Immunologic differentiation of absolute lymphocyte count with an integrated flow cytometric system: a new concept for absolute T cell subset determinations

Evaluation of a biosimilar granulocyte colony-stimulating factor (filgrastim XM02) for peripheral blood stem cell mobilization and transplantation: a single center experience in Japan

Background

Biosimilar granulocyte colony-stimulating factor (G-CSF) has recently been introduced into clinical practice. G-CSFs are used to mobilize CD34⁺ cells and accelerate engraftment after transplantation. However, in Asia, particularly in Japan, data for peripheral blood stem cell (PBSC) mobilization by this biosimilar G-CSF are currently lacking. Therefore, the clinical efficacy and safety of biosimilar G-CSF for hematopoietic stem cell transplantation needs to be evaluated in a Japanese context.

Materials and methods

The subjects included two groups of patients with malignant lymphoma and multiple myeloma. All patients received chemotherapy priming for the mobilization of PBSCs. All patients were treated with chemotherapy followed by the administration of either the biosimilar G-CSF, filgrastim XM02 (FBNK), or the originators, filgrastim, or lenograstim.

Results

There were no significant differences among FBNK, filgrastim, and lenograstim treatments in the numbers of CD34⁺ cells in harvested PBSCs, the scores for granulocyte/macrophage colony forming units, or for malignant lymphoma and multiple myeloma patients evaluated as separate or combined cohorts. In addition, there were no significant differences in safety, side effects, complications, or the time to engraftment after autologous hematopoietic stem cell transplantation.

Conclusion

Biosimilar FBNK shows the same efficacy and safety as originator G-CSFs for facilitating bone marrow recovery in Japanese malignant lymphoma and multiple myeloma patients undergoing stem cell transplantation. In addition, it is less expensive than the originators, reducing hospitalization costs.

Single Versus Dual Platform Analysis for Hematopoietic Stem Cell Enumeration Using ISHAGE Protocol

Hematopoietic stem cell transplantation is curative therapy in benign and malignant diseases. Adequate stem cell dose is one of the most important marker of engraftment. Several methods have been developed to enumerate CD34+ cells. We present our data on 147 samples analysis. There was a clear linear correlation between two methods. Both methods were effective. Both single vs dual platform analysis yield similar results. Single platform analysis is easier to perform. In terms of cost reduction dual platform analysis is better.

Platelet Procoagulant Activity During,Peripheral Blood Stem Cell Harvest

We used flow cytometry to measure platelet-derived microparticle levels in plasma obtained from 16 patients during peripheral blood stem cell harvest (PBSC) and in platelet concentrates prepared by apheresis from 10 normal controls. We also studied the binding of an anti-P-selectin antibody and annexin-V to platelets. When all 60 harvests were assessed, we noted a significant difference in microparticle levels between patients with a platelet count >10 x 104/μl and those with a platelet count <10 X 104/μl (12.3 ± 4.4 vs. 75 ± 3.9%). In both the first and total harvests, the percentage of platelets and microparticles positive for anti-P-selectin and annexin-V were significantly higher than the normal control levels. These results suggest that patients undergoing mobilization by granulocyte colony-stimulating factor (G-CSF) who have a platelet count >10 X 104/μl are at risk of increased procoagulant activity after retransfusion following PBSC harvest. Key Words: Platelet-derived microparticle— Peripheral blood stem cell harvest—Granulocyte colony-stimulating factor.

Field evaluation in Chad of community usage of CD4 T lymphocyte counting by alternative single-platform flow cytometry

Background

Field and community evaluation of the routine usage of CD4 T counting platforms is essential in resource-poor countries for efficient and cost-effective monitoring of HIV-infected adults and children attending health care centers.

Methods

We herein addressed the principal issues raised by the implementation of the single-platform, volumetric Auto40 flow cytometer (Apogee Flow Systems Ltd, Hemel Hempstead, UK) in 8 community HIV monitoring laboratories of different levels throughout Chad. This is a country with particularly difficult conditions, both in terms of climate and vast geographical territory, making the decentralization of the therapeutic management of HIV-infected patients challenging.

Results

The routine usage of the Auto40 flow cytometers for a period of 5 years (2008–2013) confirms the reliability and robustness of the analyzer for community-based CD4 T cell enumeration in terms of both absolute numbers and percentages to enable accurate monitoring of HIV-infected adults and children. However, our observations suggest that the Auto40 mini flow cytometer is not suitable for all laboratories as it is oversized and ultimately very expensive.

Conclusion

The Chad experience with the Auto40 flow cytometer suggests that its usage in resource-limited settings should be mainly reserved to reference (level 1) or district (level 2) laboratories, rather than to laboratories of health care centres (level 3).

Single-platform, volumetric, CD45-assisted pan-leucogating flow cytometry for CD4 T lymphocytes monitoring of HIV infection according to the WHO recommendations for resource-constrained settings

Background

Validation of new affordable CD4 T cell measurement technologies is crucial specifically in resource-poor countries for antiretroviral treatment eligibility and immunologic CD4 monitoring of HIV-infected patients.

Methods

The absolute and percentage CD4 T cell counts of 258 HIV-1-infected blood samples (182 adults and 76 children), living in N’Djamena, Chad, were performed by single-platform, volumetric, CD45-assisted pan-leucogating Auto40 flow cytometer (Apogee Flow Systems Ltd, Hemel Hempstead, UK) comparing to the FACSCalibur flow cytometer as a reference method.

Results

Absolute and percentage CD4 T cell counts obtained by Auto40 and FACSCalibur of 258 HIV-1-infected blood samples were highly correlated (r = 0.99 and r = 0.96, respectively). The mean absolute bias and percent bias between Apogee Auto40 and FACSCalibur absolute CD4 T cell counts, were −9.4 cells/μl with limits of agreement from −15 to 93 cells/μl, and +2.0% with limits of agreement from −0.9 to 4.9%, respectively. The mean of absolute bias and percent bias between Apogee Auto40 and FACSCalibur of CD4 percentage results were +0.4% (95% CI: -0.02 – 0.86) with limits of agreement from −2.4 to 0.3%, and +3.0% with limits of agreement from −6.6 to 0.6%, respectively. The Auto40 counting allowed to identify the majority of adults with CD4 T cells below 200 cells/μl (sensitivity: 89%; specificity: 99%) or below 350 cells/μl (sensitivity: 94%; specificity:98%); and of children below 750 cells/μl (sensitivity: 99%; specificity: 96%) or below 25% CD4+ (sensitivity: 94%; specificity: 98%).

Conclusion

The Auto40 analyzer is an alternative flow cytometer for CD4 T lymphocyte enumeration to be used in routine for immunological monitoring according to the current WHO recommendations in HIV-infected adults as well as children living in resource-constrained settings like Chad.

