Plasma HIV-1 viremia in HIV-1 infected individuals assessed by polymerase chain reaction

Update on HIV viral-load assays: new technologies and testing in resource-limited settings

Assessment of viral load is one of the best predictors of clinical progression, as well as the main parameter to assess treatment response in HIV-positive patients. Reproducible and sensitive assays based on real-time PCR technology have been developed to quantify HIV in the bloodstream of infected persons. Recent improvements have allowed reliable measurements of viremia in non-B subtypes. Testing of samples other than serum or plasma has been challenging, but is particularly important for developing countries.

Protective effect of CCR5 delta 32 heterozygosity is restricted by SDF-1 genotype in children with HIV-1 infection

OBJECTIVE

To determine the influences on pediatric AIDS of a heterozygous 32 base pair deletion in the CC-chemokine receptor 5 gene (CCR5 wt/Delta 32) and a common polymorphism in the 3' untranslated region of stromal cell-derived factor-1 beta gene transcript (SDF1-3'A).

DESIGN

The rate of HIV-1 disease progression and viral burden were compared according to the CCR5 and SDF-1 genotypes in 127 (58 Caucasians, 60 African-Americans and nine Hispanics) perinatally HIV-1-infected children.

RESULTS

Regardless of ethnic background, the CCR5 wt/Delta 32 genotype was associated with a delayed onset of AIDS-defining infectious complications during the first 5 years of infection [relative hazard (RH) = 0.22; 95% confidence interval (CI), 0.012--1.02; P = 0.053]. Similarly, CCR5 wt/Delta 32 conferred an early protection against severe immune suppression and HIV-1 encephalopathy, but only in those without SDF1-3'A (RH = 0; 95% CI, 0--0.70; P = 0.020, and RH = 0; 95% CI, 0--0.71; P = 0.021, respectively). When examined before 5 years of age (n = 81), the children with CCR5 wt/Delta 32 had significantly lower levels of cell-associated HIV-1 DNA than wild-type homozygotes (P = 0.016, adjusted by race), while SDF1-3'A carriers had relatively higher levels (P = 0.047, adjusted by race). Although the disease-retarding effect of CCR5 wt/Delta 32 subsequently disappeared, time to death was still significantly delayed in the CCR5 Delta 32 heterozygotes without SDF1-3'A (RH = 0; 95% CI, 0--0.53; P = 0.008).

CONCLUSION

In pediatric AIDS, the protective effect of CCR5 wt/Delta 32 is more pronounced in early years of infection and appears to be abrogated by the SDF1-3'A genotype.

Identification of a key target sequence to block human immunodeficiency virus type 1 replication within the gag-pol transframe domain

Although the full sequence of the human immunodeficiency virus type 1 (HIV-1) genome has been known for more than a decade, effective genetic antivirals have yet to be developed. Here we show that, of 22 regions examined, one highly conserved sequence (ACTCTTTGGCAACGA) near the 3' end of the HIV-1 gag-pol transframe region, encoding viral protease residues 4 to 8 and a C-terminal Vpr-binding motif of p6(Gag) protein in two different reading frames, can be successfully targeted by an antisense peptide nucleic acid oligomer named PNA(PR2). A disrupted translation of gag-pol mRNA induced at the PNA(PR2)-annealing site resulted in a decreased synthesis of Pr160(Gag-Pol) polyprotein, hence the viral protease, a predominant expression of Pr55(Gag) devoid of a fully functional p6(Gag) protein, and the excessive intracellular cleavage of Gag precursor proteins, hindering the processes of virion assembly. Treatment with PNA(PR2) abolished virion production by up to 99% in chronically HIV-1-infected H9 cells and in peripheral blood mononuclear cells infected with clinical HIV-1 isolates with the multidrug-resistant phenotype. This particular segment of the gag-pol transframe gene appears to offer a distinctive advantage over other regions in invading viral structural genes and restraining HIV-1 replication in infected cells and may potentially be exploited as a novel antiviral genetic target.

HIV-1 infection induces differentiation of immature neural cells through autocrine tumor necrosis factor and nitric oxide production

Immature neural cell lines could be productively infected by HIV-1. Interestingly, this infection was associated with a differentiation to a mature neuronal phenotype, characterized by the expression of mature neurofilaments and cell adhesion molecules, intercellular cell adhesion molecule-1, and vascular cell adhesion molecule-1. Infection also induced TNF-alpha and IL-1beta mRNA expression, as well as the synthesis of inducible nitric oxide synthase by neuroblastoma cells. Exogenous addition of TNF-alpha, but not of IL-1beta or many other cytokines, including nerve growth factor, mimicked those effects induced by infection. Moreover, blocking endogenous TNF-alpha or NO production in cultures of infected cells with a neutralizing anti-TNF-alpha antibody or inducible nitric oxide synthase inhibitors prevented the expression of the mature cell phenotype as well as expression of intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1. Addition of NO generators and TNF-alpha activated NF-kappaB- and intercellular cell adhesion molecule-1-dependent promoter transcription, whereas inducible nitric oxide synthase inhibitors prevented the transcriptional activation of intercellular cell adhesion molecule-1 promoter that was induced by TNF-alpha. Those results suggest that HIV can infect immature neural cells and this infection induces their neural development via a TNF-alpha- and NO-mediated mechanism.

Amplicor HIV monitor, NASBA HIV-1 RNA QT and quantiplex HIV RNA version 2.0 viral load assays: a Canadian evaluation

BACKGROUND

HIV-1 viral load quantitation is now recognized as a useful tool to monitor the efficiency of antiviral treatment and a powerful predictor of disease outcome. Three HIV-1 viral load quantitation methods have been currently available as commercial kits in Canada since 1996.

OBJECTIVE

To evaluate the ability to quantify HIV-1 RNA in plasma of the Amplicor HIV Monitor Test, the NASBA HIV-1 RNA QT Assay and the Quantiplex HIV RNA Assay, version 2.0, at comparable lower detection limits.

STUDY DESIGN

Blood was collected from 50 HIV-1-infected patients at various stages of infection and therapy. CD4+ cell count were estimated by flow cytometry. Plasma was isolated and tested in duplicate on four occasions using viral load kits from a single lot. HIV RNA data, performance, sensitivity and intra- and inter-assay variability were compared.

