Accuracy of quantitative viral secondary standards: a re-examination

Interlaboratory agreement of viral load assays depends on the accuracy and uniformity of quantitative calibrators. Previous work demonstrated poor agreement of secondary cytomegalovirus (CMV) standards with nominal values. This study re-evaluated this issue among commercially produced secondary standards for both BK virus (BKV) and CMV, using digital polymerase chain reaction (dPCR) to compare the materials from three different manufacturers. Overall, standards showed an improved agreement compared to prior work, against nominal values in both log10 copies/mL and log10 international unit (IU)/mL, with bias from manufacturer-assigned nominal values of 0.0-0.9 log10 units (either copies or IU)/mL. Standards normalized to IU and those values assigned by dPCR rather than by real-time PCR (qPCR) showed better agreement with nominal values. The latter reinforces prior conclusions regarding the utility of using such methods for quantitative value assignment in reference materials. Quantitative standards have improved over the last several years, and the remaining bias from nominal values might be further reduced by universal implementation of dPCR methods for value assignment, normalized to IU.

IMPORTANCE

Interlaboratory agreement of viral load assays depends on accuracy and uniformity of quantitative calibrators. Previous work, published in JCM several years ago, demonstrated poor agreement of secondary cytomegalovirus (CMV) standards with nominal values. This study re-evaluated this issue among commercially produced secondary standards for both BK virus (BKV) and CMV, using digital polymerase chain reaction (dPCR) to compare the materials from three different manufacturers. Overall, standards showed an improved agreement compared to prior work, against nominal values, indicating a substantial improvement in the production of accurate secondary viral standards, while supporting the need for further work in this area and for the broad adaption of international unit (IU) as a reporting standard for quantitative viral load results.

Matrix Matters: Assessment of Commutability among BK Virus Assays and Standards

Quantitative testing of BK virus (BKPyV) nucleic acid has become the standard of care in transplant patients. While the relationship between interassay harmonization and commutability has been well characterized for other transplant-related viruses, it has been less well studied for BKPyV, particularly regarding differences in commutability between matrices. Here, interassay agreement was evaluated among six real-time nucleic acid amplification tests (NAATs) and one digital PCR (dPCR) BKPyV assay. Differences in the commutability of three quantitative standards was examined across all assays using a variety of statistical approaches. Panels, including 40 samples each of plasma and urine samples previously positive for BKPyV, together with one previously negative plasma sample and four previously negative urine samples, were tested using all assays, with each real-time NAAT utilizing its usual quantitative calibrators. Serial dilutions of WHO, National Institute for Standards and Technology (NIST), and commercially produced (Exact/Bio-Rad) reference materials were also run by each assay as unknowns. The agreement of the clinical sample values was assessed as a group and in a pairwise manner. The commutability was estimated using both relativistic and quantitative means. The quantitative agreement across assays in the urine samples was within a single log10 unit across all assays, while the results from the plasma samples varied by 2 to 3 log10 IU/mL. The commutability showed a similar disparity between the matrices. Recalibration using international standards diminished the resulting discrepancies in some but not all cases. Differences in the sample matrix can affect the commutability and interassay agreement of quantitative BKPyV assays. Differences in commutability between matrices may largely be due to factors other than those such as amplicon size, previously described as important in the case of cytomegalovirus. Continued efforts to standardize viral load measurements must address multiple sources of variability and account for differences in assay systems, quantitative standards, and sample matrices.

Interlaboratory comparison of epstein-barr virus viral load assays

To assess interlaboratory variability in qualitative and quantitative Epstein-Barr virus (EBV) viral load (VL) testing, we distributed a panel of samples to 28 laboratories in the USA, Canada and Europe who performed testing using commercially available reagents (n = 12) or laboratory-developed assays (n = 18). The panel included two negatives, seven constructed samples using Namalwa and Molt-3 cell lines diluted in plasma (1.30-5.30 log(10) copies/mL) and three clinical plasma samples. Significant interlaboratory variation was observed for both actual (range 1.30-4.30 log(10) copies/mL) and self-reported (range, 1.70-3.30 log(10) copies/mL) lower limits of detection. The variation observed in reported results on individual samples ranged from 2.28 log(10) (minimum) to 4.14 log(10) (maximum). Variation was independent of dynamic range and use of commercial versus laboratory-developed assays. Overall, only 47.0% of all results fell within acceptable standards of variation: defined as the expected result +/- 0.50 log(10). Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). Kinetics of change in VL appears more relevant than absolute values and clinicians should understand the uncertainty associated with absolute VL values at their institutions. The creation of an international reference standard for EBV VL assay calibration would be an initial important step in quality improvement of this laboratory tool.

Interlaboratory comparison of cytomegalovirus viral load assays

To assess interlaboratory variability in qualitative and quantitative cytomegalovirus (CMV) viral load (VL) testing, we distributed a panel of samples to 33 laboratories in the USA, Canada and Europe who performed testing using commercial reagents (n = 17) or laboratory-developed assays (n = 18). The panel included two negatives, seven samples constructed from purified CMV nucleocapsids in plasma (2.0-6.0 log(10) copies/mL) and three clinical plasma samples. Interlaboratory variation was observed in both actual (range, 2.0-4.0 log(10) copies/mL) and self-reported lower limits of detection (range, 1.0-4.0 log(10) copies/mL). Variation observed in reported results for individual samples ranged from 2.0 log(10) (minimum) to 4.3 log(10) (maximum)(.) Variation was greatest at low VLs. Assuming +/- 0.5 log(10) relative to the expected result represents an acceptable result, 57.6% of results fell within this range. Use of commercially available reagents and procedures was associated with less variability compared with laboratory-developed assays. Interlaboratory variability on replicate samples was significantly greater than intralaboratory variability (p < 0.0001). The significant interlaboratory variability in CMV VL observed may be impacting patient care and limiting interinstitutional comparisons. The creation of an international reference standard for CMV VL assay calibration would be an important step in quality improvement of this laboratory tool.

