Monitoring of cytomegalovirus infections by the CD8+CD38+ T-cell subset in kidney transplant recipients

High proportion of CD95(+) and CD38(+) in cultured CD8(+) T cells predicts acute rejection and infection, respectively, in kidney recipients

The aim of this study was to find noninvasive T-cell markers able to predict rejection or infection risk after kidney transplantation. We prospectively examined T-lymphocyte subsets after cell culture stimulation (according to CD38, CD69, CD95, CD40L, and CD25 expression) in 79 first graft recipients from four centers, before and after transplantation. Patients were followed up for one year. Patients who rejected within month-1 (n=10) showed high pre-transplantation and week-1 post-transplantation percentages of CD95(+), in CD4(+) and CD8(+) T-cells (P<0.001 for all comparisons). These biomarkers conferred independent risk for early rejection (HR:5.05, P=0.061 and HR:75.31, P=0.004; respectively). The cut-off values were able to accurately discriminate between rejectors and non-rejectors and Kaplan-Meier curves showed significantly different free-of-rejection time rates (P<0.005). Patients who rejected after the month-1 (n=4) had a higher percentage of post-transplantation CD69(+) in CD8(+) T-cells than non-rejectors (P=0.002). Finally, patients with infection (n=41) previously showed higher percentage of CD38(+) in CD8(+) T-cells at all post-transplantation times evaluated, being this increase more marked in viral infections. A cut-off of 59% CD38(+) in CD8(+) T-cells at week-1, week-2 and month-2 reached 100% sensitivity for the detection of subsequent viral infections. In conclusion, predictive biomarkers of rejection and infection risk after transplantation were detected that could be useful for the personalized care of kidney recipients.

CMV driven CD8(+) T-cell activation is associated with acute rejection in lung transplantation

Lung transplantation is the definitive treatment for terminal respiratory disease, but the associated mortality rate is high. Acute rejection of the transplanted lung is a key determinant of adverse prognosis. Furthermore, an epidemiological relationship has been established between the occurrence of acute lung rejection and cytomegalovirus infection. However, the reasons for this association remain unclear. Here, we performed a longitudinal characterization of CMV-specific T-cell responses and immune activation status in the peripheral blood and bronchoalveolar lavage fluid of forty-four lung transplant patients. Acute rejection was associated with high levels of cellular activation in the periphery, reflecting strong CMV-specific CD8(+) T-cell activity post-transplant. Peripheral and lung CMV-specific CD8(+) T-cell responses were very similar, and related to the presence of CMV in the transplanted organ. These findings support that activated CMV-specific CD8(+) T-cells in the lung may play a role in promoting acute rejection.

Peripheral blood sampling for the detection of allograft rejection: biomarker identification and validation

Currently, acute allograft rejection can only be detected reliably by deterioration of graft function confirmed by allograft biopsy. A huge drawback of this method of diagnosis is that substantial organ damage has already taken place at the time that rejection is diagnosed. Discovering and validating noninvasive biomarkers that predict acute rejection, and chronic allograft dysfunction, is of great importance. Many studies have investigated changes in the peripheral blood in an attempt to find biomarkers that reflect changes in the graft directly or indirectly. Herein, we will review the promises and limitations of the peripheral blood biomarkers that have been described in the literature so far.

Parallel decline of CD8+CD38+ lymphocytes and viremia in treated hepatitis B patients

AIM: To assess the peripheral T lymphocyte subsets in chronic hepatitis B virus (HBV) infection, and their dynamics in response to adefovir dipivoxil monotherapy.

METHODS: Proportions and absolute counts of peripheral natural killer cells, B cells, CD8+, CD4+, CD8+CD38+, CD8+CD28+ and CD4+CD28+ T cells were determined using three-color flow cytometry in chronic hepatitis B patients (n = 35), HBV carriers (n = 25) and healthy controls (n = 35). Adefovir dipivoxil was initiated in 17 chronic hepatitis B patients who were regularly followed for 72 wk, during which period the T cell subsets and serum viral load were measured at each follow-up point.

