Factors Associated With the Use of Hypothermic Machine Perfusion in Kidney Transplant Recipients: A Multicenter Retrospective Cohort Study

Background:

Delayed graft function (DGF) is associated with an increased risk of graft loss. The use of cold hypothermic machine perfusion (HMP) has been shown to reduce the incidence of DGF in kidney transplant recipients (KTRs), especially when extended-criteria donors (ECDs) are used. HMP can also improve graft survival. However, there is a paucity of data on the determinants of HMP use in clinical practice.

Objective:

We aimed to determine the factors associated with the use of HMP in a cohort of donors and KTRs.

Design:

Multicenter retrospective cohort study.

Setting:

5 transplant centers in Quebec.

Patients:

159 neurologically deceased donors (NDD) and 281 KTR.

Measurements:

Use of HMP.

Methods:

We collected data on consecutive NDD admitted to a dedicated donor unit in a single university-affiliated center and their KTRs between June 2013 and December 2018 in 5 adult transplant centers across the province of Quebec, Canada. All organs were recovered in a single hospital center where a HMP device was available for every organ recovered and the decision to use HMP was left at the discretion of the procurement surgeon. Generalized estimating equations were used to predict the use of HMP.

Results:

The cohort included 159 NDDs and their 281 KTRs. Thirty-three percent of donors were ECDs, and 59% of KTRs received organs placed on HMP. The median cold ischemia time (CIT) was 12.5 (IQR 7.9-16.3) hours. In univariate analysis, none of the donors’ characteristics were associated with the use of HMP. ECD represented 33% of KTR on HMP vs 35% of those not placed on HMP (P = .77). In univariate analysis, the use of HMP was associated with KTR race (non-Caucasian), longer CIT, use of basiliximab/alemtuzumab, year of transplant, and transplant center. The use of HMP varied largely across transplant centers, ranging from 15% to 82%. In multivariate analysis, use of HMP was associated with longer CIT (odds ratio [OR] 1.15, 95% confidence interval [CI] = 1.07-1.25), transplant center as well as transplantations performed after 2013.

Limitations:

One dedicated donor unit including NDD only, absence of specific data on surgeons’ experience and personal or logistic reasons for using or not HMP.

Conclusions:

We found that use of HMP remains low and varies largely across transplant centers. The use of HMP was strongly associated with the transplant center where the surgeons practiced, suggesting that surgeon preference/training plays an important role in determining the use of HMP. Availability of HMP at the time of organ procurement might also be limited by logistic issues such as difficulty in returning the device. Further studies aimed at determining the reasons underlying the barriers precluding the use of HMP could help increasing its use and improve transplant outcomes.

A Sequential Two-Step Cell-Based Assay Predicts Immunosuppression-Related Adverse Events

Immunosuppressants are associated with serious and often life-threatening adverse effects. To optimize immunotherapy, a tool that measures the immune reserve is necessary. We validated that a cell-based assay that measures TNF-α production by CD14⁺16⁺ intermediate monocytes following stimulation with EBV peptides has high sensitivity for the detection of over-immunosuppression (OIS) events. To develop a sequential, two-step assay with high specificity, we used PBMCs from kidney recipients (n = 87). Patients were classified as cases or controls, according to the occurrence of opportunistic infection, recurring bacterial infections, or de novo neoplasia. Patients who tested positive in the first step were randomly allocated to a training or a testing set for the development of the second step. In the discovery phase, an assay based on the examination of early mature B (eBm5) cells was able to discriminate OIS patients from controls with a specificity of 88%. The testing set also revealed a specificity of 88%. The interassay coefficient of variability between the experiments was 6.1%. Stratified analyses showed good diagnostic accuracy across tertiles of age and time posttransplant. In the adjusted model, the risk of OIS was more than 12 times higher in patients classified as positive than in those who tested negative (adjusted hazard ratio, 12.2; 95% confidence interval: 4.3-34.6). This sequential cell-based assay, which examines the monocyte and eBm5 cell response to EBV peptides, may be useful for identifying OIS in immunosuppressed patients.

Canadian Society of Transplantation and Canadian Society of Nephrology Commentary on the 2017 KDIGO Clinical Practice Guideline on the Evaluation and Care of Living Kidney Donors

Purpose of review:

To review an international guideline on the evaluation and care of living kidney donors and provide a commentary on the applicability of the recommendations to the Canadian donor population.

Sources of information:

We reviewed the 2017 Kidney Disease: Improving Global Outcomes (KDIGO) Clinical Practice Guideline on the Evaluation and Care of Living Kidney Donors and compared this guideline to the Canadian 2014 Kidney Paired Donation (KPD) Protocol for Participating Donors.

Methods:

A working group was formed consisting of members from the Canadian Society of Transplantation and the Canadian Society of Nephrology. Members were selected to have representation from across Canada and in various subspecialties related to living kidney donation, including nephrology, surgery, transplantation, pediatrics, and ethics.