Multilaboratory comparison of hepatitis C virus viral load assays

We report a multilaboratory evaluation of hepatitis C virus (HCV) viral load assays to determine their linear range, reproducibility, subtype detection, and agreement. A panel of HCV RNA samples ranging in nominal concentration from 1.0 to 7.0 log10 IU/ml was constructed by diluting a clinical specimen (genotype 1b). Replicates of the panel were tested in multiple laboratories using the Abbott TaqMan analyte-specific reagent (Abbott reverse transcription-PCR [RT-PCR]), Roche TaqMan RUO (Roche RT-PCR), Roche Amplicor Monitor HCV 2.0 (Roche Monitor), and Bayer VERSANT HCV RNA 3.0 (Bayer bDNA) assays. Bayer bDNA-negative specimens were tested reflexively using the Bayer VERSANT HCV RNA qualitative assay (Bayer TMA). Abbott RT-PCR and Roche RT-PCR detected all 28 replicates with a concentration of 1.0 log10 IU/ml and were linear to 7.0 log10 IU/ml. Roche Monitor and Bayer bDNA detected 27 out of 28 and 13 out of 28 replicates, respectively, of 3.0 log10 IU/ml. Bayer TMA detected all seven replicates with 1.0 log10 IU/ml. Bayer bDNA was the most reproducible of the four assays. The mean viral load values for panel members in the linear ranges of the assays were within 0.5 log10 for the different tests. Eighty-nine clinical specimens of various genotypes (1 through 4) were tested in the Bayer bDNA, Abbott RT-PCR, and Roche RT-PCR assays. For Abbott RT-PCR, mean viral load values were 0.61 to 0.96 log10 greater than the values for Bayer bDNA assay for samples with genotype 1, 2, or 3 samples and 0.08 log10 greater for genotype 4 specimens. The Roche RT-PCR assay gave mean viral load values that were 0.28 to 0.82 log10 greater than those obtained with the Bayer bDNA assay for genotype 1, 2, and 3 samples. However, for genotype 4 samples the mean viral load value obtained with the Roche RT-PCR assay was, on average, 0.15 log10 lower than that of the Bayer bDNA. Based on these data, we conclude that the sensitivity and linear range of the Abbott and Roche RT-PCR assays enable them to be used for HCV diagnostics and therapeutic monitoring. However, the differences in the viral load values obtained with the different assays underscore the importance of using one assay when monitoring response to therapy.

Real-time PCR improves detection of Trichomonas vaginalis infection compared with culture using self-collected vaginal swabs

OBJECTIVE: To compare a real-time polymerase chain reaction (PCR) assay with broth culture for the detection of Trichomonas vaginalis using self-collected vaginal swabs. METHODS: Self-collected vaginal swabs were obtained from adolescent and young adult African-American women participating in HIV-1 prevention programs. T. vaginalis culture was performed using the InPouch TV System. Samples for the real-time PCR assay were collected using the BDProbeTec ET Culturette Direct Dry Swab system and tested in a laboratory-developed assay which targeted a repeated sequence of the genome. Discrepant samples that were culture negative and positive in the real-time PCR assay were tested in a confirmatory PCR which targeted a different region of the T. vaginalis genome, the18S ribosomal DNA gene. RESULTS: Of the 524 specimens tested by both culture and real-time PCR, 36 were culture positive and 54 were positive in the real-time PCR assay; 16 of the 18 discrepant specimens were also positive in the confirmatory PCR assay. Using a modified gold standard of positive by culture or positive in both PCR assays, the sensitivity of the real-time PCR assay was 100% and the specificity was 99.6%, whereas culture had a sensitivity of 69.2% and a specificity of 100%. CONCLUSIONS: The real-time PCR assay was sensitive and specific for the detection of T. vaginalis DNA from self-collected vaginal swab specimens. The ability to use the BDProbeTec dry swab system for the real-time PCR testing allowed for the detection of Chlamydia trachomatis, Neisseria gonorrhoeae, and T. vaginalis from a single specimen.

Human immunodeficiency virus in plasma and cervicovaginal secretions in Filipino women

This study examined 30 HIV-infected women in Manila to assess the relationship between cervicovaginal and plasma HIV-1 viral load. An interview and gynaecologic examination was conducted and cervicovaginal lavage (CVL) and venous blood specimens were collected. HIV-1 RNA was detected in plasma samples of 24 patients (80%) and in CVL samples of 18 women (60%); 16 patients (53%) had detectable levels in both. CVL HIV-1 RNA was detectable in 75% of women (6/8) with plasma viral loads between 10,000 and 100,000 copies/mL and in 77% of women (10/13) with plasma viral loads higher than 100,000 copies/mL (P =0.0086). Among women with CD4 cell counts of less than 200, 200-500, and greater than 500/mm(3), CVL HIV-1 RNA was detected in 73%, 69%, and 17% of women, respectively (P =0.1428). HIV-1 RNA shedding in the genital tract was significantly associated with plasma viral load.