Validation of a single-platform, volumetric, CD45-assisted PanLeucogating Auto40 flow cytometer to determine the absolute number and percentages of CD4 T cells in resource-constrained settings using Cameroonian patients' samples

The study evaluated the single-platform, volumetric, CD45-assisted PanLeucogating Auto40 flow cytometer (Apogee Flow Systems Ltd., Hemel Hempstead, United Kingdom) for CD4 T cell numeration, compared to the reference FACSCalibur flow cytometer. Results of absolute counts and percentages of CD4 T cells by Auto40 and FACSCalibur of 234 tripotassium EDTA (K3-EDTA)-blood samples from 146 adults and 88 children (aged from 18 months to 5 years), living in Yaoundé, Cameroon, were highly correlated (r(2) = 0.97 and r(2) = 0.98, respectively). The mean absolute bias and relative bias between Apogee Auto40 and FACSCalibur absolute CD4 T cell counts were +9.6 cells/μl, with limits of agreement from -251 to 270 cells/μl, and +4.1%, with limits of agreement from -16.1 to 24.4%, respectively. The mean absolute bias and relative bias between Apogee Auto40 and FACSCalibur CD4 T cell results expressed as percentages were +0.05% CD4 (95% confidence interval [CI], -0.03 to 0.41), with limits of agreement from -6.0 to 5.9% CD4, and +1.0%, with limits of agreement from -32.3 to 34.4%, respectively. The Auto40 counting allowed identification of the majority of adults with CD4 T cell counts below 200 cells/μl (sensitivity, 87%; specificity, 98%) or below 350 cells/μl (sensitivity, 92%; specificity, 98%) and of children with CD4 T cell counts below 750 cells/μl (sensitivity, 82%; specificity, 98%) or below 25% CD4(+) (sensitivity, 96%; specificity, 99%). The Auto40 analyzer is a reliable alternative flow cytometer for CD4 T lymphocyte enumeration to be used in routine immunological monitoring according to the WHO recommendations for HIV-infected adults as well as children living in resource-constrained settings.

Validation of a single-platform, volumetric, flow cytometry for CD4 T cell count monitoring in therapeutic mobile unit

Background

A mobile health unit may be useful to follow up adult and pediatric patients on antiretroviral treatment and living in remote areas devoid of laboratory facilities. The study evaluated the use of the simplified, robust, single-plateform, volumetric, pan-leucogating Auto40 flow cytometer (Apogee Flow Systems Ltd, Hemel Hempstead, UK) for CD4 T cell numeration in a mobile unit, compared against a reference flow cytometry method.

Methods

The therapeutic mobile unit of the Laboratoire National de Santé Hygiène Mobile, Yaoundé, Cameroon, was equipped with the Auto40. A FACSCalibur flow cytometer (Becton Dickinson Immuno-cytometry System, San Jose, CA, USA) was used as reference method. EDTA-blood samples from volunteers were first subjected to CD4 T cell count in the mobile unit, and an aliquot was sent within 4 hours to Centre International de Référence Chantal Biya, Yaoundé, for FACSCalibur assay.

Results

Two HIV screening campaigns with the mobile unit were organised in December 2009 and January 2010. The campaign in the suburb of Yaoundé which was 20 km from the reference laboratory included 188 volunteers comprising 93 children less than 5 years old. The campaign in Ambang Bikok (53 km far from Yaoundé) included 69 adult volunteers. In Yaoundé suburb, mean ± standard deviation (SD) CD4 T cell count was 996 ± 874 cells/μl by Auto40, and 989 ± 883 cells/μl by FACSCalibur; in Ambang Bikok, mean ± SD CD4 T cell count was 1041 ± 317 cells/μl by Auto40, and 1032 ± 294 cells/μl by FACSCalibur. Results by Auto40 and FACSCalibur were highly correlated in Yaoundé (r² = 0.982) as in Ambang Bikok (r² = 0.921). Bland-Altman analysis showed a close agreement between Auto40 and FACSCalibur results expressed in absolute count as in percentage in Yaoundé and Ambang Bikok. When pooling the 257 CD4 T cell count measurements, the Auto40 yielded a mean difference of +7.6 CD4 T cells/μl higher than by reference flow cytometry; and the sensitivity and specificity of Auto40 in enumerating absolute CD4 T cell counts of less than 200 cells/μl were 87% and 99%, respectively, and in enumerating absolute CD4 T cell counts of less than 350 cells/μl were 87% and 98%, respectively. The intrarun and interun precisions of the Auto40 assay assessed in the mobile unit were 5.5% and 7.9%, respectively.

Conclusions

The Auto40 flow cytometer installed in a therapeutic mobile unit and operated far from its reference laboratory gave a perfect correlation with the reference method, and could be useful in carrying out immunological monitoring of HIV-infected patients living in areas without access to laboratory facilities.

Evaluation of a flow cytometry method for CD4 T cell enumeration based on volumetric primary CD4 gating using thermoresistant reagents

Laboratory follow-up of HIV patients in resource-limited settings requires appropriate instruments for CD4 T cell enumeration. In this study, we evaluated the application of a simplified, mobile and robust flow cytometry system, the Apogee Auto 40 analyzer (Auto40) using thermoresistant reagents, for CD4 T cell enumeration. We measured the absolute CD4 counts in fresh whole blood samples from 170 Senegalese subjects, including 129 HIV-positive (HIV+) patients and 41 HIV-negative (HIV-) controls. Based on volumetric primary CD4 gating, cells were stained with commercially available reagents (Easy MoAb CD4;Bio-D, Valenzano, Italy) and analyzed on the Auto40. The results were compared with those from the FACSCount system (Becton Dickinson, San Jose, USA). Repeatability analysis was performed on duplicate testing of 49 samples on both FACSCount and Auto40. The intra-run precision was measured by 10 replicates using 3 clinical blood samples with low, intermediate and high CD4 concentrations. The results from the two instruments were in good agreement. The percent similarity between the results of both instruments was 99%±relative standard deviation of 12.7%. The concordance correlation coefficient was 0.99. The absolute bias and limits of agreement (LOA) between the two instruments, calculated by Bland-Altman analysis, were clinically acceptable (bias: +4 cells/μl; LOA: -111 to +120 cells/μl). The clinical agreement between the two instruments at a cutoff of 200 CD4 cells/μl was 94%. The repeatability of measurements on the Auto40 was also similar to that observed with FACSCount system (bias +0.1 cells/μl, coefficient of variation 2.5% vs bias -1.1cells/μl, coefficient of variation 2.9% respectively). In conclusion, our results indicate that the Auto 40 system, using thermoresistant reagents, is suitable for CD4 T cell enumeration and will be a helpful tool to improve HIV laboratory monitoring in resource-limited settings.

CD34+ Cell Enumeration by Flow Cytometry: A Comparison of Systems and Methodologies

Context.—An increasing number of medical centers can collect bone marrow, peripheral blood, or umbilical cord stem cells. Pathology laboratories should accommodate this trend, but investment in additional equipment may be impractical.

Objectives.—To compare CD34+ cell counting results by using 2 widely available flow cytometry systems, with and without the use of a separate hematology analyzer (ie, single-platform versus dual-platform methodologies).

Design.—Whole blood and peripheral blood stem cell (PBSC) samples were analyzed from 13 healthy allogeneic PBSC donors and 46 autologous PBSC donors with various malignancies. The Cytomics FC500 (Beckman Coulter, Fullerton, California) was compared with the FACSCalibur (BD Biosciences, San Jose, California). Dual-platform CD34+ cell counting incorporated data from a KX-21 hematology analyzer (Sysmex, Kobe, Japan).

Results.—Subtle differences in CD34+ cell counting between 2 systems and 2 methods did not achieve statistical significance.

Conclusion.—Different systems and methods for CD34+ cell enumeration, properly validated, can support care for patients undergoing transplants and provide meaningful data for multicenter studies or meta-analyses.

Enumeration of absolute cell counts using immunophenotypic techniques

Absolute counting of cells or cell subsets has a number of significant clinical applications: monitoring the disease status of HIV-infected patients, enumerating residual white blood cells in leukoreduced blood products, and assessing immunodeficiency in a variety of situations. The single-platform method (flow cytometry alone) has emerged as the method of choice for absolute cell enumeration. This technology counts only the cells of interest in a precisely determined blood volume. Exact cell identification is accomplished by a logical electronic gating algorithm capable of identifying lineage-specific immunofluorescent markers. Exclusion of unwanted cells is automatic. This extensive and detailed unit presents protocols for both volumetric and flow-rate determination of residual white blood cells and of leukocyte subsets.

