Quantitative detection of human immunodeficiency virus type 1 (HIV-1) viral load by SYBR green real-time RT-PCR technique in HIV-1 seropositive patients

HIV-1 viral load represents a basic marker for evaluation of the rate and severity of HIV-1 related disease and to monitor the effectiveness of treatment. An SYBR green-based real-time RT-PCR (SYBR green real-time RT-PCR) revealed by Light Cycler technology was evaluated for quantitation of HIV-1 RNA viral load in plasma of HIV-1 seropositive patients. The performance of the SYBR green real-time PCR was assessed on 56 HIV-1 seropositive patients under highly active retroviral therapy (HAART) and 25 blood donors. The results demonstrated that this technique detected 50 HIV-1 RNA copies per millilitre of plasma. Moreover, we compared real-time RT-PCR with the b-DNA technique considered widely a reference technique for HIV-1 RNA viral load measurement. The parallel quantitative analysis of HIV-1 positive samples showed a high correlation (r=0.908) between the two methods. Although b-DNA and the real-time-based method gave similar sensitivity, the assay determined quantitatively HIV-1 RNA copies in 4 out of 16 samples shown as undetectable by b-DNA. The SYBR green real-time RT-PCR represents a good alternative to b-DNA assay in HIV-1 viral load determination especially during the monitoring of HAART treatment.     

Diagnosis of human immunodeficiency virus infection by a polymerase chain reaction assay evaluated in patients harbouring strains of diverse geographical origin

Since the development of the highly sensitive polymerase chain reaction, PCR has been increasingly used for the diagnosis of viral infections, including the detection of human immunodeficiency virus (HIV), the causative agent of AIDS. In our laboratory a diagnostic PCR is carried out on proviral HIV-1 DNA using a standardised algorithm based on three HIV-1 primer sets. The three primer sets, amplifying a fragment in the LTR-gag gene, in the pol gene and in the env gene, are situated within conserved regions of the HIV-1 genome. These primers allow us to detect not only HIV strains from Belgian patients but also from African patients, who are, for historical reasons, a substantial part of the HIV-positive patients in Belgium. We are able to detect 1–5 copies of proviral HIV-1 DNA with each of the three nested primer sets. A sensitivity and specificity of 92 and 100%, respectively, were achieved when testing 24 Belgian and African HIV-1 seropositive samples. In our lab, the same PCRs are also used for the detection of viral RNA in cases of a doubtful undetectable viral load when using a commercial HIV-1 viral load assay. This is because present-day commercial assays are not entirely reliable with divergent strains. Both our ‘in-house’ diagnostic DNA and RNA-PCR can also be used semiquantitatively with limiting dilutions.     

Comparison of the COBAS TAQMAN HIV-1 HPS with VERSANT HIV-1 RNA 3.0 assay (bDNA) for plasma RNA quantitation in different HIV-1 subtypes

Quantitation of HIV-1 RNA levels in plasma has an undisputed prognostic value and is extremely important for evaluating response to antiretroviral therapy. The purpose of this study was to evaluate the performance of the real-time PCR COBAS TaqMan 48 analyser, comparing it to the existing VERSANT 3.0 (bDNA) for HIV-1 RNA quantitation in plasma of individuals infected with different HIV-1 subtypes (104 blood samples). A positive linear correlation between the two tests (r2 = 0.88) was found. Quantitation by the COBAS TaqMan assay was approximately 0.32log10 higher than by bDNA. The relationship between the two assays was similar within all subtypes with a Deming regression of <1 and <0 for the Bland-Altman plots. Overall, no significant differences were found in plasma viral load quantitation in different HIV-1 subtypes between both assays; therefore these assays are suitable for viral load quantitation of highly genetically diverse HIV-1 plasma samples.     

Evaluation of the Abbott Real-Time HIV-1 quantitative assay with dried blood spot specimens

The Abbott Real-Time HIV-1 assay was evaluated for its performance in quantification of human immunodeficiency virus type 1 (HIV-1) RNA in dried blood spot (DBS) samples. In total, 169 blood samples with detectable plasma HIV-1 RNA were used to extract RNA from paired DBS and liquid plasma samples, using the automated Abbott m Sample Preparation System (m2000sp). HIV-1 RNA was then quantitated by the m2000rt RealTime analyser. RNA samples suitable for real-time PCR were obtained from all but one (99.4%) of the DBS samples and HIV-1 RNA was detected in 163/168 (97.0%) samples. The correlation between HIV-1 RNA values measured in paired DBS and plasma samples was very high ( r  = 0.882), with 78.5% and 99.4% of cases differing by <0.5 and 1.0 log, respectively. Retesting of DBS replicates following 6 months of storage at 2–8°C showed no loss of HIV-1 RNA in a subset of 89 samples. The feasibility of DBS testing coupled with automated sample processing, and the use of a latest-generation FDA-approved real-time PCR-based system, represents an encouraging first step for viral load measurement in reference centres in developing countries where access to antiretroviral therapy is expanding.     