Cytomegalovirus (CMV) and human immunodeficiency virus (HIV) burden, CMV end-organ disease, and survival in subjects with advanced HIV infection (AIDS Clinical Trials Group Protocol 360)

We undertook a prospective study to analyze cytomegalovirus (CMV) end-organ disease (EOD) in subjects with advanced human immunodeficiency virus (HIV) infection. Of 403 individuals without prior CMV EOD who were followed up for a median of 151 weeks, 56 died and 21 developed CMV EOD. Twenty of the subjects with CMV EOD had CD4 cell counts of < or =50 cells/mm3 and HIV RNA level of >10,000 copies/mL of plasma at baseline; in these 20 subjects, an increase of CMV DNA level to greater than the quantification limits was associated with CMV EOD. A CD4 cell count of < or =100 cells/mm3 and an HIV RNA level of >10,000 copies/mL of plasma at baseline, a CMV DNA level of >200 copies/mL of blood during follow-up, or development of CMV EOD were all associated with decreased survival. HIV-infected subjects with CD4 cell counts of < or =50 cells/mm3 and HIV RNA levels of >10,000 copies/mL of plasma should have blood fractions screened for CMV DNA; if CMV DNA is detected, CMV prophylaxis might be considered.

Failure of linezolid treatment for enterococcal endocarditis

We describe a patient with Enterococcus faecalis endocarditis who failed to respond to treatment with linezolid.

Testing for HIV-1 drug resistance

Viral resistance to antiretroviral agents may limit the efficacy of current treatment regimens for HIV-1 infection. The mutational patterns underlying resistance to each antiretroviral agent are often quite diverse, and cross-resistance patterns in each of the currently available classes are complex. Current methods for determining drug resistance include genotypic and phenotypic assays, and each has advantages and limitations. Prospective clinical trials assessing the utility of HIV-1 drug resistance testing have shown significant but modest improvement in virologic outcomes with genotypic assays. Some, but not all, trials of phenotypic resistance testing have demonstrated improved virologic outcomes. Resistance testing is currently recommended for patients who have virologic failure or have no response to an antiretroviral regimen, and for pregnant women. Testing should also be considered in treatment-naive patients in areas of high prevalence of transmitted drug-resistant virus.

Association between bacterial vaginosis and expression of human immunodeficiency virus type 1 RNA in the female genital tract

We assessed the effect of lower genital tract infections on human immunodeficiency virus type 1 (HIV-1) RNA shedding in the female genital tract. Bacterial vaginosis was significantly associated with HIV-1 RNA expression in the female genital tract of HIV-infected women.

Successful testing protocols in virology

Molecular methods have had a significant impact on the diagnosis of viral infections because of their superior sensitivity and rapid turnaround time compared with conventional diagnostic methods. These characteristics have allowed molecular tests to play a central role in the use of testing protocols for managing viral infections. Several examples of such protocols are reviewed in this report, including the use of molecular testing for early disease detection to improve overall disease management and to direct antiviral therapy.

Comparison of quantitative and qualitative PCR assays for cytomegalovirus DNA in plasma

We analyzed the performance characteristics of the qualitative AMPLICOR CMV Test (Roche Molecular Systems, Pleasanton, Calif.) and quantitative COBAS AMPLICOR CMV MONITOR Test (Roche Molecular Systems) assays and compared the performance of the AMPLICOR quantitative assay with an in-house-developed cytomegalovirus (CMV) DNA PCR assay. The quantitative AMPLICOR assay was found to be more sensitive than the qualitative AMPLICOR assay. The quantitative AMPLICOR assay has a lower limit of sensitivity of 400 CMV DNA copies/ml of plasma and is linear to 50,000 CMV DNA copies/ml of plasma. Compared to the in-house PCR assay, the AMPLICOR quantitative assay gave lower viral load values at all concentrations tested, but the difference between the two assays was not consistent across the entire dynamic range of the AMPLICOR quantitative assay. At the lower end of the assay, the viral load values obtained with the in-house PCR assay were three- to fivefold (0.5 to 0.7 log units) higher than those measured with the AMPLICOR assay. At higher input concentrations, the differences between the two assays approached 10-fold. This direct comparison of the in-house assay and the quantitative AMPLICOR assay provides the ability to compare previously published in-house data with an assay widely available for future research and clinical monitoring of patients with CMV infections.

Analytical performance and clinical utility of a nucleic acid sequence-based amplification assay for detection of cytomegalovirus infection

A nucleic acid sequence-based amplification (NASBA) assay for qualitative detection of human cytomegalovirus (CMV) pp67 mRNA was evaluated in a multicenter study. Negative results were obtained for all specimens from 50 CMV-seronegative and 50 CMV-seropositive low-risk whole-blood donors. No interference with CMV mRNA amplification was observed in the testing of 288 specimens containing various potential interfering substances, nonspecifically reacting substances (including mRNA from other herpesviruses), and three anticoagulants. A total of 95% (50 of 51) of CMV-positive (cell culture- and antigenemia immunofluorescence [AG-IFA]-positive) clinical specimens were positive by the NASBA assay. Results from different operators over multiple testing days were consistent for each of four panel members containing different concentrations of CMV mRNA, indicating the reproducibility of the assay. The estimated 95% reliable upper detection limit of the assay was 600 mRNA copies; the lower limit of detection was less than 25 mRNA copies. The clinical utility of the assay was evaluated with longitudinally collected specimens from solid-organ transplant patients (n = 21). A total of 98% (81 of 83) of the specimens from CMV-negative patients were negative by the NASBA assay, while 90% (10 of 11) of patient specimens that were positive by cell culture or AG-IFA were positive by the NASBA assay. Positive NASBA assay results were obtained earlier than AG-IFA or cell culture results for 55% of the patients and at the same time for the remainder of the patients (45%). The overall agreement between the NASBA assay and current reference tests was 86% when active CMV infection was present. These studies indicate that the CMV pp67 mRNA NASBA assay has reproducible and sensitive performance characteristics that should enable more rapid diagnosis of CMV infection.