A randomised trial of subcutaneous intermittent interleukin-2 without antiretroviral therapy in HIV-infected patients: the UK-Vanguard Study

Objective:

The objective of the trial was to evaluate in a pilot setting the safety and efficacy of interleukin-2 (IL-2) therapy when used without concomitant antiretroviral therapy as a treatment for HIV infection.

Design and Setting:

This was a multicentre randomised three-arm trial conducted between September 1998 and March 2001 at three clinical centres in the United Kingdom.

Participants:

Participants were 36 antiretroviral treatment naïve HIV-1-infected patients with baseline CD4 T lymphocyte counts of at least 350 cells/mm³.

Interventions:

Participants were randomly assigned to receive IL-2 at 15 million international units (MIU) per day (12 participants) or 9 MIU/day (12 participants) or no treatment (12 participants). IL-2 was administered by twice-daily subcutaneous injections for five consecutive days every 8 wk.

Outcome Measures:

Primary outcome was the change from baseline CD4 T lymphocyte count at 24 wk. Safety and plasma HIV RNA levels were also monitored every 4 wk through 24 wk. The two IL-2 dose groups were combined for the primary analysis.

Results:

Area under curve (AUC) for change in the mean CD4 T lymphocyte count through 24 wk was 129 cells/mm³ for those assigned IL-2 (both dose groups combined) and 13 cells/mm³ for control participants (95% CI for difference, 51.3–181.2 cells/mm³; p = 0.0009). Compared to the control group, significant increases in CD4 cell count were observed for both IL-2 dose groups: 104.2/mm³ (p = 0.008) and 128.4 cells/mm³ (p = 0.002) for the 4.5 and 7.5 MIU dose groups, respectively. There were no significant differences between the IL-2 (0.13 log₁₀ copies/ml) and control (0.09 log₁₀ copies/ml) groups for AUC of change in plasma HIV RNA over the 24-wk period of follow-up (95% CI for difference, −0.17 to 0.26; p = 0.70). Grade 4 and dose-limiting side effects were in keeping with those previously reported for IL-2 therapy.

Conclusions:

In participants with HIV infection and baseline CD4 T lymphocyte counts of at least 350 cells/mm³, intermittent subcutaneous IL-2 without concomitant antiretroviral therapy was well tolerated and produced significant increases in CD4 T lymphocyte counts and did not adversely affect plasma HIV RNA levels.

Background: There is very good trial evidence that combinations of antiretroviral drugs improve the prognosis of people with HIV infection. However, these drugs can have major side effects, and HIV can become resistant to them. The development of alternative treatments might allow antiretroviral use to be delayed in some people, thereby reducing toxicity and the emergence of resistant strains of HIV.

What this trial shows: The researchers studied 36 adult patients in the United Kingdom who were infected with HIV and who had not previously been prescribed antiretrovirals. Participants in the trial were given either one of two different dosage levels of IL-2 (a chemical messenger normally produced in the body by particular immune cells) by injection under the skin or no treatment at all. Patients given IL-2 at either dosage experienced an increase in levels of CD4 T lymphocytes, the type of immune cell depleted by HIV infection, as compared to patients receiving no treatment. The viral load in patients receiving IL-2 did not differ from that of patients in the control arm.

Strengths and limitations: The rationale for this trial—to delay administration of antiretroviral drugs—is sound, as is the experimental design. The results are limited, however, by the short follow-up of patients in the trial and by the lack of clinical endpoints (such as disease progression), so it is not possible to tell whether patients in the trial benefited directly from the IL-2 treatment.

Contribution to the evidence: The clinical effectiveness and safety of IL-2 together with antiretrovirals as a treatment for HIV infection is currently being evaluated in other, large-scale trials. To date, no other study has assessed the outcomes arising from administration of IL-2 alone. Data from the current trial will be useful in planning further research to examine whether IL-2 might help delay antiretrovirals in HIV-positive people.

A simplified flow cytometry method of CD4 and CD8 cell counting based on thermoresistant reagents: implications for large scale monitoring of HIV-infected patients in resource-limited settings

OBJECTIVE

To validate a simplified flow cytometry assay for CD4 and CD8 T cell counting based on monoclonal antibodies which are made resistant to high temperatures (simplified thermoresistant assay (STRA)).

METHOD

The STRA employs FITC-conjugated anti-CD4 and anti-CD8 monoclonal antibodies, predispensed into test tubes and chemically treated to be resistant to high temperatures. Five correlation studies were performed in three different laboratories on a total of 560 blood samples from HIV-1 infected patients. Each study correlated the STRA with either double or single platform assays currently available. Accelerated stability tests on the FITC-conjugated monoclonal antibodies were performed to assess the resistance of the STRA to high temperatures.

RESULTS

Comparison of STRA with both single platform and double platform assays gave correlation coefficients ranging 0.957-0.987 for CD4+ T cells and 0.946-0.968 for CD8+ T cells. In all correlation studies there was a perfect data overlapping in the low-pathological interval of CD4+ T cells (0-400 cells/ml). The FITC-conjugated CD4 and CD8 monoclonal antibodies maintained intact binding activity and fluorescence brightness after storage for 4 weeks at 45 degrees C and can be stored for up to 8 years in regular conditions (+4 degrees C).

CONCLUSIONS

The STRA correlates well with both single-platform and double-platform flow-cytometry assays currently used to assess CD4+ T cells. The test procedure is simple, rapid, and easy to perform. The reagents can be stored under unfavorable environmental conditions for long period of time. These features should facilitate access to flow cytometry testing in resource-poor settings.

Identification of compounds that enhance the anti-lymphoma activity of rituximab using flow cytometric high-content screening

In this report, we describe a new flow cytometry technique termed flow cytometric high-content screening (FC-HCS) which involves semi-automated processing and analysis of multiparameter flow cytometry samples. As a first test of the FC-HCS technique, we used it to screen a 2000-compound library, called the National Cancer Institute (NCI) Diversity Set, to identify agents that would enhance the anti-lymphoma activity of the therapeutic monoclonal antibody rituximab. FC-HCS identified 15 compounds from the Diversity Set that significantly enhanced the ability of rituximab to inhibit cell cycle progression and induce apoptosis in lymphoma cells. The validity of the screening results was confirmed for several compounds using additional assays of cell proliferation, apoptosis and cell growth. The FC-HCS technique was relatively simple and reliable and could process up to 1000 samples/day on a single flow cytometer. The FC-HCS technique may be useful for a variety of applications including drug discovery, immunologic monitoring of patients, functional genomics studies and tissue engineering efforts.

Elevation of Platelet Activation Markers and Chemokines during Peripheral Blood Stem Cell Harvest with G-CSF

The kinetics of peripheral blood stem cell mobilization in response to recombinant human granulocyte colony-stimulating factor is well established. However, there have been few investigations of platelet activation markers during peripheral blood stem cell harvest. We measured the levels of the platelet activation markers, chemokines, and soluble factors in plasma obtained from patients undergoing peripheral blood stem cell harvest. The number of leukocytes, CD34+ cells, neutrophils, monocytes, and lymphocytes peaked on day 5 after granulocyte colony-stimulating factor treatment, but the numbers of eosinophils and basophils showed no significant change. Regulated on activation normally T-cell expressed and secreted (RANTES) level increased through day 10, and the monocyte chemotactic peptide-1 (MCP-1) level peaked on day 5. Platelet counts continued to increase through day 10. The level of thrombopoietin significantly increased on day 3, peaked on day 5, and decreased slightly by day 10. The levels of soluble CD40 ligand and soluble P-selectin increased up to day 5. The platelet-derived microparticle level peaked on day 5, and then began to decline. CD34+ cell numbers significantly correlated with those of leucocytes, neutrophils, monocytes, and lymphocytes, as well as levels of MCP-1, and the CD34+ cells exhibited changes similar to platelet-derived microparticles. The patterns of change in MCP-1, platelet-derived microparticles, and the CD34+ cell count are similar in that each peaks on day 5 and decreases thereafter. Further study is required to determine if a cause-and-effect relationship in their pattern of change exists among them.