Plasma viral RNA assay in HIV-1 group O infection by real-time PCR

HIV-1 group O infections remains essentially restricted to central Africa, and particularly Cameroon, although isolated cases have been reported in Western countries. Genomic differences explain why commercial tests used to quantify HIV-1 group M plasma load are unsuitable for HIV-1 group O. This lack of a quantitative tool hinders the clinical management of HIV-O-infected patients. We have therefore developed a real-time PCR assay, based on LightCycler technology, to quantify HIV-1 group O RNA in plasma. The primers were selected in the LTR 3' region. Forty-eight plasma samples containing strains belonging to the different HIV-1 type O clades (O:A, O:B and O:C) were tested. RNA was quantifiable in 40 of these samples. RNA was always detected in samples from untreated patients, except for one patient infected by a highly divergent strain. The kinetics of plasma viral load were also examined in seven patients for whom clinical and immunologic follow-up data were available. HIV-1 group O plasma load was high in the absence of treatment and correlated negatively with the CD4 cell count. Serial samples obtained during treatment allowed us to compare viral load changes with immunologic outcome. Despite the high initial cost of acquiring the required cycling device, the per-sample cost of this real-time quantitative PCR assay for HIV-1 group O is low, making it suitable for use in endemic zones.     

Dried blood spots for the diagnosis and quantitation of HIV-1: stability studies and evaluation of sensitivity and specificity for the diagnosis of infant HIV-1 infection in Thailand

Molecular methods for HIV-1 infection using dried blood-spot (DBS) for HIV-1 CRF01_AE subtypes have not been fully optimized. In this study assays for HIV-1 diagnosis or quantitation were evaluated using infant DBS from Thailand. Paired DBS and whole blood samples from 56 HIV-1 CRF01_AE or B'-infected infants were tested for infant diagnosis using modified Amplicor DNA PCR and NucliSens RNA NASBA and an in-house real-time PCR assay. The Amplicor Monitor viral load (VL) assay, with modifications for DBS, was also evaluated. DBS VL were hematocrit corrected. Stability studies were done on DBS stored at -70 degrees C to 37 degrees C for up to 1 year. The DBS diagnostic assays were 96-100% sensitive and 100% specific for HIV-1 diagnosis. DBS HIV-1 VL were highly correlated with plasma VL when corrected using the actual or an assumed hematocrit factor (r(c)=0.88 or 0.93, respectively). HIV-1 DNA in DBS appeared to be more stable than RNA and could be detected after up to 9 months at most temperatures. DBS VL could be consistently determined when stored frozen. These results show that DBS can be used accurately instead of whole blood for the diagnosis of HIV-1 infection and VL quantitation, particularly if samples are appropriately stored.     

TaqMan RT-PCR and VERSANT HIV-1 RNA 3.0 (bDNA) assay Quantification of HIV-1 RNA viral load in breast milk.

BACKGROUND: Transmission of HIV via breast milk is a primary cause of pediatric HIV infection in developing countries. Reliable methods to detect breast milk viral load are important. OBJECTIVE: To correlate the ability of the VERSANT HIV 3.0 (bDNA) assay to real-time (RT) TaqMan PCR in quantifying breast milk HIV-1 RNA. STUDY DESIGN: Forty-six breast milk samples that had been spiked with cell-free HIV-1 and eight samples spiked with cell-associated HIV-1 were assayed for HIV-1 RNA by both VERSANT HIV 3.0 and TaqMan RNA assays. RESULTS: Only assays on the cell-free samples were statistically compared. Both a Deming regression slope and a Bland-Altman slope indicated a linear relationship between the two assays. TaqMan quantitations were on average 2.6 times higher than those of HIV 3.0. A linear relationship was observed between serial dilutions of spiked cell-free HIV-1 and both the VERSANT HIV 3.0 and the TaqMan RNA assays. CONCLUSION: The two methods correlated well although the VERSANT HIV 3.0 research protocol quantified HIV-1 RNA slightly lower than TaqMan.     