RESULTS: The peripheral CD4+ T cell counts and CD8+ T cell counts decreased in chronic HBV infection. In chronic hepatitis B patients, proportions of CD8+CD38+ T cells were 62.0% ± 14.7%, much higher than those of HBV carriers and healthy controls. In the 13 hepatitis B patients who were treated and responded to adefovir dipivoxil, proportions of CD8+CD38+ T cells decreased from 53.9% ± 18.4% pre-therapy to 20.1% ± 11.3% by week 72 (P < 0.001), concomitant with viral load decline (HBV DNA fell from 7.31 to 3 log copies/mL). CD8+ T cell counts also underwent an average increase of 218 cells/μL by the end of 72-wk treatment. In those who failed the therapy, the CD8+CD38+ T cell population had more fluctuations.

CONCLUSION: CD8+ T cells abnormally activated in chronic HBV infection can be partially reversed by antiviral therapy. HBV-associated immune activation may be a crucial part of the pathogenesis and a promising target of treatment.

CD28 expression by peripheral blood lymphocytes as a potential predictor of the development of de novo malignancies in long-term survivors after liver transplantation

At present, no method is available for accurately monitoring the degree of immunosuppression induced by antirejection therapies. The aim of this study was to determine whether CD28 and CD38 expression by peripheral blood mononuclear cells could be useful in predicting the development of de novo malignancies after liver transplantation. Flow cytometry analysis was used to measure the expression of CD28 and CD38 by peripheral blood lymphocytes in 134 stable, long-term survivors of liver transplantation. Patients who developed a de novo malignancy after undergoing a medical checkup were entered into a cancer group. Twenty-two patients (16.4%) developed at least 1 de novo malignancy over a mean interval of 22 ± 14 months (1.2-49.4 months) after the checkup. The mean frequency of CD28(+)CD8(+) cells was significantly lower in the cancer group versus the noncancer group (39% ± 22 versus 51% ± 21, P = 0.008), but CD38 expression was similar in the 2 groups. Multivariate analysis indicated that an age greater than 50 years (odds ratio = 5.81) and a low frequency of CD28(+)CD8(+) cells at the time of the checkup (odds ratio =3.16) were the only significant predictors of the development of de novo malignancies (P = 0.027). The actuarial proportion of patients with de novo malignancies was significantly lower when the frequency of CD28(+)CD8(+) cells was greater than or equal to 40% instead of less than 40% (P = 0.01). Flow cytometry measurements of CD28 expression by peripheral blood lymphocytes may facilitate the identification of patients at a high risk of developing de novo malignancies. Further prospective studies are necessary to determine whether such measurements could have a place in routine clinical practice to enable the intensity of immunosuppression to be minimized in patients who have an increased risk of developing cancer.

Quantification of CD8(+)CD38(+) T lymphocytes by flow cytometry does not represent a good biomarker to monitor the reactivation of cytomegalovirus infection after allogeneic hematopoietic stem cell transplantation

BACKGROUND

Infection/reactivation of cytomegalovirus is a major cause of morbidity and mortality in immunocompromised transplant patients. It has already been observed in kidney and liver transplantation patients that cytomegalovirus disease is accompanied by significant increases in circulating CD8(+)CD38(+) T lymphocytes. There are no reports that study CD8(+)CD38(+) T lymphocytes to monitor/diagnose cytomegalovirus disease in hematopoietic stem cell transplantation patients.

OBJECTIVE

The aim of this study was to evaluate some cellular activation markers on circulating mononuclear cells (CD38 and HLA-DR) in patients submitted to hematopoietic stem cell transplantation and to establish any correlation with cytomegalovirus disease as diagnosed by antigenemia.

METHODS

Blood samples of 15 transplant patients were analyzed by flow cytometry using anti-CD3, anti-CD4, anti-CD8, anti-CD38, CD16, CD56 and anti-HLA-DR monoclonal antibodies and the results were evaluated in respect to cytomegalovirus antigenemia measured by indirect immunofluorescence. Minitab for Windows was used for statistical analysis and a p-value < 0.05 was considered significant.