RESULTS

RNA could be quantified in 33 patients by each technique. An inverse correlation was observed between viral load level and CD4+ cell counts in patients with counts below 200. Monitor could detect RNA in 94% of patients, but it showed the greatest variability and failure rate. Quantiplex 2.0 could detect HIV-1 RNA in 78%, and NASBA in 88% of the patients at theoretically equivalent lower detection limits, suggesting that the detection limit of Quantiplex 2.0 may be higher than 500 HIV-1 RNA copies per ml. NASBA had the fewest invalid tests and good reproducibility, comparable to that of Quantiplex 2.0. The mean values from NASBA and Monitor were the most similar but the best correlation was observed between Monitor and Quantiplex 2.0 results.

CONCLUSIONS

Monitor, NASBA and Quantiplex results were comparable, although those obtained by Quantiplex were significantly lower. Performing this study at comparable detection limits showed that the detection limit of Quantiplex 2.0 may be higher than stated by the manufacturer.

Serum retinol and HIV-1 RNA viral load in rapid and slow progressors

Few studies have addressed the relation between serum vitamin A levels and HIV disease progression. Thirty HIV-infected women in Rwanda were studied over a time span of 26 to 99 months. Fourteen subjects seroconverted and died of HIV-related disease at a mean of 44 months (range, 26-69 months) after their first HIV-positive test and were termed "rapid progressors," (RPs). A comparison group of 16 "slow progressors" (SPs) were HIV-positive at the time of their first HIV serology and had asymptomatic HIV infections at a mean of 96 months (range, 93-99 months) after their first HIV serology. Baseline mean serum retinol values were the same in RPs and SPs: 0.65 + 0.08 micromol/L versus 0.67 + 0.09 micromol/L (p = .7). Lower serum retinol levels were observed in RPs compared with SPs for the second and third measurements, obtained at a median of 12 and 24 months past baseline: 0.51 + 0.07 micromol/L versus 0.76 + 0.14 micromol/L (p = .3) and 0.44 + 0.09 micromol/L versus 0.64 + 0.08 micromol/L (p = .08), respectively. Median retinol levels for the third sample measurement were similar in RPs with lower viral load (LVL) and SPs (0.49 micromol/L and 0.52 micromol/L, respectively) compared with only 0.19 micromol/L in RPs with higher viral load (HVL; p = .02). A trend toward decreasing serum retinol levels and increasing HIV-1 RNA viral load was observed at the third sample measurement (p = .04). Subjects with LVL, higher serum retinol levels (> or =0.70 micromol/L), or both had more favorable rates of survival than subjects with HVL, low serum retinol levels (<0.70 micromol/L), or both. Although sample size does not permit definitive conclusions, this study demonstrates an association of high HIV load, rapid progression, and low serum retinol late but not early in disease progression.

Cartesian coordinate analysis of viral burden and CD4+ T-cell count in human immunodeficiency virus type-1 infection

We have used a Cartesian coordinate plot to analyze the inverse relationship between viral burden (x-axis) and peripheral blood CD4+ cell count (y-axis) to extend our understanding of the mechanisms of antiviral drugs and differences in outcome resulting from variability in virus and host responses. Each of 186 subjects studied were assigned to one of four response quadrants. Quadrants A (x-, y+) and D (x+, y-) defined the effect of a change in virus load on the inverse change in CD4+ cell count expected from the natural history of HIV infection or antiretroviral therapy. Quadrants B (x+, y+) and C (x-, y-) defined the dissociation of the inverse relationship between the relative changes in CD4+ cell count and viral load that resulted from the hypothesized effect of putative virologic or immunologic response modifiers. Of the response modifiers studied, only the syncytium-inducing phenotype resulted in a complete dissociation of this inverse relationship. The analysis provided an integrated virological and immunological approach to better understand therapeutic responses and potential dissociation between changes in viral RNA and CD4+ cell count. This type of analysis may be helpful for individualizing patient management as well as designing and analyzing studies of HIV-1 antiretroviral drugs and disease pathogenesis.

Serum retinol and HIV-1 RNA viral load in rapid and slow progressors

Few studies have addressed the relation between serum vitamin A level and HIV disease progression. Thirty HIV-infected women in Rwanda were studied over a time span of 26 to 99 months. Fourteen subjects seroconverted and died of HIV-related disease at a mean of 44 months (range, 26-69 months) after their first HIV-positive test and were termed "rapid progressors," (RPs). A comparison group of 16 "slow progressors" (SPs) were HIV-positive at the time of their first HIV serology and had asymptomatic HIV infections at a mean of 96 months (range, 93-99 months) after their first HIV serology. Baseline mean serum retinol values were the same in RPs and SPs: 0.65 + 0.08 mmol/L versus 0.67 + 0.09 micromol/L (p = .7). Lower serum retinol levels were observed in RPs compared with SPs for the second and third measurements, obtained at a median of 12 and 24 months past baseline: 0.51 + 0.07 mmol/L versus 0.76 + 0.14 mmol/L (p = .3) and 0.44 + 0.09 mmol/L versus 0.64 + 0.08 mmol/L (p = .08), respectively. Median retinol levels for the third sample measurement were similar in RPs with lower viral load (LVL) and SPs (0.49 mmol/L and 0.52 mmol/L, respectively) compared with only 0.19 mmol/L in RPs with higher viral load (HVL; p = .02). A trend toward decreasing serum retinol levels and increasing HIV-1 RNA viral load was observed at the third sample measurement (p = .04). Subjects with LVL, higher serum retinol levels (> or =0.70 mmol/L), or both had more favorable rates of survival than subjects with HVL, low serum retinol levels (<0.70 mmol/L), or both. Although sample size does not permit definitive conclusions, this study demonstrates an association of high HIV load, rapid progression, and low serum retinol late but not early in disease progression.

