First report on a T69-ins insertion in CRF06_cpx HIV type 1.

Insertion mutations at codon 69 (T69-ins insertion) of the human immunodeficiency virus type 1 (HIV-1) reverse transcriptase confer full resistance to all approved nucleoside reverse transcriptase inhibitors. To date, nearly all reports on T69-ins insertions have described subtypes B and rarely subtypes A, C, and F of HIV-1. Here, we provide the first report of a T69-ins insertion in circulating recombinant form (CRF) 06_cpx in a patient who had been treated with a zidovudine/didanosine combination for 18 months and then shifted to lamivudine, stavudine, and nelfinavir for 76 months. Thereafter, the patient was additively administered Korean red ginseng. This is the first report on the appearance of the T69-ins insertion mutation in CRF HIV-1.

[Etravirine: genetic barrier and resistance development]. / Etravirina: barrera genética y desarrollo de resistencias.

Unlike first-generation non-nucleoside reverse transcriptase inhibitors (NNRTI), to develop complete resistance to etravirine (ETR), various mutations must be accumulated. This drug shows an intermediate barrier against partial resistance and a high barrier to complete resistance. Some mutations selected by nevirapine or efavirenz affect the activity of ETR, the most frequent being Y181C, G190A/S, K101E, L100I, Y188L and V90I. The grade of resistance conferred by each mutation differs. Currently, there are at least three lists of mutations that confer an exact score to each mutation. These lists have been validated with the grade of resistance observed in paired phenotypes and with clinical response in the DUET studies. The three scores show a high degree of agreement. ETR is currently one of the antiretroviral drugs whose activity can be calculated simply and accurately on the basis of genotypic data. The mutations selected after failure to nucleoside reverse transcriptase inhibitors, thymidine analogue, T69D/N and M184I/V, confer hypersusceptibility to ETR (fold change < 0.4) in up to 1 out of every 3 samples analyzed. The early withdrawal of first-generation NNRTIs in patients with virological failure is essential to avoid the accumulation of mutations that could compromise the activity of this drug.

The A-rich RNA sequences of HIV-1 pol are important for the synthesis of viral cDNA.

The bias of A-rich codons in HIV-1 pol is thought to be a record of hypermutations in viral genomes that lack biological functions. Bioinformatic analysis predicted that A-rich sequences are generally associated with minimal local RNA structures. Using codon modifications to reduce the amount of A-rich sequences within HIV-1 genomes, we have reduced the flexibility of RNA sequences in pol to analyze the functional significance of these A-rich 'structurally poor' RNA elements in HIV-1 pol. Our data showed that codon modification of HIV-1 sequences led to a suppression of virus infectivity by 5-100-fold, and this defect does not correlate with, viral entry, viral protein expression levels, viral protein profiles or virion packaging of genomic RNA. Codon modification of HIV-1 pol correlated with an enhanced dimer stability of the viral RNA genome, which was associated with a reduction of viral cDNA synthesis both during HIV-1 infection and in a cell free reverse transcription assay. Our data provided direct evidence that the HIV-1 A-rich pol sequence is not merely an evolutionary artifact of enzyme-induced hypermutations, and that HIV-1 has adapted to rely on A-rich RNA sequences to support the synthesis of viral cDNA during reverse transcription, highlighting the utility of using 'structurally poor' RNA domains in regulating biological process.

Testing genotypic and phenotypic resistance in human immunodeficiency virus type 1 isolates of clade B and other clades from children failing antiretroviral therapy.