RESULTS

Patients with positive antigenemia did not show any significant increase in the percentages of cells expressing the CD38 or HLADR activation markers when compared to patients with negative antigenemia. On the contrary, all patients showed high percentages of these cells independent of the presence of cytomegalovirus disease.

CONCLUSIONS

This study suggests that the investigation of these lymphocyte sub-populations in patients submitted to hematopoietic stem cell transplantation does not seem to contribute to the early identification of cytomegalovirus disease.

Close association of CD8+/CD38 bright with HIV-1 replication and complex relationship with CD4+ T-cell count

BACKGROUND

Measuring lymphocyte activation provides information in addition to CD4(+) T-cell count for immune monitoring of HIV-1 infected patients. CD38 is a well-established activation marker that is generally analyzed on the whole population of CD8(+) T-cells. Focusing specifically on CD38 high expression (CD8(+)/CD38(bright)) may be an interesting surrogate gating strategy because CD38(bright) characterizes principally activated memory cells.

METHODS

CD8(+)/CD38(bright) was investigated in 1,353 HIV-1 infected patients over a one-year period to establish relevant cutoff values and clarify the relationships of this marker with HIV-1 RNA viral load (VL) and CD4(+) T-cell count.

RESULTS

The CD8(+)/CD38(bright) (>8,500 CD38 binding site per cells) is well correlated with HIV-1 VL (r = 0.87, P < 0.001) in this longitudinal follow-up of nonimmunodepressed patients that initiated antiviral therapy (ART). In aviremic patients on ART, the marker was highly predictive of VL rebound (sensitivity 93%, specificity 64% for a VL level of detection >200 copies/ml). While the CD8(+)/CD38(bright) moderately correlated with CD4(+) T-cell count independently of the VL (r = -0.37, P < 0.001), it increased dramatically in aviremic patient groups that exhibited profound CD4(+) T-cell depletion (median 39% for CD4(+) T-cell counts <50/mm(3)). This result indicates that other additional immunological and/or viral factors than readily detectable HIV-1 replication appears to be involved in T-cell activation of immunodepressed individuals.

CONCLUSIONS

CD8(+)/CD38(bright) is an effective marker for monitoring T-cell activation, which is a central factor of HIV-1 pathogenesis. This gating strategy requires only a single additional staining in conventional four color CD4 protocols.

Early immunological predictors of neurodevelopmental outcomes in HIV-infected children

BACKGROUND

A previous analysis of children infected with human immunodeficiency virus (HIV) in the Women and Infants Transmission Study showed a strong correlation between low activated CD8(+) T lymphocytes in the first 2 months of life and good immunological prognosis. We sought to extend these observations to neurodevelopmental prognosis.

METHODS

Ninety-eight HIV-infected children born before 1994 with flow cytometric data from the first 2 months of life and adequate neurodevelopmental testing through age 30 months were studied. Children were divided into those with low (<or=5% CD8(+)HLA-DR(+) cells or <or=25% CD8(+)CD38(+) cells) or high (>5% CD8(+)HLA-DR(+) cells or >25% CD8(+)CD38(+) cells) immune activation at 1 and/or 2 months of age. Analysis was performed using survival analysis, Cox's proportional hazard regression, and longitudinal regression models.

RESULTS

Absence of immune activation, measured as <or=5% CD8(+)HLA-DR(+) cells, was strongly associated with better performance on the psychomotor developmental index of the Bayley scales of infant development through the third year of life. This association persisted after adjustment for CD4 cell count, viral load, and progression to acquired immunodeficiency syndrome (P= .005). An association with the mental development index was also present (P= .048). Significant association between neurodevelopmental outcomes and <or=25% CD8(+)CD38(+) cells was not seen.

