units ml-1). This method detected RT activity in unconcentrated supernatants of cell cultures infected with human T-cell leukemia virus, Moloney murine leukemia virus, Moloney murine sarcoma virus, or Rous sarcoma virus. This nonisotopic method provides results within 10 h and is useful for quality control to detect retroviruses in cell cultures.

Immunogenicity of a chimeric hepatitis A virus (HAV) carrying the HIV gp41 epitope 2F5

Its stable particle structure combined with its high immunogenicity makes the hepatitis A virus (HAV) a perfect carrier to expose foreign epitopes to the host immune system. In an earlier report [Beneduce, F., Kusov, Y., Klinger, M., Gauss-Müller, V., Morace, G., 2002. Chimeric hepatitis A virus particles presenting a foreign epitope (HIV gp41) at their surface. Antiviral Res. 55, 369-377] chimeric virus-like particles (HAV-gp41) were described that carried at their surface the dominant gp41 epitope 2F5 (2F5e) of the human immunodeficiency virus HIV-1. Extending this work, we now report that chimeric virus HAV-gp41 replicates in HAV-susceptible cells as well as in non-human primates. Infected marmosets developed both an anti-HAV and anti-2F5 epitope immune response. Furthermore, an HIV-neutralizing antibody response was elicited in guinea pigs immunized with HAV-gp41 chimeric particles. The results demonstrate that the replication-competent chimeric HAV-gp41 can serve as either a live or a subunit vaccine for eliciting of antibodies directed against a foreign antigenic epitope.

Modulation of HIV-1 enhancer activity and virus production by cAMP

The effect of cAMP on the transcriptional activity of the HIV-1 long terminal repeat/enhancer was investigated and compared to the effect of cAMP on virus replication. In culture cAMP repressed virus replication in vivo using different cell types. Transient transfection studies with HIV-1 enhancer-derived luciferase reporter gene constructs identified the minimal DNA sequence mediating the negative regulatory effect of cAMP on HIV-1 transcription. A single nuclear factor kappaB element from the HIV-1 enhancer mediates the repressive effect on transcription. AP-2 is not involved in cAMP repression. Stable transfection of Jurkat T cells with the co-activators CREB binding protein (CBP) and p300 completely abolished the cAMP repressive effect, supporting the hypothesis that elevation of intracellular cAMP increases phosphorylation of CREB, which then competes with phosphorylated p65 and Ets-1 for limiting amounts of CBP/p300 thereby mediating the observed repressive effect on transcription. These findings suggest an important role of cAMP on HIV-1 transcription.