Celera Diagnostics Research Articles

Анализ частоты формирования мутаций резистентности ВИЧ, ассоциированных с устойчивостью к антиретровирусным препаратам

Актуальность. В Украине проводится широкомасштабная антиретровирусная терапия (АРТ) больных ВИЧ-инфекцией. Необходимо постоянное наблюдение за развитием устойчивости ВИЧ к антиретровирусным препаратам (АРВП). Цель: проанализировать влияние продолжительности АРТ, возраста и пола пациентов на частоту формирования мутаций резистентности (МР) ВИЧ к АРВП разных классов. Материал и методы. Исследовали образцы плазмы крови ВИЧ-инфицированных пациентов с вирусологической неэффективностью АРТ. Секвенирование генома ВИЧ проводили на тест-системах ViroSeqTM Genotyping System v.2.1 (Celera Diagnostics, США) согласно инструкции производителя. Результаты. Достоверно чаще (р ≤ 0,05) МР ВИЧ к АРВП выявлялись у ВИЧ-инфицированных мужчин (59,70 %), чем у женщин (40,3 %). Установлено, что в 59,9 % случаев вирусологическая неэффективность АРТ была обусловлена формированием МР ВИЧ хотя бы к одному из АРВП. Среди МР ВИЧ к ненуклеозидным ингибиторам обратной транскриптазы наиболее распространенными были G190S (75,8 %); K101E (72,7%); Y181C (68,1 %); K103N (38,8 %); среди МР к нуклеозидным ингибиторам обратной транскриптазы преобладали: M184V (69 %), K65R (61 %), D67N (20 %). МР ВИЧ к ингибитору протеазы встречались редко. Выводы. Показано, что продолжительность АРТ и возраст пациентов существенного влияния на устойчивость ВИЧ к АРВП не оказывали. Решающее значение имел генетический барьер АРВП: на фоне приема препаратов с низким генетическим барьером частота выявления МР ВИЧ составляла 5,3 %; прием препаратов с высоким генетическим барьером сопровождался формированием МР ВИЧ значительно реже — в 1,1 % случаев. Доказано, что биоповеденческие особенности пациентов-мужчин являются фактором, ассоциирующимся с повышенным риском формирования МР ВИЧ к АРВП.

LETTER TO THE EDITOR Performance of the ViroSeq® HIV-1 Genotyping System v2.0 in Central Africa.

Resistance genotypes in pol gene of HIV-1 were obtained by the ViroSeq® HIV-1 Genotyping System v2.0 (Celera Diagnostics, Alameda, CA, USA) in 138 of 145 (95%) antiretroviral treatment-experienced adults in virological failure living in Central Africa (Cameroon, Central African Republic, Chad, Gabon). HIV-1 group M exhibited broad genetic diversity. Performance of the 7 ViroSeq® sequencing primers showed high failure rate, from 3% to 76% (D: 76%; F: 17%; A and H: 15%; G and B: 4%; C: 3%). These findings emphasize the need of updating the ViroSeq® HIV-1 genotyping system for non-B subtypes HIV-1.

Evaluation of a Cost Effective In-House Method for HIV-1 Drug Resistance Genotyping Using Plasma Samples

ObjectivesValidation of a cost effective in-house method for HIV-1 drug resistance genotyping using plasma samples.DesignThe validation includes the establishment of analytical performance characteristics such as accuracy, reproducibility, precision and sensitivity.MethodsThe accuracy was assessed by comparing 26 paired Virological Quality Assessment (VQA) proficiency testing panel sequences generated by in-house and ViroSeq Genotyping System 2.0 (Celera Diagnostics, US) as a gold standard. The reproducibility and precision were carried out on five samples with five replicates representing multiple HIV-1 subtypes (A, B, C) and resistance patterns. The amplification sensitivity was evaluated on HIV-1 positive plasma samples (n = 88) with known viral loads ranges from 1000–1.8 million RNA copies/ml.ResultsComparison of the nucleotide sequences generated by ViroSeq and in-house method showed 99.41±0.46 and 99.68±0.35% mean nucleotide and amino acid identity respectively. Out of 135 Stanford HIVdb listed HIV-1 drug resistance mutations, partial discordance was observed at 15 positions and complete discordance was absent. The reproducibility and precision study showed high nucleotide sequence identities i.e. 99.88±0.10 and 99.82±0.20 respectively. The in-house method showed 100% analytical sensitivity on the samples with HIV-1 viral load >1000 RNA copies/ml. The cost of running the in-house method is only 50% of that for ViroSeq method (112$ vs 300$), thus making it cost effective.ConclusionsThe validated cost effective in-house method may be used to collect surveillance data on the emergence and transmission of HIV-1 drug resistance in resource limited countries. Moreover, the wide applications of a cost effective and validated in-house method for HIV-1 drug resistance testing will facilitate the decision making for the appropriate management of HIV infected patients.

