We have recently discovered that 6-aminoquinolone derivatives could be valid leads for the development of new anti-HIV agents because of their new and diversified mode of action. In fact, studies carried out on the lead WM5 showed that this derivative is able to inhibit the Tat-mediated long terminal repeat driven transcription, an essential step in the HIV-1 replication cycle. Thus, starting from lead WM5, we performed the design and synthesis of an enlarged series of 6-aminoquinolones, which permitted some very potent anti-HIV 6-amino derivatives to be obtained and the structure−activity relationship to be delineated. Some derivatives, 26c, 26e, 26i, and 26j, proved to be highly effective in inhibiting HIV replication at 50% inhibitory concentration in the range of 0.0087−0.7 μg/mL in MT-4, PBMCs and CEM cell lines coupled with positive selectivity indexes that reach values higher than 1000 on CEM cell lines for compounds 26e and 26i. Time-of-addition experiments clearly confirm that the new, potent 6-aminoquinolones interact at a postintegration step in the replication cycle of HIV.
Various carbocyclic analogues of adenosine, including aristeromycin (carbocyclic adenosine), carbocyclic 3-deazaadenosine, neplanocin A, 3-deazaneplanocin A, the 5'-nor derivatives of aristeromycin, carbocylic 3-deazaadenosine, neplanocin A and 3-deazaneplanocin A, and the 2-halo (i.e., 2-fluoro) and 6'-R-alkyl (i.e., 6'-R-methyl) derivatives of neplanocin A have been recognized as potent inhibitors of S-adenosylhomocysteine (AdoHcy) hydrolase. This enzyme plays a key role in methylation reactions depending on S-adenosylmethionine (AdoMet) as methyl donor. AdoHcy hydrolase inhibitors have been shown to exert broad-spectrum antiviral activity against pox-, paramyxo-, rhabdo-, filo-, bunya-, arena-, and reoviruses. They also interfere with the replication of human immunodeficiency virus through inhibition of the Tat transactivation process.
Intravenous inoculation of mice with vaccinia virus produced characteristic lesions of the tail surface which were suppressed by intraperitoneal administration of interferon and polyacrylic acid (PAA). Polymethacrylic acid (PMAA) stimulated the formation of vaccinia virus lesions. For full activity, both interferon and PAA must be given prior to infection. PAA was still significantly effective at small dose levels (3 mg/kg) and achieved protection for at least 4 weeks. Protection increased with increasing molecular weight of the polymer. The mode of action of PAA is discussed.
Poly(c 3 A) (poly 3-deazaadenylic acid) and poly(c 3 I) (poly 3-deazainosinic acid) differ in biological reactivity from their parent compounds poly(A) and poly(I) and from their 7-deaza counterparts poly(c 7 A) and poly(c 7 I). Three parameters of biological reactivity were evaluated : (1°) interferon induction, (2°) anti-complement activity, (3°) reverse transcriptase inhibition. Unlike poly(A).poly(U), poly(I).poly(C) and poly(I).poly(br 5 C), the mixtures of poly(c 3 A) + poly(U), poly(c 3 I) + poly(C), and poly(c 3 I) + poly(br 5 C) failed to elicit an interferon response in “superinduced” primary rabbit kidney cells. Poly(I) and its analogs poly(c 3 I) and poly(c 7 I) inhibited hemolytic complement activity, whereas poly(A) and its analogs poly(c 3 A) and poly(c 7 A) failed to do so. Both poly(I) and poly(c 7 I), but not poly(c 3 I), lost their anti-complement potency when annealed to either poly(C) or poly(A).poly(U). Similarly, poly(I) and poly(c 7 I), but not poly(c 3 I), suppressed the interferon inducing ability of poly(A).poly(U), suggesting that both poly(I) and poly(c 7 I), but not poly(c 3 I), added to poly(A).poly(U) to form a triple-helical structure. Poly(I), poly(c 7 I) and poly(c 7 A) exerted a distinct inhibitory effect on the endogenous RNA directed DNA polymerase (reverse transcriptase) activity of murine leukemia virus, while under the same conditions poly(c 3 I) and poly(c 3 A) showed little, if any, inhibitory effect.
The ribonucleoside analogues (E)-5-(2-bromovinyl)uridine (5-BV-Urd) and 3'-spiro-(4'-amino-1',2'-oxathiole-2',2'-dioxide)-5-methyluridine (3'-AOD-5-MeUrd) emerged as potent and selective competitive inhibitors of mitochondrial thymidine kinase (TK)-2 with respect to thymidine (K(i)/K(m) values of 9.0 and 1.2 respectively). Cytosolic TK-1 did not show measurable affinity for these compounds. [(32)P]Phosphate transfer studies from [gamma-(32)P]ATP to 5-BV-Urd and 3'-AOD-5-MeUrd revealed extremely poor substrate activity but potent inhibitory potential of the compounds. It was concluded that the ribonucleosides 5-BV-Urd and 3'-AOD-5-MeUrd represent two new lead compounds for potent and selective inhibitors of mitochondrial TK-2.
SUMMARY The acid-insoluble radioactivity associated with the cells following incubation of the cells with [3H]-labelled poly(I).poly(C) [poly(I).poly(C)* for 1 h has been analysed by sucrose gradient velocity ultracentrifuging. Intact (poly(I).poly(C)* was recovered from primary rabbit kidney (PRK) cells, partially degraded poly(I). poly(C)* was recovered from mouse L 929 cells and completely degraded material was recovered from HeLa and VERO cells. Priming of the cells with homologous interferon did not alter the sedimentation profile of cell-associated poly(I).poly(C)* in PRK, L 929 or HeLa cells.
Since the Human Immunodeficiency Virus Type 1 (HIV-1) was identified as the etiologic agent of the Acquired Immune Deficiency Syndrome (AIDS), the HIV-1 reverse transcriptase (RT) has been the subject of intensive study. The reverse transcription entails the transition of the single-stranded viral RNA into double-stranded proviral DNA, which is then integrated into the host chromosome. Therefore, the HIV-1 reverse transcriptase plays a pivotal role in the life cycle of the virus and is consequently an interesting target for anti-HIV drug therapy. In the first section, we describe the complex process of reverse transcription and the different activities involved in this process. We then highlight the structure-function relationship of the HIV-1 reverse transcriptase, which is of great importance for a better understanding of resistance development, a major problem in anti-AIDS therapies. Finally, we summarize the mechanisms of HIV resistance toward various RT inhibitors and the implications thereof for the current anti-HIV drug therapies.
