Amplicor Monitor Assay Research Articles

Duplicate HIV-1 viral load testing in HAART-treated patients with low level viraemia on the Roche COBAS Ampliprep Taqman assay: Category: Scientific free paper

The aim of highly-active antiretroviral therapy (HAART) is to suppress HIV-1 viral load (VL) to undetectable levels. All patients on HAART should have a VL measured at regular intervals in order to monitor the success of therapy. In October 2006 the Newcastle Health Protection Agency (HPA) laboratory replaced the Roche COBAS HIV-1 Ampliprep Amplicor Monitor (CAP/CA) assay with the more-sensitive Roche COBAS Ampliprep Taqman HIV-1 (CAP/CTM1) assay. Both locally and internationally the introduction of the CAP/CTM1 assay was associated with a significant unexplained increase in the detection of low level HIV-1 viraemia (VL 50 to 1000 copies/ml).

Transient reappearance of serum hepatitis C virus RNA observed by real-time PCR during antiviral therapy with peginterferon and ribavirin in patients with HCV genotype 1b

Background The “response-guided therapy” based on response of hepatitis C virus (HCV) during antiviral combination therapy with peginterferon and ribavirin is important for patients with HCV genotype 1. However, the sensitivity of previous assays for serum HCV RNA is limited. Objectives We evaluated the changes in serum HCV RNA during the combination therapy using a novel method for measurement based on real-time PCR. Study design Changes in serum HCV RNA during the combination therapy were reanalyzed using TaqMan PCR assay in 144 patients with chronic HCV genotype 1b infection who underwent the therapy under HCV RNA monitoring with the Amplicor Monitor assay. Treatment duration was elongated from 48 weeks to 72 weeks in 17 patients based on the time when serum HCV RNA became negative. Results In 9 of 144 (6.3%) patients, serum HCV RNA transiently appeared again on the TaqMan PCR assay after having previously become negative. At the point of reappearance, the Amplicor Monitor assay gave a negative result in all patients, and no flare of alanine aminotransferase activity was observed. Each of the 9 patients achieved an end-of-treatment response but relapsed after the end of treatment, including 3 patients in whom the treatment duration was elongated to 72 weeks. Conclusions Attention should be paid to this phenomenon in the antiviral treatment for patients with HCV infection. The transient reappearance of HCV RNA in the serum indicates a high likelihood of relapse, and is likely to be missed without frequent measurements by a sensitive detection method.

Hepatitis B virus: molecular genotypes and HBeAg serological status among HBV-infected patients in the southeast of Brazil.

BackgroundKnowledge of HBV genotype is very important for clinical treatment. Studies have suggested possible pathogenic and therapeutic differences among HBV genotypes. The aim of this study was to determine HBV subtypes and genotypes in HBV-infected patients in our region (southeast Brazil) and to correlate results with clinical and histopathological data.MethodsOne hundred and thirty-nine HBsAg-positive patients were included in the study. All patients were anti-HCV and anti-HIV negative (64% male; mean age 42 ± 14.5 years; range 7-80 years; 84% Caucasian) and were followed up at the University Hospital. A method for genotyping and subtyping HBV by partial HBsAg gene sequencing with primers common to all known genotypes was used. The viral load was measured by Amplicor Monitor assay (Roche).ResultsHBV genotype A was the most prevalent (55%), while genotypes C, D and F were found in 3%, 38% and 4% of HBV-infected patients, respectively. Among the patients infected by genotype A, 18.3% (14/76) were African descendents and, among the patients infected by genotype D, 11.3% (6/53) were also African descendents. In the four patients infected with genotype C, 2 were Asian descendents and 2 were Caucasians. All (7) genotype F infected patients were Caucasians. Seventy percent of our HBsAg-positive patients were HBeAg negative (62% genotypes A; 26.2% D; 7.1% C and 4.7%F). The viral load of HBV-DNA was about 5 times higher in HBeAg-positive than in HBeAg-negative patients. About 40% of these patients had alanine aminotransferase of up to 1.5 times the normal level. The mean stage of fibrosis in genotype A patients (2.8) was significantly higher than the mean stage of fibrosis in genotype D patients (2.0) (P = 0.0179).ConclusionThe genotypes encountered in our HBV-infected patients were apparently a consequence of the types of immigration that occurred in our region, where European and African descendents predominate. The HBeAg-negative status predominated, possibly due to the length of time of infection. The viral load in HBeAg-positive patients was higher than in HBeAg-negative individuals. The fibrosis grade in genotype A-infected patients was more advanced than genotype D-infected patients.