Evaluations of an in-house drug resistance method for HIV-1 drug resistance using ViroSeq™ 2.0 genotyping system as a gold standard

An in-house method was evaluated for its efficiency to detect the HIV-1 drug resistance mutations. This method was compared with the ViroSeq™ Genotyping System 2.0 (Celera Diagnostics, US) a gold standard. Sixty-five stored plasma samples, previously tested for HIV-1 drug resistance using the ViroSeq™ method were used to evaluate the in-house method. Out of the sixty five plasma samples, sixty were HIV-1 positive clinical samples; four samples from the Virology Quality Assessment (VQA) program and one positive control from the ViroSeq™ kit were used in this study. The sequences generated by the ViroSeq™ and an in-house method showed 99.5±0.5% and 99.7±0.4% (mean±SD) nucleotide and amino acid identity, respectively. Out of 214 Stanford HIVdb listed HIV-1 drug resistance mutations in the protease and reverse transcriptase regions, concordance was observed in 203 (94.9%), partial discordance in 11 (5.1%) and complete discordance was absent. The in-house primers are broadly sensitive in genotyping multiple HIV-1 group M subtypes. The amplification sensitivity of the in-house method was 1000 copies/ml. The evaluation of the in-house method provides results comparable with that of ViroSeq™ method thus, making the in-house method suitable for HIV-1 drug resistance testing in the developing countries.

Expanded evaluation of blood donors in the United States for human immunodeficiency virus type 1 non‐B subtypes and antiretroviral drug–resistant strains: 2005 through 2007

In a previous study of 66 human immunodeficiency virus (HIV)-infected US blood donors from 1999 to 2005, HIV-1 non-B and antiretroviral drug-resistant strains accounted for 4.7 and 6.5% of HIV infections, respectively. This study was expanded to include an additional 11 recently acquired infections and 197 established infections collected from January 2005 through December 2007. HIV-infected donors were detected using FDA-licensed assays. Drug resistance profiles for protease and reverse transcriptase (RT) genes were determined using a genotyping system (ViroSeq, Celera Diagnostics); genetic subtype was determined by phylogenetic analysis of these sequences. Drug resistance profiles were obtained for 203 of 208 specimens; 9.9% had mutations that confer drug resistance. Ten showed resistance to a single drug class: nine to nonnucleoside RT inhibitors (NNRTIs) and one to nucleoside RT inhibitors (NRTIs). Eight showed two drug class resistance: five NRTI plus NNRTI, two NRTI plus protease inhibitor (PI), and one NNRTI plus PI. Two showed three drug class resistance. Non-B strains were identified in 2.5% of donors and consisted of subtypes A1 and D, CRF02_AG, CRF43-02G, and URF_BF. Data from this and the previous study show that antiretroviral drug-resistant HIV-1 is present in 9.1% of HIV-infected donors from 1999 through 2007; 9.3% of established infections and 6.9% of recent infections. Diverse HIV-1 non-B strains presently account for 3.0% of HIV infections in US donors.