The effect of extracorporeal photopheresis on intracellular cytokine expression in chronic cutaneous graft-versus-host disease

BACKGROUND

Cytokines derived from T helper (Th)1 lymphocytes are thought to be involved in the pathogenesis of graft-versus-host disease (GVHD) and extracorporeal photopheresis (ECP) has been reported to affect Th1/Th2 lymphocyte ratios. It may also influence the balance of cytotoxic Tcells (Tc1/Tc2).

OBJECTIVES

This study was formulated to assess the effect of ECP on the cytokine profiles of peripheral blood (PB) lymphocytes from patients with chronic GVHD.

PATIENTS AND METHODS

Nine patients were studied. Peripheral blood was sampled at baseline and between 3 and 4 months of therapy when clinical effects are demonstrable. Intracellular cytokine production was assessed in vitro by stimulating PB lymphocytes with phorbol-12-myristate 13-acetate (PMA), inhibiting cytokine release and staining with fluorescein-labelled monoclonal antibodies to interleukin (IL)-2, interferon gamma (IFN-gamma) and IL-4. Flow cytometry analysis gave the absolute number and the percentage of cells expressing a particular cytokine within each lymphocyte subset.

RESULTS

Absolute counts of CD3, CD4, CD8, CD19 and CD16+ cells per microlitre were recorded before and after ECP. There was a small but non-significant reduction in all subsets after 3 months of ECP. The percentage of cells expressing IL-2 and IFN-gamma rose following ECP in both the CD4 and CD8 subsets. However, only the percentage of CD4 cells expressing IFN-gamma reached statistical significance (P = 0.02; 95% confidence interval, CI 0.6-15.6). There were no significant changes in the percentage of CD4 cells expressing IL-4.

CONCLUSIONS

Our findings appear to be inconsistent with current theories regarding the pathogenesis of GVHD as increased production of Th1 or Tc1 cytokines might be expected to exacerbate GVHD. However, chronic GVHD is characterized by a relative deficiency of IL-2 and IFN-gamma producing cells compared with other patients post-bone marrow transplantation (BMT). This indicates that Th1 and Tc1 cytokines are depleted in chronic GVHD. Thus, by reducing disease activity, ECP could allow cytokine production by these cells to recover. This indicates that the therapeutic effect of ECP is mediated by a different mechanism, and that the changes observed in this study are epiphenomena.

Optimal gating strategies for determining bronchoalveolar lavage CD4/CD8 lymphocyte ratios by flow cytometry

Alterations in bronchoalveolar lavage (BAL) CD4/CD8 T cell subset ratios have been demonstrated in a variety of different respiratory disorders and the measurement of these changes may be diagnostically helpful. Flow cytometry (FCM) is a precise technology that offers many advantages over conventional cytospin techniques to determine T cell subset ratios in tissue fluids such as BAL. However, the optimum gating strategies for evaluating these parameters by FCM have not been evaluated. Here, the CD4/CD8 ratios in 33 BAL samples were compared using three different methods by FCM with two different flow cytometers. Bland Altman analysis demonstrated clinically insignificant differences between two simplified staining and gating strategies and a more complex "gold standard" method. These findings confirm the precision of FCM for BAL T cell subset ratio analysis and suggest that the optimal gating strategy may be a simple panel using only CD45, CD4 and CD8.

24. Clinical and laboratory assessment of immunity

Clinicians order specific laboratory tests and interpret laboratory data that will be useful in establishing a diagnosis of immunodeficiency, either inherited (primary) immunodeficiencies or acquired (secondary) immunodeficiencies. The clinical immunologic evaluation of patients for immunodeficiency proceeds in an orderly fashion, from screening tests to sophisticated tests. The medical history and physical examination of the patient frequently provide clues guiding the level of entry into this testing program. Specific tests have been designed to screen for the four basic mechanisms of host defense: Antibody, T cell, phagocyte, and complement. The clinical immunology laboratory is a powerful adjunct to the clinician in the initial evaluation of immunodeficiency disorders and in the design of more sophisticated testing for selected patients.

Comparison of single- and dual-platform approaches to enumerate CD34(+) cells in bone marrow and mobilized peripheral blood stem cells

BACKGROUND

Different flow cytometric methods have been developed to derive absolute CD34(+) cells in predicting transplant outcome. Two techniques for preparing cells for quantification of CD34(+) cells were compared.

METHODS

Enumeration of CD34(+) cells in 16 samples of bone marrow (BM) and in 29 samples of mobilized peripheral blood stem cells (PBSC) obtained by leukapheresis was assessed simultaneously by single-platform (ProCOUNT kit) and dual-platform (Milan protocol) approaches within the first 3 h of collection.

RESULTS

Absolute number of CD34(+) cells obtained in PBSC and BM using single- and dual-platform methods showed high determination coefficients as follows: for PBSC, slope = 1.0515 +/- 0.048, y-intercept = 88.638 +/- 52.45, and r(2) = 0.941, and for BM, slope = 1.0203 +/- 0.093, y-intercept = 122.25 +/- 20.65, and r(2) = 0.878. There were no statistically significant differences in absolute number of CD34(+) cells from PBSC between single-platform (mean 575/microL, range 70-3683/microL) and dual-platform (786/microL, range 51-3804/microL) assays. In contrast, absolute number of CD34(+) cells from BM was significantly lower (p = 0.0002) when enumerated by ProCount kit (135/microL, 14-758/microL) than with dual-platform method (260/microL, 74-889/microL).

CONCLUSIONS

Both approaches can be used indistinctly to estimate absolute number of CD34(+) cells in PBSC but not in BM.

Affordable CD4(+)-T-cell counting by flow cytometry: CD45 gating for volumetric analysis

The flow cytometers that are currently supported by industry provide accurate CD4(+)-T-cell counts for monitoring human immunodeficiency virus disease but remain unaffordable for routine service work under resource-poor conditions. We therefore combined volumetric flow cytometry (measuring absolute lymphocyte counts in unit volumes of blood) and simpler protocols with generic monoclonal antibodies (MAbs) to increase cost efficiency. Volumetric absolute counts were generated using CD45/CD4 and CD45/CD8 MAb combinations in two parallel tubes. The percentage values for the various subsets were also determined within the leukocyte and lymphocyte populations utilizing a fully automated protocol. The levels of agreement between the newly developed method and the present industry standards, including both volumetric and bead-based systems using a full MAb panel for subset analysis, were tested by Bland-Altman analyses. The limits of agreement for CD4 counts generated by the volumetric methods using either CD45/CD4 (in a single tube) or the full Trio MAb panel (in three tubes) on the CytoronAbsolute flow cytometer were between -29 and +46 cells/mm(3) with very little bias for CD4 counts (in favor of the Trio method: +8 CD4(+) lymphocytes/mm(3); 0.38% of lymphocytes). The limits of agreement for absolute CD4 counts yielded by the volumetric CD45/CD4 method and the bead-based method were between -118 and +98 cells/mm(3), again with a negligible bias (-10 CD4(+) lymphocytes/mm(3)). In the volumetric method using CD45/CD8, the strongly CD8(+) cells were gated and the levels of agreement with the full Trio showed a minor bias (in favor of the Trio; +40 CD8(+) cells/mm(3); 5.2% of lymphocytes) without a significant influence on CD4/CD8 ratios. One trained flow cytometrist was able to process 300 to 400 stained tubes per day. This workload extrapolates to a throughput of >30,000 samples per year if both CD45/CD4 and CD45/CD8 stainings are performed for each patient or a throughput of >60,000 samples if only CD45/CD4 counts are tested in a single tube. Thus, on the basis of the high efficiency and excellent agreement with the present industry standards, volumetric flow cytometers with automated gating protocols and autobiosamplers, complemented by generic CD45, CD4, and CD8 MAbs used in two-color immunofluorescence, represent the most suitable arrangements for large regional laboratories in resource-poor settings.