CONCLUSIONS

In this prospective cohort study of HIV-infected children, there was a significant favorable association of low immune activation in peripheral T cells at age 1 or 2 months, measured by a low percentage of CD8(+)HLA-DR(+) cells, with subsequent psychomotor and mental development. This association was independent of other indices of severity and progression of HIV infection.

CD25, CD28 and CD38 expression in peripheral blood lymphocytes as a tool to predict acute rejection after liver transplantation

BACKGROUND/AIM

The aim of this study was to determine whether the expression of CD25, CD28 and CD38 (which reflects the degree of T-cell activation) by peripheral blood mononuclear cells constitutes a useful means of measuring the immune status of liver transplant recipients.

METHODS

Fifty-two patients enrolled in a prospective randomized study comparing cyclosporine and tacrolimus as the principal immunosuppressive drugs were monitored prospectively. The expression of CD25, CD28 and CD38 was analyzed on CD3-, CD4- and CD8-positive cells from whole blood using flow cytometry. The prognostic value of baseline and day 14 measurements regarding acute rejection was examined using Kaplan-Meier estimates for univariate analyses and the Cox model for multivariate analyses.

RESULTS

The mean frequencies of CD28 and CD38-expressing T cells were significantly higher in patients with acute rejection (p = 0.01 and p = 0.001, respectively), whereas the frequency CD25-expressing T cells did not differ significantly. Under univariate analysis, baseline CD25 levels, the type of calcineurin inhibitor, as well as the CD28 and CD38 frequencies obtained at day 14 were associated with the subsequent development of acute rejection. Under multivariate analysis, only CD28 and CD38 frequencies obtained at day 14 were independently associated with acute rejection.

CONCLUSIONS

The evaluation of CD28 and CD38 expression in peripheral blood lymphocytes is a simple marker that could be used routinely in clinical practice to assess the level of immunosuppression.

The changing pattern of "smart" flow cytometry (S-FC) to assist the cost-effective diagnosis of HIV, tuberculosis, and leukemias in resource-restricted conditions

There is a need to introduce cytometry into areas of the globe that have remained virtually untouched by modern laboratory medicine. With the demand to carry out tests on 100,000 s of individuals requiring antiretroviral therapy (ART), flow cytometry must remain simple and cost-effective - while being sustainable and industry supported as well as proven by quality assessment (QA). This outlook is referred to as "smart flow cytometry" (S-FC). There are five main areas where the power of S-FC is demonstrated. These are: (i) the use of CD45 to assist precise cell counting in blood and tissue samples; (ii) the primary CD4 gating to count CD4+ T cells in patients waiting for ART, including the combination (i) and (ii) in the panleucogating (PLG) protocol; (iii) monitoring of human immunodeficiency virus (HIV+) patients during ART by the decreasing levels of lymphocyte activation in a CD8/CD38 test - leading to economies of viral-load assays; (iv) in tuberculosis and HIV-TB coinfections the use of TB-antigen-stimulated cytokine-synthetic CD4+ T cells to identify active disease; and (v) the utilization of "minimal residual disease (MRD)-Lite" technology in patients 19 days after the start of antileukemic therapy to detect MRD. These methods of S-FC have been successfully introduced in "resource-restricted" countries with international and local QA.

Increased association of CD38 with lipid rafts in T cells from patients with systemic lupus erythematosus and in activated normal T cells

In this study we have determined whether there is a relationship between CD38 expression on T cells, its distribution in different membrane microdomains, and T cell activation in SLE patients. The data show that CD38 expression is augmented in ex vivo CD3+, CD4+, CD8+, and CD25+ SLE T cells, which correlates with its increased insolubility in Brij 98 detergent, and its translocation into lipid rafts. Moreover, SLE T cells show an altered CD4:CD8 ratio, which is due to a decreased proportion of CD4+ T cells and a concomitant increase in the proportion of CD8+ T cells. These data are consistent with the increased CD38 expression and lipid raft formation, and the significant reduction in the CD4:CD8 ratio observed in mitogen-stimulated normal T cells as compared with that in ex vivo untouched normal T cells. Increased expression of CD38 in floating rafts from SLE T cells, or from activated normal T cells may modulate TCR signaling by providing or sequestering signaling molecules to the engaged TCR.

