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PubMed2004

Detection and quantification of copper-denitrifying bacteria by quantitative competitive PCR.

We developed a quantitative competitive PCR (QC-PCR) system to detect and quantify copper-denitrifying bacteria in environmental samples. The primers were specific to copper-dependent nitrite reductase gene (nirK). We were able to detect about 200 copeis of nirK in the presence of abundant non-specific target DNA and about 1.2 x 10(3)Pseudomonas sp. G-179 cells from one gram of sterilized soil by PCR amplification. A 312-bp nirK internal standard (IS) was constructed, which showed very similar amplification efficiency with the target nirKfragment (349 bp) over 4 orders of magnitude (10(3)-10(6)). The accuracy of this system was evaluated by quantifying various known amount of nirK DNA. The linear regressions were obtained with a R(2) of 0.9867 for 10(3)copies of nirK, 0.9917 for 10(4) copies of nirK, 0.9899 for 10(5) copies of nirK and 0.9846 for 10(6) copies of nirK. A high correlation between measured nirK and calculated nirK (slope of 1.0398, R(2)=0.9992) demonstrated that an accurate measurement could be achieved with this system. Using this method, we quantified nirK in several A-horizon and stream sediment samples from eastern Tennessee. In general, the abundance of nirK was in the range of 10(8)-10(9) copies g soil(-1) dry weight. The nirK content in the soil samples appeared correlated with NH(4)(N) content in the soil. The activities of copper-denitrifying bacteria were evaluated by quantifying cDNA of nirK. In most of sample examined, the content of nirK cDNA was less than 10(5) copies g soil(-1) dry weight. Higher nirK cDNA content (>10(6) copies g soil(-1) dry weight) was detected from both sediment samples at Rattlebox Creek and the Walker Branch West Ridge. Although the stream sediment samples at the Walker Branch West Ridge contained less half of the nirK gene content as compared to A-horizon sample, the activities of copper-denitrifying bacteria were almost 600 times higher than in the A-horizon sample.

Copper↗
PubMed2002

Quantitative CSF PCR in Epstein-Barr virus infections of the central nervous system.

Acute Epstein-Barr virus (EBV) infection of the central nervous system (CNS) is associated with meningoencephalitis and other neurological syndromes and with CNS lymphomas (CNSLs). Diagnosis is based on serological studies and more recently on detection of EBV DNA in cerebrospinal fluid (CSF) by polymerase chain reaction (PCR). We measured EBV DNA by quantitative PCR and EBV mRNA by RT-PCR in the CSF in patients with EBV-associated neurological disorders. EBV was identified as the cause of CNS infection in 28 patients: 14 with CNSL, 10 with encephalitis, and 4 with postinfectious neurological complications. CSF analysis showed that patients with CNSL had high EBV load (mean +/- standard error of 4.8 +/- 0.2 log(10) DNA copies/ml) and low leukocyte counts (22 +/- 7 cells/microl); encephalitis was characterized by high EBV load (4.2 +/- 0.3 log(10) DNA copies/ml) and high leukocyte counts (143 +/- 62 cells/microl); and patients with postinfectious complications showed low EBV load (3.0 +/- 0.2 log(10) DNA copies/ml) with high leukocyte counts (88 +/- 57 cells/microl). Lytic cycle EBV mRNA, a marker of viral replication, was identified in 10 CSF samples from patients with CNSL and encephalitis. These studies demonstrate the utility of quantitative CSF PCR and establish the presence of lytic cycle EBV mRNA in CSF of patients with EBV-associated neurological disease.

Adult↗
PubMedDate not supplied

The use of competitive PCR for quantitation of HSV-1 DNA.

PURPOSE: Polymerase chain reaction (PCR) detects the genomic materials of etiological agents with high specificity and sensitivity. However, in herpes simplex virus type 1 (HSV-1) infection, the clinical significance of the results often poses controversy because of the subclinical viral shedding during latent infection. Quantitative PCR might provide additional information to help clinical evaluation of the results. METHODS: Virus DNA was extracted from high titer stock of human HSV-1 (FK 25) by phenol/chloroform treatment. Construct (p/HSV-1) was made by inserting the glycoprotein D gene obtained from virus DNA into p(GEM-T) vector. Competitor (p/DeltaHSV-1) was made by deleting the inner 40 bp of construct (p/HSV-1) with restriction enzyme. Competitive PCR was performed using primers that amplify the glycoprotein D gene, and a template made of a 1:1 molar mixture of HSV-1 DNA and the competitor. RESULTS: The PCR product reflected the initial template dose from 20 to 30 cycles. Minimum detection level of HSV-1 DNA was 0.01 ng. CONCLUSION: Competitive PCR can quantitate HSV-1 DNA.