Precise CD4 T-cell counting using red diode laser excitation: for richer, for poorer

BACKGROUND

Measuring CD4 T-cell counts at low cost is relevant in dealing with the human immunodeficiency virus (HIV) epidemic throughout the developing world. The recently introduced novel concepts in gating strategies and sample stabilization facilitate affordable immunophenotyping by flow cytometry. However, the impact of these developments is still limited by the high cost of currently available flow cytometers.

METHODS

Diode lasers emitting 10-15 mW at 635 nm are one-tenth the size and cost and require one thousandth the power of an equivalent 488-nm argon ion laser. We used the available 635-nm diode-based flow cytometers, including PA-II, Luminex 100, SuperMot, and FACSCalibur, to investigate whether these instruments can generate reliable CD4 counts when used with allophycocyanin (APC) and cyanin-5 (Cy5)-labeled CD4 antibodies.

RESULTS

We document the feasibility of obtaining leucocyte differential counts using orthogonal side scatter (SSC) without the need for forward scatter (FSC). Accurate CD4% values among lymphocytes and leucocytes can be obtained by primary CD4 gating using a single CD4 monoclonal antibody conjugated to APC or Cy5. Double immunofluorescence (IF) staining with CD4-APC (FL1) and CD45-APC-Cy7 (FL2) introduces pan-leucogating for a convenient assessment of absolute CD4 counts on double platforms. We demonstrate that small flow cytometers with laser diodes are capable of delivering absolute CD4 T-cell counts with a precision similar to the performance of the current state-of-the-art single-platform instruments (e.g., the CytoronAbsolute; R(2) = 0.961). In this respect, they appear to be superior to the nonflow CD4 counting techniques.

CONCLUSIONS

Accurate CD4 counts can be generated at minimal cost on red diode laser-operated flow cytometers, retaining the potential for high throughput capacity without compromising precision. With further improvements in volumetric technology and clinical software, these cytometers may develop into a new generation of inexpensive battery-operated laboratory hardware that combines cellular phenotyping with bead-based multiplexing immunoassays for (HIV) serology.

Evaluation of a universal template for single-platform absolute T-lymphocyte subset enumeration

The single-platform absolute T-lymphocyte subset analysis was evaluated utilizing a universal protocol in a Canadian multicenter study with the collaboration of the members of the Canadian HIV Trials Network (CTN). Participants used flow cytometers and reagents of their choice for labeling and lysing whole blood. Over a 2-year period, CTN laboratories performed single-platform absolute T-lymphocyte subset enumerations on fresh and commercial stabilized blood products using commercially available microfluorospheres TruCount and Flow-Count. This multicenter evaluation demonstrated that the application of a universal template for single-platform analysis provides a generic approach that embraces a wide array of immunophenotyping settings available in clinical laboratory.

CD45-assisted PanLeucogating for accurate, cost-effective dual-platform CD4+ T-cell enumeration

BACKGROUND

North American and European guidelines for dual-platform (DP) flow cytometry recommend absolute CD4 T-cell counts to be calculated from two parameters: the absolute lymphocyte counts obtained on a hematology analyzer and the percentages of CD4+ cells among lymphocytes (CD4%/lympho) obtained by flow cytometry. Nevertheless, the identification of lymphocytes is error-prone: a poor match between these common denominators in the two systems is the main source of inaccuracy. In contrast, total leucocyte counts (white cell counts [WCC]) and CD4% among the gated CD45+ leucocytes (CD4%/leuco) can be determined with greater accuracy.

METHODS

We introduced "PanLeucogating," i.e., we used total leucocytes as the common denominator for improving the precision of DP absolute CD4 counting. Correlations and Bland-Altman tests were used for statistical analysis.

RESULTS

First, 22 stabilized blood product samples were provided by U.K. National External Quality Assessment Scheme (NEQAS) and a higher accuracy and precision of CD4 counts were documented using PanLeucogating compared with lymphocyte gating. Next, 183 fresh and 112 fixed (TransFix) whole blood samples were used to compare DP methods and single-platform (SP) methodology, including both volumetric and bead-based techniques. A particularly high correlation and comparable precision of absolute CD4 counts were observed between the SP volumetric method and DP PanLeucogating (R(2) = 0.990; bias 6 +/- SD 17%). The SP volumetric method showed lower levels of agreement with the DP lymphocyte gating (R(2) = 0.758; bias 14 +/- SD 51%) and with the SP bead-based method (R(2) = 0.923; bias 4 +/-SD 31%).

CONCLUSIONS

These observations show that DP leucocyte counts (WCC) should replace lymphocyte counts as the "common denominator" although CD4%/lympho values can, as an extra step, be also provided readily if requested. When coupled with quality control for WCC on hematology analyzers, the DP method with CD45 PanLeucogating represents a robust CD4 T-cell assay that is as accurate as the SP volumetric technique. This DP method uses only two, CD45 and CD4, antibody reagents and can be run on any pair of hematological analyzer plus flow cytometer.

Parallel decline of CD8+/CD38++ T cells and viraemia in response to quadruple highly active antiretroviral therapy in primary HIV infection

OBJECTIVES

To monitor changes in the numbers of CD8 lymphocytes expressing the activated CD38++ phenotype in peripheral blood samples from patients with primary HIV infection (PHI) treated with highly active antiretroviral therapy (HAART).

METHODS

Zidovudine, lamivudine, abacavir and amprenavir were initiated during PHI as part of the Quest study. Absolute numbers of CD8+/CD38++ T cells were determined using three-colour flow cytometry, and plasma viral load (VL) was measured using the Roche Amplicor method.

RESULTS

The median, pre-therapy CD8+/CD38++ T cell count was 461/mm(3)(interquartile range 216, 974) in 131 patients compared with normal control values of less than 20 cells/mm(3). Levels fell markedly in parallel with VL within the first 2 weeks of HAART initiation, to a median of 47 cells/mm(3) at 28 weeks (median 436 cell decline; P < 0.001). At that time, 80% of patients had a VL less than 50 copies/ml, and 16.3% of all patients had less than 20 CD8+/CD38++ T cells/mm(3). A continued decrease in CD8+/CD38++ T cell count occurred in 67.2% of patients whose VL was maintained below 50 copies/ml (median change from first to last value -18 cells/mm(3); P < 0.001).

CONCLUSION

After the initiation of HAART in PHI, CD8+/CD38++ lymphocytes declined rapidly in parallel with VL, and allowed for a normalization of CD8+/CD38++ T cell numbers in a subset of patients at week 28. Cell numbers continued to decline in patients who maintained VL below 50 copies/ml, indicating that the CD8+/CD38++ T cell count may represent a marker of residual viral replication when VL falls below detectable levels after HAART intervention.