Evaluation of HIV-1 viral load and genotypic resistance assays for resource-limited settings

There is an urgent need for low-cost assays for HIV-1 quantitation to ensure adequate follow-up of HIV-infected patients on antiretroviral therapy (ART) in resource-limited countries. Two low-cost viral load assays are evaluated, a reverse transcriptase activity assay (ExavirLoad v2, Cavidi) and a real-time reverse transcriptase PCR assay (Generic HIV viral load, Biocentric). Both tests were compared with the ultrasensitive HIV Amplicor Monitor assay. Samples were collected in Mombasa, Kenya, from 20 HIV-1 seronegative and 150 HIV-1 seropositive individuals of whom 50 received antiretroviral treatment (ART). The ExavirLoad and the Generic HIV viral load assay were performed in a local laboratory in Mombasa, the Amplicor Monitor assay (version 1.5, Roche Diagnostics) was performed in Ghent, Belgium. ExavirLoad and Generic HIV viral load reached a sensitivity of 98.3% and 100% and a specificity of 80.0% and 90.0%, respectively. Linear regression analyses revealed good correlations between the Amplicor Monitor and the Generic HIV viral load (r= 0.935, p< 0.001) with high accuracy (100.1%), good precision (5.5%) and a low percent similarity coefficient of variation (5.4%). Bland–Altman analysis found 95% of the samples within clinically acceptable limits of agreement (−1.19 to 0.87 log copies/ml). Although, the ExavirLoad also showed a good linear correlation with the Amplicor Monitor (r= 0.901, p< 0.001), a problem with false positive results was more significant. The cost per test remains relatively high (US$ 30 for ExavirLoad and US$ 20 for the Generic HIV viral load). Hence, false positive results and the need for an expensive PCR instrument for the Generic HIV viral load assays still limit the implementation of these tests in less equipped, less experienced laboratories. © 2007 Elsevier B.V. All rights reserved.

Evaluation of two commercially available alternatives for HIV-1 viral load testing in resource-limited settings

There is an urgent need for low-cost assays for HIV-1 quantitation to ensure adequate follow-up of HIV-infected patients on antiretroviral therapy (ART) in resource-limited countries. Two low-cost viral load assays are evaluated, a reverse transcriptase activity assay (ExavirLoad v2, Cavidi) and a real-time reverse transcriptase PCR assay (Generic HIV viral load, Biocentric). Both tests were compared with the ultrasensitive HIV Amplicor Monitor assay. Samples were collected in Mombasa, Kenya, from 20 HIV-1 seronegative and 150 HIV-1 seropositive individuals of whom 50 received antiretroviral treatment (ART). The ExavirLoad and the Generic HIV viral load assay were performed in a local laboratory in Mombasa, the Amplicor Monitor assay (version 1.5, Roche Diagnostics) was performed in Ghent, Belgium. ExavirLoad and Generic HIV viral load reached a sensitivity of 98.3% and 100% and a specificity of 80.0% and 90.0%, respectively. Linear regression analyses revealed good correlations between the Amplicor Monitor and the Generic HIV viral load ( r = 0.935, p < 0.001) with high accuracy (100.1%), good precision (5.5%) and a low percent similarity coefficient of variation (5.4%). Bland–Altman analysis found 95% of the samples within clinically acceptable limits of agreement (−1.19 to 0.87 log copies/ml). Although, the ExavirLoad also showed a good linear correlation with the Amplicor Monitor ( r = 0.901, p < 0.001), a problem with false positive results was more significant. The cost per test remains relatively high (US$ 30 for ExavirLoad and US$ 20 for the Generic HIV viral load). Hence, false positive results and the need for an expensive PCR instrument for the Generic HIV viral load assays still limit the implementation of these tests in less equipped, less experienced laboratories.