The activation profile of tumour-associated reactive T-cells differs in the nodular and diffuse patterns of lymphocyte predominant Hodgkin's disease

AIMS

To compare the activation profile of T-cells in reactive lymphoid follicles with that of tumour-associated T-cells in lymphocyte predominant Hodgkin's disease (LPHD) with a nodular pattern (n = 21), LPHD with partial diffuse growth pattern (n = 11) and T-cell-rich large B-cell lymphoma (TCRLBCL, n = 8).

METHODS AND RESULTS

Reactive germinal centres showed sparse numbers of T-cells positive for CD134, a transient/early T-cell activation marker, and only scattered T-cells in the interfollicular areas positive for CD38, a marker of persistent activation. Lymphoid follicles showing progressive transformation of germinal centres (PTGC) had more numerous CD134+ T-cells which were negative for CD38. Tumour-associated T-cells in nodular LPHD were frequently positive for CD134 (15 of 16 cases, 94%), but negative or only focally positive for CD38 (three of 21 cases, 14%). LPHD with diffuse areas, however, showed increased CD38+ T-cells in the diffuse component in 10 of 11 (90%) cases, with CD134+ T-cells being more prominent in the nodular tumour component. TCRLBCL showed strong, uniform CD38 expression in T-cells and histiocytes in eight cases.

CONCLUSIONS

T-cells in nodular LPHD express markers of transient/early T-cell activation. By contrast, T-cells in the diffuse form of LPHD, similar to those in TCRLBCL, have an immunostaining profile consistent with persistent cellular activation. T-cell activation may precede or accompany histological progression in nodular LPHD and immunostaining for these markers, in small samples or in difficult cases, may be useful in highlighting those cases of LPHD undergoing histological progression.

Cellular responses to cytomegalovirus in immunosuppressed patients: circulating CD8+ T cells recognizing CMVpp65 are present but display functional impairment

The availability of tetrameric complexes of HLA class I molecules folded with immunodominant peptides makes it possible to utilize flow cytometry for rapid and highly specific visualization of virus specific CD8+ T cells. An alternate technique is to incubate whole blood with specific antigens and to subsequently detect and characterize responding T cells (e.g. by performing intracellular staining of interferon-gamma). By using an HLA-A2 tetramer construct folded with the same immunodominant CMV-peptide as that used for peptide pulsing, we monitored both the presence and functional capacity of CMV-specific CD8+ T cells. In addition T cell activation was assayed by determination of CD38 and CD69 expression. Twelve organ transplant patients and 31 healthy blood donors with latent CMV infection were investigated using CMV pp65 tetramer staining and intracellular staining of interferon-gamma after CMV pp65 peptide pulsing or CMV lysate pulsing. CMV-specific T cells were detected in similar absolute numbers as well as frequencies of T cells in the two groups investigated. However, the CMV-specific CD8+ T cells in immunosuppressed individuals showed a decreased functional response to the CMV-peptide, as evidenced by reduced interferon-gamma production when compared to healthy blood donors (19%; 42%, P < 0.005). In addition, CD38 expression was markedly higher in immunosuppressed patients compared to healthy blood donors (24%; 6%, P < 0.005). In a case report we demonstrate that reactivation of CMV can occur in an immunosuppressed patient with high number of CMV-specific T cells, but without functional capacity. Hence, these findings reflect impaired activation of cytotoxic T cells controlling latent CMV infection in immunosuppressed patients.

CD4(+) T cell levels are decreased during active CMV infection in kidney transplant recipients

The numbers of T lymphocytes and T cell subsets (CD2(+), CD3(+), CD4(+), CD8(+)), activated T cells (CD26(+)), B cells (CD19(+)), granulocytes (CD15(+)) and natural killer cells (CD16/56) were monitored by flow cytometry in 79 kidney transplant recipients, 35 of whom had cytomegalovirus infection. The percentages of these cells were correlated with viral load, as determined by cytomegalovirus antigenemia. Development of cytomegaloviral infection coincided with a significant reduction in the percentages of CD4(+) (P < 0.005) and CD3(+) (P < 0.05) cells. Monitoring of lymphocyte subsets may provide useful information on immunological events during cytomegaloviral infection.

