Improvement of an ultrasensitive human immunodeficiency virus type 1 real-time reverse transcriptase-polymerase chain reaction targeting the long terminal repeat region

Reliability of CE-marked NATs for HIV-1 subtype C detection and quantitation

We compared seven CE-marked HIV-1 RNA nucleic acid amplification technology (NAT) based assays for their detection efficiency and quantitation concordance in regard to HIV-1 subtype C. We used 398 plasma samples from South African repeat blood donors identified as HIV positive at occasion of routine screening NAT performed mainly during the years 2010-2013, with most plasma samples reflecting recent HIV-1 infections. All HIV-1 subtype C specimens were detected, independent of mono- or dual-target assay design. In the same time period new variants of HIV-1 subtype B had been identified which were missed by some mono-target assays, a finding which was not corroborated for subtype C in our study. A high level of concordance of HIV-1 subtype C quantitation was determined for the HIV-1 NATs, showing successful standardization in this diagnostic field.

Development and Evaluation of a Duo Chikungunya Virus Real-Time RT-PCR Assay Targeting Two Regions within the Genome

Chikungunya virus (CHIKV) re-emerged as a globalized health threat fifteen years ago. There are dozens of RT-PCR assays published. An inventory of the latter was made, and after in silico analysis, two assays were selected for their ability to detect strains belonging to the five CHIKV genetic lineages. They were combined in order to provide a robust assay not affected by genetic point mutations and the resulting Duo CHIKV real-time RT-PCR assay was compared to the two parental single-plex tests against five strains belonging to the five genetic lineages. The Duo CHIKV assay performed equally, or better, in terms of sensitivity, specificity, linearity and signal intensity. Dual-target assays are better suited for viruses having the propensity to evolve into new variants via point mutations or major sequence deletions/insertions. Here, we demonstrated that combining two single systems into a dual-target assay did not impair sensitivity and specificity, and proved a potent diagnostic tool to face a potential emergence of CHIKV variants by newly evolving mutations.

A cascade toehold-mediated strand displacement strategy for label-free and sensitive non-enzymatic recycling amplification detection of the HIV-1 gene

In this work, a label-free fluorescence biosensor for simple detection of the HIV-1 gene was proposed by using toehold-mediated strand displacement reactions (TMSDRs) combined with a non-enzymatic target recycling amplification strategy. In this system, two TMSDRs were used. In the presence of the HIV-1 gene, an autocatalytic DNA machine can be activated. This leads to the generation of numerous free G-rich sequences, which can associate with a fluorescent dye N-methylmesoporphyrin IX (NMM) to yield an amplified fluorescence signal for the target detection. This sensing platform showed a high sensitivity towards the HIV-1 gene with a detection limit as low as 1.9 pM without any labelling, immobilization, or washing steps. The designed sensing system also exhibits an excellent selectivity for the HIV-1 gene compared with other interference DNA sequences. Furthermore, the presented biosensor is robust and has been successfully applied for the detection of the HIV-1 gene in a real biological sample with satisfactory results, suggesting that this method is promising for simple and early clinical diagnosis of HIV infection. Thanks to its simplicity, cost-effectiveness and ultrasensitivity, our proposed sensing strategy provides a universal platform for the detection of other genes by substituting the target-recognition element.

Implementation of an HIV-1 Triple-Target NAT Assay in the Routine Screening at Three German Red Cross Blood Centres

BACKGROUND

Blood product safety was significantly improved by the introduction of NAT testing in the late 1990s, resulting in a strong decrease of transfusion-transmitted infections (TTIs). Due to the occurrence of HIV-1 NAT test failures as a consequence of mismatch mutations in the amplicon regions of mono-target NAT assays, the Paul Ehrlich Institute mandated the implementation of multi-target NAT assays for HIV-1 in 2014. Commercial suppliers mostly developed dual-target NAT assays, with only one implementing a triple-target NAT assay.

METHODS

The HIV-1 triple-target NAT assay v3 (GFE Blut) was tested on mutated specimens and synthetic DNA bearing mutations that resulted in sample underquantification or false-negative test results. In addition, data from 2 years routine testing at three German Red Cross Blood centres were analysed.

