PubMed · 12089516
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2002. Interfering with HIV.. https://doi.org/10.1038/ng0702-231
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The interferon sensitivity-determining region (ISDR) is useful as a predictive marker of the response to interferon (IFN) therapy for chronic hepatitis patients with a Japan-specific subtype (J-type) of hepatitis C virus (HCV) genotype 1b. This marker is not useful for predicting responsiveness of a worldwide subtype (W-type) of HCV 1b, which could explain the restricted usefulness of this system only to Japan. In the present study, we examined the predictive value of the ISDR for ribavirin combination therapy. A total of 79 patients with HCV 1b comprising 35 patients with J-type and 44 patients with W-type were treated with IFN in combination with ribavirin for more than 48 weeks. Mutations in the ISDR were detected more frequently often seen in J-type HCV 1b than in W-type; however, the sustained virological response (SVR) rate for the combination therapy was similar between the two subtypes. Multivariate analysis revealed that factors associated with SVR were IFN dose and the number of amino acid substitutions in ISDR but not with subtypes J and W. The correlation between the number of substitutions in ISDR and responses to IFN-ribavirin combination therapy was restricted to patients with J-type HCV 1b. The ISDR is a useful predictive marker for response to IFN-ribavirin combination therapy in J-type HCV.
Expression of the pol-encoded proteins of human immunodeficiency virus type 1 (HIV-1) requires a programmed -1 ribosomal frameshift at the junction of the gag and pol coding sequences. Frameshifting takes place at a heptanucleotide slippery sequence, UUUUUUA, and is enhanced by a stimulatory RNA structure located immediately downstream. In patients undergoing viral protease (PR) inhibitor therapy, a p1/p6(gag) L449F cleavage site (CS) mutation is often observed in resistant isolates and frequently generates, at the nucleotide sequence level, a homopolymeric and potentially slippery sequence (UUUUCUU to UUUUUUU). The mutation is located within the stimulatory RNA downstream of the authentic slippery sequence and could act to augment levels of pol-encoded enzymes to counteract the PR deficit. Here, RNA secondary structure probing was employed to investigate the structure of a CS-containing frameshift signal, and the effect of this mutation on ribosomal frameshift efficiency in vitro and in tissue culture cells was determined. A second mutation, a GGG insertion in the loop of the stimulatory RNA that could conceivably lead to resistance by enhancing the activity of the structure, was also tested. It was found, however, that the CS and GGG mutations had only a very modest effect on the structure and activity of the HIV-1 frameshift signal. Thus the increased resistance to viral protease inhibitors seen with HIV-1 isolates containing mutations in the frameshifting signal is unlikely to be accounted for solely by enhancement of frameshift efficiency.
OBJECTIVE: To determine whether the level of persistent HIV-1 viremia is affected by simplifying standard antiretroviral therapy to lopinavir/ritonavir (LPV/r) alone. DESIGN: Measurement of HIV-1 RNA levels < 50 copies/ml in longitudinal plasma samples from 41 of 42 subjects enrolled in the 'Only Kaletra' study that compared maintenance therapy with LPV/r alone to standard of care (SOC) with two nucleoside reverse transcriptase inhibitors (NRTI) and LPV/r. METHODS: Plasma samples for each subject from study screening to week 48 were tested using a modified Roche Amplicor HIV-1 RNA assay with a quantification limit of 3 copies/ml. RESULTS: Median plasma HIV-1 RNA values at baseline and weeks 4, 8, 12, 24 and 48 were not significantly different between the LPV/r alone and the SOC arms, being 5.1 versus 3.0 (P = 0.29), 4.5 versus 2.9 (P = 0.44), 3.3 versus 2.9 (P = 0.99), 1.9 versus 1.0 (P = 0.68), 3.7 versus 3.6 (P = 0.49), and 2.8 versus 1.6 copies/ml (P = 0.78), respectively. In the 17 of 21 subjects who maintained virus suppression < 50 copies/ml on LPV/r alone, median HIV-1 RNA values did not increase significantly from baseline at any time point after discontinuing NRTI, in comparison to the three subjects with virologic failure whose median HIV-1 RNA levels began to rise at week 8. CONCLUSIONS: The level of persistent viremia did not increase after stopping NRTI therapy among subjects who maintained virus suppression < 50 copies/ml on LPV/r alone through 48 weeks. This supports further studies of induction-simplification therapy for treatment of HIV-1 infection including the identification of factors predicting success or failure of simplified therapy.