Affordable CD4+ T cell counts by flow cytometry. II. The use of fixed whole blood in resource-poor settings

We tested the feasibility and precision of affordable CD4+ T cell counting in resource-poor settings using a recently standardised fixative, TransFix in whole blood (WB) by flow cytometry (FCM). The precision of the assays was established under optimal conditions for single-platform FCM such as the volumetric CytoronAbsolute and the bead-based FACSCan. Fresh WB samples from HIV-seropositive and seronegative patients were tested in Tanzania and South Africa, fixed and sent to the UK for reanalysis 7 days later. Correlation, bias and limits of agreements were analysed by linear regression and the Bland-Altman test. Absolute CD4+ T cell counts remained stable for at least 10 days when TransFix was added to WB in 1:10 dilution at 20-25 degrees C, and for 7 days when added in 1:10 or 1:5 dilution to samples stored to mimic 'tropical' conditions at 37 degrees C. Higher temperatures such as 42 degrees C were tolerated for only short periods since the recovery had decreased to 63% by day 3. The reproducibility of lymphocyte subset analysis remained unchanged by TransFix with coefficient of variations <6% for all T cell subsets. Absolute CD4+ T cell counts and CD4+ T cell % values on fixed samples in the UK showed a high correlation with the results using fresh samples in Tanzania (r=0.993 and 0.969, respectively) and with the samples handled in Johannesburg (r=0.991 and 0.981) with minimal bias. Primary CD4 gating using only a single CD4 antibody also remained accurate in TransFixed samples (r=0.999). Thus, TransFix permits optimal fixation and transport of WB samples in the developing world for FCM to local regional laboratories and for quality assurance in international centres. When used together with inexpensive primary CD4 gating, TransFix will allow reliable and affordable CD4+ T cell counting by FCM in resource-poor settings.

Molecular correlates in AIDS patients following antiretroviral therapy: diversified T-cell receptor repertoires and in vivo control of cytomegalovirus replication

OBJECTIVES

To evaluate whether successful, long-term immune reconstitution in vivo can be achieved in end-stage AIDS patients following antiretroviral therapy (ART).

METHODS

A 1-year prospective study of changes of CD4+ and CD8+ T-cell surface phenotypes, T-cell receptor (TCR) repertoires and capacity to control in vivo replication of cytomegalovirus (CMV) was performed in five treatment-naive end-stage AIDS patients (median CD4+ T-cell counts of 19 cells/microL) following therapy. Proportions of CD45RA+, CD45RO+ and CD28+ cells within the CD4+ and CD8+ subsets, were determined by flow cytometry. Changes in TCR Vbeta repertoires within the CD4+ and CD8+ T-cell compartments were evaluated using CDR3 spectratyping. CMV replication was determined by a sensitive polymerase chain reaction (PCR) assay using whole blood.

RESULTS

Following ART, proportionate increases in 'naive' (CD45RA+) and 'memory' (CD45RO+) T cells were observed within both CD4+ and CD8+ T-cell subsets, while increased numbers of CD28+ T cells were mainly observed within the CD4+ subset. Diversification of CD4+ and CD8+ TCR repertoires was established concomitantly with renewed in vivo control of CMV replication.

CONCLUSIONS

An important degree of molecular and functional immune recovery is possible in end-stage AIDS patients introduced to therapy. Diversification of TCR repertoires and the in vivo restoration of immunocompetence to control opportunistic infections clearly show that an important degree of molecular immune reconstitution is established following the initiation of ART even in late-stage AIDS.

Cytofluorometric methods for assessing absolute numbers of cell subsets in blood. European Working Group on Clinical Cell Analysis

The enumeration of absolute levels of cells and their subsets in clinical samples is of primary importance in human immunodeficiency virus (HIV)+ individuals (CD4+ T- lymphocyte enumeration), in patients who are candidates for autotransplantation (CD34+ hematopoietic progenitor cells), and in evaluating leukoreduced blood products (residual white blood cells). These measurements share a number of technical options, namely, single- or multiple-color cell staining and logical gating strategies. These can be accomplished using single- or dual-platform counting technologies employing cytometric methods. Dual-platform counting technologies couple the percentage of positive cell subsets obtained by cytometry and the absolute cell count obtained by automated hematology analyzers to derive the absolute value of such subsets. Despite having many conceptual and technical limitations, this approach is traditionally considered as the reference method for absolute cell count enumeration. As a result, the development of single-platform technologies has recently attracted attention with several different technical approaches now being readily available. These single-platform approaches have less sources of variability. A number of reports clearly demonstrate that they provide better coefficients of variation (CVs) in multicenter studies and a lower chance to generate aberrant results. These methods are therefore candidates for the new gold standard for absolute cell assessments. The currently available technical options are discussed in this review together with the results of some cross-comparative studies. Each analytical system has its own specific requirements as far as the dispensing precision steps are concerned. The importance of precision reverse pipetting is emphasized. Issues still under development include the establishment of the critical error ranges, which are different in each test setting, and the applicability of simplified low-cost techniques to be used in countries with limited resources.

Affordable CD4(+) T-cell counts on 'single-platform' flow cytometers I. Primary CD4 gating

Here, we demonstrate the flow cytometric concept of 'primary CD4 gating' utilizing three different CD4 monoclonal antibodies (mAbs) conjugated with five different fluorochromes. CD4(+) lymphocytes were defined by an autogate in a single histogram of CD4 fluorescence intensity (FI) (y-axis) vs. side light scatter (x-axis). A wide range of absolute counts for > 600 individuals, including HIV(+) patients, were compared with those obtained by 'state-of-the-art' single-platform flow cytometers such as the volumetric Ortho CytoronAbsolute and the Becton Dickinson FACSCalibur using TruCount beads. The correlation between CD4 counts obtained with primary CD4 gating and the full test panel on the Ortho Cytoron was excellent (R(2) = 0.999). Bland-Altman statistics showed a mean difference of -2 cells/mm(3) [confidence interval (CI) 95% = -3 to -1; limits of agreement -27 to +23]. In addition to absolute CD4 counts, CD4% values and CD4/CD8 ratios are also frequently requested. To obtain these, lymphocytes need to be counted using scatter gates, and a second tube stained with a CD8 mAb to count CD8(++) lymphocytes can be incorporated. We conclude that primary CD4 gating on single-platform volumetric flow cytometers is one of the most economical and flexible technologies for routine cost-conscious service work, particularly during the follow-up of patients undergoing anti-HIV therapy and/or vaccination in the developing world.

Changes in CD4 lymphocyte counts after interruption of therapy in patients with viral failure on protease inhibitor-containing regimens. Royal Free Centre for HIV Medicine

OBJECTIVE

To describe the short-term changes in CD4 lymphocyte counts after the interruption of antiretroviral HIV therapy in order to increase the understanding of CD4 lymphocyte dynamics, and so that appropriate monitoring strategies can be designed.

METHODS

We studied 35 HIV-infected patients with late-stage disease who had therapy interruptions leading to high viral load levels, median greater than 750 000 RNA log10 copies/ml, and in whom two CD4 cell counts (median 28 days apart) were available before beginning a salvage regimen.

RESULTS

Overall, there was a substantial decline in CD4 cell counts from a median of 125 to 83 cells/mm3 in the average 28 day period, with median proportionate and absolute losses of 26% and 24 cells/mm3 per month, respectively (P < 0.008). This tended to be greater in individuals studied sooner after interrupting therapy (P = 0.03) and in those with CD4 cell counts above the pre-therapy baseline (P = 0.06). There was a strong negative correlation between the proportionate increase in viral load and the absolute change in CD4 cell count (-0.66, P = 0.0002).

CONCLUSION

Patients with relatively advanced HIV infection interrupting antiretroviral therapy after failing a protease inhibitor-containing regimen require frequent monitoring because CD4 cell counts appear to fall quite rapidly, at least in the first few weeks after interruption.