DNA, Viral↗
PubMed2002

Application of real-time fluorescent PCR for quantitative assessment of Neospora caninum infections in organotypic slice cultures of rat central nervous system tissue.

The previously described Nc5-specific PCR test for the diagnosis of Neospora caninum infections was used to develop a quantitative PCR assay which allows the determination of infection intensities within different experimental and diagnostic sample groups. The quantitative PCR was performed by using a dual fluorescent hybridization probe system and the LightCycler Instrument for online detection of amplified DNA. This assay was successfully applied for demonstrating the parasite proliferation kinetics in organotypic slice cultures of rat brain which were infected in vitro with N. caninum tachyzoites. This PCR-based method of parasite quantitation with organotypic brain tissue samples can be regarded as a novel ex vivo approach for exploring different aspects of cerebral N. caninum infection.

Animals↗
PubMed1999

Detection of BCR-ABL transcripts in chronic myeloid leukemia (CML) using a 'real time' quantitative RT-PCR assay.

Quantitative competitive RT-PCR techniques have been developed to detect BCR-ABL fusion transcripts in CML but they are hardly reproducible. In this work, we have developed BCR-ABL quantification by real time RT-PCR using the ABI PRISM 7700 (Perkin Elmer), a new technique which allows simple and rapid quantification of a target sequence during the extension phase of PCR amplifications. A fluorogenic probe labeled with both a reporter dye at the 5' end and a quencher-dye at the 3' end hybridizes to the target sequence on the third exon of the ABL gene. The exonuclease activity of the Taq DNA polymerase cleaves the probe and releases the reporter dye, resulting in an increase in the fluorescence signal. The absolute copy number of the target sequence (BCR-ABL) or a control gene (ABL) in an unknown sample can then be calculated using a calibration curve prepared from a set of BCR-ABL RNA standards, and results are expressed as a BCR-ABL/ABL ratio. In our hands, the sensitivity of a serial dilution of total RNA from a positive cell line (K562) in a negative cell line (HL60) was 10(-4). Fifteen CML patients in cytogenetic CR, including 11 allografted patients, two autografted patients and two patients treated by IFN were studied sequentially by this new real time quantitative RT-PCR technique in parallel with conventional qualitative two round nested RT-PCR. The two autografted patients showed high BCR-ABL/ABL ratio in all samples. The two patients treated by IFN showed a progressive decrease in the ratio. In the 11 allografted patients, four were sequentially studied 2 years or more after allo-BMT, and all ratios were below 10(-4). The four patients remained in clinical and cytogenetic CR. The seven other allografted patients were studied immediately after the procedure. Three of them showed a progressive decrease in the BCR-ABL/ABL ratio which reached 10(-4) 7 months after allo-BMT. The three patients remained in hematologic and cytogenetic CR. The remaining four allografted patients had progressive increase of BCR-ABL ratio; three developed cytogenetic relapse 9, 11, 28 months after allo-BMT, and the last patient remained in cytogenetic CR in the bone marrow but developed granulocytic sarcoma. Results of real-time quantitative RT-PCR were in agreement with those of qualitative two round nested PCR. However, evolution changes in the results of real-time quantitative RT-PCR often preceded those of the conventional technique: a decrease of the BCR-ABL/ABL ratio preceded progression from first round to second round positivity and then negativity with the classical technique; conversely, an increase in the ratio preceded evolution with the classical technique. Thus, real-time quantitative RT-PCR may show better correlation with clinical and cytogenetic evolution than conventional qualitative techniques and may help in making early therapeutic decisions in CML, especially after molecular relapse.

Adult↗
PubMed2004

Library screening for D-amino-acid oxidase gene: application of real-time PCR.

Quantitative real-time PCR shows the quantity in addition to the presence of the target sequence. This property seemed very useful for library screening. Then, real-time PCR was employed to screen for lambda phages carrying D-amino-acid oxidase gene from mouse genomic library. Using stepwise dilution screening combined with real-time PCR, positive phages were isolated in a short time.