RESULTS

The HIV-1 triple-target PCR could compensate for all mutations tested and could compensate the loss of one amplicon without a significant loss of sensitivity. Data from 2 years routine testing showed a solid performance.

CONCLUSION

The HIV-1 triple-target v3 assay (GFE Blut) can compensate mutations in target sequences better than a dual-target assay and is applicable to high-throughput screening, thus increasing blood product safety.

Evaluation of the Aptima(®) HIV-1 Quant Dx assay for HIV-1 RNA viral load detection and quantitation in plasma of HIV-1-infected individuals: A comparison with Abbott RealTime HIV-1 assay

The Hologic Aptima^® HIV‐1 Quant Dx assay (Aptima HIV) is a real‐time transcription‐mediated amplification method CE‐approved for use in diagnosis and monitoring of HIV‐1 infection. The analytical performance of this new assay was compared to the FDA‐approved Abbott RealTime HIV‐1 (RealTime). The evaluation was performed using 220 clinical plasma samples, the WHO 3rd HIV‐1 International Standard, and the QCMD HIV‐1 RNA EQA. Concordance on qualitative results, correlation between quantitative results, accuracy, and reproducibility of viral load data were analyzed. The ability to measure HIV‐1 subtypes was assessed on the second WHO International Reference Preparation Panel for HIV‐1 Subtypes. With clinical samples, inter‐assay agreement for qualitative results was high (91.8%) with Cohen's kappa statistic equal to 0.836. For samples with quantitative results in both assays (n = 93), Lin's concordance correlation coefficient was 0.980 (P  < 0.0001) and mean differences of measurement, conducted according to Bland–Altman method, was low (0.115 log₁₀ copies/ml). The Aptima HIV quantified the WHO 3rd HIV‐1 International Standard diluted from 2000 to 31 cp/ml (5,700–88 IU/ml) at expected values with excellent linearity (R² > 0.970) and showed higher sensitivity compared to RealTime being able to detect HIV‐1 RNA in 10 out of 10 replicates containing down to 7 cp/ml (20 IU/ml). Reproducibility was very high, even at low HIV‐1 RNA values. The Aptima HIV was able to detect and accurately quantify all the main HIV‐1 subtypes in both reference panels and clinical samples. Besides excellent performance, Aptima HIV shows full automation, ease of use, and improved workflow compared to RealTime. J. Med. Virol. 88:1535–1544, 2016. © 2016 Wiley Periodicals, Inc.

High sensitivity detection of HIV-1 using two genomic targets compared with single target PCR

The genetic diversity of Human Immunodeficiency Virus type-1(HIV-1) has been shown to affect the performance of Nucleic Acid Testing (NAT) of Human Immunodeficiency Virus type-1. Although, majority NAT assays were designed to detect the conserved regions of HIV-1 mutations at the primer or probe binding regions may lead to false negatives. In this study, we evaluated the feasibility of detecting two genomic targets for enhanced sensitivity. A total of 180 tests using HIV-1 VQA RNA quantitation standard, 240 tests using EQAPOL HIV-1 viral diversity subtype panel, and 30 clinical plasma samples from Cameroon were evaluated. The analysis was based on probit and hit rate. The genomic targets LOD estimated by PROBIT for the gag target was 118 cps/ml (95%CI 64 cps/ml lower bound), Pol or POL/LTR was at 40 cps/ml (95%CI 17, 16 cps/ml), LTR 45 cps/ml (95%CI 20 cps/ml lower bound), and Gag/LTR at 67.8 cps/ml (95%CI 32 cps/ml lower bound). For HIV-1 subtypes the overall reactivity was 55-100% when tested at 100 and 1000 cps/ml and combination of genomic targets detection increased the reactivity to 100%. The plasma samples evaluation showed LTR or pol/LTR combination yielded higher sensitivity for patients with lower viral load (<40 cps/ml). We conclude that detection of two HIV-1 genomic targets improved sensitivity for detection of genetically diverse HIV-1 strains.