Comparison of culture- and non-culture-based methods for quantification of viral load and resistance to antiretroviral drugs in patients given zidovudine monotherapy

Virological assays for human immunodeficiency virus type 1 load and drug resistance can broadly be divided into culture-based and molecular biology-based methods. Culture-based methods give a direct measure of infectious virus load and phenotypic drug resistance, whereas molecular biology-based methods are indirect, assaying nucleic acid levels to determine virus load and point mutations associated with drug resistance. We have compared culture-based and non-culture-based methods for patients enrolled in a placebo-controlled trial of zidovudine (the Concorde Trial). Virus loads were assayed by culture of peripheral blood mononuclear cells (PBMCs) or quantitative PCR, and drug resistance was assayed in culture or in a quantitative, PCR-based point mutation assay. The rates of detection of viremia and drug resistance were higher by PCR than by culture for this population of subjects. Comparison of the virus loads by the two measures showed a good correlation for virus loads in PBMCs but a poor correlation for virus loads in plasma. The latter result probably reflected the inaccuracies of culture in assaying plasma with the low infectious virus titers seen in the study population. The concordance of phenotypic and genotypic drug resistance methods was high, with all phenotypically resistant isolates having at least one resistance-associated mutation and with no mutations being found in a drug-sensitive isolate. Genomic resistance scores (weighted sums of levels of resistance mutations) showed good correlations with the levels of phenotypic resistance, and both resistance measures were observed to increase as the duration of exposure to drug increased. Overall, non-culture-based methods were shown to correlate well with culture-based methods and offer a low-cost, high-throughput alternative. However, culture-based methods remain the final arbiters of infectious virus load and phenotypic drug resistance and are unlikely to be superseded entirely.

Quantitative competitive RNA PCR for quantitation of virion-associated HIV-1 RNA

Quantitative competitive PCR is a highly sensitive technique that allows accurate quantitation of small amounts of RNA. We have modified the original method to include the use of an internal standard at all stages of sample analysis. In this way, the method can accommodate for variations in the recovery of viral particles and in the isolation of genomic RNA as well as provide a suitable competitive substrate during quantitative RNA PCR. We have used this method to characterize changes in virus load in plasma of HIV-1-seropositive individuals following their vaccination against opportunistic infections.

Correlation of ribonucleic acid polymerase chain reaction, acid dissociated p24 antigen, and neopterin with progression of disease. A retrospective, longitudinal study of vertically acquired human immunodeficiency virus type 1 infection in children

OBJECTIVE

We investigated the relationship between cell-free viral load, neopterin, age-adjusted CD4+ cell concentration, and clinical events in 49 children with vertically acquired human immunodeficiency virus type 1 infection.

STUDY DESIGN

Viral load was measured by quantitating viral ribonucleic acid in serum by polymerase chain reaction and measurement of immune complex dissociated p24 antigen in serum and plasma. Children were followed for an average of 2 1/2 years, with an average of 6 samples per child. Medical records were reviewed for weight, CD4+ cell count and clinical events.

RESULTS

High virus copy number in serum was predictive of a decrease in weight-for-age zscore during the subsequent 6 months. High viral load, low CD4+ cell count, and high neopterin level were correlated with encephalopathy. High viral load correlated with opportunistic infections. All of these relationships held regardless of treatment status, although viral load decreased significantly after treatment was begun.

CONCLUSIONS

Measurements of viral load were useful prognostic indicators for poor weight gain. Elevated serum virus levels and neopterin values and low CD4+ cell counts were all associated with encephalopathy.

Comparison of serum and plasma viral RNA measurements in primary and chronic human immunodeficiency virus type 1 infection

We sought to define the relation between serum and plasma HIV-1 viral RNA load in patients with primary and chronic HIV-1 disease. HIV-1 viral load was determined from 116 serum and plasma samples, including 33 matched pairs, from five patients with primary and three patients with chronic HIV disease using the Roche HIV Monitor assay. The mean +/- standard deviations of the serum and plasma viral RNA levels from the 33 matched pairs were 4.372 +/- 0.885 and 4.478 +/- 0.950 log10 (copies/ml), respectively. This -0.106 log difference between serum and plasma viral RNA levels, which equates to 21% of non-log-transformed values, was not statistically significant by the Wilcoxon sign rank test (p = 0.09). The distributions of serum and plasma viral load slopes, calculated from all available viral RNA load data for each patient, were also not statistically different (p = 0.07). The levels of HIV-1 RNA measured in the serum or plasma of HIV-seropositive patients yield equivalent biologic information.

Plasma viremia in macaques infected with simian immunodeficiency virus: plasma viral load early in infection predicts survival

A reliable method for the quantitation of plasma viremia in nonhuman primates infected with simian immunodeficiency virus (SIV) and related viruses is described. This method is based on an established quantitative-competitive PCR format and includes a truncated control for internal assay calibration. Optimization of assay conditions has significantly improved amplification specificity, and interassay variability is comparable to that of commercially available assays for human immunodeficiency virus (HIV) quantitation. This procedure was used to monitor viral loads in a group of Macaca mulatta animals that were infected with SIVsmE660 for over 2 years. Highly diverse profiles of plasma viremia were observed among animals, and high viral loads were associated with more rapid disease progression. Spearman rank correlation analyses were done for survival versus three parameters of viral load: plasma viremia, p27 core antigen, and frequency of infected peripheral blood mononuclear cells. Plasma viremia had the strongest overall correlation and was significantly (P < 0.05 to P < 0.01) associated with survival at 10 of the 13 time points examined. Plasma viremia did not correlate with survival during the primary viremia phase; however, the strength of this correlation increased with time postinfection and, remarkably, viremia levels as early as week 6 postinfection were highly predictive (P < 0.01) of relative survival. These findings are consistent with the available clinical data concerning viral load correlates early in HIV infection, and they provide further support for the view that disease outcome in lentiviral infection may be largely determined by events that occur shortly after infection.

An enhanced-sensitivity branched-DNA assay for quantification of human immunodeficiency virus type 1 RNA in plasma

The quantification of human immunodeficiency virus type 1 (HIV-1) RNA has facilitated clinical research and expedited the development of antiretroviral drugs. The branched-DNA (bDNA) assay provides a reliable method for the quantification of HIV-1 RNA in human plasma and is considered one of the most reproducible assays ready for use in clinical trials. A series of oligonucleotide probe design and solution changes have been developed to enhance the sensitivity of the bDNA assay while maintaining its performance characteristics. Among the changes incorporated into the enhanced-sensitivity bDNA (ES bDNA) assay to reduce the background level and enhance the signal are the use of shorter overhang sequences of target probes for capture, the cruciform design of target probes for amplification, and the addition of preamplifier molecules. The ES bDNA assay is at least 20-fold more sensitive than the first-generation bDNA assay, yet it maintains a high level of accuracy, linearity, and reproducibility. Further, quantification values obtained with the ES bDNA assay and the first-generation bDNA assay are highly correlated, thus allowing for meaningful comparisons of HIV-1 RNA levels in specimens tested with either assay. The ES bDNA assay may be useful in determining the prognostic value of HIV-1 RNA levels of below 10,000 copies per ml and in assessing the clinical benefit of antiretroviral therapy-induced decreases in plasma HIV-1 RNA sustained at levels of below 10,000 copies per ml.

