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.     

Using RT-PCR and bDNA assays to measure non-clade B HIV-1 subtype RNA.

The performance of the new version of RT-PCR assay (Amplicor HIV-1 Monitor v1.5) was assessed. The quantification of non-B subtype HIV-1 plasma RNA (30A, 1C, 1D, 3E, 2F, 3G) obtained using Monitor v1.5 was compared to the former version of this assay (Monitor v1.0) and to the Quantiplex v2.0 bDNA assay. The new primers used in Monitor v1.5 were similar to the former version in both specificity and sensitivity. The new primers corrected the detection and quantification defect observed previously for HIV-1 non-B subtypes and gave slightly higher RNA concentrations than those measured using the bDNA assay (+0.39 log copies/ml).     

Comparative analysis of HIV-1 viral load assays on subtype quantification: Bayer Versant HIV-1 RNA 3.0 versus Roche Amplicor HIV-1 Monitor version 1.5

Quantification of HIV-1 subtypes is essential for appropriate clinical management. Whereas viral load assays were initially developed to accurately quantify subtype B, the recent worldwide spread of non-B subtypes and the introduction of treatment programs in regions with non-B subtypes have prompted adaptations of these assays. The Bayer Versant HIV-1 RNA 3.0 Assay (branched DNA [bDNA] 3.0) and the Roche Amplicor HIV-1 Monitor version 1.5 (Amplicor 1.5) assays are reported to quantify all subtypes in group M; however, evaluation of performance characteristics remains limited. In this study, we evaluated the accuracy and reliability of bDNA 3.0 and Amplicor 1.5 on multiple serially diluted viral isolates from HIV-1 group M, subtypes A through F. Testing was conducted on both assay systems in two independent laboratories. Comparative pansubtype quantification from regression analysis showed that quantification by bDNA 3.0 was approximately 0.3 log-fold lower than that by Amplicor 1.5. Comparative pansubtype accuracy analysis showed data points more closely distributed about their respective regression lines and thus showing greater reliability by bDNA 3.0 than by Amplicor 1.5.     

Evaluation of the clinical sensitivities of three viral load assays with plasma samples from a pediatric population predominantly infected with human immunodeficiency virus type 1 subtype G and BG recombinant forms

The viral load assays AMPLICOR HIV-1 Monitor Test 1.5, Nuclisens HIV-1 QT, and Quantiplex HIV RNA 3.0 (bDNA) were evaluated for their abilities to quantify human immunodeficiency virus type 1 (HIV-1) RNA in 64 plasma samples from 21 children infected in Portugal. The children were infected with HIV-1 subtypes A1, B, F1, G, and BG recombinant virus. AMPLICOR v1.5 and Quantiplex v3.0 detected all samples, and there was a good correlation of results between the two kits. Thirty-eight specimens containing HIV-1 subtype B, G, or recombinant BG, could not be detected by Nuclisens HIV-1 QT. We also evaluated the new Retina HIV-1 assay on 21 samples that were HIV-1 positive; Retina HIV-1 failed to detect 5 of 11 subtype G specimens. AMPLICOR v1.5 and Quantiplex v3.0 assays may be used for HIV-1 RNA quantification in Portugal, whereas an improvement in sensitivity for subtype G and recombinant BG is required for Nuclisens HIV-1 QT and Retina HIV-1.     

Evaluation of the clinical sensitivity for the quantification of human immunodeficiency virus type 1 RNA in plasma: Comparison of the new COBAS TaqMan HIV-1 with three current HIV-RNA assays--LCx HIV RNA quantitative, VERSANT HIV-1 RNA 3.0 (bDNA) and COBAS AMPLICOR HIV-1 Monitor v1.5

The COBAS TaqMan HIV-1 test (Roche Diagnostics) was compared with the LCx HIV RNA quantitative assay (Abbott Laboratories), the Versant HIV-1 RNA 3.0 (bDNA) assay (Bayer) and the COBAS Amplicor HIV-1 Monitor v1.5 test (Roche Diagnostics), using plasma samples of various viral load levels from HIV-1-infected individuals. In the comparison of TaqMan with LCx, TaqMan identified as positive 77.5% of the 240 samples versus 72.1% identified by LCx assay, while their overall agreement was 94.6% and the quantitative results of samples that were positive by both methods were strongly correlated (r=0.91). Similarly, in the comparison of TaqMan with bDNA 3.0, both methods identified 76.3% of the 177 samples as positive, while their overall agreement was 95.5% and the quantitative results of samples that were positive by both methods were strongly correlated (r=0.95). Finally, in the comparison of TaqMan with Monitor v1.5, TaqMan identified 79.5% of the 156 samples as positive versus 80.1% identified by Monitor v1.5, while their overall agreement was 95.5% and the quantitative results of samples that were positive by both methods were strongly correlated (r=0.96). In conclusion, the new COBAS TaqMan HIV-1 test showed excellent agreement with other widely used commercially available tests for the quantitation of HIV-1 viral load.     

