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The configurations of metallocyclams are of interest in relation to protein recognition and anti-HIV activity. We have synthesised four novel zinc(II) complexes with hexyl-Me(2)-cyclam (HMC; 3,14-dimethyl-2,6,13,17-tetraazatricyclo(16.4.0.0(7,12))docosane), 1, and naphthyl-hexyl-Me(2)-cyclam (NHMC; 2,13-bis(1-naphthylmethyl)-5,16-dimethyl-2,6,13,17-tetraazatricyclo(16.4.0.0(7,12))docosane), 2, as ligands. X-ray crystallographic data for Zn(II)-HMC diacetate, 3 show that zinc is six-coordinate in a distorted octahedral environment bound to four equatorial N atoms from the macrocycle and two axial acetato O atoms. The 14-membered metallo-macrocycle adopts a trans-III (RRSS) configuration with two six-membered rings in chair forms and two five-membered rings in gauche forms. In the chlorido Zn(II)-HMC complex 5, zinc appears to be 5-coordinate with square-pyramidal geometry. Interestingly, the chlorido Zn(II)-NHMC complex 6 crystallised in a trans-I configuration containing 4-coordinate tetrahedral zinc bound to three cyclam ring N atoms, a possible model for intermediates formed during the uptake and release of metals by cyclams. The ligand 1 and the zinc complex 3 were active towards viral strains HIV-1 (III(B)) (IC(50) values of 10.51 ± 0.23 and 3.50 ± 0.33 μM, respectively), and HIV-2 (ROD) (IC(50) values of 133.78 ± 14.10 and >110.67 μM, respectively). 2D [(1)H, (13)C] and [(1)H, (15)N] NMR spectroscopic studies suggested that the types of configurational isomers present in solution depend on the axial ligand.
There are a number of virus-specific processes within the virus replicative cycle or virus-infected cell that have proven to be attractive targets for chemotherapeutic intervention, i.e., virus adsorption and entry into the cells, reverse (RNA --> DNA) transcription, viral DNA polymerization, and cellular enzymatic reactions that are associated with viral DNA and RNA synthesis and viral mRNA maturation (i.e., methylation). A variety of chemotherapeutic agents, both nucleoside (and nucleotide) and non-nucleoside entities, have been identified that specifically interact with these viral targets, that selectively inhibit virus replication, and that are either used or considered for clinical use in the treatment of virus infections in humans. Their indications encompass virtually all major human viral pathogens, including human immunodeficiency virus (HIV), hepatitis B virus (HBV), herpes simplex virus (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV), human papilloma virus (HPV), orthomyxoviruses (influenza A and B), paramyxoviruses [e.g., respiratory syncytial virus (RSV)] and hemorrhagic fever viruses (such as Ebola virus).
The role of host defense mechanism against murine cytomegalovirus (MCMV) infection in mice with severe combined immunodeficiency (SCID) was investigated using polyinosinic:polycytidylic acid (poly I:C) as a nonspecific stimulator of the immune system. When administered ip at doses of 3.7 or 15 mg/kg 18 hr prior to infection of SCID mice with 10(3) or 10(4) plaque-forming units of MCMV, poly I:C significantly increased the animals' life span. Poly I:C enhanced, in a dose-dependent manner (0.01-1 mg/kg), the peritoneal natural killer (NK)-cell activity and macrophage activity of SCID mice. When SCID mice were pretreated with anti-asialo GM1 antibody (against NK cells) or anti-Mac1 antibody (against macrophages), poly I:C failed to stimulate the activity of NK cells and macrophages. Intraperitoneal administration of poly I:C also induced both early (2 hr) and late (18 hr) type interferon (IFN) in the peritoneal fluid and blood. The IFN-inducing activity of polyl:C was not affected by pretreatment of the mice with anti-asialo GM1 or anti-Mac1 antibody. Poly I:C also caused a significant but less pronounced increase in the life span of MCMV-infected SCID mice in which the NK cells or macrophages had been depleted by treatment with anti-asialo GM1 or anti-Mac1 antibody, respectively. These results suggest that poly I:C-induced interferon as well as activation of NK cell and macrophages contribute to the host defense mechanism against MCMV infection in SCID mice.
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HIV inhibitors targeted at the virus-associated reverse transcriptase (RT) can be divided into two groups, depending on whether they are targeted at the substrate or nonsubstrate binding site. To the first group belong the 2',3'-dideoxynucleosides (i.e., DDC, DDI), 3'-azido-2',3'-dideoxynucleosides (i.e., AZT), 3'-fluoro-2',3'-dideoxynucleosides (i.e., FLT), 2',3'-didehydro-2',3'-dideoxynucleosides (i.e., D4C, D4T) and carbocyclic derivatives thereof (i.e., carbovir), 2'-fluoro-ara-2',3'-dideoxynucleosides, 1,3-dioxolane derivatives (i.e., 2',3'-dideoxyl-3'-thiacytidine), oxetanocin analogues and carbocyclic derivatives thereof (i.e., cyclobut-G) and the 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and 9-(3-fluoro-2-phosphonylmethoxypropyl)adenine (FPMPA) derivatives. These compounds need to be phosphorylated intracellularly to their triphosphate forms before they act as competitive inhibitors or alternate substrates (chain terminators) of HIV RT. The second group includes the tetrahydro-imidazo[4,5,l-jk][1,4]-benzodiazepin-2(1H)one (TIBO), 1-[(2-hydroxyethoxy)-methyl]-6-(phenylthio)thymine (HEPT), dipyrido[3,2-b:2',3'-e]-[1,4]diazepin-6-one (nevirapine) and pyridin-2(1H)one derivatives, which interact as such, noncompetitively, with a specific allosteric binding site of HIV-1 RT. Compounds belonging to the two different groups may give rise to synergism which combined, and, likewise, viral resistance to the compounds may arise through different mutations, depending on the nature of the compounds and the group to which they belong.