Amino Acid Oxidoreductases↗
PubMed2004

Comparison of two quantitative CMV PCR tests, Cobas Amplicor CMV Monitor and TaqMan assay, and pp65-antigenemia assay in the determination of viral loads from peripheral blood of organ transplant patients.

BACKGROUND: Quantitative PCR assays have become the most common methods in the determination of viral load during cytomegalovirus (CMV) infection of transplant patients. However, usually these tests are still quite time-consuming and labor-intensive which diminishes their utility of these tests in routine diagnostic laboratories. OBJECTIVES: The objective of this study was to develop a quantitative CMV PCR test which is time-saving and easy to perform for the detection and monitoring of CMV infection of transplant patients. STUDY DESIGN: The quantitative real time CMV PCR assay using TaqMan chemistry and an automated sample preparation system, MagNA Pure LC, was developed. The designed quantitative CMV test was compared to commercial quantitative PCR test, Cobas Amplicor Monitor, in the determination of CMV DNA loads in plasma samples of liver and kidney transplant patients. The results were also correlated with the CMV pp65-antigenemia test. The clinical material of 270 blood specimens of transplant patients were tested using these two PCR methods and pp65-antigenemia test in parallel. Plasma samples were used for PCR assays and leucocytes for the antigenemia test. RESULTS: The TaqMan assay described was easy to perform, it was rapid (3-4 h) and hands-on time needed for performing the test was short. The detection limit of the assay was 250 copies/ml (cps/ml) plasma and the linear range up to 25,000,000 cps/ml. TaqMan assay was the most sensitive test detecting 92% of the CMV positive findings. Cobas Monitor detected 80% and pp65 test 88% of the positive findings. The correlations between TaqMan and antigenemia assays, and between Cobas Amplicor and antigenemia were statistically significant and high, R = 0.84 (P < 0.0001) and R = 0.80 (P < 0.0001), respectively. Also correlation between two PCR tests was statistically significant (R = 0.64, P < 0.0001). Of the 27 patient studied, 19 demonstrated CMV antigenemia and DNAemia in their blood during the post transplant monitoring. Thirteen of these patients developed a symptomatic CMV infection and were treated with ganciclovir. The peak viral loads of symptomatic patients were statistically higher by all three methods than those of asymptomatic patients. CONCLUSIONS: The developed real time TaqMan assay was rapid and easily performed and could be the best alternative for the diagnosis of CMV infection and monitoring of liver and kidney transplant patients.

Cytomegalovirus↗
PubMed1995

Ganciclovir therapy for cytomegalovirus (CMV) infection of the central nervous system in AIDS patients: monitoring by CMV DNA detection in cerebrospinal fluid.

Seven AIDS patients with central nervous system (CNS) disease and cytomegalovirus (CMV) DNA in cerebrospinal fluid (CSF) were evaluated before and 3 weeks after standard ganciclovir treatment by nested polymerase chain reaction (PCR) on limiting dilutions and by quantitative PCR. After therapy, PCR CSF was negative for CMV in 3 patients with low baseline levels of CMV DNA and positive with decreased DNA titers in 4 patients with higher baseline levels. CMV pp65 antigen in polymorphonuclear leukocytes was found in 6 of 7 patients before therapy and in none of 5 after therapy. At autopsy, CMV was found in the CNS of the 4 cases examined, including 3 whose CSF was continuously positive by PCR. Quantitative PCR of CSF is useful for monitoring ganciclovir treatment in CMV infection of the CNS. In AIDS patients, standard ganciclovir treatment seems effective in reducing but not suppressing viral replication in severe cases of CMV infection of the CNS.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Bacterial lipopolysaccharide protects gastric mucosa against acute injury in rats by activation of genes for cyclooxygenases and endogenous prostaglandins.