Investigation of Human Cancers for Retrovirus by Low-Stringency Target Enrichment and High-Throughput Sequencing

Although nearly one fifth of all human cancers have an infectious aetiology, the causes for the majority of cancers remain unexplained. Despite the enormous data output from high-throughput shotgun sequencing, viral DNA in a clinical sample typically constitutes a proportion of host DNA that is too small to be detected. Sequence variation among virus genomes complicates application of sequence-specific, and highly sensitive, PCR methods. Therefore, we aimed to develop and characterize a method that permits sensitive detection of sequences despite considerable variation. We demonstrate that our low-stringency in-solution hybridization method enables detection of <100 viral copies. Furthermore, distantly related proviral sequences may be enriched by orders of magnitude, enabling discovery of hitherto unknown viral sequences by high-throughput sequencing. The sensitivity was sufficient to detect retroviral sequences in clinical samples. We used this method to conduct an investigation for novel retrovirus in samples from three cancer types. In accordance with recent studies our investigation revealed no retroviral infections in human B-cell lymphoma cells, cutaneous T-cell lymphoma or colorectal cancer biopsies. Nonetheless, our generally applicable method makes sensitive detection possible and permits sequencing of distantly related sequences from complex material.

Risk Minimization Measures for Blood Screening HIV-1 Nucleic Acid Amplification Technique Assays in Germany

BACKGROUND

Several publications describe HIV-1 RNA false-negative results or viral load underquantitation associated with Communauté Européenne(CE)-marked qualitative or quantitative nucleic acid amplification technique (NAT) assays. 6 cases occurred during blood screening in Germany, with 2 of them causing HIV-1 transmissions to recipients of blood components. The implicated NAT assays were mono-target assays amplifying in different viral genome regions (gag or long terminal repeat).

METHODS

Specimens characterized by HIV-1 NAT underquantitation or false-negative NAT results were comparatively investigated in CE-marked HIV-1 NAT systems of different design to identify potential reasons. The target regions of the viral nucleic acids were sequenced and these sequences compared to primers and probes of the assays. Potential risk minimization measures were considered for quantitative and blood-screening HIV-1 NAT systems.

RESULTS

Nucleotide sequencing of the viral target region in cases of HIV-1 RNA underquantitation or false-negative test results revealed new HIV-1 variants that were mismatched with primers and probes used in some mono-target assays. So far, dualtarget NAT assays have not been associated with mismatch-based false-negative test results. From 2015, the Paul Ehrlich Institute will request HIV-1 NAT assays of dual-target design or an analogous solution for further reducing the risk in blood screening.

CONCLUSION

HIV differs from other blood-borne viruses with regard to its fast evolution of new viral variants. The evolution of new sequences is hardly predictable; therefore, NAT assays with only 1 target region appear to be more vulnerable to sequence variations than dual-target assays. The associated risk may be higher for HIV-1 NAT assays used for blood screening compared to quantitative assays used for monitoring HIV-1-infected patients. In HIV-1 screening NAT assays of dual-target design may adequately address the risk imposed by new HIV-1 variants.

Pilot studies for development of an HIV subtype panel for surveillance of global diversity

The continued global spread and evolution of HIV diversity pose significant challenges to diagnostics and vaccine strategies. NIAID partnered with the FDA, WRAIR, academia, and industry to form a Viral Panel Working Group to design and prepare a panel of well-characterized current and diverse HIV isolates. Plasma samples that had screened positive for HIV infection and had evidence of recently acquired infection were donated by blood centers in North and South America, Europe, and Africa. A total of 80 plasma samples were tested by quantitative nucleic acid tests, p24 antigen, EIA, and Western blot to assign a Fiebig stage indicative of approximate time from initial infection. Evaluation of viral load using FDA-cleared assays showed excellent concordance when subtype B virus was tested, but lower correlations for subtype C. Plasma samples were cocultivated with phytohemagglutinin (PHA)-stimulated peripheral blood mononuclear cells (PBMCs) from normal donors to generate 30 viral isolates (50-80% success rate for samples with viral load >10,000 copies/ml), which were then expanded to 10(7)-10(9) virus copies per ml. Analysis of env sequences showed that sequences derived from cultured PBMCs were not distinguishable from those obtained from the original plasma. The pilot collection includes 30 isolates representing subtypes B, C, B/F, CRF04_cpx, and CRF02_AG. These studies will serve as a basis for the development of a comprehensive panel of highly characterized viral isolates that reflects the current dynamic and complex HIV epidemic, and will be made available through the External Quality Assurance Program Oversight Laboratory (EQAPOL).