Comparative evaluation of the Cobas Amplicor HIV-1 Monitor Ultrasensitive Test, the new Cobas AmpliPrep/Cobas Amplicor HIV-1 Monitor Ultrasensitive Test and the Versant HIV RNA 3.0 assays for quantitation of HIV-1 RNA in plasma samples.

BACKGROUND: There are several commercially available assays for the quantitation of HIV RNA. A new automated specimen preparation system, the Cobas AmpliPrep, was developed to automate this last part of the PCR. OBJECTIVES AND STUDY DESIGN: We compared the results obtained by the Roche Cobas Amplicor HIV-1 Monitor Ultrasensitive Test (MCA, manual sample preparation) with those by the Versant HIV-1 RNA 3.0 assay (bDNA). Secondly we compared the MCA with the new Cobas AmpliPrep/Cobas Amplicor HIV Monitor Ultrasensitive Test (CAP/CA, automated specimen preparation) by investigating clinical patient samples and a panel of HIV-1 non-B subtypes. Furthermore, we assessed the assay throughput and workflow (especially hands-on time) for all three assays. RESULTS: Seventy-two percent of the 140 investigated patient samples gave concordant results in the bDNA and MCA assays. The MCA values were regularly higher than the bDNA values. One sample was detected only by the MCA within the linear range of quantification. In contrast, 38 samples with results <50 copies/ml in the MCA showed in the bDNA results between 51 and 1644 copies/ml (mean value 74 copies/ml); 21 of these specimens were shown to have detectable HIV RNA < 50 copies/ml in the MCA assay. The overall agreement between the MCA and the CAP/CA was 94.3% (551/584). The quantification results showed significant correlation, although the CAP/CA generated values slightly lower than those generated by the manual procedure. We found that the CAP/CA produced comparable results with the MCA test in a panel of HIV-1 non-B subtypes. CONCLUSIONS: All three assays showed comparable results. The bDNA provides a high sample throughput without the need of full automation. The new CAP/CA provides reliable test results with no HIV-subtype specific influence and releases time for other works in the laboratory; thus it is suitable for routine diagnostic PCR.     

Comparison of the RealTime HIV-1, COBAS TaqMan 48 v1.0, Easy Q v1.2, and Versant v3.0 assays for determination of HIV-1 viral loads in a cohort of Canadian patients with diverse HIV subtype infections

HIV clinics in Canada provide care to an increasing number of patients born outside of Canada with HIV-1 non-B subtype infections. Because the Easy Q HIV-1 v1.2 assay (EQ; bioMérieux) failed to detect some non-B subtype infections, a multiassay HIV-1 viral load (VL) study was conducted with patients with diverse HIV subtype infections. Patients were enrolled from the Southern Alberta HIV Clinic (SAC), Calgary, Alberta, Canada (n = 349) and the McGill HIV Clinic (MHC), Montreal, Quebec, Canada (n = 20) and had four or five tubes of blood drawn for testing by EQ and three other commercial HIV VL assays: (i) the Versant 3.0 HIV-1 test, with the Versant 440 instrument (branched DNA [bDNA]; Siemens), (ii) the RealTime HIV-1 test, with the m2000rt instrument (m2000rt; Abbott Molecular Diagnostics), and (iii) the COBAS AmpliPrep TaqMan HIV-1 48 test (CAP-CTM; Roche Molecular Diagnostics). Blood was processed according to the individual manufacturer's requirements and stored frozen at -86°C. The HIV subtype was known for patients who had undergone HIV genotypic resistance testing (Virco, Belgium). Data analyses were done using standard statistical methods within Stata 9.0 (StataCorp, College Station, TX). A total of 371 samples were tested on 369 patients, of whom 291 (81%) had a Virco genotype result of B (195; 53%) or non-B (96; 26%) subtypes A to D and F to K, as well as circulating recombinant forms (CRFs) (i.e., CRF01_AE and CRF02_AG). Most (58/78; 74%) patients of unknown subtype were recent African emigrants who likely have non-subtype B infection. Overall bias was small in pairwise Bland-Altman plots, but the limits of agreement between assays were wide. Discordant viral load results occurred for 98 samples and were due to missing values, false negatives, and significant underquantification that varied by HIV subtype. Results were obtained for all 371 samples with m2000rt, but for only 357 (97%) with CAP-CTM, 338 (92%) with EQ, and 276 (75%) with bDNA due to errors/equipment failures. False-negative results (nondetection of viral RNA versus other assay results) occurred for all platforms, as follows: for m2000rt, 8 (2%) [B(4) and non-B(4) subtypes], CAP-CTM, 9 (2.5%) [B(6) and non-B(3) subtypes]; EQ, 20 (6%) [B(7) and non-B(13) subtypes]; bDNA, 5 (2%) [B(1) and C(4)]. EQ and bDNA had the highest rates of underquantification by ≥ 1.0 log(10) copies/ml, mainly for HIV non-B subtypes. Performance significantly varied between HIV VL platforms according to subtype. HIV viral diversity in the population being tested must be considered in selection of the viral load platform.     

