Jean-Claude Schmit

Resistance-related mutations in the HIV-1 protease gene of patients treated for 1 year with the protease inhibitor ritonavir (ABT-538)

Objective:To define genotypic and phenotypic resistance patterns following prolonged therapy with the protease inhibitor ritonavir (ABT-538). Design:Seven HIV-1-infected patients, all but one previously treated with dideoxynucleoside analogues (zidovudine, didanosine, zalcitabine), were treated for 1 year with ritonavir. Methods:Direct solid-phase sequencing of the protease gene starting from plasma derived viral RNA followed by comparison to phenotypic drug resistance data. Results:The most frequent amino-acid substitutions occurring upon administration of the protease inhibitor were V82A/F (substrate binding site), I54V (flap region), A71V and L10I. Additional mutations found in more than one patient were I15V, M36I, I84V and I93L. Mutation L63P was found both in pre- and post-ritonavir samples. Phenotypic drug resistance assays confirmed resistance to ritonavir in post-treatment samples (~170-fold) and showed cross-resistance to indinavir (~30-fold) and partially to saquinavir (~fivefold). At 1 year of treatment, one patient without known resistance-associated mutations in the protease gene still showed a substantial rise in CD4 cell count accompanied by a more than 2.4 log decrease in RNA viral load. However, at week 78, mutations R8Q, E34K, R57K, L63P and I84V were detected and the treatment benefit was partially lost. Conclusions:Long-term treatment with ritonavir is associated with the emergence of multiple mutations in the HIV-1 protease gene. The mutations L10I, I54V, L63P, A71V, V82A/F and I84V correspond to known drug-resistance mutations for ritonavir and other protease inhibitors. Phenotypic resistance to ritonavir was detected in a majority of ritonavir-treated patients at 1 year of treatment. In addition, long-term ritonavir treatment selects for cross-resistance to the protease inhibitors indinavir and saquinavir. This argues against sequential therapy with several protease inhibitors. Delayed resistance in one patient was accompanied with a prolonged increase in CD4 cell count and decrease in viral load suggesting a temporary benefit of treatment.

Tracing the HIV-1 subtype B mobility in Europe: a phylogeographic approach

BackgroundThe prevalence and the origin of HIV-1 subtype B, the most prevalent circulating clade among the long-term residents in Europe, have been studied extensively. However the spatial diffusion of the epidemic from the perspective of the virus has not previously been traced.ResultsIn the current study we inferred the migration history of HIV-1 subtype B by way of a phylogeography of viral sequences sampled from 16 European countries and Israel. Migration events were inferred from viral phylogenies by character reconstruction using parsimony. With regard to the spatial dispersal of the HIV subtype B sequences across viral phylogenies, in most of the countries in Europe the epidemic was introduced by multiple sources and subsequently spread within local networks. Poland provides an exception where most of the infections were the result of a single point introduction. According to the significant migratory pathways, we show that there are considerable differences across Europe. Specifically, Greece, Portugal, Serbia and Spain, provide sources shedding HIV-1; Austria, Belgium and Luxembourg, on the other hand, are migratory targets, while for Denmark, Germany, Italy, Israel, Norway, the Netherlands, Sweden, Switzerland and the UK we inferred significant bidirectional migration. For Poland no significant migratory pathways were inferred.ConclusionSubtype B phylogeographies provide a new insight about the geographical distribution of viral lineages, as well as the significant pathways of virus dispersal across Europe, suggesting that intervention strategies should also address tourists, travellers and migrants.

Quantification of HIV-1 RNA in plasma: comparable results with the NASBA HIV-1 RNA QT and the AMPLICOR HIV monitor test.

We investigated and compared the reproducibility, accuracy, detection limits, and dynamic ranges of two commercial kits for quantification of RNA viral load using a titrated virus stock (laboratory strain HIV-1 IIIB) and 107 plasma samples of 25 HIV-1-infected patients. The high reproducibility of both methods (SD = 0.2-0.3 log for both methods) allowed reliable detection of a 0.5 log change in RNA viral load. Both methods had a similar detection limit (at least 10(3) RNA copies/ml plasma) and a dynamic range that extended over a 5 log (AMPLICOR) or a 6 log (NASBA) range of HIV-1 input. For HIV-1 IIIB, the viral load was compatible with measurements of virus-associated p24 antigen. For 21 patients (91 samples), the RNA viral load was similar with both methods differing by no more than 0.5 log. For four patients, the difference in viral load between the two methods was > 0.5 log for all 16 samples. For three of these patients, this could be explained by mismatches with primers or probes in the gag sequence: there was no correlation to the viral subtype. The RNA viral load determination was highly sensitive compared with p24 antigen measurement (> 95% of patients had a detectable viral load vs. 40% who had a detectable p24 level), but in the p24-positive samples the correlation between the antigen level and the RNA viral load was of only borderline significance. We also found that the viral RNA in whole blood was stable for at least 48 h during transport at room temperature. These observations show that both the NASBA HIV-1 RNA QT test and the AMPLICOR HIV monitor test are reliable parameters of the viral load, with great promise for their use as potential surrogate markers.