Evaluation of a quality assurance program for quantitation of human immunodeficiency virus type 1 RNA in plasma by the AIDS Clinical Trials Group virology laboratories

A number of quantitative assays have been developed by using amplification techniques to measure human immunodeficiency virus type 1 RNA in the plasma of infected individuals. The Virology Committee of the AIDS Clinical Trials Group in the Division of AIDS, National Institute of Allergy and Infectious Diseases, has established a quality assurance program (QAP) for quantitative assays of HIV-1 RNA levels in plasma. The primary objective of the QAP was to ascertain that a laboratory could maintain the precision required to have a 90% power to detect a fivefold difference in RNA copy number between two samples in the same batch. To achieve this goal, the QAP required an intra-assay standard deviation of no greater than 0.15 log10 RNA copies per ml. Panels for proficiency testing consisted of coded replicate samples and a common set of standards. To date, 41 laboratories have participated in the program and have used both commercial and in-house assays. We demonstrated that 65% of the laboratories were capable of attaining the necessary level of intra-assay precision. The fitted regressions indicated that the differences among laboratories that used the same kit were generally greater than the differences among population-average regressions for the kits themselves. The use of an external QAP and a common set of standards reduced differences both among laboratories that used the same kit and among laboratories that used different kits. Thus, use of a common set of standards across clinical trial protocols would allow for cross-protocol comparisons.

Individualisation of HIV therapy based on HIV RNA load: the virologist's perspective

There is increasing evidence that direct quantification of viral load by quantitative HIV RNA polymerase chain reaction (PCR) may be one of the more useful markers of disease status and antiviral treatment efficacy. Given the central role of viral replication in the pathogenesis of HIV infection, it is logical to assume that monitoring levels of cell-free virus in the plasma will be predictive of disease status. Furthermore, since the primary aim of treatment with current antiretroviral therapies is reduction of viral load, changes in plasma viraemia may be expected to be predictive of treatment effects. Preliminary data indeed suggest that viral load, is a useful marker of baseline prognosis, disease status and the effectiveness of antiretroviral therapy in individual patients. These data support the concept that measurement of viral RNA may eventually be of clinical utility in managing therapy of individual patients. However, prospective viral load studies are required to validate such a strategy.

Assessment of a standardized reverse-transcriptase PCR assay for quantifying HIV-1 RNA in plasma and serum

The analytical variability of the new commercially available Reverse Transcriptase-Polymerase Chain Reaction (RT-PCR) assay, Amplicor HIV-1 Monitor, has been assessed to establish criteria for assessing the significance of HIV-1 RNA level measurements. Estimations of the standard deviations (SD) of log-copies in inter-assay (mean 0.09 log) and in inter-laboratory (mean 0.14 log) reproducibility experiments demonstrated that the assay can discriminate with 95% confidence between 3-fold (inter-assay) and 5-fold differences (inter-laboratory). The inter-lot reproducibility (mean 0.10 log) was similar to the inter-assay reproducibility. The HIV-1 RNA concentrations measured in plasma collected in potassium EDTA anticoagulant were slightly higher than those measured in plasma collected in sodium citrate. The HIV-1 RNA concentrations measured in sera were about 50% of the HIV-1 RNA concentrations measured in paired plasma samples. However, there was a strong correlation between these two measurements (P < 0.0001). The assay was used to measure viral RNA in the plasma of 50 HIV-1 positive individuals at different stages of infection. All the individuals had detectable HIV-1 RNA (300-957000 copies/ml). There was no correlation between HIV-1 RNA and Immune Complex Dissociated (ICD) p24 antigen, but HIV-1 RNA was correlated with CD4+ cell counts (P < 0.0001) and the clinical stage (P = 0.0042), with higher HIV-1 RNA concentrations in patients with a more advanced stage of the disease. The significant association of HIV-1 RNA with major markers of HIV infection and the reliability of this sensitive, easy-to-use RT-PCR assay indicate its suitability for use in clinical trials and suggest that this assay is appropriate for routine clinical applications.

Virus load as a marker of disease progression in HIV-infected children

The relationship of virus load to clinical disease progression in HIV-infected children remains to be elucidated. In this study, HIV-1 proviral DNA load was determined in peripheral blood mononuclear cells (PBMCs) by the quantitative competitive DNA polymerase chain reaction assay (QC-PCR) in 47 HIV-infected children subdivided by age (group I, < or = 2 years; group II, > or = 5 years), who were further categorized to include 12 rapid progressors (RP, age < or = 2 years, Centers for Disease Control [CDC] defined clinical category C and/or immune category 3, or death before age 2 years) and slow progressors (SP, age > or = 5 years, excluding CDC categories C and/or immune category 3). Significantly higher mean proviral copies/10(3) PBMCs were detected in group I versus group II (75.4 +/- 104.3 and 13.0 +/- 17.8 respectively, p < 0.0001) and in RP (158.0 +/- 118.2) as compared to either SP (11.8 +/- 18.8, p < 0.0001) or other age-matched infected children (20.3 +/- 38.8, p < 0.0001). Thus HIV-infected children appear to have a higher cell-associated virus load early in life, especially in association with rapid disease progression.

Direct hybridization and amplification applications for the diagnosis of infectious diseases

We are entering an exciting new era of molecular diagnostics in the clinical microbiology laboratory. A number of perspectives are presented in this review. First presented was a discussion of molecular diagnostics for detection of the bacterium, Chlamydia trachomatis. This is especially relevant since the tests available for this organism represent the forefront of commercial systems. Also, these tests exemplify the difficulties and advantages inherent to future molecular diagnostics for all types of disease processes. Next, a discussion of the techniques thus far employed in the field of clinical microbiology is presented. Obvious overlap exists with other areas of molecular pathology. However, the emphasis is on which techniques have proven most useful in identifying infectious agents. Finally, the features of a successful clinical microbiology diagnostics laboratory are presented, including test component requirements, laboratory personnel, quality assurance techniques, and physical laboratory setting. It is hoped that helpful advice and references are provided that will assist individual clinical laboratories as they enter the field of molecular diagnostics of infectious diseases.