Abbott RealTime HIV-1 m2000rt viral load testing: manual extraction versus the automated m2000sp extraction

The Abbott RealTime HIV-1 assay is a real-time nucleic acid amplification assay available for HIV-1 viral load quantitation. The assay has a platform for automated extraction of viral RNA from plasma or dried blood spot samples, and an amplification platform with real time fluorescent detection. Overall, this study found no clinically relevant differences in viral load, if samples were extracted manually.     

一种简易的HIV-1病毒载量定量筛查方法的建立

目的 建立一种基于RT-PCR法的简易的HIV-1感染者或艾滋病患者血浆病毒载量筛查方法.方法 在广西南宁市采集18例HIV-1感染者和18例阴性对照者血液标本,提取RNA,以引物LTR-1/LTR-2对待测样本进行PCR扩增,获得Ct值.同时,应用Nuclisens EasyQ HIV-1 v1.2法作为对照对这些样本进行病毒载量检测.对Ct值与病毒载量之间进行相关性分析,获得相应的回归方程.结果 待测样本中HIV-1感染者Ct值在29.103～31.610个循环之间,阴性对照者未能扩增出产物.RT-PCR法Ct值与Nuclisens EasyQ HIV-1 v1.2法检测出的病毒载量对数值之间具有良好的线性关系（r=-0.51,P=0.03）,回归方程为logY（viral road）=57.55-1.56＆#215;（Ct value）.结论 所建立的HIV-1病毒载量RT-PCR检测方法操作简单,价格便宜,与商业化试剂盒具有较好的一致性,可用于HIV-1感染定量筛查.     

Comparative evaluation of the performance of the Abbott real-time human immunodeficiency virus type 1 (HIV-1) assay for measurement of HIV-1 plasma viral load following automated specimen preparation

The performance of the new Abbott real-time human immunodeficiency virus type 1 (HIV-1) assay for HIV-1 RNA load determination in plasma was compared to that of the Abbott LCx HIV-1 RNA quantitative assay following automated RNA isolation by the Abbott m1000 extractor. The measured viral loads of 89 clinical specimens differed by mean 0.19 log10 copies/ml (95% confidence interval, 0.12 to 0.26 log10 copies/ml). Although the difference in viral load determinations was positively skewed in favor of the LCx assay, it did not reach statistical significance (P = 0.42). Results were linearly associated (R2 = 0.94) and strongly correlated (R = 0.96). Good performance was observed with HIV-1 subtypes other than B and circulating recombinant forms, although results obtained with two subtype G specimens and one H specimen showed a more substantial difference.     

Evolution in the sensitivity of quantitative HIV-1 viral load tests

Significant advancements in molecular diagnostics have been made since the inception and application of PCR-based technologies in clinical diagnostic laboratories and the management of HIV-1 infected patients. More recently, real-time PCR has improved the overall performance of assays used for detecting and quantifying HIV-1 RNA viral load in patients undergoing antiretroviral treatment. The effects of these changes and the interpretations of the HIV-1 viral load results are discussed in this review in the context of the different assays used, the viral dynamics of the HIV-1 virus, and the recent changes to HIV-1 treatment guidelines.     

Quantitation of HIV-1 RNA levels in plasma and CSF of asymptomatic HIV-1 infected patients from South India using a TaqMan real time PCR assay.

BACKGROUND: Most of the quantitation assays for HIV-1 RNA used currently are designed and optimized for HIV-1 subtype B viruses and hence may not be suitable for India, where the predominant subtype is HIV-1 subtype C. OBJECTIVES: Development and standardization of HIV-1 TaqMan real time PCR assay suitable for measuring plasma and CSF viral RNA levels in HIV subtype C infected individuals. STUDY DESIGN: A TaqMan real time PCR was developed using primers and probes selected in the gag region for detection of Indian HIV-1 subtype C strain. Plasma (n=120) and CSF samples (n=46) obtained from HIV infected subjects were used to evaluate the sensitivity and specificity of the assay. A comparative evaluation was carried out with a commercially available quantitative HIV viral load assay (Roche Amplicor Version 1.5). RESULTS: The TaqMan assay was able to amplify all HIV-1 group M subtypes except subtype E. Viral loads could be estimated in all the plasma (n=120) and 40/46 CSF samples obtained from HIV positive subjects. Sensitivity of this assay was found to be 180 copies/ml. Correlation with the commercially available viral load assay was very good (r=0.885). CONCLUSIONS: A TaqMan real time PCR was standardized for HIV-1 subtype C and it was more sensitive (180 copies/ml) than standard Amplicor monitor assay, Version 1.5 (400 copies/ml).     