Evaluation of two human immunodeficiency virus-1 genotyping systems: ViroSeq™ 2.0 and an in-house method

Commercial HIV-1 genotypic resistance assays are very expensive, particularly for use in resource-constrained settings like India. Hence a cost effective in-house assay for drug resistance was validated against the standard ViroSeq™ HIV-1 Genotyping System 2.0 (Celera Diagnostics, CA, USA). A total of 50 samples were used for this evaluation (21 proficiency panels and 29 clinical isolates). Known resistance positions within HIV-1 protease (PR) region (1–99 codons) and HIV-1 reverse-transcriptase (RT) region (1–240 codons) were included. The results were analysed for each codon as follows: (i) concordant; (ii) partially concordant; (iii) indeterminate and (iv) discordant. A total of 2750 codons (55 codons per patient sample × 50 samples) associated with drug resistance (1050 PR and 1700 RT) were analysed. For PR, 99% of the codon results were concordant and 1% were partially concordant. For RT, 99% of the codon results were concordant, 0.9% were partially concordant and 0.1% were discordant. No indeterminate results were observed and the results were reproducible. Overall, the in-house assay provided comparable results to those of US FDA approved ViroSeq™, which costs about a half of the commercial assay ($ 100 vs. $ 230), making it suitable for resource-limited settings.

Analysis of Nevirapine (NVP) Resistance in Ugandan Infants Who Were HIV Infected Despite Receiving Single-Dose (SD) NVP versus SD NVP Plus Daily NVP Up to 6 Weeks of Age to Prevent HIV Vertical Transmission

Single-dose nevirapine (SD NVP) at birth plus NVP prophylaxis for the infant up to 6 weeks of age is superior to SD NVP alone for prevention of vertical transmission of human immunodeficiency virus (HIV) through breastfeeding. We analyzed NVP resistance in HIV-infected Ugandan infants who received either SD NVP or extended NVP prophylaxis. We tested plasma HIV by using a genotyping assay (ViroSeq; Celera Diagnostics), a phenotypic resistance assay (PhenoSense; Monogram Biosciences), and sensitive point mutation assay (LigAmp, for K103N, Y181C, and G190A). When infants were 6 weeks old, ViroSeq detected NVP resistance in a higher proportion of infants in the extended NVP arm than in the SD NVP arm (21 of 25 [84%] vs. 12 of 24 [50%]; P = .01). Similar results were obtained with LigAmp and PhenoSense. In both study arms, infants who were HIV infected at birth frequently had NVP resistance detected. In contrast, infants in the extended NVP arm who were HIV infected after birth were more likely to have resistance detected at 6 weeks, compared with infants in the SD NVP arm. The use of extended NVP prophylaxis was also associated with detection of NVP resistance by ViroSeq at 6 months (7 of 7 [100%] infants in the extended NVP arm had resistance detected, compared with 1 of 6 [16.7%] infants in the SD NVP arm; P = .005). The use of extended NVP prophylaxis was associated with increased selection for and persistence of NVP resistance in HIV-infected Ugandan infants.

Consensus Characterization of 16 FMR1 Reference Materials: A Consortium Study

Fragile X syndrome, which is caused by expansion of a (CGG)(n) repeat in the FMR1 gene, occurs in approximately 1:3500 males and causes mental retardation/behavioral problems. Smaller (CGG)(n) repeat expansions in FMR1, premutations, are associated with premature ovarian failure and fragile X-associated tremor/ataxia syndrome. An FMR1-sizing assay is technically challenging because of high GC content of the (CGG)(n) repeat, the size limitations of conventional PCR, and a lack of reference materials available for test development/validation and routine quality control. The Centers for Disease Control and Prevention and the Association for Molecular Pathology, together with the genetic testing community, have addressed the need for characterized fragile X mutation reference materials by developing characterized DNA samples from 16 cell lines with repeat lengths representing important phenotypic classes and diagnostic cutoffs. The alleles in these materials were characterized by consensus analysis in nine clinical laboratories. The information generated from this study is available on the Centers for Disease Control and Prevention and Coriell Cell Repositories websites. DNA purified from these cell lines is available to the genetics community through the Coriell Cell Repositories. The public availability of these reference materials should help support accurate clinical fragile X syndrome testing.