Short-term stability of HIV provirus levels in the peripheral blood of HIV-infected individuals

Changes in viral load have been reported to reflect disease progression or response to therapy; however, the stability of HIV DNA levels in HIV-infected individuals has not been extensively studied. Cellular HIV DNA levels in infected individuals were evaluated over a short time period to determine degree of variability as well as any correlation with other measurements of virus load or immune status. Peripheral blood mononuclear cells (PBMC) were obtained several times over 1 month from 32 asymptomatic or symptomatic non-AIDS, HIV-infected individuals currently on AZT therapy. PCR amplification of the HIV gag region was performed with DNA from PBMC lysates and the PCR amplified products quantitated by liquid phase hybridization. HIV DNA levels in the majority of the patients were relatively stable, with 26 of 32 persons having less than threefold change. Changes over the study period were both positive and negative, and the median change in HIV DNA levels was 68.6%. These changes were found to positively correlate with fluctuations in plasma p24 levels. In contrast, no correlations were found with other measurements of immune system activity, including changes in CD4 number, CD4 percent, and beta 2-microglobulin when compared with provirus changes. This study shows that levels of HIV DNA can be relatively stable over short periods in most non-AIDS, HIV-infected persons.

Persistence of attenuated rev genes in a human immunodeficiency virus type 1-infected asymptomatic individual

With the goal of examining the functional diversity of human immunodeficiency virus type 1 (HIV-1) env genes within the peripheral blood mononuclear cells of an asymptomatic individual, we substituted four complete env genes into the replication-competent NL4-3 provirus. Despite encoding full-length open reading frames for gp120 and gp41 and the second coding exon of tat and rev, each chimera was replication defective. Site-directed mutagenesis of codon 78 in the Rev activation domain (from a hitherto unique Ile to the subtype B consensus Leu) partially restored infectivity for two of three chimeras tested. Similarly, mutagenesis of rev codon 78 of NL4-3 from Leu to Ile partially attenuated this virus. Ile-78 was found in all 13 clones examined from samples taken from this asymptomatic subject 4.5 years after infection, including 9 from peripheral blood mononuclear cells and 4 from a virus isolate, as well as 4 additional clones each from peripheral blood mononuclear cells sampled 37 and 51 months later. We next examined conservation of the Rev activation domain within and among long-term survivors (LTS) and patients with AIDS, as well as T-cell-line-adapted strains of HIV-1. Putative attenuating mutations were found in a minority of sequences from all five LTS and two of four patients with AIDS. Of the 11 T-cell-line-adapted viruses examined, none had these changes. Among and within LTS virus population had marginally higher levels of diversity in Rev than in Env; patients with AIDS had similar levels of diversity in the two reading frames; and T-cell-line-adapted viruses had higher levels of diversity in Env. These results are consistent with the hypothesis that asymptomatic individuals harbor attenuated variants of HIV-1 which correlate with and contribute to their lack of disease progression.

Pharmacokinetic optimisation of antiretroviral therapy in patients with HIV infection

More than 7 years after the introduction of zidovudine for treatment of HIV infection, little use has been made of the pharmacokinetic properties of this or any of the subsequently approved antiretroviral agents to optimise therapy. This is partly because of the limits of technologies developed to measure clinically relevant forms and concentrations of these drugs, and partly because the clinical community has been slow to recognise the potential benefits of pharmacokinetic optimisation of nucleoside analogue therapy in any disease. Nonetheless, for some of these agents, progress in understanding the relationship between pharmacokinetics and pharmacodynamics has been made. With zidovudine, for example, even though plasma concentrations have little clinical utility, evidence suggests that concentrations of active phosphorylated forms of zidovudine inside target cells are related to disease progression and toxicity. Furthermore, a decreased ability to phosphorylate zidovudine might be a prerequisite for the emergence of zidovudine-resistant HIV strains. Measurements of phosphorylated zidovudine inside cells similarly suggest that 100 mg of oral zidovudine every 8 hours approximates the optimal initial dosage regimen in asymptomatic patients. Increased plasma didanosine concentrations have been associated with several measures of clinical improvement in patients, and may be associated with an increased risk of toxicity as well. For zalcitabine and stavudine, however, the picture is much less clear. Their pharmacokinetic and pharmacodynamic relationships have not been studied in patients. Furthermore, there is insufficient data on the effects of age, gender, race and concurrent underlying conditions on the pharmacokinetics of all of these agents. Mounting evidence suggests that monitoring of these compounds could lead to individually optimised intervention strategies. Given the marginal benefits of therapy with these agents, their proven toxic effects and the lack of proven alternatives, it is critical that the clinical community strive to make the most effective use of these agents in the treatment of their patients.

Longitudinal assessment of feline immunodeficiency virus kinetics in plasma by use of a quantitative competitive reverse transcriptase PCR

Cats infected with feline immunodeficiency virus (FIV) develop a disease syndrome similar to that caused by human immunodeficiency virus type 1 (HIV-1) infection in humans. HIV-1 replication has been shown to correlate with the disease stage and progression. To assess replication kinetics and disease progression in early FIV infection, we developed a quantitative competitive reverse transcriptase PCR to measure the plasma virus load at serial time points after virus exposure. We found that an early peak viremia immediately preceded the onset of acute-phase symptoms in infected cats. Plasma virus levels remained high throughout the symptomatic phase of infection, which lasted for 8 to 10 weeks, and then declined as clinical symptoms resolved; however, all cats maintained significant plasma virus titers through 36 weeks postinfection. Early peak viral replication coincided with the initial precipitous decline in circulating CD4+ T lymphocytes. These results indicate that FIV kinetics are similar to those of HIV-1 during the acute and secondary phase of infection and that the plasma FIV load correlates with the disease stage. These results serve to further develop the FIV model and to enhance its usefulness for pathogenesis, vaccine development, and therapeutic studies related to HIV.