Why do cytotoxic T lymphocytes fail to eliminate hepatitis C virus? Lessons from studies using major histocompatibility complex class I peptide tetramers

Hepatitis C virus (HCV) infection is a major public health problem, affecting an estimated 3% of the world's population, and over 10% in some countries. Infection in most cases becomes persistent, and can lead to hepatic inflammation, fibrosis and liver failure. The T lymphocyte reponse, in particular that mediated by cytotoxic T lymphocytes (CTLs), is likely to be involved in determining the outcome of infection, although its overall role is not clear. The use of major histocompatibility complex (MHC) class I peptide tetrameric complexes (tetramers) to study antiviral CTL responses has revolutionized our approach to the study of human infection. We have used a panel of MHC class I tetramers to analyse immune responses in HCV-infected individuals at various stages of disease. We find that the CTL response against HCV is vigorous in its early phases but dwindles over time both in terms of lymphocyte number and function. A number of potential explanations for this 'CTL failure' are discussed.

Characterization of CMVpp65-specific CD8+ T lymphocytes using MHC tetramers in kidney transplant patients and healthy participants

BACKGROUND

Cytomegalovirus (CMV) is a ubiquitous herpesvirus that infects 50-90% of individuals in different populations. After primary infection, the virus persists latently in myeloid cells under the control of specific T-cells. Reactivation of CMV infection may cause lethal organ dysfunction and is frequently seen in immunosuppressed individuals. CD8+ cytotoxic T-cells (CTL) have a primary role in suppressing CMV reactivation, and the dominating CTL response is directed against pp65.

METHODS

MHC tetramers, that is, complexes between HLA class I (or class II) molecules and antigenic peptides conjugated to fluorochromes allow the direct visualization of antigen-specific receptor-carrying T-cells using flow cytometry. We constructed a novel MHC tetramer for identification of CMVpp65-specific CD8+ T-cells using HLA-A2 molecules folded with the immunodominant NLVPMVATV peptide.

RESULTS

The A2/pp65 tetramer specifically stained CMV-directed T-cell lines, and sorted cells showed CMV-specific cytotoxicity. High proportions (0.1-9%) of the CD8+ T-cells were A2/pp65 tetramer+ in healthy HLA-A2+ CMV carriers and in immunosuppressed kidney transplant patients with latent infection. Patients with reactivated CMV infection exhibited up to 15% A2/pp65 tetramer+ cells, which seemed to correlate with CMV load over time. A2/pp65 tetramer+ cells expressed T-cell activation markers.

CONCLUSIONS

The construction of a novel A2/pp65 MHC tetramer enabled the design of a rapid and precise flow cytometric method allowing quantitative and qualitative analysis of CMV-specific T-cells. The number of A2/pp65 tetramer binding CTLs in blood may prove to be clinically relevant in assessing the immune response to CMV.

Applications of flow cytometry to clinical microbiology

Classical microbiology techniques are relatively slow in comparison to other analytical techniques, in many cases due to the need to culture the microorganisms. Furthermore, classical approaches are difficult with unculturable microorganisms. More recently, the emergence of molecular biology techniques, particularly those on antibodies and nucleic acid probes combined with amplification techniques, has provided speediness and specificity to microbiological diagnosis. Flow cytometry (FCM) allows single- or multiple-microbe detection in clinical samples in an easy, reliable, and fast way. Microbes can be identified on the basis of their peculiar cytometric parameters or by means of certain fluorochromes that can be used either independently or bound to specific antibodies or oligonucleotides. FCM has permitted the development of quantitative procedures to assess antimicrobial susceptibility and drug cytotoxicity in a rapid, accurate, and highly reproducible way. Furthermore, this technique allows the monitoring of in vitro antimicrobial activity and of antimicrobial treatments ex vivo. The most outstanding contribution of FCM is the possibility of detecting the presence of heterogeneous populations with different responses to antimicrobial treatments. Despite these advantages, the application of FCM in clinical microbiology is not yet widespread, probably due to the lack of access to flow cytometers or the lack of knowledge about the potential of this technique. One of the goals of this review is to attempt to mitigate this latter circumstance. We are convinced that in the near future, the availability of commercial kits should increase the use of this technique in the clinical microbiology laboratory.