Current understanding of the genetic aetiology of rheumatoid arthritis and likely future developments

Most of the work described herein was performed by the North American Rheumatoid Arthritis Consortium (NARAC). After a brief description of the NARAC and the multiplex family resource that has been developed by this consortium, we will summarize the current status of genome-wide screens using this valuable family collection. Next, we describe work that is under way to further delineate the genes on chromosome 18q that demonstrate linkage to rheumatoid arthritis (RA), including an analysis of candidate genes in the region and results of dense association mapping. We also describe an extensive analysis of functional single-nucleotide polymorphisms (SNPs) that is under way in collaboration with Celera Diagnostics, as well as studies designed to further dissect the phenotypic and genotypic heterogeneity of RA. We conclude by briefly summarizing our future plans to elucidate the genetic aetiology of RA.

A machine to make a future Biotech chronicles

A machine to make a future Biotech chronicles

Distinct Patterns of Emergence and Fading of K103N and Y181C in Women With Subtype A vs. D After Single-Dose Nevirapine

The HIVNET 012 trial in Uganda demonstrated that single-dose nevirapine (NVP) can prevent HIV-1 mother-to-child transmission. NVP resistance (NVPR) mutations were detected in 25% of women 6 to 8 weeks after NVP, with a higher rate of NVPR in women with subtype D than A. This study examined emergence and fading of specific NVPR mutations in women with these subtypes. Plasma HIV-1 was analyzed with the ViroSeq genotyping system (Celera Diagnostics, Alameda, CA). Genotypes were obtained from paired samples collected 7 days and 6 to 8 weeks after NVP from 140 women, 83 with subtype A and 57 with subtype D. The rate of NVPR was similar in women with subtype A vs. D at 7 days but was higher in subtype D than A at 6 to 8 weeks. The higher rate of NVPR in subtype D was explained by at least 2 factors: Y181C faded from detection at a greater rate in women with subtype A (odds ratio = 3.06; 95% CI, 1.04, 8.90) and K103N accumulated at a greater rate in women with subtype D (odds ratio = 1.74; 95% CI, 0.62, 4.87). HIV-1 subtype influences selection and fading of HIV-1 variants with specific drug resistance mutations after antiretroviral drug exposure.

Anthropologists in the Lab

A Machine to Make a Future Biotech Chronicles. By Paul Rabinow and Talia Dan-Cohen . Princeton University Press, Princeton, NJ, 2004. 204 pp. $24.95, £15.95. ISBN 0-691-12050-1. The authors, anthropologists who focus their attention on the current practices of science, offer a behind-the-scenes look at the intersection of genomics, medicine, and commerce that is focused on Celera Diagnostics

Performance of the Celera Diagnostics ViroSeq HIV-1 Genotyping System for sequence-based analysis of diverse human immunodeficiency virus type 1 strains.

The Celera Diagnostics ViroSeq HIV-1 Genotyping System is a Food and Drug Administration-cleared, integrated system for sequence-based analysis of drug resistance mutations in subtype B human immunodeficiency virus type 1 (HIV-1) protease and reverse transcriptase (RT). We evaluated the performance of this system for the analysis of diverse HIV-1 strains. Plasma samples were obtained from 126 individuals from Uganda, Cameroon, South Africa, Argentina, Brazil, and Thailand with viral loads ranging from 2.92 to >6.0 log(10) copies/ml. HIV-1 genotyping was performed with the ViroSeq system. HIV-1 subtyping was performed by using phylogenetic methods. PCR products suitable for sequencing were obtained for 125 (99%) of the 126 samples. Genotypes including protease (amino acids 1 to 99) and RT (amino acids 1 to 321) were obtained for 124 (98%) of the samples. Full bidirectional sequence data were obtained for 95 of those samples. The sequences were categorized into the following subtypes: A1/A2 (16 samples), B (12 samples), C (13 samples), D (11 samples), CRF01_AE (9 samples), F/F2 (9 samples), G (7 samples), CRF02_AG (32 samples), H (1 sample), and intersubtype recombinant (14 samples). The performances of the individual sequencing primers were examined. Genotyping of duplicate samples in a second laboratory was successful for 124 of the 126 samples. The identity level for the sequence data from two laboratories ranged from 98 to 100% (median, 99.8%). The ViroSeq system performs well for the analysis of plasma samples with diverse non-B subtypes. The availability of this genotyping system should facilitate studies of HIV-1 drug resistance in non-subtype B strains of HIV-1.