Reduction of intra- and interlaboratory variation in CD34+ stem cell enumeration using stable test material, standard protocols and targeted training. DK34 Task Force of the European Working Group of Clinical Cell Analysis (EWGCCA)

The European Working Group on Clinical Cell Analysis (EWGCCA) has, in preparation for a multicentre peripheral blood stem cell clinical trial, developed a single-platform flow cytometric protocol for the enumeration of CD34+ stem cells. Using this protocol, stabilized blood and targeted training, the EWGCCA have attempted to standardize CD34+ stem cell enumeration across 24 clinical sites. Results were directly compared with participants in the UK National External Quality Assessment Scheme (NEQAS) for CD34+ Stem Cell Quantification that analysed the same specimens using non-standardized methods. Two bead-counting systems, Flow-Count and TruCount, were also evaluated by the EWGCCA participants during trials 2 and 3. Using Flow-Count, the intralaboratory coefficient of variation (CV) was </= 5% in 39% of the laboratories (trial 1), increasing to 65% by trial 3. Interlaboratory variation was reduced from 23.3% (trial 1) to 10.8% in trial 3. In trial 2, 70% of laboratories achieved an intralaboratory CV </= 5% using TruCount, increasing to 74% for trial 3; the interlaboratory CV was reduced from 23.4% to 9.5%. Comparative analysis of the EWGCCA and the UK NEQAS cohorts revealed that EWGCCA laboratories, using the standardized approach, had lower interlaboratory variation. Thus, the use of a common standardized protocol and targeted training significantly reduced intra- and interlaboratory CD34+ cell count variation.

Course of viral load throughout HIV-1 infection

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

Absolute CD4+ T-lymphocyte and CD34+ stem cell counts by single-platform flow cytometry: the way forward

To determine the potential advantage of single-platform technology in the enumeration of CD4+ T lymphocyte and CD34+ stem cells, data has been analysed from the UK NEQAS for Leucocyte Immunophenotyping schemes. The inter-laboratory CVs for CD4+ T lymphocyte counts were consistently lower for single-platform (mean 13.7%, range 10-18.3%) compared to dual-platform methodology (mean 23.4%, range 14.5-43.7%). Subgroup analysis of single-platform users demonstrated mean overall inter-laboratory CVs of 17.2%, 13% and 7.1% for the FlowCount, TruCount and volumetric approach respectively. The lowest inter-laboratory CVs obtained for a single sample by each single platform approach were 4% (TruCount), 4.4% (volumetric), 4.6% (FACSCount) and 12.7% (FlowCount). Similarly, the mean inter-laboratory CV for CD34+ stem cell enumeration using non-standardized single-platform approaches was 18.6% (range 3.1-36.9%) compared to 28.6% (range 19-44.2%) for the dual-platform technology. Our results suggest absolute cell subset enumeration should be performed by single-platform technology and that such an approach should improve the quality control of multi-centre clinical trial data for CD4+ T lymphocyte and CD34+ stem cells.

Immune markers and viral load after HIV-1 seroconversion as predictors of disease progression in a cohort of haemophilic men

OBJECTIVE

To assess the prognostic value of HIV RNA levels measured shortly after HIV seroconversion and whether markers of immune response (CD4+ and CD8+ T-cell counts, IgA and IgG) measured at the same time, continue to provide prognostic information once the HIV RNA level is known.

DESIGN AND METHODS

HIV RNA levels were measured approximately 2.5 years after seroconversion in 97 haemophilic men followed for up to 17 years. Levels of CD4+ and CD8+ T cells, IgA and IgG were measured within 1 year of the HIV RNA level. The relationships between these markers and progression to AIDS and death were studied using Kaplan-Meier plots and proportional hazards regression models.

RESULTS

High HIV RNA levels were associated with faster progression to AIDS and shorter survival in univariate Cox regression models. High IgA and IgG levels were also associated with faster disease progression. In multivariate models, high HIV RNA levels remained independently associated with faster disease progression [relative hazard (RH), 1.86; P = 0.01 for AIDS; RH, 1.66; P = 0.05 for death). However, high IgA and IgG levels provided strong independent prognostic information for AIDS and death (IgA: RH, 1.38; P = 0.006 for AIDS; RH, 1.33; P = 0.07 for death; IgG: RH, 1.10; P = 0.02 for AIDS; RH, 1.12; P = 0.01 for death).

CONCLUSIONS

Our results confirm the importance of the HIV RNA level in assessing the long-term prognosis in individuals infected with HIV. However, our results suggest that immune activation markers, rather than merely reflecting high HIV RNA levels are important in assessing prognosis in their own right. These findings may improve our understanding of HIV pathogenesis and may aid clinical management of patients.

Quality assessment of CD34+ stem cell enumeration: experience of the United Kingdom National External Quality Assessment Scheme (UK NEQAS) using a unique stable whole blood preparation

CD34+ peripheral blood stem cell (PBSC) mobilization and harvesting has rapidly replaced autologous bone marrow as a source of stem cells for transplantation. Timing and adequacy of harvests rely upon the accurate enumeration of circulating CD34+ cells. However, previous EQA programmes have reported interlaboratory CVs as high as 284%, suggesting the need for greater standardization. In addition the routine use of fresh and/or frozen cells as analytes also introduces antigen instability as a variable factor. To circumvent this problem and achieve a true reflection of interlaboratory variation, we have used a novel whole blood preparation in which the antigenic profiles of PBSCs, as determined by flow cytometry, are retained for > 200 d. This international scheme, currently the largest in the world, distributes aliquots of stabilized whole blood bi-monthly to 91 laboratories in 20 countries (44 U.K., 47 overseas). Participants are required to determine the percentage and absolute values for CD34+ PBSCs using in-house techniques. Adopting such a preparation, a more accurate determination of interlaboratory variation has been possible when compared to previous EQA studies, with CVs as low as 22% and 24% for percentage and absolute counts. In addition the programme has established that a wide range of methods are in routine use, emphasizing the urgent requirement for national/international consensus guidelines.

Absolute CD4 counts obtained by a three-color flow-cytometric method without the use of a hematology analyzer

We evaluated the Ortho TRIO-Cytoronabsolute system for determining absolute CD4 counts. The CD4 counts in our blood specimens from 100 individuals ranged from 3 to 1,962; the percent CD4 ranged from 1.3 to 62.2, respectively. The TRIO system was biased toward lower absolute counts than a combination of flow cytometry and hematology but showed no bias in percent CD4 calculations.

The Italian quality control study for evaluation of CD4 cells in centres involved in the treatment of HIV-1 patients. Italian CD4 Quality Control Group

We report on the experience of establishing a national network for a quality control programme in evaluating CD4 cell counts in most Italian centres involved in the care of patients with HIV disease. The 68 centres were divided according to their geographical location into eight groups, and twice a year (tests A and B) they received three coded whole blood samples (two were replicates of the same sample) obtained from two informed HIV+ patients, one with CD4 counts/mm3 expected to be < 200 and one with values > 300. The medians of the determinations performed by the labs involved in each of the eight areas were taken as the 'true' values for each sample. Unsatisfactory performances for percentage of CD4 cells were identified as a CD4 analysis with residual values > or = +/- 5% and with deviates > or = +/- 2. For absolute numbers of CD4 cells, an unsatisfactory performance was defined as CD4 counts with residual > +/- 100 CD4 cells/mm3 and with deviates > or = +/- 2. The residual value is the CD4 value reported by each lab minus the median value. The deviate is the residual divided by the modified interquartile range (IQR x 0.75). Most of the centres provided reliable results. However, some labs failed to provide satisfactory results for percentages (6.25% of the tested labs for test A and 6.17% for test B) or absolute numbers (16.25% test A and 12.34% test B). Only 3.7% of the labs gave unsatisfactory results in both tests. Four of the unsatisfactory results from the two tests gave an error in absolute numbers > +/- 200 CD4 cells/mm3. Our data suggest that most Italian labs provide reliable results in evaluating the numbers of CD4 cells in HIV-1+ samples, but the importance of running a quality control programme is highlighted by our experience with those centres which provide unsatisfactory data which may lead to incorrect classification of the patients or assessment of treatment.