Quantification of HIV-1-specific T-cell responses at the mucosal cervicovaginal surface

OBJECTIVE

To characterize HIV-1 specific cellular immune responses at mucosal surfaces using a rapid, sensitive enzyme-linked immuno-spot (ELISPOT) technique.

DESIGN

Cervicovaginal mononuclear cells obtained from cytobrush and cervicovaginal lavage were assessed for production of interferon-gamma (IFN-gamma) in response to stimulation by HIV-1 antigens. HIV-1 specific responses were compared in a cross-sectional study of two HIV-1-positive patient groups: women not currently on antiretroviral therapy with peripheral CD4 cell counts > 250 x 10(6)/l (n = 12); and women on highly active antiretroviral therapy (HAART) (n = 9).

METHODS

Mononuclear cells from peripheral blood or cervicovaginal specimens were assessed in an ELISPOT assay for responses to HIV-1 antigens expressed by recombinant vaccinia viruses. This assay detects primarily CD8 T cells and shows good correlation with MHC class I tetramer staining of cytotoxic T lymphocytes.

RESULTS

HIV-1 specific IFN-gamma spot-forming cells were detected in cervicovaginal samples of one out of nine women (11%) on HAART and five out of 12 women (42%) not currently on HAART. In peripheral blood mononuclear cells, HIV-1 specific IFN-gamma spot-forming cells were significantly more numerous in women not currently on HAART than in women on HAART (P = 0.009). In most cases, antigens recognized by mucosal T cells were also recognized by PBMC; however, there were exceptions.

CONCLUSIONS

HIV-1-specific antigen-reactive T cells may be detected in routine, noninvasive gynecological specimens. The results suggest that cervicovaginal HIV-1-specific T cells may be less numerous in individuals on HAART than in those not on HAART, as shown previously for HIV-1-specific cytotoxic T lymphocytes in the peripheral blood.

Comparison of quantitative cytomegalovirus (CMV) PCR in plasma and CMV antigenemia assay: clinical utility of the prototype AMPLICOR CMV MONITOR test in transplant recipients

The correlation between the prototype AMPLICOR CMV MONITOR test (Roche Molecular Systems), a quantitative PCR assay, and the cytomegalovirus (CMV) pp65 antigenemia assay was evaluated in transplant recipients. Sequential blood specimens were collected on 29 patients (491 specimens), the leukocyte fraction was tested by CMV antigenemia, and quantitative PCR was performed on plasma specimens. None of the 15 patients (242 specimens) who were antigenemia negative were positive for CMV DNA by PCR, and none of these patients developed active CMV disease. There were 14 antigenemia-positive patients, 8 of whom developed active CMV disease. In all patients, there was a good association between the antigenemia and PCR assays. Ganciclovir-resistant virus was isolated from three patients with active CMV disease. These three patients had persistently elevated levels of antigenemia and CMV DNA by PCR when resistance to ganciclovir developed. This standardized, quantitative CMV PCR assay on plasma has clinical utility for the diagnosis of active disease and in monitoring the response to antiviral therapy in transplant recipients.

Effect of highly active antiretroviral therapy on cervicovaginal HIV-1 RNA

OBJECTIVES

To determine the frequency of cervicovaginal lavage and plasma HIV-1 RNA levels that are below detectable levels (< 400 copies/ml) among women on highly active antiretroviral therapy (HAART), non-HAART and on no therapy. To compare the effect of initiating HAART on the timing of HIV-1 RNA suppression in the blood plasma and genital tract among antiretroviral-naïve women.

METHODS

Data were obtained from 205 HIV-infected women with paired plasma and cervicovaginal lavage viral load measurements. Seven antiretroviral-naïve women starting HAART had viral load measurements performed daily for one week, at 2 weeks and at 1 month after initiating therapy. Viral load quantification was carried out by nucleic acid sequence-based amplification assay. The lower limit of detection was 400 copies/ml.

RESULTS

Plasma and cervicovaginal HIV-1 RNA was detectable in 71 and 26% of the women, respectively. Among women with plasma viral loads less than 400, 400-9999, and 10,000 copies/ml or over, genital tract HIV-1 RNA was detected in 3, 17 and 48%, respectively (P < 0.001). Fifty-one per cent of the women with CD4 cell counts of less than 200/mm3 had detectable cervicovaginal viral loads compared with 18% among women with CD4 cell counts of 200/mm3 or over (P < 0.001). Cervicovaginal HIV-1 RNA was less than 400 copies/ml in 85% of those on HAART, 69% of those on non-HAART and 69% of those on no therapy (P < 0.045). In seven antiretroviral-naïve women initiating HAART, cervicovaginal HIV-1 RNA decreased by 0.7-2.1 log10 within 1-14 days of starting therapy.