Key findings:

Many of the KDIGO Guideline recommendations align with the KPD Protocol recommendations. Canadian researchers have contributed to much of the evidence on donor evaluation and outcomes used to support the KDIGO Guideline recommendations.

Limitations:

Certain outcomes and risk assessment tools have yet to be validated in the Canadian donor population.

Implications:

Living kidney donors should be counseled on the risks of postdonation outcomes given recent evidence, understanding the limitations of the literature with respect to its generalizability to the Canadian donor population.

TNF-α Production by Monocytes Stimulated With Epstein-Barr Virus-Peptides as a Marker of Immunosuppression-Related Adverse Events in Kidney Transplant Recipients

Introduction

Infections and cancers now outnumber rejection as a cause of morbidity in transplant recipients, likely as a result of over-immunosuppression. Currently, there is no clinical tool to detect over-immunosuppression. We recently reported that tumor necrosis factor alpha (TNF-α) production by CD14⁺CD16⁺ intermediate monocytes, following ex vivo stimulation by Epstein-Barr virus–peptides, could identify over-immunosuppressed patients.

Methods

We conducted a pilot study the assay using 142 peripheral blood mononuclear samples from a cohort of 71 kidney transplant recipients. Patients were classified as cases or controls according to the occurrence of opportunistic infection, recurring bacterial infections or de novo neoplasia in the 12 months following blood collection. We used both the classifier rule and a threshold of <73% of CD14⁺CD16⁺TNFα⁺ cells developed in a previous training set.

Results

Cases were detected with 83% sensitivity and 68% specificity. The negative predictive value of the assay was 89%. The hazard ratio for the occurrence of the endpoint was 6.8 (95% confidence interval 2.0–23.9; P = 0.003) in patients with a positive test. Multivariable linear regression analysis revealed that the association was independent of baseline clinical characteristics, renal function, and immunosuppressive regimen.

Conclusion

These data validate this cell-based assay as a promising tool for personalizing immunotherapy. Studies are under way for a 2-step assay with improved specificity.

Comparison of the effects of standard vs low-dose prolonged-release tacrolimus with or without ACEi/ARB on the histology and function of renal allografts

Targeting the renin-angiotensin system and optimizing tacrolimus exposure are both postulated to improve outcomes in renal transplant recipients (RTRs) by preventing interstitial fibrosis/tubular atrophy (IF/TA). In this multicenter, prospective, open-label controlled trial, adult de novo RTRs were randomized in a 2 × 2 design to low- vs standard-dose (LOW vs STD) prolonged-release tacrolimus and to angiotensin-converting enzyme inhibitors/angiotensin II receptor 1 blockers (ACEi/ARBs) vs other antihypertensive therapy (OAHT). There were 2 coprimary endpoints: the prevalence of IF/TA at month 6 and at month 24. IF/TA prevalence was similar for LOW vs STD tacrolimus at month 6 (36.8% vs 39.5%; P = .80) and ACEi/ARBs vs OAHT at month 24 (54.8% vs 58.2%; P = .33). IF/TA progression decreased significantly with LOW vs STD tacrolimus at month 24 (mean [SD] change, +0.42 [1.477] vs +1.10 [1.577]; P = .0039). Across the 4 treatment groups, LOW + ACEi/ARB patients exhibited the lowest mean IF/TA change and, compared with LOW + OAHT patients, experienced significantly delayed time to first T cell-mediated rejection. Renal function was stable from month 1 to month 24 in all treatment groups. No unexpected safety findings were detected. Coupled with LOW tacrolimus dosing, ACEi/ARBs appear to reduce IF/TA progression and delay rejection relative to reduced tacrolimus exposure without renin-angiotensin system blockade. ClinicalTrials.gov identifier: NCT00933231.

Organ donor management and delayed graft function in kidney transplant recipients: A multicenter retrospective cohort study

Meeting donor management goals (DMGs) has been reported to decrease the incidence of delayed graft function (DGF) after kidney transplant, but whether this relationship is independent of cold machine perfusion is unclear. We aimed to determine whether meeting DMGs is associated with a reduced incidence of DGF, independent of the use of machine perfusion. We collected data on consecutive brain-dead donors and their KT recipients (KTRs) between June 2013 and December 2016 in 5 adult transplant centers. We evaluated whether DMGs were met at donor neurologic death (DND) and later time points. We defined a priori meeting optimal DMG as achieving ≥7 DMGs. Generalized estimating equations were used to predict DGF. Among 122 donors, 34% were extended-criteria donors (ECDs). The number of DMGs met increased over time (5.6 ± 1.4 at DND and 6.1 ± 1.3 at organ procurement [P < .001]). DGF occurred in 23% of 214 KTRs, and 55% received organs placed on machine perfusion. In multivariate analysis, ECD (odds ratio [OR] 2.24, 95% confidence interval [CI] 1.13-4.45), use of machine perfusion (OR 0.45, 95% CI 0.22-0.94), and optimal DMG at DND (OR 0.39, 95% CI 0.16-0.99) were associated with DGF. Early achievement of DMGs was associated with a reduced risk of the development of DGF, independent of the use of machine perfusion.