Impact of human immunodeficiency virus type 1 (HIV-1) genetic diversity on performance of four commercial viral load assays: LCx HIV RNA Quantitative, AMPLICOR HIV-1 MONITOR v1.5, VERSANT HIV-1 RNA 3.0, and NucliSens HIV-1 QT

Human immunodeficiency virus type 1 (HIV-1) evolution and changing strain distribution present a challenge to nucleic acid-based assays. Reliable patient monitoring of viral loads requires the detection and accurate quantification of genetically diverse HIV-1. A panel of 97 HIV-1-seropositive plasma samples collected from Cameroon, Brazil, and South Africa was used to compare the performance of four commercially available HIV RNA quantitative tests: Abbott LCx HIV RNA Quantitative assay (LCx), Bayer Versant HIV-1 RNA 3.0 (bDNA), Roche AMPLICOR HIV-1 MONITOR v1.5 (Monitor v1.5), and bioMérieux NucliSens HIV-1 QT (NucliSens). The panel included group M, group O, and recombinant viruses based on sequence analysis of gag p24, pol integrase, and env gp41. The LCx HIV assay quantified viral RNA in 97 (100%) of the samples. In comparison, bDNA, Monitor v1.5, and NucliSens quantified viral RNA in 96.9%, 94.8%, and 88.6% of the samples, respectively. The two group O specimens were quantified only by the LCx HIV assay. Analysis of nucleotide mismatches at the primer/probe binding sites for Monitor v1.5, NucliSens, and LCx assays revealed that performance characteristics reflected differences in the level of genetic conservation within the target regions.     

Evaluation of performance across the dynamic range of the Abbott RealTime HIV-1 assay as compared to VERSANT HIV-1 RNA 3.0 and AMPLICOR HIV-1 MONITOR v1.5 using serial dilutions of 39 group M and O viruses

Performance of the Abbott m2000 instrument system and the Abbott RealTime HIV-1 assay was evaluated using a panel of 37 group M (subtypes A-D, F, G, CRF01_AE, CRF02_AG and unique recombinant forms) and 2 group O virus isolates. Testing was performed on 273 sample dilutions and compared to VERSANT HIV-1 RNA 3.0 (bDNA) and AMPLICOR HIV-1 MONITOR v1.5 (Monitor v1.5) test results. RealTime HIV-1, bDNA, and Monitor v1.5 tests quantified 87%, 78%, and 81% of samples, respectively. RealTime HIV-1 detected an additional 31 samples at < 40 copies/mL. For group M, RealTime HIV-1 dilution profiles and viral loads were highly correlated with bDNA and Monitor v1.5 values; 87% and 89% of values were within 0.5 log(10) copies/mL. In contrast, the group O viruses were not detected by Monitor v1.5 and were substantially underquantified by approximately 2 log(10) copies/mL in bDNA relative to the RealTime HIV-1 assay. Sequence analysis revealed that RealTime HIV-1 primer/probe binding sites are highly conserved and exhibit fewer nucleotide mismatches relative to Monitor v1.5. The automated m2000 system and RealTime HIV-1 assay offer the advantages of efficient sample processing and throughput with reduced "hands-on" time while providing improved sensitivity, expanded dynamic range and reliable quantification of genetically diverse HIV-1 strains.     