CONCLUSION

The cervicovaginal HIV-1 RNA level was positively correlated with plasma HIV-1 RNA and negatively with the CD4 cell count. The use of HAART was significantly associated with below-detectable levels of HIV-1 RNA in both plasma and the genital tract. HIV-1 RNA suppression in the genital tract may occur rapidly after initiating therapy.

Relationship of incremental specimen volumes and enhanced detection of human immunodeficiency virus type 1 RNA with nucleic acid amplification technology

The relationship between specimen input volume and the frequency of reported human immunodeficiency virus type 1 (HIV-1) RNA copy numbers by nucleic acid amplification technology (the NASBA HIV-1 RNA QT system) was investigated. Results obtained with both clinical specimens and dilution panels indicated that both the absolute number of reported results and the reported HIV-1 RNA copy number were directly proportional to the specimen input volumes evaluated (0.1, 0.5, and 1.0 ml). Conversion of the reported HIV-1 RNA copy numbers to a constant 1.0-ml volume indicated that the numerical relationship among the specimen input volumes and the HIV-1 RNA copy numbers was multiplicative. The HIV-1 RNA copy numbers reported for the 0.5-ml input volume were approximately 5-fold increased over those reported for the 0.1-ml input volume, and those reported for the 1.0-ml input volume were 10-fold increased over those reported for the 0.1-ml input volume. For the specimen input volumes investigated, a common linear range of 264 to 5,400,000 HIV-1 RNA copies was observed. The use of increased specimen input volumes did not result in a loss of assay specificity, as the results reported for specimens from 50 seronegative blood donors were negative at all three specimen input volumes. In conclusion, an increase in the input volume of specimens analyzed by nucleic acid amplification technology can be useful for the enhanced detection of HIV-1 RNA.

Clinical utility of quantitative cytomegalovirus viral load determination for predicting cytomegalovirus disease in liver transplant recipients

BACKGROUND

The early detection of cytomegalovirus (CMV) after liver transplantation may form the basis of a preemptive strategy for prevention of active CMV disease.

METHODS

We prospectively analyzed the clinical use of weekly quantitative polymerase chain reaction-(PCR) based plasma viral load determinations and the antigenemia assay for predicting the development of active CMV disease in 97 consecutive liver transplant recipients.

RESULTS

CMV disease occurred in 21/97 patients. Using a positive cut-off of >400 copies/ml plasma, PCR had a sensitivity of 100%, specificity 47.4%, positive predictive value 34.4% and negative predictive value 100% for prediction of CMV disease. Respective values for a positive antigenemia (>0 positive cells/slide) were 95.2, 55.3, 37.0, and 97.7%. Different cut-off points for a positive test were analyzed using receiver-operating characteristic (ROC) curves. The optimal cut-off for viral load was in the range of 2000-5000 copies/ml (sensitivity 85.7%, specificity 86.8%, PPV 64.3%, NPV 95.7% for >5000 copies/ml). The optimal cut-off for antigenemia was in the range of four to six positive cells/slide. Mean peak viral load in symptomatic patients was 73,715 copies per/ml versus 3615 copies/ml in patients with asymptomatic CMV reactivation (P<0.001). In a multivariate logistic regression analysis of risk factors for CMV disease (CMV serostatus, acute rejection, and induction immunosuppression), peak viral load and peak antigenemia emerged as the only significant independent predictors of CMV disease (for PCR, odds ratio=1.40/1000 copy/ml increase in viral load, P=0.0001; for antigenemia odds ratio=1.17/1 positive cell/slide).

CONCLUSIONS

Plasma viral load by quantitative PCR is useful for predicting CMV disease and could be used in a preemptive strategy.

Cerebrospinal fluid human immunodeficiency virus type 1 (HIV-1) suppression and efavirenz drug concentrations in HIV-1-infected patients receiving combination therapy

Efavirenz, a potent inhibitor of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase, is a promising addition to the antiretroviral armamentarium. Efavirenz levels and HIV-1 RNA levels were measured in cerebrospinal fluid (CSF) and plasma of 10 HIV-1-infected patients taking efavirenz, 600 mg daily, in combination with other antiretroviral medications. Efavirenz was detected in the CSF at a mean concentration of 35.1 nM (range, 6. 6-58.9 nM), which was above the IC95 for wild-type HIV-1. The mean CSF-to-plasma ratio was 0.61% (range, 0.26%-0.99%). CSF HIV-1 RNA levels were ascertained in 9 of the patients; all were <400 copies/mL after a mean of 26 weeks on therapy. Eight of the 9 patients had no detectable virus in plasma. These results indicate that efavirenz is present in the CSF at low levels and is effective in suppressing CSF viral levels when used in combination therapy.