Emergence of human immunodeficiency virus type 1 variants with resistance to multiple dideoxynucleosides in patients receiving therapy with dideoxynucleosides

A set of mutations [Ala-62-->Val(A62V), V75I, F77L, F116Y, and Q151M] in the polymerase domain of reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) confers on the virus a reduced sensitivity to multiple antiretroviral dideoxynucleosides and has been seen in HIV-1 variants isolated from patients receiving combination chemotherapy with 3'-azido-3'-deoxythymidine (AZT) plus 2',3'-dideoxycytidine (ddC) or 2',3'-dideoxyinosine (ddI). The IC50 values of AZT, ddC, ddI, 2',3'-dideoxyguanosine, and 2',3'-didehydro-3'-deoxythymidine against an infectious clone constructed to include the five mutations were significantly higher than those of a wild-type infectious clone. The K1 value for AZT 5'-triphosphate determined for the virus-associated RT from a posttherapy strain was 35-fold higher than that of RT from a pretherapy strain. Detailed analysis of HIV-1 strains isolated at various times during therapy showed that the Q151M mutation developed first in vivo, at the time when the viremia level suddenly increased, followed by the F116Y and F77L mutations. All five mutations ultimately developed, and the viremia level rose even further. Analyses based on the three-dimensional structure of HIV-1 RT suggest that the positions where at least several of the five mutations occur are located in close proximity to the proposed dNTP-binding site of RT and the first nucleotide position of the single-stranded template.

Clinical evaluation of branched DNA signal amplification for quantifying HIV type 1 in human plasma

Quantification of HIV-1 RNA in human plasma has provided unique insight into AIDS pathogenesis and promises to hasten progress in antiretroviral therapy and vaccine research. However, no generally available HIV-1 RNA assay has yet been subjected to rigorous clinical testing or to comparative evaluation with research-based RNA assays using large numbers of well-characterized clinical specimens. In this study, the Chiron Quantiplex branched DNA (bDNA) signal amplification assay was used to measure viral RNA in the plasma of 152 HIV-1-positive individuals at all stages of infection and in 12 patients before and after initiating zidovudine therapy. Eighty-six percent of patients had bDNA assay results above the 10,000-RNA Eq/ml sensitivity cutoff. Branched DNA values were significantly correlated with plasma viral RNA levels determined by quantitative competitive polymerase chain reaction (QC-PCR) assay (Spearman rank correlation, r = 0.89), infectious plasma virus titers (r = 0.72), p24 antigen levels (r = 0.51), immune complex dissociated p24 antigen levels (r = 0.56), and CD4+ lymphocyte counts (r = -0.72; p < 0.0001 for all comparisons). Plasma viral RNA determinations by bDNA and QC-PCR assays were quantitatively similar in the range of 10(4) to 10(7) RNA molecules/ml [log bDNA = 0.93 + 0.80 (log QC-PCR); R2 = 0.81, p < 0.0001] and declined identically following the institution of zidovudine therapy (68-73% decrease from baseline). The close quantitative correlation between bDNA and QC-PCR results, and their significant association with other viral markers and CD4+ counts, support the use of plasma viral RNA measurement in HIV-1 clinical trials.

(R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine is a potent inhibitor of feline immunodeficiency virus infection

The antiviral efficacy of acyclic nucleoside phosphonates, including 9-(2-phosphonylmethoxyethyl)adenine (PMEA) and (R)-9-(2-phosphonylmethoxypropyl)-2,6-diaminopurine [(R)-PMPDAP] against feline immunodeficiency virus (FIV) infection was determined. (R)-PMPDAP showed the highest selectivity index (> 2,000) in vitro. Treatment of experimentally FIV-infected asymptomatic cats with PMEA or (R)-PMPDAP had no effect on the CD4+/CD8+ ratio. However, mean plasma viral RNA concentrations decreased significantly in the (R)-PMPDAP-treated cats. Our data show that, in comparison to PMEA, (R)-PMPDAP is a more potent and less toxic inhibitor of FIV replication both in vitro and in vivo.

Viral dynamics in human immunodeficiency virus type 1 infection

The dynamics of HIV-1 replication in vivo are largely unknown yet they are critical to our understanding of disease pathogenesis. Experimental drugs that are potent inhibitors of viral replication can be used to show that the composite lifespan of plasma virus and virus-producing cells is remarkably short (half-life approximately 2 days). Almost complete replacement of wild-type virus in plasma by drug-resistant variants occurs after fourteen days, indicating that HIV-1 viraemia is sustained primarily by a dynamic process involving continuous rounds of de novo virus infection and replication and rapid cell turnover.

Parallel evolution in the V3 region of HIV type 1 after infection of hemophiliacs from a homogeneous source

To determine the genetic diversification in the highly functional V3 loop, we followed up five hemophiliacs who were infected by a homogeneous HIV-1 population from a contaminated clotting factor lot. Initially, all patients displayed identical DNA sequences in this part of the proviral env gene. Therefore, this unique outbreak allows us to investigate the biological and genetic development of a common ancestor virus in different patients. A high degree of homology is maintained in the predominant sequences from 5 until 35 months after seroconversion. Only one patient showed a remarkable diversification 3 years postinfection. However, these genetic changes in the V3 region were not associated with disease progression. Discontinuous sequence changes were observed mainly in a region downstream of the V3 loop. Two positions in particular are involved in a sequence evolution within the V3 loop leading to the same amino acids in different patients. These directed changes occurred at sites that are reported to be critical for the specificity of antibodies (position 308) and viral cytopathicity (position 324). However, the parallel evolution was associated neither with differentiation of the viral phenotype nor with progression of the disease.

Identification of drug-related genotypic changes in HIV-1 from serum using the selective polymerase chain reaction

We attempted to detect drug-related HIV-1 pol gene mutations by selective polymerase chain reaction (PCR) using both proviral DNA and viral RNA isolated from patients (pts) with AIDS or ARC receiving antiretroviral therapy. Peripheral blood mononuclear cell (PBM)-associated proviral DNA and serum-derived viral RNA were obtained from eight patients before and after receiving an alternating regimen of AZT and ddC for 15-41 months or ddI monotherapy for 12-26 months. These specimens were examined for the presence of mutations at positions 70, 74, 215 and 219. We noted that selective PCR results can be ambiguous depending on the quantity of DNA template employed. We, therefore, used the minimal quantity of DNA templates that yielded evaluable PCR products in this study. For all the eight pairs of pre- and post-therapy proviral DNA samples, selective PCR results agreed with independently determined nucleotide sequences. Results of reverse transcription of serum-derived viral RNA followed by selective PCR differed in some cases from those using the proviral DNA. In particular, the use of serum viral RNA appeared to allow earlier detection of changes in drug-related mutations than the use of PBM-associated proviral DNA. We conclude that (i) selective PCR using the minimum and sufficient number of PBM-associated proviral DNA and serum viral RNA copies successfully detects the presence of known pol gene mutations; (ii) drug-related mutations may be distinguished earlier in virions in serum (or plasma) than in proviral DNA in PBM; and (iii) quantification of HIV-1 prior to selective PCR may be an important component in monitoring the therapy of HIV-1 infection.