Overview of molecular biological methods for the detection of pathogens causing sexually transmitted infections

We review here different state-of-the-art molecular methods currently used in the diagnosis of sexually transmitted infections.

Blood screening nucleic acid amplification tests for human immunodeficiency virus Type 1 may require two different amplification targets

BACKGROUND

Five cases of human immunodeficiency virus Type 1 (HIV-1) RNA-positive blood donations are described that escaped detection by three different CE-marked nucleic acid amplification technique (NAT) screening assays. These events were associated with two HIV-1 transmissions to recipients of blood components. The implicated NAT assays are monotarget assays and amplify in different viral genome regions (group-specific antigen or long terminal repeat). Investigations into the cause of the false-negative test results were initiated.

STUDY DESIGN AND METHODS

Plasma specimens of the five NAT false-negative cases were comparatively investigated in 12 CE-marked HIV-1 NAT systems of differing design. The relative amplification efficiency for the HIV-1 variant was determined for each assay. Sequencing of the variants in the region targeted by each false-negative NAT assay allowed comparison with the respective primers and probes.

RESULTS

Some of the NAT assays designed in a similar way to false-negative monotarget NATs also revealed deficiencies in detecting the viral variants. In each case sequencing of the assay target region in the variants demonstrated mismatches with primers and probes used by the assays. Some dual-target assays showed decreased amplification efficiency, but not false-negative results.

CONCLUSION

HIV is characterized by its rapid evolution of new viral variants. The evolution of new sequences is unpredictable; NAT screening assays with a single target region appear to be more vulnerable to sequence variations than dual-target assays. Based on this experience with false-negative tests results by monotarget NAT assays, the Paul-Ehrlich-Institut is considering requesting dual-target NAT assays for HIV-1 blood donation screening in Germany.

Standardization and performance evaluation of "modified" and "ultrasensitive" versions of the Abbott RealTime HIV-1 assay, adapted to quantify minimal residual viremia

BACKGROUND

Numerous studies investigating clinical significance of HIV-1 minimal residual viremia (MRV) suggest potential utility of assays more sensitive than those routinely used to monitor viral suppression. However currently available methods, based on different technologies, show great variation in detection limit and input plasma volume, and generally suffer from lack of standardization.

OBJECTIVES

In order to establish new tools suitable for routine quantification of minimal residual viremia in patients under virological suppression, some modifications were introduced into standard procedure of the Abbott RealTime HIV-1 assay leading to a "modified" and an "ultrasensitive" protocols.

STUDY DESIGN

The following modifications were introduced: calibration curve extended towards low HIV-1 RNA concentration; 4 fold increased sample volume by concentrating starting material; reduced volume of internal control; adoption of "open-mode" software for quantification. Analytical performances were evaluated using the HIV-1 RNA Working Reagent 1 for NAT assays (NIBSC). Both tests were applied to clinical samples from virologically suppressed patients.

RESULTS

The "modified" and the "ultrasensitive" configurations of the assay reached a limit of detection of 18.8 (95% CI: 11.1-51.0 cp/mL) and 4.8 cp/mL (95% CI: 2.6-9.1 cp/mL), respectively, with high precision and accuracy. In clinical samples from virologically suppressed patients, "modified" and "ultrasensitive" protocols allowed to detect and quantify HIV RNA in 12.7% and 46.6%, respectively, of samples resulted "not-detectable", and in 70.0% and 69.5%, respectively, of samples "detected <40 cp/mL" in the standard assay.

CONCLUSIONS

The "modified" and "ultrasensitive" assays are precise and accurate, and easily adoptable in routine diagnostic laboratories for measuring MRV.