Multiple dideoxynucleoside analogue-resistant (MddNR) HIV-1 strains isolated from patients from different European countries

Objective:To study the prevalence of multiple dideoxynucleoside (ddN)-resistant (MddNR) HIV-1 in European patients under treatment with multiple ddN analogues, and to characterize MddNR strains genotypically and phenotypically. Design and methods:Blood samples from patients after ≥ 6 months of treatment with multiple ddN were screened for the MddNR mutation Q 151M. After confirmation of MddNR in 15 patients from five European countries, genotypic resistance was evaluated by DNA sequencing of the reverse transcriptase (RT) gene. Phenotypic resistance was measured by the recombinant virus assay. Results were compared with the clinical evolution of the patients. Results:The prevalence of MddNR strains in European patients treated with multiple ddN analogues was 3.5%. Viruses typically contained amino acid substitutions V75F, F77L, F116Y and Q151M in the RT gene. A new mutation, S68G, was frequently associated with MddNR. Phenotypically, viruses displayed high-level resistance to zidovudine (ZDV), didanosine (ddl), zalcitabine (ddC), stavudine (d4T) and partial resistance to lamivudine (3TC) once multiple mutations were present. Under in-vivo treatment pressure, some MddNR strains additionally developed resistance to protease inhibitors or non-nucleoside RT inhibitors (NNRTI). Clinically, most patients had advanced HIV disease with low CD4 cell counts, high viral loads and a rapid progression, but two patients harbouring MddNR virus responded well to dual protease inhibitor associations. Conclusions:MddNR resistant HIV-1 can be found in European patients. MddNR is characterized by a specific set of drug resistance mutations, cross-resistance to most ddN analogues and a fast clinical progression. MddNR can be associated with protease inhibitor or NNRTI resistance.

Simple DNA extraction method for dried blood spots and comparison of two PCR assays for diagnosis of vertical human immunodeficiency virus type 1 transmission in Rwanda

ABSTRACT Dried blood spots (DBS) on filter paper facilitate the collection, transport, and storage of blood samples for laboratory use. A rapid and simple DNA extraction procedure from DBS was developed and evaluated for the diagnosis of human immunodeficiency virus type 1 (HIV-1) infection in children by an in-house nested-PCR assay on three genome regions and by the Amplicor HIV-1 DNA prototype assay version 1.5 (Roche Molecular Systems). A total of 150 samples from children born to HIV-1-infected mothers were collected in Kigali, Rwanda, in parallel as DBS and as peripheral blood mononuclear cell (PBMC) pellets. The results obtained on DBS by the two PCR assays were compared to the results of nested PCR on PBMCs. Of 150 PBMC samples, 10 were positive, 117 were negative, and 23 were indeterminate for HIV-1 infection. In DNA extracted from filter papers and amplified by using the in-house nested PCR, 9 of these 10 positive samples (90%) were found to be positive, and 1 was found to be indeterminate (only the pol region could be amplified). All of the negative samples and all of the 23 indeterminate samples tested negative for HIV-1 infection. When we used the Amplicor DNA test on DBS, all of the 10 PBMC-positive samples were found to be positive and all of the 23 indeterminate samples were found to be negative. Of the PBMC-negative samples, 115 were found to be negative and 2 were found to be indeterminate. We conclude that this simple rapid DNA extraction method on DBS in combination with both detection methods gave a reliable molecular diagnosis of HIV-1 infection in children born to HIV-infected mothers.

COMET: adaptive context-based modeling for ultrafast HIV-1 subtype identification

Viral sequence classification has wide applications in clinical, epidemiological, structural and functional categorization studies. Most existing approaches rely on an initial alignment step followed by classification based on phylogenetic or statistical algorithms. Here we present an ultrafast alignment-free subtyping tool for human immunodeficiency virus type one (HIV-1) adapted from Prediction by Partial Matching compression. This tool, named COMET, was compared to the widely used phylogeny-based REGA and SCUEAL tools using synthetic and clinical HIV data sets (1 090 698 and 10 625 sequences, respectively). COMETs sensitivity and specificity were comparable to or higher than the two other subtyping tools on both data sets for known subtypes. COMET also excelled in detecting and identifying new recombinant forms, a frequent feature of the HIV epidemic. Runtime comparisons showed that COMET was almost as fast as USEARCH. This study demonstrates the advantages of alignment-free classification of viral sequences, which feature high rates of variation, recombination and insertions/deletions. COMET is free to use via an online interface.