Treatment with amprenavir alone or amprenavir with zidovudine and lamivudine in adults with human immunodeficiency virus infection. AIDS Clinical Trials Group 347 Study Team

Amprenavir is a human immunodeficiency virus (HIV) protease inhibitor with a favorable pharmacokinetic profile and good in vitro activity. Ninety-two lamivudine- and protease inhibitor-naive individuals with >/=50 CD4 cells/mm3 and >/=5000 HIV RNA copies/mL were assigned amprenavir (1200 mg) alone or with zidovudine (300 mg) plus lamivudine (150 mg), all given every 12 h. After a median follow-up of 88 days, the findings of a planned interim review resulted in termination of the amprenavir monotherapy arm. Among 85 subjects with confirmed plasma HIV RNA determination, 15 of 42 monotherapy versus 1 of 43 triple-therapy subjects had an HIV RNA increase above baseline or 1 log10 above nadir (P=.0001). For subjects taking triple therapy at 24 weeks, the median decrease in HIV RNA was 2.04 log10 copies/mL, and 17 (63%) of 27 evaluable subjects had <500 HIV RNA copies/mL. Treatment with amprenavir, zidovudine, and lamivudine together reduced the levels of HIV RNA significantly more than did amprenavir monotherapy.

Bilateral acute retinal necrosis caused by cytomegalovirus in an immunocompromised patient

PURPOSE

To report a case of bilateral acute retinal necrosis caused by cytomegalovirus.

METHODS

A diagnostic vitrectomy was performed on a patient with non-Hodgkin lymphoma who presented with a bilateral, rapidly progressing necrotizing retinitis and uveitis.

RESULTS

Immunohistochemical studies and polymerase chain reaction disclosed cytomegalovirus as the cause of retinitis. The patient was treated with intravitreal and intravenous ganciclovir.

CONCLUSIONS

Although rare, cytomegalovirus may lead to an appearance identical to acute retinal necrosis and should be considered among the viral etiologies of this syndrome.

Performance of a PCR assay for detection of Pneumocystis carinii from respiratory specimens

This study evaluates the performance of a PCR assay for the detection of Pneumocystis carinii from respiratory specimens that has been designed for use in the clinical microbiology laboratory. The test includes a simple method for nucleic acid extraction and amplification, a colorimetric probe hybridization technique for detection of amplicons, and an internal control to evaluate for the presence of inhibitors of amplification. Two hundred thirty-two clinical specimens (120 induced-sputum [IS] and 112 bronchoalveolar lavage [BAL] specimens) from 168 patients were tested by both immunofluorescent (direct fluorescent-antibody [DFA]) staining and PCR. Of the 112 BAL specimens, 17 were positive for P. carinii by DFA staining and PCR. An additional two specimens were DFA negative and PCR positive. For BAL specimens, the sensitivity and specificity of PCR compared to DFA were 100 and 98%, respectively. Eighteen IS specimens were positive for P. carinii by DFA, and 27 were positive by PCR. One of the 18 DFA-positive IS specimens was negative by PCR; this patient had just completed therapy for P. carinii pneumonia. Of the 10 specimens that were PCR positive and DFA negative, 4 were from patients who had a subsequent BAL specimen that was positive by DFA and PCR. For IS specimens, the sensitivity of DFA and PCR was 82 and 95%, respectively. The specificity of PCR for IS specimens was 94%. Due to the high sensitivity of PCR for the detection of P. carinii from IS specimens, a PCR-based diagnostic test may be a useful screening test and may alleviate the need for bronchoscopy in some patients.

Vigorous HIV-1-specific CD4+ T cell responses associated with control of viremia

Virus-specific CD4+ T helper lymphocytes are critical to the maintenance of effective immunity in a number of chronic viral infections, but are characteristically undetectable in chronic human immunodeficiency virus-type 1 (HIV-1) infection. In individuals who control viremia in the absence of antiviral therapy, polyclonal, persistent, and vigorous HIV-1-specific CD4+ T cell proliferative responses were present, resulting in the elaboration of interferon-gamma and antiviral beta chemokines. In persons with chronic infection, HIV-1-specific proliferative responses to p24 were inversely related to viral load. Strong HIV-1-specific proliferative responses were also detected following treatment of acutely infected persons with potent antiviral therapy. The HIV-1-specific helper cells are likely to be important in immunotherapeutic interventions and vaccine development.

Colonization of skin by Helcococcus kunzii

In order to investigate the role of Helcococcus kunzii as a colonizer of skin and as a possible participant in diabetic foot ulcers, we used a selective medium to culture both lower- and upper-extremity skin from a study group of podiatry patients (60 diabetics and 60 nondiabetics) and a control group of 50 healthy volunteers. Although differences in colonization were not statistically significant, a trend toward higher colonization rates in the group of podiatry patients was noted. H. kunzii appears to preferentially colonize the skin of the feet, and while its pathogenic role in diabetic foot ulcers is difficult to establish, it may be a previously unrecognized component of the polymicrobial flora characteristically isolated from patients with these infections.

Cervicovaginal human immunodeficiency virus secretion and plasma viral load in human immunodeficiency virus-seropositive women

OBJECTIVE

To evaluate human immunodeficiency virus (HIV)-1 RNA burden in paired plasma and cervicovaginal lavage specimens and to assess the relation of plasma HIV-1 RNA level, CD4 cell count, and antiretroviral therapy with cervicovaginal HIV-1 viral load.

METHODS

Paired blood and cervicovaginal lavage specimens were collected from 72 HIV-infected women. Quantitation of HIV-1 RNA from plasma and cervicovaginal lavage specimens was performed by using the nucleic acid sequence-based amplification assay. Analyses examined relations between cervicovaginal HIV-1 RNA and plasma HIV-1 RNA level, CD4 count, and antiretroviral therapy.