Mobilization of CD34+ cells by glycosylated and nonglycosylated G-CSF in healthy volunteers--a comparative study

In vitro studies indicate that lenograstim (glycosylated G-CSF) is more potent than filgrastim (nonglycosylated G-CSF) on a weight for weight basis. However, such a difference has not yet been shown in vivo. The primary objective of this trial was to compare the efficacy of equivalent doses (microgram) of lenograstim and filgrastim in mobilizing CD34+ cells. Thirty-two healthy male volunteers, median age 27 yr (19-44 yr), were randomized to receive either lenograstim 10 micrograms/kg followed by filgrastim 10 micrograms/kg or vice versa with a washout period of a minimum 4 wk. Both drugs were administered as s.c. injections once daily for 5 d (d 1-5). CD34+ cells were mobilized with a similar kinetics, peaking at median d 6 (5-6) for both drugs. A significant difference in favour of lenograstim was shown for peak number of CD34+ cells/microliter blood (104 +/- 38 vs. 82 +/- 35, mean +/- 1 SD, p < 0.0001, paired t-test, n = 30) and number of CFU-GM/microliter blood at d 6 (14.6 +/- 8.4 vs. 10.2 +/- 4.6, p < 0.0001), respectively. There was no difference in the d 6 number of CD3+ cells. Both drugs were generally well tolerated and did not differ with respect to number of adverse events. In conclusion, lenograstim 10 micrograms/kg/d mobilizes PBPC more efficiently than the identical dose of filgrastim, indicating a difference in in vivo potency between the two G-CSFs.

Evaluation of a method for counting absolute numbers of cells with a flow cytometer

We evaluated a method for performing absolute cell counts of lymphocyte populations with a flow cytometer. In this method, TruCount, test tubes that contain a known number of brightly fluorescent polystyrene beads are provided by the manufacturer. Whole anticoagulated blood is accurately pipetted into the tubes and mixed with fluorochrome-labeled monoclonal antibodies, the erythrocytes are lysed, and this mixture is analyzed on the flow cytometer. Absolute counts of lymphocyte subsets are calculated by determining the ratio of beads to the cell population of interest and then multiplying this ratio by the number of beads in the tube. We found this method to be reproducible. The values we obtained by the TruCount method were 5 to 10% higher than those obtained by conventional methods (flow cytometry and automated hematology) used to determine absolute numbers of cells. We believe that these differences are due to the methods of determining absolute cell counts and not to faulty identification of lymphocyte subsets.

CD8+,CD38+ lymphocyte percent: a useful immunological marker for monitoring HIV-1-infected patients

We investigated the relationship between three prognostic markers, CD4 lymphocyte count, serum beta2-microglobulin (beta2M) levels, and CD8+,CD38+ lymphocyte percent, and the association with the rate of development of AIDS. The markers were measured regularly throughout follow-up in 224 patients. The risk of developing AIDS during follow-up was investigated using Cox proportional hazards models. Time-updated values of the prognostic markers were used, which modelled the risk of AIDS according to the latest measurement of the marker rather than using a single value of the marker at baseline. During a median follow-up period of 13.6 months (range 0.5-31.9 months), 34 cases of AIDS occurred. In a univariate analysis, all three markers predicted the development of AIDS; a 10% increase in the percentage of CD8+ T cells expressing CD38+ resulted in an 88% increase in the risk of AIDS (95% confidence interval: 53-130%; p < 0.0001). After adjustment for the current CD4 count and beta2M, a 10% increase in the CD8+,CD38+ population was associated with a 37% increase in the risk of AIDS (95% confidence interval: 4-81%; p = 0.02). Thus, the percentage CD8+,CD38+ level predicts the development of AIDS independently of the latest CD4 count and beta2M. This assay is therefore potentially useful in conjunction with blood CD4 counts and serum beta2M levels in patient management and clinical trial design.

Rapid single-step method for flow cytometric detection of surface and intracellular antigens using whole blood

Fixation/permeabilization methods used for the detection of intracellular antigens by flow cytometry often result in the destruction of cellular morphology and surface immunoreactivity, properties useful in flow cytometry for the characterization of cells in heterogeneous populations. In addition, a majority of these methods are incompatible with whole blood and require that peripheral blood leukocytes (PBLs) be purified prior to fixation. This article describes a new technique for the rapid detection of both intracellular and cell surface antigens, while preserving cell morphology, through the use of a single-step fixation/permeabilization reagent, ORTHO PermeaFix (OPF). OPF is compatible with whole blood, allowing for the direct preparation of PBLs without prior cell separation. An additional red blood cell lysing reagent was not required because RBC lysis occurred upon resuspension of OPF-treated whole blood samples in isotonic solution. Discrimination of leukocyte populations by light scatter after OPF treatment was comparable to matched unfixed live cells. In addition, absolute lymphocyte and white blood cell (WBC) counts were not significantly affected when OPF-treated cells were compared with unfixed cells. Treatment of whole blood from 7 normal donors showed no significant difference in percentage of cells positive for CD2, CD3, CD4, CD8, CD16, or CD19 between fixed and unfixed samples when cells were stained before fixation, and no difference in CD3, CD4, CD8, CD16, or CD19 percentages when cells were stained following fixation. Monoclonal antibodies specific for intracellular antigens located at various sites within the cell were tested on fixed samples. OPF-treated peripheral blood lymphocytes showed greater than 95% reactivity for the inner mitochondrial membrane protein bcl-2, and the cytoskeletal cytoplasmic protein vimentin. TIA-1, a cytolytic granule-associated protein, showed differential reactivity within lymphocyte subsets, from a low of 8 +/- 2% in CD4+ cells to 89 +/- 6% in CD16+ cells, when whole blood from five normal donors was fixed and stained. Reh cells treated with OPF showed greater than 95% reactivity for the internuclear protein TdT. A comparison of OPF with two other fixation/permeabilization procedures, 1% paraformaldehyde followed by 45% ethanol and 0.25% paraformaldehyde followed by 0.2% Tween 20, showed that only OPF could be used both prior to or following cell surface staining with no effect on antigen detection while allowing optimal detection of all of the intracellular antigens tested.

Standardization of absolute CD4+ lymphocyte counts across laboratories: an evaluation of the Ortho CytoronAbsolute flow cytometry system on normal donors

The Ortho CytoronAbsolute is a flow cytometer designed to provide direct absolute counts of lymphocytes and their subsets from a single instrument. This study was designed to determine the performance of four geographically separated CytoronAbsolute instruments using 24-h-old, shipped, whole blood samples and to compare the results obtained on the CytoronAbsolute to those obtained using combinations of hematology instruments and other flow cytometers. The absolute count feature of the CytoronAbsolutes located at the four sites were cross calibrated and gave across-site coefficients of variation (CVs) of <4.0% for absolute count and 8.2% for absolute lymphocyte count. The calibration was stable for at least 2 months. Absolute lymphocyte counts and lymphocyte percentage immunophenotypes were determined on blood from 50 healthy human immunodeficiency virus (HIV)-seronegative donors. There were no significant site-to-site differences (each P > .05) in CD3+/CD4+ absolute lymphocyte counts determined on the CytoronAbsolute. In contrast, there was a significant site-to-site difference (P < .001) between sites 2 and 3 and sites 3 and 4 in the absolute CD3+/CD4+ lymphocyte counts determined via the conventional method of combining a flow cytometry-derived percentage with a hematology instrument-derived lymphocyte count. There was no significant difference (P = .388) in CD3+/CD4+ lymphocyte percent determinations between the CytoronAbsolute and the FACScan or Profile II flow cytometers used in this study. These results demonstrate that different operators can cross calibrate CytoronAbsolutes for absolute CD3+/CD4+ lymphocyte subset determinations, even over large geographic distances.