Lipopolysaccharides (LPS) derived from gram-negative bacteria were reported to impair gastrointestinal mucosal integrity, but the results obtained are controversial. This study was undertaken to determine the effects of short-term administration of LPS on gastric secretion and gastric damage induced by 100% ethanol and to assess the role of the gene expression of two isoforms of cyclooxygenase (COX), constitutive (COX-1) and inducible (COX-2), and endogenous prostaglandins (PG) on these effects of LPS. Fasted rats received vehicle (control) or LPS (0.1-40 mg/kg i.g. or i.p.) without or with pretreatment with nonselective inhibitors of COX activity, indomethacin (5 mg/kg i.p.) and meloxicam (2 mg/kg i.g.), or the selective COX-2 inhibitor NS-398 (10 mg/kg i.g.), followed by intragastric application of 100% ethanol. The area of gastric lesions was determined by planimetry, gastric blood flow (GBF) was measured by the H2-gas clearance technique, mucosal PGE2 generation was measured by radioimmunoassay, and expression of COX-1 and COX-1 mRNA was determined by reverse transcription polymerase chain reaction (RT-PCR), quantitative RT-PCR with [32P]dCTP and immunohistochemistry. LPS applied intraperitoneally in various doses (0.1-10 mg/kg), dose dependently inhibited gastric acid and pepsin secretion and significantly reduced the area of gastric lesions induced by ethanol, and this was accompanied by an attenuation of the ethanol-induced fall in GBF and increased mucosal generation of PGE2. LPS applied in higher doses, such as 20 or 40 mg/kg, that caused systemic hypotension failed to protect the mucosa against 100% ethanol. Suppression of mucosal PGE2 generation by indomethacin or meloxicam, significantly reduced the inhibitory action of LPS on gastric secretion and abolished LPS-induced gastroprotection and elevation of GBF. NS-398 did not influence PGE2 generation, but significantly attenuated the protection and hyperemia induced by LPS suggesting that COX-2-derived products play an important role in gastroprotection. The expression of COX-1 mRNA, as determined by RT-PCR, quantitative RT-PCR and immunohistochemistry was found in intact gastric mucosa and after LPS administration. In contrast, the expression of COX-2 mRNA was undetectable in intact gastric mucosa but appeared in this mucosa 2, 4 and 8 h after LPS administration. COX-2 mRNA was not detected in rats treated with ethanol but, when LPS was applied before ethanol, the enhanced expression of COX-2 was detected without affecting COX-1 mRNA expression. We conclude that acute parenteral LPS affords gastroprotection against ethanol-damage through an increase in gastric microcirculation and overexpression of COX-2 and enhanced endogenous PG release.

Animals↗
PubMed1999

Quantitation of hepatitis B virus genomic DNA by real-time detection PCR.

Quantitation of hepatitis B virus (HBV) DNA in serum is a useful method for the monitoring of HBV replication. We attempted to develop a quantitative assay system for HBV DNA that is more sensitive, accurate, and reproducible than existing systems. We detected HBV DNA by real-time detection PCR (RTD-PCR) based on Taq Man chemistry. The efficacy of this assay was evaluated by quantitatively measuring sequential levels of synthetic DNA and DNA in clinical serum samples. The detection limit of this system was as few as 10 DNA copies/reaction. A linear standard curve was obtained between 10(1) and 10(8) DNA copies/reaction. The coefficient of variation for both intra- and interexperimental variability indicated remarkable reproducibility. This system detected HBV DNA in 100% of chronic hepatitis B patients tested and never detected HBV DNA in healthy volunteers who were negative for HBV markers. These observations suggest that RTD-PCR is an excellent candidate for a standard HBV quantification method.

Adult↗
PubMed2004

[Prospects and applications of innovated quantitative fluorescent PCR (IQF PCR) in analyses of genetic mosaics using gonosomal sequences].

BACKGROUND: Quantification of fluorescence labelled PCR products on capillary electrophoresis (QF PCR) has limits primarily in the possibility of more sensitive analyses to detect minority cell lines and small time related variations. PCR efficiency and human factor affect measuring error and reproducibility of results in these cases. The aim of this work was to assess and optimise of innovated (I)QF PCR in quantification of Y sequences in gonosomal mosaics. METHODS AND RESULTS: Artificially prepared Y/X mosaics were tested and quantified by IQF PCR, which replaces real-time PCR. Comparison of relative fluorescence to PCR cycles in different Y/X dilutions was plotted on the graphs. Calibration curve for Y sequences quantification was set by the analyses of ratio of Y/X fluorescent signals. An empirical formula was created for the rare mosaic calculation. CONCLUSIONS: QF PCR refined by manual real-time PCR eliminates limits of QF PCR and specifies quantitative analyses based on PCR. The outstanding feature of IQF PCR is its high sensitivity and accuracy in quantification of Y/X gonosomal mosaics.

Cell Line↗
PubMed2000

Enumeration of Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans in subgingival plaque samples by a quantitative-competitive PCR method.