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).

Comparison of the Roche COBAS Amplicor™ Monitor, Roche COBAS Ampliprep™/COBAS Taqman™ and Abbott RealTime™ Test assays for quantification of hepatitis C virus and HIV RNA

We have evaluated the performance of two newly developed automated real-time PCR assays, the COBAS Ampliprep/COBAS TaqMan (CAP/CTM) and the Abbott RealTime tests, in the quantification of human immunodeficiency virus (HIV) and hepatitis C virus (HCV) RNA. The widely used semi-automated COBAS Amplicor Monitor (CAM) assay served as the reference test. Several specimens were analyzed, including 102 plasma samples from HCV patients and 109 from HIV patients and 10 samples from negative donors, as well as Quality Control in Molecular Diagnostics (QCMD) and National Institute for Biological Standards and Controls (NIBSC) proficiency program panels. Good correlation was observed among the three assays, with correlation coefficients (R2) of 0.8 (CAM-CAP/CTM), 0.89 (CAM-RealTime) and 0.91 (CAP/CTM-RealTime) for HCV and 0.83 (CAM-RealTime), 0.85 (CAM-CAP/CTM) and 0.89 (CAP/CTM-RealTime) for HIV. The overall concordance for negative/positive results was 100% for HCV and 98% for HIV. All assays were equally able to quantify HCV genotypes 1, 3, 5 and HIV group M (subtypes A-H) and N from QCMD and NIBSC panels. In terms of workflow, the RealTime assay requires more hands-on-time than the CAP/CTM assay. The results indicate that real-time PCR assays can improve the efficiency of end-point PCR tests by better covering viral dynamic ranges and providing higher throughput and automation.

Frequency and significance of antibodies against hepatitis B core (anti-HBc) antigen as the only serological marker for hepatitis B infection in Lebanese blood donors

During a 2-year period, blood samples from 2505 Lebanese blood donors were chosen at random, at various periods of time at one blood donation centre (Hotel Dieu de France, Beirut, Lebanon) and were screened for markers of HBV infection (HBsAg, anti-HBc and anti-HBs). The study showed HBsAg positivity of 0.6% and an overall exposure rate to HBV of 10.0%. Out of the 2505 blood donors screened, 56 (22%) were found to be 'anti-HBc alone' positive which is almost four times the HBsAg positivity. The 56 'anti-HBc alone' samples were retested by another ELISA kit commercially available and 54 samples were 'anti-HBc alone' positive by both assays. The 54 samples had no serological markers as evidence of infection with human immunodeficiency virus (HIV) or hepatitis C virus (HCV). Only seven (13%) out of the 54 samples were HBV DNA positive by PCR and all were HBV genotype D. All seven HBV DNA-positive samples had HBV DNA levels below 400 copies/ml. Although any circulating HBV DNA among our 'anti-HBc alone' blood donors was below the detection limit of our Amplicor Monitor assay, some of these samples had circulating virus. A national study, where a larger number of blood donors from different blood donation centres across the country will perhaps determine whether screening for anti-HBc in addition to HBsAg detection is needed in Lebanese blood donors.

