PubMed · 9254795
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C Bloch. 1997. Virodene--support misguided.. https://pubmed.ncbi.nlm.nih.gov/9254795/
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BACKGROUND: HIV proviral sequencing overcomes the limit of plasma viral load requirement by detecting all the 'archived mutations', but the clinical relevance remains to be evaluated. METHODS: We included 25 participants with available proviral sequences (both intact and defective sequences available) and utilized the genotypic sensitivity score (GSS) to evaluate the level of resistance in their provirus and plasma virus. Defective sequences were further categorized as sequences with and without hypermutations. Personalized GSS score and total GSS score were calculated to evaluate the level of resistance to a whole panel of antiretroviral therapies and to certain antiretroviral therapy that a participant was using. The rate of sequences with drug resistance mutations (DRMs) within each sequence compartment (intact, defective and plasma viral sequences) was calculated for each participant. RESULTS: Defective proviral sequences harbored more DRMs than other sequence compartments, with a median DRM rate of 0.25 compared with intact sequences (0.0, P = 0.014) and plasma sequences (0.095, P = 0.30). Defective sequences with hypermutations were the major source of DRMs, with a median DRM rate of 1.0 compared with defective sequences without hypermutations (0.042, P < 0.001). Certain Apolipoprotein B Editing Complex 3-related DRMs including reverse transcriptase gene mutations M184I, E138K, M230I, G190E and protease gene mutations M46I, D30N were enriched in hypermutated sequences but not in intact sequences or plasma sequences. All the hypermutated sequences had premature stop codons due to Apolipoprotein B Editing Complex 3. CONCLUSION: Proviral sequencing may overestimate DRMs as a result of hypermutations. Removing hypermutated sequences is essential in the interpretation of proviral drug resistance testing.
BACKGROUND: To initiate immunity, dendritic cells (DCs) capture antigens or viruses at body surfaces, undergo maturation to express T-cell costimulatory molecules, and then migrate to lymphoid organs. DCs at body surfaces can capture human immunodeficiency virus 1 (HIV-1), but mature DCs do not support replication of the virus unless T cells are added. The initial site for HIV-1 replication remains unknown and it is unclear whether replication can take place in DCs or whether the virus must first be transmitted from DCs to T cells. RESULTS: We generated mature DCs from monocyte precursors. Upon infection with HIV-1, reverse transcription was completed only when T cells were added. When the reverse transcriptase inhibitor azidothymidine was added to the DCs during exposure to HIV-1, the DCs remained fully infectious, as long as the drug was removed just before culturing the DCs with T cells. HIV-1 variants that were engineered to undergo only one cycle of replication were able to infect DCs and replicate once in these cells. When T cells were added, newly produced HIV-1 Gag protein was exclusively localized to the DCs. With wild-type virus, subsequent rounds of replication took place in T cells. Soluble CD40 ligand (CD40L) and CD40L-transfected fibroblasts stimulated HIV-1 replication in purified mature DCs. CONCLUSIONS: Mature DCs provide a drug-resistant reservoir for HIV-1. This reservoir is activated within DCs by CD40L and upon interaction with T cells, and the virus then spreads rapidly to other T cells.
Among the nucleoside inhibitors used clinically as anti-HIV drugs which target HIV-1 reverse transcriptase (RT), (-)-2', 3'-dideoxy-3'-thiacytidine [(-)SddC or 3TC] is the only analogue with the unnatural L(-) nucleoside configuration. 3TC has been shown to be more potent and less toxic than the D(+) isomer, (+)SddC, which has the natural nucleoside configuration. The mechanistic basis for the stereochemical selectivity and differential toxicity of the isomeric SddC compounds is not completely understood although a number of factors may clearly come into play including differences in uptake, metabolic activation, degradation, and transport. We used a pre-steady-state kinetic analysis to determine the maximum rate of incorporation, kpol, nucleotide-binding affinity, Kd, and efficiency of incorporation, kpol/Kd, for the (-) and (+) isomeric SddCTP compounds as well as the corresponding dideoxy and natural nucleoside triphosphates into a primer-template complex using HIV-1 reverse transcriptase. The affinity (Kd) of the dNTP was much tighter and the efficiency (kpol/Kd) of incorporation by enzyme into the primer-template complex was much higher for the DNA/RNA primer-template compared to DNA/DNA. The maximum rate of incorporation, kpol, followed the trend of dCTP > ddCTP > (+)SddCTP > (-)SddCTP while the Kd values determined for the DNA/RNA primer-template followed the order (-)SddCTP congruent with (+)SddCTP congruent with ddCTP > dCTP. The corresponding efficiency of incorporation followed the trend dCTP > ddCTP > (+)SddCTP > (-)SddCTP. These data suggest that perturbations on the ribose ring of cytidine analogues (C --> S) decrease the rate and efficiency of incorporation but enhance the binding affinity. These results are discussed in the context of a computer modeled structure of the ternary complexes of RT, DNA/RNA primer-template, and SddCTP analogues as well as implications for structure-activity relationships and further drug design. This information provides a mechanistic basis for understanding the inhibition of HIV-1 reverse transcriptase by 3TC.