Porphyromonas gingivalis, Prevotella intermedia and Actinobacillus actinomycetemcomitans are believed to play an important role in adult periodontitis, but the significance of their relative numbers and progress of the disease is still unclear. Traditional quantitative methods are generally time-consuming and inaccurate. The aim of this study was to develop a sensitive, quantitative PCR technique that would be useful for enumerating P. gingivalis, Pr. intermedia and A. actinomycetemcomitans in subgingival plaque samples from subjects with adult periodontitis. Primers to the following genes were employed: the fimbrial gene (fimA) of P. gingivalis, the 16S rRNA gene of Pr. intermedia and the leukotoxin-A (lktA) gene of A. actinomycetemcomitans. Competitive templates were constructed either by sequence deletion between primer binding sites or by annealing of the primer binding sites to an appropriate DNA core so as to yield products of a different size from that obtained with the target template. Coamplification of target and competitive templates yielded products of expected size and non-specific recognition by the primers was not found. The sensitivity of the designed primers was 100 cells of P. gingivalis, 100 cells of Pr. intermedia and 10 cells of A. actinomycetemcomitans. The three species were found in subgingival plaque samples collected from both healthy and diseased sites by the quantitative-competitive (QC)-PCR method and the technique was more sensitive than cultural methods. For determining the proportions of each of the three periodontopathogens, the total number of bacteria in the samples was enumerated by quantitative-PCR with 16S rRNA universal primers (27f and 342r). The findings indicate that QC-PCR is a useful method for enumerating bacteria in clinical oral specimens and the technique could play a role in the investigation of disease progression.

Actinobacillus Infections↗
PubMed2001

Quantitative analysis of herpesvirus sequences from normal tissue and fibropapillomas of marine turtles with real-time PCR.

Quantitative real-time PCR has been used to measure fibropapilloma-associated turtle herpesvirus (FPTHV) pol DNA loads in fibropapillomas, fibromas, and uninvolved tissues of green, loggerhead, and olive ridley turtles from Hawaii, Florida, Costa Rica, Australia, Mexico, and the West Indies. The viral DNA loads from tumors obtained from terminal animals were relatively homogeneous (range 2-20 copies/cell), whereas DNA copy numbers from biopsied tumors and skin of otherwise healthy turtles displayed a wide variation (range 0.001-170 copies/cell) and may reflect the stage of tumor development. FPTHV DNA loads in tumors were 2.5-4.5 logs higher than in uninvolved skin from the same animal regardless of geographic location, further implying a role for FPTHV in the etiology of fibropapillomatosis. Although FPTHV pol sequences amplified from tumors are highly related to each other, single signature amino acid substitutions distinguish the Australia/Hawaii, Mexico/Costa Rica, and Florida/Caribbean groups.

Amino Acid Sequence↗
PubMed2000

Application of 5'-nuclease PCR for quantitative detection of Listeria monocytogenes in pure cultures, water, skim milk, and unpasteurized whole milk.

PCR techniques have significantly improved the detection and identification of bacterial pathogens. Countless adaptations and applications have been described, including quantitative PCR and the latest innovation, real-time PCR. In real-time PCR, e.g., the 5'-nuclease chemistry renders the automated and direct detection and quantification of PCR products possible (P. M. Holland et al., Proc. Natl. Acad. Sci. USA 88:7276-7280, 1991). We present an assay for the quantitative detection of Listeria monocytogenes based on the 5'-nuclease PCR using a 113-bp amplicon from the listeriolysin O gene (hlyA) as the target. The assay was positive for all isolates of L. monocytogenes tested (65 isolates including the type strain) and negative for all other Listeria strains (16 isolates from five species tested) and several other bacteria (18 species tested). The application of 5'-nuclease PCR in diagnostics requires a quantitative sample preparation step. Several magnetic bead-based strategies were evaluated, since these systems are simple and relatively easy to automate. The combination of nonspecific binding of bacteria to paramagnetic beads, with subsequent DNA purification by use of the same beads, gave the most satisfactory result. The detection limit was approximately 6 to 60 CFU, quantification was linear over at least 7 log units, and the method could be completed within 3 h. In conclusion, a complete quantitative method for L. monocytogenes in water and in skimmed and raw milk was developed.

Animals↗
PubMed2003

Validation and clinical implication of a quantitative real-time PCR determination of MDR1 gene expression: comparison with semi-quantitative PCR in 101 patients with acute myeloid leukemia.