Multicenter evaluation of the NucliSens EasyQ HIV-1 v1.1 assay for the quantitative detection of HIV-1 RNA in plasma

The Nuclisens EasyQ HIV-1 v1.1 assay (Biomerieux) is a real-time detection method combined with NASBA technology designed to measure plasma HIV-RNA. Its performance was assessed in 1008 clinical specimens collected from individuals infected with clade B (774) and non-B (234) HIV-1 variants at four European laboratories. The results were compared with those obtained using three other commercial viral load assays: Cobas Amplicor Monitor HIV-1 v1.5 (Roche), Versant HIV-1 RNA assay (Bayer) and Nuclisens HIV-1 QT (Biomerieux). Overall, the linearity, specificity and reproducibility of the EasyQ assay was comparable with that from the other tests. The correlation coefficient (R) between methodologies was 0.85 for Amplicor; 0.87 for Versant; and 0.91 for Nuclisens. The specificity of the assay was 99.4%. Of note, Versant missed 17% of specimens with non-B subtypes which could be detected by EasyQ, while Amplicor provided similar results than EasyQ. HIV-1 group O specimens were only detected by the EasyQ assay. In conclusion, the performance of the EasyQ assay seems to be similar to that of other HIV-1 viral load tests currently on the market, but it is more sensitive than Versant for HIV-1 non-B subtypes and shows a wider dynamic range than Amplicor. Moreover, as it incorporates the advantage of real-time detection procedures, it facilitates high throughput and short turnaround time.     

Performance evaluation of the COBAS/TaqMan HIV-1 v2.0 in HIV-1 positive patients with low viral load: a comparative study

HIV-1 viral load determination is a crucial step for monitoring the efficacy of highly active antiretroviral therapy (HAART) and predicts disease progression. Real-time PCR based assays are available for monitoring the viral load. They differ in sensitivity, genomic target region and dynamic range. In this study, the performance of the Roche Cobas Taqman HIV-1 v2.0 was evaluated on plasma samples from HIV-1 positive patients in parallel with the Abbott RealTime HIV-1 assay in a routine diagnostic setting. Overall, there was a good agreement between the two assays. However, some samples detected by the Abbott RealTime HIV-1 assay but below the limit of quantitation of the assay were found negative result when tested with the Roche Cobas Taqman HIV-1 v2.0. It is conceivable that signal anomalies or background noise may affect the lower-end precision of the Abbott RealTime HIV-1 assay. Based on these results, it is concluded that it is not recommended to switch platform during longitudinal viral load monitoring of HIV-1 positive patients.     

Comprehensive comparison of the VERSANT HIV-1 RNA 3.0 (bDNA) and COBAS AMPLICOR HIV-1 MONITOR 1.5 assays on 1,000 clinical specimens.

BACKGROUND: Plasma human immunodeficiency virus type 1 (HIV-1) RNA level is an important parameter for patient management, yet viral load assays from different manufacturers are not standardized. OBJECTIVES AND STUDY DESIGN: In this study, we evaluated the concordance between test results obtained for 1,000 plasma specimens collected from HIV-1-infected individuals measured with the VERSANT HIV-1 RNA 3.0 assay (bDNA) and the COBAS AMPLICOR HIV-1 MONITOR 1.5 test (PCR). We compared viral load values obtained by each of these assays throughout their dynamic ranges, with particular focus on samples with low viral load (i.e. 50-250 copies/mL), and calculated the estimated distribution of distinct plasma viral load levels for the entire study population modeled from the data observed in the study. RESULTS: We found that these two assays show excellent agreement, with a correlation (R(2)) of 0.957 and a slope of 1.004. The mean difference in viral load values between the two assays was less than 0.10-log(10) throughout the dynamic range and 98.2% of all samples had bDNA and PCR results within 0.5-log(10) of each other, a difference that is within the range considered to be a minimal change in plasma viremia. Moreover, the two assays show very similar results across all assay ranges tested. The estimated prevalence of samples with results <50 copies/mL, 50-250 copies/mL, and 250-500,000 copies/mL were 41.6%, 7.7%, and 49.7%, respectively, by the bDNA assay, and 42.4%, 6.9%, and 50.7%, respectively, by the PCR assay. CONCLUSION: Based on our findings from 1,000 clinical specimens, we do not see the need to re-establish a baseline value or apply a conversion factor when switching from one assay to the other. Since the majority of our patient population likely is infected with subtype B virus, it is unclear if our findings will apply to other patient populations with a greater incidence of infection with non-B subtypes.