Intravirion reverse transcripts in the peripheral blood plasma on human immunodeficiency virus type 1-infected individuals

Variable levels of viral DNA have been demonstrated within human immunodeficiency virus type 1 (HIV-1) virions purified from cell cultures. In the present studies, it is demonstrated that DNase-resistant viral DNA is associated with HIV-1 virions purified from the peripheral blood plasma of both symptomatic and asymptomatic HIV-1-infected individuals. The differences in viral DNA copy numbers, detected by quantitative PCR in various regions of the HIV-1 genome, indicated that the intravirion HIV-1 DNA is frequently, but perhaps not totally, the result of partial reverse transcription. These in vivo data suggest that it may be valuable to further investigate the impact of virion-associated viral DNA upon the efficiency of intra- and interhost HIV-1 transmission modes.

Splicing variability in HIV type 1 revealed by quantitative RNA polymerase chain reaction

A quantitative RNA-polymerase chain reaction (PCR) method able to detect the majority of mRNAs produced by human immunodeficiency virus type 1 (HIV-1) was developed and used to study expression of different HIV-1 clones in human cells. Amplified mRNAs were compared to known cDNA standards. This comparison permitted the optimization of PCR conditions and eliminated the generation of artifactual PCR bands. The use of RNA and cDNA standards demonstrated that the RNA amplification is linear within the tested range and suggested that it can be used to quantitate individual mRNAs. The results demonstrate the overall conservation of splicing in different HIV-1 clones. Although, in general, splicing was conserved, extensive qualitative and quantitative variability was observed in different HIV-1 clones. This variability is likely one determinant of the biological characteristics of the different HIV-1 clones, and demonstrates a great plasticity of the HIV-1 genome. The described RNA-PCR methodology was used for the study of HIV-1 expression in unstimulated peripheral blood mononuclear cells (PBMCs) of infected individuals. In general, the same mRNAs were identified in HIV-infected cultured cell lines and in unstimulated PBMCs. Analysis of a variant band found after amplification of PBMC RNA from an HIV-infected individual revealed a new splice site for the generation of Rev/Nef-encoding mRNAs. The availability of a sensitive, rapid, and essentially quantitative method to examine the major HIV-1 mRNAs will facilitate the detailed analysis of HIV-1 expression in human cells.

A one-tube quantitative HIV-1 RNA NASBA nucleic acid amplification assay using electrochemiluminescent (ECL) labelled probes

Quantification of HIV-1 viral RNA based on co-amplification of an internal standard Q-RNA dilution series requires a number of NASBA nucleic acid amplification reactions. For each internal standard Q-RNA concentration a separate NASBA amplification has to be performed. The development of an electrochemiluminescent (ECL) detection system with a dynamic signal detection range over 5 orders of magnitude enabled simplification of the Q-NASBA protocol. Three distinguishable Q-RNAs (QA, QB and QC) are mixed with the wild-type sample at different amounts (i.e. 10(4) QA, 10(3) QB and 10(2) QC molecules) and co-amplified with the wild-type RNA in one tube. Using ECL-labelled oligonucleotides the wild-type, QA, QB and QC amplificates are separately detected with a semi-automated ECL detection instrument and the ratio of the signals determined. The amount of initial wild-type RNA can be calculated from the ratio of wild-type signal to QA, QB and QC signals. This one-tube Q-NASBA protocol was compared to the earlier described protocol with six amplifications per quantification using model systems and HIV-1 RNA isolated from plasma of HIV-1-infected individuals. In all cases the quantification results of HIV-1 RNA were comparable between the two methods tested. Due to the use of only one amplification per quantification in the one-tube Q-NASBA protocol the QA, QB and QC internal standard RNA molecules can be added to the sample before nucleic acid isolation. The ratio of QA:QB:QC:WT RNAs, from which the initial input of WT-RNA is calculated, will remain constant independent of any loss that might occur during the nucleic acid isolation.

Quantification of human immunodeficiency virus in plasma by RNA PCR, viral culture, and p24 antigen detection

A semiquantitative PCR technique for detecting human immunodeficiency virus type 1 (HIV-1) RNA in plasma was compared with quantitative viral culture and p24 antigen detection in plasma. Ninety-three samples from 20 symptomatic, 10 asymptomatic, and 10 seronegative individuals were tested. For most of the seropositive patients, consecutives samples were examined. Viral RNA was extracted from plasma by the method described by Boom et al. (R. Boom, C.J. A. Sol, M. M. M. Salimans, C.L. Jansen, P. M. E. Wertheim-van Dillen, and J. van der Noordaa, J. Clin. Microbiol. 28:495-503, 1990). The RNA PCR was the most sensitive method (100 and 74% sensitivity for symptomatic and asymptomatic patients, respectively) and produced less divergent results with the consecutive samples from individual patients compared with the other techniques. All samples positive by viral culture or p24 antigen assay were also positive in the RNA PCR. For each of the three assays, the number of positive results obtained correlated with the disease stage. The estimated mean number of HIV-1 RNA copies was significantly higher in symptomatic patients (22,750 copies per ml) than in asymptomatic patients (1,820 copies per ml). It was also higher in samples positive for viral culture than in culture-negative samples. No close correlation was found between the amount of HIV-1 RNA and the amount of p24 antigen or the titer of infectious virus in plasma or between this titer and the level of p24 antigen. The plasma RNA PCR may be a useful additional marker of disease progression and may be valuable for monitoring the effects of antiviral therapy.

A C2 symmetry-based HIV protease inhibitor, A77003, irreversibly inhibits infectivity of HIV-1 in vitro

A C2 symmetry-based HIV protease inhibitor, A77003, exerts potent antiviral activity against a wide spectrum of HIV isolates in vitro. In this study, we asked whether A77003 could cause irreversible conformational changes to HIV-1, whether the amounts of viral RNA and p24 capsid protein per virion were altered, and how the infectivity of the virus produced in the presence of the drug was affected. We found that the number of viral particles and per-virion viral RNA content of the virus produced in the presence of A77003 did not significantly differ from those of the virus produced in the absence of the drug, whereas significant morphological changes were observed as assessed by transmission electron microscopy. However, the virus produced in the presence of A77003 contained substantially less p24gag protein per virion particle as compared to those produced in the absence of the drug or in the presence of AZT. Virions produced in the presence of A77003 showed up to 50-fold less infectious capability in subsequent tissue culture than control virions produced in the absence of drug or in the presence of AZT. This reduction in infectivity was maintained for at least 10 days in culture. The present data suggest that A77003 impairs HIV-1 protease-mediated Gag processing, interferes with the assembly and maturation of the virus, and leads to an irreversible loss of the infectivity of the virus, although a low but positive level of reversion to infectivity during the 10-day assay occurs. These features of A77003 (and perhaps similar HIV protease inhibitors as well) anti-HIV activity should represent desirable properties for antiviral therapy of AIDS and related diseases.