INTRODUCTION: The multidrug resistance protein 1 (MDR1) has the capacity to extrude chemotherapeutics and has been implicated in treatment failure in acute myeloid leukemia (AML). Previous methods for determination of MDR1 expression have included dye exclusion, demonstration of P-glycoprotein by flow cytometry and/or immunohistochemistry, and molecular polymerase chain reaction (PCR)-based assays for RNA expression. However, these assays have either proven difficult to standardize or tedious to perform. We have therefore designed a real-time quantitative (RQ)-PCR based assay measuring MDR1 gene expression and validated it in AML patients by direct comparison with a competitive reverse transcriptase polymerase chain reaction (RT-PCR) assay. PATIENTS AND METHODS: Bone marrow or peripheral blood from 101 AML patients diagnosed (1987-96) at our department were assessed for quantitative expression of MDR1 employing TaqMan RQ-PCR. These data were compared with results obtained by a semi-quantitative competitive PCR assay employing an artificial internal RNA construct. RESULTS: While the RQ-PCR method was able to determine MDR1 gene expression in a continuous fashion over five logs, the semi-quantitative PCR only yielded data in a discontinuous fashion and over four logs at best. Compared with the MDR1 positive and negative cell lines 8226 DOX40 and REH AML cells exhibited variation of 10 PCR cycles, equivalent to a 1000-fold difference. A significant correlation was observed between the two methods, Spearman's correlation coefficient = -0.502, P-value = 10-5. CONCLUSION: We conclude that, RQ-PCR is a novel methodology, which enables sensitive and quantitative measurement of MDR1 gene expression. This assay is moreover suitable because of its high throughput for longitudinal follow-up and large number of patients.

Base Sequence↗
PubMed2000

Optimized multiplex IgH/ras PCR: a tool for quantitative monitoring of B-lymphoproliferative disorders.

The use of quantitative PCR is recommended to monitor the level of residual hematological malignancies. The proposed multiplex IgH/ras PCR uses a co-amplification of the clonal CDR3 rearrangement of the immunoglobulin heavy chain gene (IgH) as a disease marker and a segment of the Hras 1 gene containing codon 61 (ras) as a control gene. Serial dilutions of stored diagnostic DNAs are examined together in the same PCR at a sub-plateau phase and, after analysis by densitometry, the amount of CDR3 product is related to the ras product. An increase of this ratio at comparable amounts of DNA is viewed as an increase of malignant cells. This endpoint PCR quantifying approach appears to be applicable in monitoring B-lymphoproliferative disorders as was shown to be true in B-cell non-Hodgkin's lymphoma and may provide information on disease activity and treatment outcome.

B-Lymphocytes↗
PubMed1999

Quantitation of human immunodeficiency virus type 2 DNA in peripheral blood mononuclear cells by using a quantitative-competitive PCR assay.

A new quantitative-competitive PCR-based human immunodeficiency virus type 2 (HIV-2) proviral DNA assay (QC-PCR) was developed and used to determine the proviral load in HIV-2-infected individuals. Proviral load varied considerably, with means of 1,831 copies per 10(6) peripheral blood mononuclear cells for asymptomatic subjects (n = 19) and 2,587 for AIDS patients (n = 2). HIV-2 viral and proviral loads also varied significantly over time in asymptomatic patients. These data suggest that a high level of virus replication occurs throughout the asymptomatic phase of HIV-2 infection.

Adolescent↗
PubMed1993

High levels of HIV-1 in plasma during all stages of infection determined by competitive PCR.

Quantitative competitive polymerase chain reaction (QC-PCR) methods were used to quantify virion-associated human immunodeficiency virus type-1 (HIV-1) RNA in plasma from 66 patients with Centers for Disease Control stage I to IVC1 infection. HIV-1 RNA, ranging from 100 to nearly 22,000,000 copies per milliliter of plasma (corresponding to 50 to 11,000,000 virions per milliliter), was readily quantified in all subjects, was significantly associated with disease stage and CD4+ T cell counts, and decreased by as much as 235-fold with resolution of primary infection or institution of antiretroviral therapy. Plasma virus levels determined by QC-PCR correlated with, but exceeded by an average of 60,000-fold, virus titers measured by endpoint dilution culture. Quantitation of HIV-1 in plasma by QC-PCR may be useful in assessing the efficacy of antiretroviral agents, especially in early stage disease when conventional viral markers are often negative.

Acquired Immunodeficiency Syndrome↗