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 >750 000 copies/ml (5.8 log) using the Roche Amplicor Monitor standard assay. All statistical analyses were performed using log 10-transformed values for all the variables in the analyses, i.e. log 10EasyQIU/ml, and log 10RNA (log 10 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 log 6 IU 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

High prevalence of occult hepatitis B in Baltimore injection drug users

Occult hepatitis B is defined by the presence of hepatitis B virus (HBV) DNA in a serum or liver in the absence of hepatitis B surface antigen (HBsAg). The prevalence and clinical correlates of occult hepatitis B remain incompletely defined. A cross-sectional study was performed to determine the prevalence of occult hepatitis B in a high-risk cohort composed of 188 injection drug users in Baltimore, Maryland. All individuals had chronic hepatitis C viral infections confirmed by RNA detection and liver biopsy. Serologic assays for HBsAg and core antibody (HBcAb) were performed. Serum HBV DNA was detected using the COBAS HBV AMPLICOR monitor assay (lower limit of detection, 200 HBV copies per milliliter) and a semi-nested polymerase chain reaction (PCR) assay (lower limit of detection, 15 HBV copies per milliliter). Although almost all individuals (96%) were anti-HBC positive, only 8 of 188 (4%) were HBsAg positive. Occult hepatitis B was not identified using the COBAS assay, but was found in 81 of 180 (45%) of individuals using semi-nested PCR. Of the 8 HBsAg positive individuals, HBV DNA was found in 1/8 using the COBAS assay and 6/8 using the nested PCR assay. Overall, liver disease was mild, with a median serum alanine aminotransferase (ALT) of 38 IU/L, median activity grade of 3/18, and median fibrosis stage of 1/6. No association was found between the serum AST (aspartate aminotransferase), activity grade, or stage of liver disease and the presence of occult hepatitis B. Serum ALT levels were slightly higher in patients without occult hepatitis B (46 vs. 35 IU/L), and the median years since first injection drug use was somewhat longer in those without occult hepatitis B (24 vs. 20 years). In conclusion, although further research is needed to assess its clinical significance, there is a high prevalence of occult HBV infection in this cohort of HCV-infected injection drug users.

Occurrence of HIV-1 reverse transcriptase gene mutation at codon 215 in HIV-infected infants.

The nucleoside reverse transcriptase inhibitor Zidovudine (ZDV) decreases mother to child transmission of HIV infection. Nevertheless, significant proportions of mothers who are treated during pregnancy with ZDV still transmit the virus. Along with other factors, failure of ZDV prophylaxis may be due to maternal infection with ZDV-resistant strains and their consequent vertical transmission. The purpose of the study was to investigate the occurrence of mutations at codon 215 in HIV-1 infected infants and its association with clinical status and virological parameters. The cohort consisted of 49 HIV-1 infected infants. Mononuclear cell DNA was isolated from whole blood and served as the input DNA for both a qualitative DNA PCR and the codon 215 assay (nested PCR). HIV-1 viral load (RNA PCR) was measured in plasma by the Roche Amplicor Monitor assay. Twelve of the 49 (24.5%) demonstrated viral strains with mutation at codon 215. A significant difference was found in infants born between 1992 and 1994 (6.3%) compared to those born in 1998-1999 (33.3%). Furthermore, in those infants born in 1998-1999, there was a trend toward an increase in the frequency of zidovudine resistant mutations at codon 215 corresponding to an increase in maternal zidovudine treatment. The mixture of wild and mutant HIV-1 strains was detected in two of 14 infants (14.3%) with a low viral load (<750000 c/ml) compared to nine of 19 (47.4%) infants with extremely high levels of HIV-1 RNA concentration (>750000 c/ml). Only two of 33 tested infants were HIV symptomatic and in both, a mixture of wild and mutant HIV-1 strains was detected. In both infants, the viral load was >750000 c/ml. This study showed that the overall frequency of ZDV resistant strains in infants born in 1998-1999 was significantly higher than that found in infant samples from 1992 to 1994. By 1998, the standard of care for mothers known to be infected with HIV was treatment with either monotherapy using ZDV or combined therapy using a variety of antiretroviral agents including ZDV. Although the exact role of ZDV resistance in limiting the effectiveness of therapies aimed at blocking vertical transmission of HIV remains to be defined, it is clear that drug resistant strains of HIV are occurring more frequently in all types of HIV infection, including infants.