Biological variation and quality control of plasma human immunodeficiency virus type 1 RNA quantitation by reverse transcriptase polymerase chain reaction

Quantitation of human immunodeficiency virus type 1 (HIV-1) RNA in the plasma of seropositive individuals was performed by using an external control assay with techniques to standardize and control each measurement. Rigorous study of the variability of the assay showed that the median intraassay reproducibility was log10 0.15 RNA copies per ml of plasma, while the median interassay reproducibility on replicate plasma samples was log10 0.25 copies perml. Specimen stability studies showed reproducible recovery of RNA from plasma stored at -70 degrees C for up to 12 months. In clinically stable patients who were either untreated or taking zidovudine, the average week-to-week variation in plasma RNA levels, measured in real time, was log10 0.30 RNA copies per ml. In contrast, patients either initiating or changing antiretroviral therapy showed a fall of log10 0.8 to log10 2.0 copies per ml in plasma RNA levels. Overall, 105 of 110 (96%) HIV-1-seropositive individuals with CD4 counts of 36 to 868 cells per mm3 had quantifiable HIV-1 RNA over a range of log10 2.70 to log10 6.23 RNA copies per ml, including 81% (13 of 16) of the individuals with greater than 500 CD4 cells per mm3. Accurate and reproducible quantitation of plasma viremia in real time by reverse transcriptase polymerase chain reaction, particularly in asymptomatic HIV-1-infected individuals with high CD4 counts, provides a basis for the use of this virologic measure to monitor the short- and long-term effects of early intervention therapeutic strategies on viral burden.

Peripheral blood mononuclear cell human immunodeficiency virus type 1 proviral DNA quantification by polymerase chain reaction: relationship to immunodeficiency and drug effect

Human immunodeficiency virus type 1 (HIV-1) proviral DNA from peripheral blood mononuclear cells (PBMCs) was quantitated in 61 HIV-1-seropositive individuals by a nonisotopic polymerase chain reaction assay. Primers from the gag region (SK38, SK39) were used to determine the log10 HIV-1 proviral copy number per 10(6) CD4+ T lymphocytes (peripheral blood proviral load). A standard curve was generated for each assay by using ACH-2 cell DNA. The peripheral blood proviral load was followed in 15 individuals in a longitudinal study and was measured in 45 individuals in a cross-sectional analysis. Three of four untreated patients who were followed for 14 months had stable PBMC proviral loads and CD4+ T lymphocyte counts; one untreated patient had a sustained increase in PBMC proviral load followed 5 months later by a significant decline in the CD4+ T lymphocyte count. Eleven previously untreated individuals were monitored for 1 year following initiation of zidovudine and/or 2',3'-dideoxyinosine therapy. The mean log10 number of proviral HIV-1 copies per 10(6) CD4+ T cells decreased from 4.3 +/- 0.4 at the baseline to 3.5 +/- 0.6 after 2 to 4 months of therapy (P < 0.01). This initial 0.8 log10 fall in the PBMC proviral load after the initiation of therapy was followed by a rise in the PBMC proviral load by the sixth month of therapy. The PBMC proviral load in 45 subjects, both treated (n = 25) and untreated (n = 20), correlated inversely with the CD4+ T lymphocyte count (P < 0.01, R = 0.49). PBMC proviral DNA quantification by a nonisotopic polymerase chain reaction assay correlates with HIV-1 disease progression and could be used to monitor the effect of antiretroviral therapy.

Phase I/II trial of didanosine (2',3'-dideoxyinosine) in hemophiliac patients with AIDS or AIDS-related complex

Forty-three hemophiliacs with AIDS or ARC received a daily dose of 334 or 500 mg didanosine (2',3'-dideoxyinosine or ddI) orally in 2 divided doses in phase I/II, open-label clinical trial conducted in Japan. Twenty-eight patients completed 6 months of therapy. There was an increase in circulating CD4(+) cells in 19 valuable patients from 91 +/- 25 (mean +/- SE) at entry to 131 +/- 38 at 24 weeks of therapy P = 0.01; Wilcoxon signed rank). Fourteen of 37 patients met the criteria for CD4 rise >/= 50/mm3 rise or >/= 50% increase from entry values) for more than 4 consecutive weeks. Twenty patients were p24 positive at entry. Nine out of the 10 evaluable patients (90%) showed a decline in p24 antigen at weeks 20-24 (P = 0.02). Thirty-five patients had symptoms related to HIV-1 infection at entry. Twenty-seven patients reported improvements in constitutional symptoms during therapy. Nine patients presented with possible drug-related adverse effects, and didanosine was discontinued in 6 patients (one each with edema; abdominal pain with anorexia; hematuria with edema and rash; sense of abdominal distension with anorexia; diarrhea and abdominal pain; and irritability). One patient had a transient increase in serum amylase level to twice the upper limit of normal, but he continued to receive the drug. These data suggest that didanosine was generally well tolerated in hemophiliacs with AIDS or ARC, and its administration correlated with improvement in constitutional symptoms and laboratory findings. The adverse effects of didanosine seen in this population were moderate to mild, and no complications related to hemorrhagic diathesis were observed, although the relative risk of acute pancreatitis in this population (while not seen in the present study to date) requires more study.

Immunotherapeutic strategies in the treatment of HIV infection and AIDS

The immune response against HIV does not result in complete viral clearance. Recent interventions have focused on novel strategies to modify human anti-HIV immunity. Active vaccination of patients with HIV infection (vaccine therapy) safely alters the immune repertoire against HIV. This unique approach will provide insight into the immunoregulatory consequences of HIV-specific innate and adaptive immune responses, and hopefully define the immunological Achilles heel of HIV. Once defined, researchers, aided by current biotechnological techniques, can rationally design future vaccines and immune based therapeutic products.

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.