Applications of flow cytometry to clinical microbiology

Classical microbiology techniques are relatively slow in comparison to other analytical techniques, in many cases due to the need to culture the microorganisms. Furthermore, classical approaches are difficult with unculturable microorganisms. More recently, the emergence of molecular biology techniques, particularly those on antibodies and nucleic acid probes combined with amplification techniques, has provided speediness and specificity to microbiological diagnosis. Flow cytometry (FCM) allows single- or multiple-microbe detection in clinical samples in an easy, reliable, and fast way. Microbes can be identified on the basis of their peculiar cytometric parameters or by means of certain fluorochromes that can be used either independently or bound to specific antibodies or oligonucleotides. FCM has permitted the development of quantitative procedures to assess antimicrobial susceptibility and drug cytotoxicity in a rapid, accurate, and highly reproducible way. Furthermore, this technique allows the monitoring of in vitro antimicrobial activity and of antimicrobial treatments ex vivo. The most outstanding contribution of FCM is the possibility of detecting the presence of heterogeneous populations with different responses to antimicrobial treatments. Despite these advantages, the application of FCM in clinical microbiology is not yet widespread, probably due to the lack of access to flow cytometers or the lack of knowledge about the potential of this technique. One of the goals of this review is to attempt to mitigate this latter circumstance. We are convinced that in the near future, the availability of commercial kits should increase the use of this technique in the clinical microbiology laboratory.

Early increase of peripheral B cell levels in kidney transplant recipients with CMV infection or reactivation

BACKGROUND

Cytomegalovirus (CMV) infection or reactivation is a frequent complication of renal transplantation. Diagnosis of these conditions relies on the detection of circulating antigen, or of specific IgM and/or IgG, which develop over several weeks. Evocative clinical features may be detected earlier, but lack specificity. Rapid and early changes in the partition of lymphocyte subsets could be an additional indication of pending CMV infection.

METHODS

A systematic follow-up of peripheral B lymphocytes identified immunophenotypically by the determination of surface immunoglobulins (sIg), performed in 97 kidney transplant recipients, allowed to identify transient increases apparently predictive of CMV primo-infection or reactivation over the next 3 months. To better define the nature of these B cells, an extended investigation was performed for 14 prospective patients. In addition to surface Ig, membrane CD19, HLA-DR, and CD80 expression were explored. The cytoplasmic presence of mu, kappa, and lambda chains was also examined. B cell function was investigated using the ELISPOT technique, which allows an enumeration of the populations of IgG, IgA, and IgM secreting B cells.

RESULTS

Retrospective analysis of the clinical outcome of the cohort of 97 patients evidenced that early transient increases in B cell levels were significantly (P<0.0001) associated with CMV infection. The same trend was noted in the smaller series of patients who benefited from a more extensive investigation of B cells, 10 of whom presented clinical or biological signs of CMV infection. Mature B cells, expressing surface Ig, CD19, DR, and CD80 are those presenting transient increases. No significant variation of preB (cmu+/kappalambda-) or activated (spot-forming) cells was evidenced in these patients.

CONCLUSION

Individual examination of each patient's immune reconstitution profile allows to detect transient peaks of mature B cell during the initial immunosuppressive therapy, that appear to be predictive of oncoming CMV infection or reactivation.