The emergence of resistance to antiretroviral drugs is a major obstacle to the successful treatment of human immunodeficiency virus type 1 (HIV-1)-infected patients. In this work, we correlate clinical and virological trends such as viral load (VL) and CD4 counts to genotypic and phenotypic antiretroviral (ARV) resistance profiles of HIV-1 isolates from the B and non-B subtypes found in vertically infected children failing ARV therapy. Plasma samples were collected from 52 vertically HIV-1-infected children failing different ARV therapies. Samples underwent HIV-1 pol sequencing and phenotyping and were clustered into subtypes by phylogenetic analysis. Clinical data from each patient were analyzed together with the resistance (genotypic and phenotypic) data obtained. Thirty-five samples were from subtype B, 10 samples were non-B (subtypes A, C, and F), and 7 were mosaic samples. There was no significant difference concerning treatment data between B and non-B clades. Prevalence of known drug resistance mutations revealed slightly significant differences among B and non-B subtypes: L10I, 21 and 64%, K20R, 13 and 43%, M36I, 34 and 100%, L63P, 76 and 36%, A71V/T, 24 and 0%, and V77I, 32 and 0%, respectively, in the protease (0.0001

Prevalence of genotypic and phenotypic resistance to anti-retroviral drugs in a cohort of therapy-naïve HIV-1 infected US military personnel.

OBJECTIVE: While transmission of drug-resistant HIV-1 has been reported, estimates of prevalence of resistance in drug-naïve populations are incomplete. We investigated the prevalence of genotypic mutations and phenotypic antiretroviral resistance in a cohort of HIV-1 infected U.S. military personnel prior to the institution of antiretroviral therapy. DESIGN: Cross-sectional cohort study. METHODS: Plasma was obtained from 114 recently HIV-1 infected subjects enrolled in an epidemiological study. Genotypic resistance was determined by consensus sequencing of a PCR product from the HIV-1 pol gene. Sequences were interpreted by a phenotypic-genotypic correlative database. Resistance phenotypes were determined by a recombinant virus cell culture assay. RESULTS: Genotypic mutations and phenotypic resistance were found at a higher than expected frequency. Resistance to non-nucleoside reverse transcriptase inhibitors was most common, with a prevalence of 15% of 95 subjects by genotype and 26% of 91 subjects by phenotype. Genotypic and phenotypic resistance respectively were found in 4% and 8% of subjects for nucleoside reverse transcriptase inhibitors and in 10% and 1% for protease inhibitors. One subject harbored virus with resistance to all three drug classes. CONCLUSIONS: A substantial frequency of resistance to antiretroviral drugs was identified in a therapy-naïve U.S. cohort. In most cases, the genotypic and phenotypic assays yielded similar results, although the genotypic assay could detect some protease inhibitor resistance-associated mutations in the absence of phenotypic resistance. These data suggest the need for optimization of treatment guidelines based on current estimates of the prevalence of drug resistance in HIV-1 seroconverters.

Comparison of QIAamp HCV kit spin columns, silica beads, and phenol-chloroform for recovering human immunodeficiency virus type 1 RNA from plasma.

Human immunodeficiency virus type 1 (HIV-1) pol mutations are responsible for HIV-1 resistance to current antiretroviral drugs. HIV-1 RNA extraction with QIAamp HCV kit spin columns (Qiagen, Chatsworth, Calif.) followed by reverse transcription-PCR successfully recovered a 1,008-bp pol fragment from the plasma of 31 of 34 HIV-1-infected patients that was suitable for sequencing and recombinant-virus studies. The minimum HIV-1 RNA concentration required for gene recovery was 30 to 40 copies/ml, which was similar to the minimal HIV-1 RNA concentration required when phenol-chloroform or silica beads are used for RNA extraction.

Emergence of human immunodeficiency virus type 1 variants with resistance to multiple dideoxynucleosides in patients receiving therapy with dideoxynucleosides.