Second generation amplicor HCV monitor assay, clinical features and predictors of the response to interferon

The aims of this study were to compare the amplicor-HCV monitor assay versions 1.0 and 2.0, and to investigate the clinical usefulness of this assay in patients with chronic hepatitis C. We retrospectively analyzed 154 patients, and 133 of these patients received interferon therapy. Sixty-nine patients were complete responders (CR), and 64 were non-responders. Serum HCV RNA levels of version 1.0 and version 2.0 and HCV genotypes were determined in all patients. There was a good correlation between versions 1.0 and 2.0 in both genotype 1b and 2a, 2b (r=0.907 and 0.726, respectively). In genotype 1b, the mean HCV RNA level obtained by version 1.0 was 384+/-547 kcopies/ml and that obtained by version 2.0 was 488+/-825 kI.U./ml. In genotype 2a/2b, the mean level obtained by version 1.0 was 170+/-369 kcopies/ml and that obtained by version 2.0 was 340+/-402 kI.U./ml. Discriminant analysis revealed that the discriminating points of IFN response were 168 kcopies/ml (genotype 1b, version 1.0), 106 kcopies/ml (genotype 2a and 2b, version 1.0), 102 kI.U./ml (genotype 1b, version 2.0), and 277 kI.U./ml (genotype 2a and 2b, version 2.0). When the patients were stratified according to the discriminating points, the CR rate below the discriminating points were 73.8 and 86.2% in versions 1.0 and 2.0, respectively, in genotype 1b, and the rates were 73.2 and 82.3% in genotype 2a/2b. In addition, receiver-operating characteristic analysis revealed that version 2.0 had significantly better discriminative ability in patients with genotype 1b. We conclude that the second version of the amplicor-HCV monitor assay measures HCV RNA levels with the same precision as version 1.0 and is more useful for the prediction of interferon response than version 1.0.

Course of Viral Load Throughout HIV-1 Infection

Summary: HIV-1 RNA levels are routinely monitored as part of patient management. However, little is known about the course of HIV-1 RNA levels over the entire period of infection. The aim of this study was to investigate the course of HIV-1 RNA levels in a cohort of men with hemophilia who were observed for up to 17 years after HIV-1 seroconversion, and to assess the risk of HIV disease progression at any HIV-1 RNA level. Viral loads were measured on annual stored serum samples in 107 men with hemophilia A using the Roche Amplicor Monitor assay with non-B primers. On average, HIV-1 RNA levels increased significantly by 0.11 log10 per year over the course of HIV infection. This rate of increase was significantly faster in those who developed AIDS or died over the subsequent 12 to 17 year period, and in those who were older at HIV-1 seroconversion. The risk of developing AIDS and death remained low when the HIV-1 RNA level was below 4 log10 copies/ml, but increased rapidly thereafter, supporting current guidelines for the initiation of antiretroviral therapy after the viral load has exceeded this level.

Course of viral load throughout HIV-1 infection.

HIV-1 RNA levels are routinely monitored as part of patient management. However, little is known about the course of HIV-1 RNA levels over the entire period of infection. The aim of this study was to investigate the course of HIV-1 RNA levels in a cohort of men with hemophilia who were observed for up to 17 years after HIV-1 seroconversion, and to assess the risk of HIV disease progression at any HIV-1 RNA level. Viral loads were measured on annual stored serum samples in 107 men with hemophilia A using the Roche Amplicor Monitor assay with non-B primers. On average, HIV-1 RNA levels increased significantly by 0.11 log10 per year over the course of HIV infection. This rate of increase was significantly faster in those who developed AIDS or died over the subsequent 12 to 17 year period, and in those who were older at HIV- 1 seroconversion. The risk of developing AIDS and death remained low when the HIV-1 RNA level was below 4 log10 copies/ml, but increased rapidly thereafter, supporting current guidelines for the initiation of antiretroviral therapy after the viral load has exceeded this level.