RESULTS

Plasma HIV-1 RNA was detectable in 61 of 72 women (85%), with copy numbers ranging from 330 to 1,600,000 copies/mL. Twenty-eight of 72 (39%) had detectable HIV-1 RNA in cervicovaginal lavage specimens, ranging from 320 to 440,000 copies/mL. The cervicovaginal lavage HIV-1 RNA level was detectable in 9%, 29%, 52%, and 53% of the women with plasma HIV-1 RNA of less than 400, 400-9999, 10,000-100,000, and more than 100,000 copies, respectively (P = .043). Among women with CD4 counts of less than 200, 200-500, and greater than 500/mm3, cervicovaginal lavage HIV-1 RNA was detected in 67%, 32%, and 25% of subjects, respectively (P = .018). Among women receiving antiretroviral therapy, cervicovaginal lavage revealed HIV-1 RNA in 67%, 31%, and 25% with CD4 cell counts of less than 200, 200-500, and more than 500/mm3, respectively (P = .042).

CONCLUSION

The presence of HIV-1 RNA in cervicovaginal lavage correlates significantly with the level of HIV-1 RNA in plasma and negatively with CD4 cell count.

Strong cytotoxic T cell and weak neutralizing antibody responses in a subset of persons with stable nonprogressing HIV type 1 infection

Some individuals in well-defined cohorts have now been infected with HIV-1 for well over a decade and yet remain clinically asymptomatic with normal CD4 counts. To determine immunologic and virologic parameters in these individuals, we examined 10 persons from the San Francisco City Clinic with firmly documented infection of 11-15 years duration who had maintained stable CD4 counts above 500 cells/microliters. Our results indicate that long-term nonprogressors are a heterogeneous group with respect to viral load and HIV-1-specific immune responses, and that progression can occur even after 15 years of stable infection. However, in a subset of persons with the lowest viral loads and persistent nonprogressive infection, we detected strong CTL responses, whereas neutralizing antibody studies revealed weak to undetectable titers against a panel of 10 primary isolates. This study demonstrates that a vigorous in vivo activated HIV-1-specific CTL response can be part of the host immune response in stable nonprogressive HIV-1 infection, and that circulating activated CTL can be detected in the setting of an extremely low viral load. These results also indicate that long-term nonprogressing HIV-1 infection does not require the presence of broadly cross-reactive neutralizing antibodies.

Effects of zidovudine-selected human immunodeficiency virus type 1 reverse transcriptase amino acid substitutions on processive DNA synthesis and viral replication

Certain amino acid substitutions in the reverse transcriptase (RT), including D67N, K70R, T215Y, and K219Q, cause high-level resistance of human immunodeficiency virus type 1 (HIV-1) to zidovudine (3'-azidothymidine; AZT) and appear to approximate the template strand of the enzyme-template-primer complex in structural models. We studied whether this set of mutations altered RT-template-primer interaction as well as their effect on virus replication in the absence of inhibitor. When in vitro polymerization was limited to a single association of an RT with an oligodeoxynucleotide-primed heteropolymeric RNA template (a single processive cycle), recombinant-expressed mutant 67/70/215/219 RT synthesized 5- to 10-fold more high-molecular-weight DNA products (>200 nucleotides in length) than wild-type RT. This advantage was maintained as deoxynucleoside triphosphate (dNTP) concentrations were decreased to limiting levels. In contrast, no difference was seen between wild-type and mutant RTs under conditions allowing repeated associations of enzyme with template-primer. Because intracellular dNTP concentrations are low prior to mitogenic stimulation, we compared replication of mutant 67/70/215/219 virus and wild-type virus in peripheral blood mononuclear cells (PBMC) stimulated before and after infection. In the absence of inhibitor, mutant 67/70/215/219 virus had a replication advantage in PBMC stimulated with phytohemagglutinin and interleukin-2 after infection, but virus replication was similar in PBMC stimulated before infection in vitro. The results confirm that RT mutations D67N, K70R, T215Y, and K219Q affect an enzyme-template-primer interaction in vitro and suggest that such substitutions may affect HIV-1 pathogenesis during therapy by increasing viral replication capacity in cells stimulated after infection.

Combination therapy for infection due to human immunodeficiency virus type 1

The preliminary results of the Concorde trial demonstrated the transient clinical benefit of monotherapy with zidovudine (AZT) in asymptomatic persons infected with human immunodeficiency virus type 1 (HIV-1). This result, which has been widely disseminated and discussed, was predictable given the previous demonstration of the development of resistance to AZT in isolates from individuals receiving prolonged treatment with the drug and given the finding that didanosine (ddI) is more efficacious than continued therapy with AZT in individuals who have received > or = 6 months of AZT monotherapy. On the basis of these findings, interest in combinations of antiretroviral agents has continued to grow. Many in vitro studies of nucleoside and nonnucleoside inhibitors of reverse transcriptase combined with interferon-alpha or inhibitors of protease have been published. In addition, numerous clinical trials of various combinations have been completed or are under way. Dr. Martin Hirsch and his colleagues at the Massachusetts General Hospital have been among the leaders of this effort. He and Dr. Angela Caliendo review, in this AIDS Commentary, the current state of our knowledge regarding the potential utility of combination therapy for infection with HIV-1.