Comparative evaluation of the QUANTIPLEX HIV-1 RNA 2.0 and 3.0 (bDNA) assays and the AMPLICOR HIV-1 MONITOR v1.5 test for the quantitation of human immunodeficiency virus type 1 RNA in plasma

HIV-1 RNA measurements from 84 plasma specimens obtained with the QUANTIPLEX HIV-1 RNA 2.0 and 3.0 (bDNA) assays (Chiron Diagnostics, Emeryville, CA) and with the AMPLICOR HIV-1 MONITOR Test, version 1.5 with ultra-sensitive specimen preparation (Roche Diagnostic Systems, Inc., Branchburg, NJ) were compared. The absolute RNA values of tested specimens differed significantly between bDNA 2.0 and bDNA 3.0 or Monitor v1.5 measurements (Wilcoxon signed-rank test P<0.001). Results generated with bDNA 3.0 or with Monitor v1.5 were approximately twofold greater than those generated with bDNA 2.0, with smaller differences at higher HIV-1 RNA levels and greater differences at RNA levels below 1000 copies per ml. Although highly correlated (r=0.92 and 0.86, respectively), viral load data generated with bDNA 2.0 and either bDNA 3.0 or Monitor v1.5 were in poor agreement. Concordant results (difference in log(10) copies per ml <0.5) were found at frequencies of 80% for bDNA 2.0 and bDNA 3.0 and only at 58.5% for bDNA 2.0 and Monitor v1.5. In contrast, bDNA 3.0 and Monitor v1.5 measurements were highly correlated (r=0.96) and in good agreement (92.7%).     

Prevalence of human immunodeficiency virus type 1 (HIV-1) non-B subtypes in foreigners living in Madrid, Spain, and comparison of the performances of the AMPLICOR HIV-1 MONITOR version 1.0 and the new automated version 1.5

Plasma specimens collected in 1999 from 32 human immunodeficiency virus type 1 (HIV-1)-infected foreigners living in Madrid, Spain, were examined for the presence of non-B subtypes. Furthermore, plasma viremia was quantified using two different AMPLICOR HIV-1 MONITOR tests, version 1.0 and the new upgraded and automated version 1.5 (COBAS). Most patients came from Africa, where they most likely had acquired HIV-1 infection through sexual contact. HIV-1 genetic subtyping was based on the phylogenetic analysis of the protease gene. Twenty-two subtype B, six subtype G, two subtype C, one subtype A, and one D subtype infection were found. Overall, non-B subtypes represented 31.25% of the study population. Irrespective of the HIV-1 variant, viral load values above the detection limit (200 HIV RNA copies/ml) increased from 56.2 to 71.9% for results obtained using MONITOR version 1.0 and COBAS, respectively. Moreover, significant differences in viral load values (>0.5 logs) were recognized in up to 37.5% of samples. In summary, COBAS seemed to be more reliable for testing plasma viral load in HIV-infected immigrants living in Spain, one third of whom carried non-B subtypes.     

Comparison of three current viral load assays for the quantitation of human immunodeficiency virus type 1 RNA in plasma

The LCx HIV RNA quantitative assay (Abbott Laboratories, Delkenheim, Germany) was compared with the Versant HIV-1 RNA 3.0 (bDNA) assay (Bayer, Tarrytown, NY) and the COBAS Amplicor HIV-1 Monitor v1.5 test (Roche Diagnostics, Branchburg, NJ), using plasma samples of various viral load levels from HIV-1-infected patients. Considering the lower limit of the linear range of 50 copies/ml of both assays, the detection range of the LCx was 127/151 (84.1%) versus the 131/151 (86.8%) of the bDNA 3.0 assay, while overall agreement between the two assays was 93.4% (141/151). LCx and bDNA 3.0 results were found to be strongly correlated (r = 0.96). The fitted regression line was described by the equation log10(LCx copies/ml) = 0.05 + 1.06 x log10(bDNA 3.0 copies/ml) with 95% CI for the estimated slope and intercept at 1.01, 1.12 and -0.16, 0.26, respectively. Similarly, the detection range of the LCx was 115/148 (77.7%) versus the 128/148 (86.5%) of the Monitor v1.5 test. A 91.2% concordance (135/148) was observed between these two assays at a cut-off of 50 copies/ml. LCx and Monitor v1.5 results were highly correlated (r = 0.96). The fitted regression line was described by the equation log10(LCx copies/ml) = 0.06 + 1.03 x log(10)(Monitor v1.5 copies/ml) with 95% CI for the estimated slope and intercept at 0.97, 1.09 and -0.16, 0.28, respectively.     

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.     