Comparison of the Quantiplex Version 3.0 Assay and a Sensitized Amplicor Monitor Assay for Measurement of Human Immunodeficiency Virus Type 1 RNA Levels in Plasma Samples

This study evaluated correlation and agreement between version 3 of the Quantiplex human immunodeficiency virus type 1 (HIV-1) RNA assay (v3 branched DNA [bDNA]) and a sensitized Amplicor HIV-1 Monitor assay (reverse transcription [RT]-PCR) for the measurement of HIV RNA. Three hundred eighteen samples from 59 randomly selected, HIV-1-seropositive persons on various drug protocols from the National Institute of Allergy and Infectious Diseases HIV outpatient clinic were studied. The results indicate that v3 bDNA and RT-PCR are highly correlated (r = 0.98) and are in good agreement (mean difference in log(10) copies/ml +/- 2 standard deviations = 0.072 +/- 0.371). The relationship between values obtained by both assays is given by the following equation: log(10)v3 bDNA = -0.0915 + 1. 0052. log(10)RT-PCR. This represents a 1.026-fold difference between log(10)RT-PCR values and log(10)v3 bDNA values.

Quantification of hepatitis C virus by TaqMan PCR: Comparison with HCV amplicor monitor assay

The quantitation of serum levels of hepatitis C virus RNA in chronic hepatitis C has been regarded as one of the most important indicators for the outcome of interferon therapy. A new method was used for quantitating the copy number of hepatitis C virus RNA using TaqMan polymerase chain reaction and for comparing the ability and usefulness of this assay with Amplicor Monitor assay in 138 patients. The detection range of hepatitis C virus RNA by TaqMan polymerase chain reaction was from 2 x 10(3) to 2 x 10(8) copies/ml. Hepatitis C virus RNA was detectable in 128 cases (92.8%) and undetectable in 10 cases (7.2%) by this method. The RNA levels measured by Amplicor Monitor assay correlated significantly with those measured by TaqMan polymerase chain reaction assay and the sensitivity of the two assays was almost equal. Thus, TaqMan polymerase chain reaction assay appears sufficiently sensitive for the evaluation of hepatitis C virus RNA and would be useful for the diagnosis and management of hepatitis C virus infection.

An international collaborative study on the detection of an HIV-1 genotype B field isolate by nucleic acid amplification techniques

An international collaborative study to assess inter-laboratory variation in the sensitivity of gene amplification assays for the detection of HIV-1 RNA sequences was conducted using a panel of eight duplicate dilutions of an HIV-1 genotype B clinical isolate and negative control samples. Twenty-five laboratories participated in the study and used a variety of in-house assays and commercial assay systems. With few exceptions, the assays were more sensitive than a p24 antigen assay. Overall, the PCR-based Amplicor Monitor assay was the most sensitive and gave the highest mean copy number for any one sample. Some of the in-house assays gave results comparable with the Monitor assay whilst the NASBA and bDNA assays appeared to be less sensitive. As a result of this study, an HIV-1 Working Reagent for the standardisation of nucleic acid amplification assays was developed and assessed in a subsequent study. Similar differences in sensitivity between the different assay systems was observed. The discrepancies in viral copy number obtained using the Working Reagent highlights the need for an International Standard against which all Working Reagents may be calibrated.

Quantitative assays for hepatitis C virus in serum as predictors of the long-term response to interferon

Background/Aims: Interferon therapy has a beneficial effect in patients with chronic hepatitis C who have a low viral load. The aim of this study was to compare the core protein level with HCV RNA levels and to analyze whether virus quantitation predicts the efficacy of interferon therapy. Methods: HCV core protein level assessed by the recently developed assay was compared with HCV RNA levels measured by three different methods (Amplicor-HCV monitor, competitive RT (CRT)-PCR, and bDNA probe assay) in 352 patients with chronic hepatitis C in relation to viral serotype. Results: From 91% (320/352) to 93% (299/322) of patients with viremia were detected by Amplicor- monitor and CRT-PCR, in contrast to 60% (187/312) and 74% (191/258) by bDNA and HCV core protein assay, respectively. The HCV core protein level was positively correlated with HCV RNA levels measured by the three assay ( r=0.680 to 0.731). Serum HCV RNA and core protein levels were significantly lower in patients with serotype 2 than in those with serotype 1. Viral eradication after interferon therapy was observed in 60–70% of the patients with <1 × 10 4 copies/ml of HCV RNA by Amplicor-monitor assay, <2 × 10 5 copies/ml by CRT-PCR, <0.5 Meq/ml by bDNA assay, and <20 pg/ml of core protein by HCV core protein assay. Viral eradication was uncommon (<11%) among the patients with higher viral loads. Bivariate analysis revealed that the outcome of interferon therapy was more closely associated with both HCV core protein and RNA levels than the HCV serotype. Conclusions: Quantitation of HCV core protein and HCV RNA is useful for prediction of the interferon response.