Resistance to 2',3'-dideoxycytidine conferred by a mutation in codon 65 of the human immunodeficiency virus type 1 reverse transcriptase

A human immunodeficiency virus type 1 variant resistant to zalcitabine (2',3'-dideoxycytidine [ddC]) was selected by sequential passage in the presence of increasing concentrations of ddC in peripheral blood mononuclear cell cultures. A mutation causing a lysine-to-arginine substitution was noted in reverse transcriptase (RT) codon 65 of this ddC-selected virus. A cloned mutant virus with this codon 65 mutation was constructed by using a novel PCR approach for site-directed mutagenesis. Characterization of this virus confirmed that the RT Lys-65-->Arg substitution was necessary and sufficient for a fourfold increase in the ddC 50% inhibitory concentration, as well as for resistance to didanosine (2',3'-dideoxyinosine [ddI]). Lys-65-->Arg and virus resistance to ddC and ddI also developed during therapy in isolates from one ddC-treated patient and two ddI-treated patients. Recombinant-expressed codon 65 mutant RT enzyme was resistant to ddCTP and ddATP in cell-free polymerase assays. Results of mutant enzyme studies are consistent with Lys-65-->Arg leading to changes in binding of the triphosphate forms of these nucleoside analogs to the RT. These data have implications for future studies of ddC resistance, particularly those aimed at defining its clinical relevance.

pol mutations conferring zidovudine and didanosine resistance with different effects in vitro yield multiply resistant human immunodeficiency virus type 1 isolates in vivo

Specific mutations in the human immunodeficiency virus type 1 (HIV-1) pol gene that cause zidovudine (3'-azido-2',3'-dideoxythymidine; AZT) and didanosine (2',3'-dideoxyinosine; ddI) resistance were studied. The 50% inhibitory concentrations (IC50s) of nucleosides for cloned viruses containing these mutations were compared with the IC50s of the corresponding triphosphate analogs for mutant recombinant-expressed reverse transcriptases (RTs). Changes in ddATP inhibition of RNA-dependent DNA polymerase activity fully accounted for the ddI resistance of the virus caused by a Leu-74-->Val substitution in RT, including an augmentation by the AZT-selected substitutions Thr-215-->Tyr and Lys-219-->Gln in RT. In contrast, the AZT-selected substitutions studied did not cause as great a change in the IC50 of AZT-triphosphate (AZT-TP) for polymerase as they did in the IC50 of AZT for mutant virus. In addition, the mutation at codon 74 suppressed AZT resistance in the virus caused by the mutations at codons 215 and 219 but did not suppress the AZT-TP resistance of enzyme containing these same mutations in RT. The mutation at codon 74 was found in clinical isolates whether or not the patient had received AZT prior to starting ddI therapy. AZT resistance coexisted with ddI resistance following acquisition of Leu-74-->Val in three clinical isolates, indicating that the suppressive effect of Val-74 on the AZT resistance of the virus does not occur in all genetic contexts. When this suppression of AZT resistance was seen in the virus, Val-74 did not appear to cause mutually exclusive changes in AZT-TP and ddATP binding to RT in vitro. The results of the in vitro experiments and characterization of clinical isolates suggest that there are differences in the functional effects of these AZT and ddI resistance mutations.

Identification of a cDNA clone for the beta-subunit of the pyruvate dehydrogenase component of human pyruvate dehydrogenase complex

We report the isolation of a 1.5 kb cDNA clone for the beta subunit of human pyruvate dehydrogenase (E1) from a human liver lambda gt11 cDNA library using anti-E1 serum. We generated a peptide sequence of 24 amino acids starting from the N-terminus of bovine heart mature E1 beta. The identity of the E1 beta cDNA clone was confirmed by the similarity between the amino acid sequence deduced from the cDNA nucleotide sequence and the known amino acid sequence of bovine heart E1 beta. In Northern analysis of total RNA extracted from human heart, the E1 beta cDNA clone hybridized to a major 1.6 kb and a minor 5.2 kb RNA species.

Insulin receptors in developing rat liver: acquisition of down regulation in the immediate postnatal period

Alterations in the high and low affinity insulin receptor concentrations in developing rat liver were investigated. The number of high affinity receptors in partially purified plasma membranes from fetal rats increased from Days 19 through 22 of gestation, with no further increase in binding during the postnatal period. Fetuses of diabetic rats had approximately three times as many high affinity insulin receptors as age-matched fetuses of normal rats; however, by 1 day after birth the receptor number decreased to the normal level. Neither the number of low affinity receptors nor the affinity of insulin binding to high or low affinity receptors changed during development or between offspring of normal and diabetic rats. These changes in the number of high affinity hepatic insulin receptors from prenatal animals did not correlate with the concentration of plasma insulin. When suckling pups were rendered diabetic the changes in the number of high affinity insulin receptors correlated with alterations in plasma insulin concentrations. The number of high affinity sites/microgram DNA in hepatocytes from Day 18 fetal rats was not altered when cells were cultured for 48 h in medium containing 0, 250, or 5000 microU/ml of added insulin. When cultured hepatocytes derived from 1-day-old and adult rats were maintained in medium with added insulin concentrations of 250 or 5000 microU/ml the number of high affinity receptors/microgram DNA decreased as compared to the number of high affinity receptors in hepatocytes cultured in medium with no added insulin. This decrease in receptor number was accompanied by an increase in the affinity of insulin binding to its high affinity receptors. The data show that (i) only the high affinity insulin receptor number increases in rat liver during the prenatal period, (ii) fetuses of diabetic rats show a greater increase in high affinity receptors than do fetuses of normal animals, and (iii) the phenomenon of down regulation for high affinity insulin receptors is not observed in fetal rat liver, but is acquired in the immediate postnatal period.