Multicenter comparison of Roche COBAS AMPLICOR MONITOR version 1.5, Organon Teknika NucliSens QT with Extractor, and Bayer Quantiplex version 3.0 for quantification of human immunodeficiency virus type 1 RNA in plasma

The performance and characteristics of Roche COBAS AMPLICOR HIV-1 MONITOR version 1.5 (CA MONITOR 1.5) UltraSensitive (usCA MONITOR 1. 5) and Standard (stCA MONITOR 1.5) procedures, Organon Teknika NucliSens HIV-1 RNA QT with Extractor (NucliSens), and Bayer Quantiplex HIV RNA version 3.0 (bDNA 3.0) were compared in a multicenter trial. Samples used in this study included 460 plasma specimens from human immunodeficiency virus (HIV) type 1 (HIV-1)-infected persons, 100 plasma specimens from HIV antibody (anti-HIV)-negative persons, and culture supernatants of HIV-1 subtype A to E isolates diluted in anti-HIV-negative plasma. Overall, bDNA 3.0 showed the least variation in RNA measures upon repeat testing. For the Roche assays, usCA MONITOR 1.5 displayed less variation in RNA measures than stCA MONITOR 1.5. NucliSens, at an input volume of 2 ml, showed the best sensitivity. Deming regression analysis indicated that the results of all three assays were significantly correlated (P < 0.0001). However, the mean difference in values between CA MONITOR 1.5 and bDNA 3.0 (0.274 log(10) RNA copies/ml; 95% confidence interval, 0.192 to 0.356) was significantly different from 0, indicating that CA MONITOR 1.5 values were regularly higher than bDNA 3.0 values. Upon testing of 100 anti-HIV-negative plasma specimens, usCA MONITOR 1.5 and NucliSens displayed 100% specificity, while bDNA 3.0 showed 98% specificity. NucliSens quantified 2 of 10 non-subtype B viral isolates at 1 log(10) lower than both CA MONITOR 1.5 and bDNA 3.0. For NucliSens, testing of specimens with greater than 1,000 RNA copies/ml at input volumes of 0.1, 0.2, and 2.0 ml did not affect the quality of results. Additional factors differing between assays included specimen throughput and volume requirements, limit of detection, ease of execution, instrument work space, and costs of disposal. These characteristics, along with assay performance, should be considered when one is selecting a viral load assay.     

Evaluation of the NucliSens EasyQ assay in HIV-1-infected individuals in South Africa

We compared the performance of the NucliSens EasyQ assay (bioMerieux) combined with the manual NucliSens miniMag extraction methodology to the Roche Cobas Ampliprep/Standard Amplicor Monitor methodology (Roche Diagnostics) for HIV-1 RNA quantitation in HIV-1-infected individuals in South Africa. Plasma samples (284) from HIV sero-positive patients at different stages of infection were analyzed. The distribution of results was typical of the clinical samples received at the laboratory where 20% have viral load results <400 copies/ml (2.6 log) and 18% have viral load results >750000 copies/ml (5.8 log) using the Roche Amplicor Monitor standard assay. All statistical analyses were performed using log10-transformed values for all the variables in the analyses, i.e. log10EasyQIU/ml, and log10RNA (log10 copies/ml, Amplicor). Roche values were converted from RNA copies per ml to IU/ml by multiplying the Roche value by 0.51. HIV RNA levels quantitated by the NucliSens EasyQ assay correlated significantly with those of the Roche Cobas Amplicor Monitor assay (r=0.874, p<0.0001). Reproducibility of the NucliSens EasyQ assay in the log6IU range yielded CV variance of 1.3-2.84% for two well-trained technologists. In addition, a retrospective evaluation of the performance of the NucliSens EasyQ assay in 102 runs (2448) samples was conducted in the laboratory over a 4-month interval. Factors considered during this evaluation included time taken to perform the assay, volume requirements, number of required repeats, potential for contamination.     

Undetectable plasma HIV-1 RNA with strong gag-pol specific interferon-gamma ELISPOT response in an HIV-1 clade A/E-infected child untreated with antiretroviral therapy

We report a 7-year HIV-1 clade A/E-infected child untreated with antiretroviral therapy who had positive HIV antibody testing but undetectable plasma HIV-1 RNA by Roche Amplicor version 1.5 and bDNA version 3.0. DNA PCR was positive by methods using gag/pol primers but not env/pol primers. The patient had strong HIV-1-specific cytotoxic T lymphocyte responses, which likely contributed to her low viral burden and undetectable plasma HIV-1 RNA.