A set of mutations [Ala-62-->Val(A62V), V75I, F77L, F116Y, and Q151M] in the polymerase domain of reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) confers on the virus a reduced sensitivity to multiple antiretroviral dideoxynucleosides and has been seen in HIV-1 variants isolated from patients receiving combination chemotherapy with 3'-azido-3'-deoxythymidine (AZT) plus 2',3'-dideoxycytidine (ddC) or 2',3'-dideoxyinosine (ddI). The IC50 values of AZT, ddC, ddI, 2',3'-dideoxyguanosine, and 2',3'-didehydro-3'-deoxythymidine against an infectious clone constructed to include the five mutations were significantly higher than those of a wild-type infectious clone. The K1 value for AZT 5'-triphosphate determined for the virus-associated RT from a posttherapy strain was 35-fold higher than that of RT from a pretherapy strain. Detailed analysis of HIV-1 strains isolated at various times during therapy showed that the Q151M mutation developed first in vivo, at the time when the viremia level suddenly increased, followed by the F116Y and F77L mutations. All five mutations ultimately developed, and the viremia level rose even further. Analyses based on the three-dimensional structure of HIV-1 RT suggest that the positions where at least several of the five mutations occur are located in close proximity to the proposed dNTP-binding site of RT and the first nucleotide position of the single-stranded template.

Characterization of a non-long terminal repeat retrotransposon cDNA (L1Tc) from Trypanosoma cruzi: homology of the first ORF with the ape family of DNA repair enzymes.

In the present paper we describe the characterization of a Trypanosoma cruzi cDNA (L1Tc) corresponding to a transcript from a new long terminal repeat (LTR) retrotransposon. This element is present in a high-copy number, and is found dispersed throughout the T. cruzi genome. Northern analysis shows an abundant expression of L1Tc-related sequences with a major band of about 5 kb. The transcript has at its 3' end a fragment of a highly repetitive DNA sequence (E12A), at its 5' end a ribosomal mobile element-like sequence and three putative open reading frames (ORF) in different frames. The ORF2 codes for a protein which has significant homology with the retrotranscriptase-related sequences from non-LTR retrotransposons containing the seven domains present in all the retrotranscriptase and retrotranscriptase-related proteins. The ORF3 codes for a gag-like protein showing unusual cysteine motifs present in all non-LTR trypanosomatid elements, similar to the C2H2 zinc finger family of transcription factors. Interestingly, ORF1 codes for a protein with significant homology to the major human AP endonuclease protein, and maintains in similar positions most of the amino acid domains described for all the Ape family of proteins. The presence of Ape-related sequences, described for the first time in a non-LTR retrotransposon (L1Tc), may have functional relevance for these types of elements.

pol mutations conferring zidovudine and didanosine resistance with different effects in vitro yield multiply resistant human immunodeficiency virus type 1 isolates in vivo.

Specific mutations in the human immunodeficiency virus type 1 (HIV-1) pol gene that cause zidovudine (3'-azido-2',3'-dideoxythymidine; AZT) and didanosine (2',3'-dideoxyinosine; ddI) resistance were studied. The 50% inhibitory concentrations (IC50s) of nucleosides for cloned viruses containing these mutations were compared with the IC50s of the corresponding triphosphate analogs for mutant recombinant-expressed reverse transcriptases (RTs). Changes in ddATP inhibition of RNA-dependent DNA polymerase activity fully accounted for the ddI resistance of the virus caused by a Leu-74-->Val substitution in RT, including an augmentation by the AZT-selected substitutions Thr-215-->Tyr and Lys-219-->Gln in RT. In contrast, the AZT-selected substitutions studied did not cause as great a change in the IC50 of AZT-triphosphate (AZT-TP) for polymerase as they did in the IC50 of AZT for mutant virus. In addition, the mutation at codon 74 suppressed AZT resistance in the virus caused by the mutations at codons 215 and 219 but did not suppress the AZT-TP resistance of enzyme containing these same mutations in RT. The mutation at codon 74 was found in clinical isolates whether or not the patient had received AZT prior to starting ddI therapy. AZT resistance coexisted with ddI resistance following acquisition of Leu-74-->Val in three clinical isolates, indicating that the suppressive effect of Val-74 on the AZT resistance of the virus does not occur in all genetic contexts. When this suppression of AZT resistance was seen in the virus, Val-74 did not appear to cause mutually exclusive changes in AZT-TP and ddATP binding to RT in vitro. The results of the in vitro experiments and characterization of clinical isolates suggest that there are differences in the functional effects of these AZT and ddI resistance mutations.