Predictors of the efficacy of interferon therapy in chronic hepatitis C virus infection. Tokyo-Chiba Hepatitis Research Group

BACKGROUND & AIMS: The relative role of virus load and hepatitis C virus (HCV) subtype as predictor of the efficacy of interferon (IFN) therapy is still in dispute. To resolve this issue, a multicenter, randomized, prospective study of 272 patients with chronic hepatitis C but without cirrhosis was conducted.METHODS: The patients were randomly assigned to two different dose groups: 6 million units (MU) or 9 MU IFN three times a week for 6 months. Serum HCV RNA levels and HCV subtypes were determined.RESULTS: HCV RNA negativity rate at the completion of treatment with 9 MU IFN was higher than that with 6 MU (75% vs. 44%; P < 0.05). Virus eradication at 12 months after completion of treatment was higher in the 9 MU group than in the 6 MU group (36% vs. 25%; P < 0.05), especially in patients who had an intermediate virus load (10(4)-10(5) copies/mL by Amplicor monitor assay) (52% vs. 19%; P = 0.029). Virus eradication rate in patients with serotype 2 was higher than in those with serotype 1 for both regimens (6 MU, 53% vs. 15%; 9 MU, 76% vs. 29%; each P < 0.05).CONCLUSIONS: This prospective study showed that virus load, HCV serotype, and IFN dose are important predictors of the virological response to IFN therapy but virus load is the most important factor influencing the efficacy of IFN.(Gastroenterology 1997 Aug;113(2):558-66)

Detection of human immunodeficiency virus type 1 (HIV-1) DNA and RNA sequences in HIV-1 antibody-positive blood donors in Uganda by the Roche AMPLICOR assay

The ability of commercially available PCR-based assays to accurately detect or quantitate human immunodeficiency virus type 1 (HIV-1) DNA or RNA in individuals predominantly infected with HIV-1 subtypes A and D is not known. Therefore, peripheral leukocytes from 43 individuals in Kampala, Uganda, positive for HIV by the Western blot (immunoblot) assay were tested by using the Roche AMPLICOR HIV-1 assay for the detection of DNA gag sequences. Plasma from these same individuals was tested by using the Roche HIV-1 AMPLICOR MONITOR HIV-1 assay for the quantitation of HIV-1 RNA gag sequences. In addition, peripheral leukocytes were tested for HIV-1 DNA by using a lower annealing temperature or a different primer pair for the HIV-1 pol region. The proportions of individuals with detectable HIV-1 DNA and RNA gag sequences by the Roche assays were 74 and 90%, respectively. The proportions positive for HIV-1 DNA sequences by using a 50 degrees C annealing temperature or the pol primer pair were 71 and 98%, respectively. In summary, the standard Roche assay did not detect HIV-1 DNA sequences in a significant number of HIV-1-infected individuals in Uganda. However, use of a pol primer pair increased the sensitivity of the assay to 98%. The sensitivity of the Roche AMPLICOR MONITOR assay for the detection and quantitation of HIV-1 RNA sequences was significantly higher than that of the DNA-based assay, but the efficiency of the assay, and hence, the accuracy of the values obtained with RNA, is not known. Modifications to existing assays are needed to enhance the sensitivities and accuracies of these commercially available assays for use in developing countries where non-B HIV-1 subtypes predominate.