Phenotypic assays and sequencing are less sensitive than point mutation assays for detection of resistance in mixed HIV-1 genotypic populations.

The sensitivity and discriminatory power of the 151 and 215 amplification refractory mutation system (ARMS) were evaluated, and their performance for the detection of drug resistance in mixed genotypic populations of the reverse transcription (RT) gene of HIV-1 were compared with T7 sequencing, cycle sequencing, the line probe assay (LiPA) HIV-1 RT test, and the recombinant virus assay (RVA). ARMS and the LiPA HIV-1 RT test were shown to be able to detect minor variants that in particular cases comprised only 1%. T7 sequencing on an ALF semiautomated sequencer could correctly score mixtures only when variants were present at 50%. Cycle sequencing on an ABI PRISM 310 improved the sensitivity for mixtures to about 25%. Using RVA, it was shown that at least 50% of the virus population needed to carry the resistance mutation at codon 184 to afford phenotypic resistance against lamivudine. The two point mutation assays therefore proved to be more sensitive methods than sequencing and RVA to reliably determine a gradual shift in HIV-1 drug resistance mutations in follow-up of patients infected with HIV-1. In 4 of 5 treated patients who were followed by ARMS, a gradual shift in resistant genotypic populations was observed during a period of 6 to 19 months. For 1 patient, a shift from wild to mutant type at position 151 occurred within 2 months, without mixed genotypic intermediate types being detected.

HIV-associated hematologic disorders are correlated with plasma viral load and improve under highly active antiretroviral therapy

&NA; The relationship between HIV‐1 replication and hematologic parameters was examined in two separate studies. The first study was a cross‐sectional evaluation of 207 untreated patients. In this study, the proportion of patients with hematologic disorders increased with disease progression. There was a significant inverse correlation between HIV‐1 plasma viral load and all hematologic values (r = ‐0.266 to ‐0.331). The second study was a longitudinal evaluation of patients on combination antiretroviral therapy (HAART) with hematologic alterations before treatment (N = 27 with platelets <150,000/μl, 24 with hemoglobin <12 g/dl, 36 with neutrophils <2000/&mgr;l and 29 with leukocytes <3000/&mgr;l). Samples were analyzed every 3 months for 2 years. At 2 years, >50% of patients experienced a sustained virologic response, with viral loads <500 RNA copies/ml. Hematologic reconstitution occurred progressively for all blood cell lineages and became statistically significant after the sixth month of therapy (p < .001). Mean values increased from 110 to 180 × 103/&mgr;l for platelets, from 10.7 to 12.3 g/dl for hemoglobin (stabilizing finally at 11.4 g/dl), from 1,260 to 2,240/&mgr;l for neutrophils, and from 2,260 to 3,600/&mgr;l for leukocytes. In conclusion, hematologic disorders are corrected by combination antiretroviral therapy. This suggests a causative role of HIV‐1 in hematologic disorders.

Uncommon mutations at residue positions critical for enfuvirtide (T-20) resistance in enfuvirtide-naive patients infected with subtype B and non-B HIV-1 strains.

Enfuvirtide (T-20) is the lead compound of the new class of antiretroviral drugs called fusion inhibitors. T-20 resistance-associated mutations located in the heptad repeat 1 (HR-1) domain of gp41 have been described in vitro and in clinical trials. In this study, the authors investigated the primary genotypic T-20 resistance in subtype B and non-B HIV-1 strains from patients at the beginning of their follow-up in the Luxembourg HIV Cohort as well as the emergence of primary resistance to T-20 in patients who had long-term infection with subtype B HIV-1 strains. HR-1 fragments including the gp41 amino acid 36-45, T-20-sensitive region were screened for amino acid variation. No classic T-20 resistance-associated mutations were identified in subtype B or non-B isolates. However, several uncommon mutations were found at residues 37, 39, and 42 for subtype B isolates and at residue 42 for a subtype non-B isolate. The results indicate that primary genotypic T-20 resistance seems to be rare in HIV-1, regardless of subtype or prior antiretroviral therapy (excluding fusion inhibitors). However, episodic variation within HR-1 can occur and needs further phenotypic evaluation in accurate fusion inhibitor resistance assays.

Transmission of HIV Drug Resistance and the Predicted Effect on Current First-line Regimens in Europe

Transmitted human immunodeficiency virus drug resistance in Europe is stable at around 8%. The impact of baseline mutation patterns on susceptibility to antiretroviral drugs should be addressed using clinical guidelines. The impact on baseline susceptibility is largest for nonnucleoside reverse transcriptase inhibitors.