New strategies for prevention and therapy of cytomegalovirus infection and disease in solid-organ transplant recipients

In the past three decades since the inception of human organ transplantation, cytomegalovirus (CMV) has gained increasing clinical import because it is a common pathogen in the immunocompromised transplant recipient. Patients may suffer from severe manifestations of this infection along with the threat of potential fatality. Additionally, the dynamic evolution of immunosuppressive and antiviral agents has brought forth changes in the natural history of CMV infection and disease. Transplant physicians now face the daunting task of recognizing and managing the changing spectrum of CMV infection and its consequences in the organ recipient. For the microbiology laboratory, the emphasis has been geared toward the development of more sophisticated detection assays, including methods to detect emerging antiviral resistance. The discovery of novel antiviral chemotherapy is an important theme of clinical research. Investigations have also focused on preventative measures for CMV disease in the solid-organ transplant population. In all, while much has been achieved in the overall management of CMV infection, the current understanding of CMV pathogenesis and therapy still leaves much to be learned before success can be claimed.

Soluble CD-4 and CD-8 as markers of immunological activation in renal transplant recipients

BACKGROUND

T lymphocytes are activated following kidney transplantation in cases of acute graft rejection and viral infections. In plasma, elevated levels of T-cell markers can be measured in soluble form. The reason for this shedding is still not entirely understood.

METHODS

Plasma concentrations of soluble CD-4 and CD-8 (sCD-4, sCD-8) were determined in 78 patients following kidney transplantation by commercially available enzyme-linked immunosorbent assay (ELISA) test kits.

RESULTS

The concentrations of both soluble T-cell markers increased significantly in the course of acute allograft rejections and cytomegalovirus (CMV) infections. Frequently, the parameters increased shortly before clinical diagnosis and decreased under successful therapy. Additionally, sCD-8 showed significant higher plasma concentrations in cases of CMV infection as compared with acute allograft rejections. Accordingly, the sCD-4/sCD-8 ratio increased in cases of acute allograft rejection and decreased during CMV infections. Cyclosporin A nephrotoxicity caused no significant changes in the sCD-4 and sCD-8 levels in plasma.

CONCLUSION

The present study demonstrates that sCD-4 and sCD-8 are markers of immunological activation and may enable a further differentiation of T-cell activation if serial measurements are performed. However, further prospective investigations are necessary to elucidate the diagnostic potential of sCD-4 and sCD-8 for monitoring acute rejection and viral infection in kidney graft recipients.

Increased usage of TCR V-beta8 in kidney transplant recipients with aberrant immune reconstitution and clinical complications

BACKGROUND

The efficiency of immunosuppressive drugs prescribed after organ transplantation is mostly monitored through clinical and biological signs of organ rejection or infection. However, it may be expected that some patients develop subtle alterations of their reconstituting immune system, not immediately associated with clinical events. Identification of such anomalies could be useful to alert clinicians for possible future complications.

METHODS

A systematic follow-up of peripheral lymphocyte subsets, performed in a cohort of 89 kidney transplant recipients, identified severely skewed CD4/CD8 ratios in 32 patients. For 19 patients, the expression of specific T cell receptor fragments was examined using a panel of 10 monoclonal antibodies. Abnormal control of spontaneously Epstein Barr virus-infected B cells was tested by investigating for the generation of spontaneous lymphoblastoid cell lines in 17 cases. The incidence of rejection and infectious episodes was monitored.

RESULTS

A bias in T cell receptor fragments usage was detected in 14/19 cases, involving Vbeta8 in all cases. Spontaneous lymphoblastoid cell lines of Epstein Barr positive B blasts developed in 9 of 17 cases. Eleven patients had early rejection episodes and 16 presented with viral primo-infection or reactivation. The incidence of rejection and infectious episodes was higher in the group of 32 patients who developed such abnormal patterns than in the 57 who did not.

CONCLUSION

Transient bias in the T cell receptor repertoire may be observed during immune reconstitution after kidney transplantation, perhaps related to abnormal lymphocyte functions and associated to an impaired control of rejection and/or infectious agents.