2013 Banff Criteria for Chronic Active Antibody-Mediated Rejection: Assessment in a Real-Life Setting

Significant changes in the criteria for chronic active antibody-mediated rejection (CAABMR) were made in the Banff 2013 classification. These modifications expanded the number of patients diagnosed with CAABMR, with undetermined clinical significance. We compared the 2007 and 2013 criteria for the composite end point of death-censored graft failure or doubling of serum creatinine in 123 patients meeting the criterion related to the morphologic evidence of chronic tissue injury. In all, 18% and 36% of the patients met the 2007 and 2013 criteria, respectively. For the criterion related to antibody interaction with endothelium, only 25% were positive based on the 2007 definition compared with 82% using the 2013 definition. Cox modeling revealed that a 2013 but not a 2007 diagnosis was associated with the composite end point (adjusted hazard ratio 2.5 [95% confidence interval (CI) 1.2-5.2] vs. 1.6 [95% CI 0.7-3.8], respectively). The 2013 criterion based on both the C4d score and the glomerulitis plus peritubular capillaritis score (g+ptc) was more strongly associated with the end point than the 2007 criterion based only on C4d; however, when dissected by component, only the C4d component was significant. The association with clinical outcomes improved with the 2013 criteria. This is related to the new C4d threshold but not to the g+ptc ≥2 component.

Impact of donor age on long-term outcomes after delayed graft function: 10-year follow-up

Delayed graft function (DGF) has a negative impact on graft survival in donation after brain death (DBD) but not for donation after cardiac death (DCD) kidneys. However, older donor age is associated with graft loss in DCD transplants. We sought to examine the interaction between donor age and DGF in DBD kidneys. This is a single-center, retrospective review of 657 consecutive DBD recipients transplanted between 1990 and 2005. We stratified the cohort by decades of donor age and studied the association between DGF and graft failure using Cox models. The risk of graft loss associated with DGF was not significantly increased for donor age below 60 years (adjusted hazard ratio [aHR] 1.12, 1.51, and 0.90, respectively, for age <40, 41-50 and 51-60 years) but significantly increased after 60 years (aHR 2.67; P = 0.019). Analysis of death-censored graft failure yielded similar results for donor age below 60 years and showed a substantially increased risk with donors above 60 years (aHR 6.98, P = 0.002). This analysis reveals an unexpectedly high impact of older donor age on the association between DGF and renal transplant outcomes. Further research is needed to determine the best use of kidneys from donors above 60 years old, where DGF is expected.

The CLEAR study: a 5-day, 3-g loading dose of mycophenolate mofetil versus standard 2-g dosing in renal transplantation

BACKGROUND AND OBJECTIVES

Adequate early mycophenolic acid (MPA) exposure is associated with lower rates of acute rejection in renal transplantation. The aim of this randomized controlled trial was to determine if higher initial mycophenolate mofetil (MMF) doses increased the proportion of patients reaching therapeutic MPA levels (30 to 60 mg.h/L) by day 5.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

De novo renal transplant patients were randomized to receive intensified dosing of MMF (1.5 g twice daily on days 1 to 5, then 1.0 g twice daily) or standard dosing (1.0 g twice daily). All recipients received tacrolimus and prednisone. Full MPA areas under the curve (AUCs) were completed on days 3 and 5, whereas a limited sampling strategy was utilized at four subsequent time points.

RESULTS

At day 5, 47.5% of the MMF 3-g arm achieved the MPA therapeutic window versus 54.4% of the MMF 2-g arm. However, MPA AUC levels were significantly higher in the 3-g arm at day 3 and 5. This resulted in a trend for fewer treated acute rejections at 6 months. Significantly more acute rejections (treated, biopsy-proven including and excluding borderline) occurred in patients with MPA AUC levels<30 mg.h/L compared with those >or=30 mg.h/L at day 5. No significant differences were seen in common adverse events.

CONCLUSIONS

A limited intensified dose of MMF increased early MPA exposure and was well tolerated. Further studies are required to determine whether limited intensified MMF dosing can reduce acute rejection.

Pulmonary recruitment protocol for organ donors: a new strategy to improve the rate of lung utilization

Because lung transplantation is the only effective therapy for terminal respiratory failure, the demand for donor lungs has increased steadily. However, the number of donors has remained fairly constant over the years, which results in an increasing duration of waiting for lung transplantation. To overcome the lack of organs, various strategies have been developed by transplant centers including use of marginal donors. To increase the lung utilization rate in multiorgan donors, we implemented a simple lung recruitment protocol involving a brief period of controlled sustained inflation. In 2005, the lung utilization rate in the transplant program at our institution was only 20% in multiorgan donors. With the lung recruitment protocol, the rate of lung utilization for transplantation increased to 33%, in 2006, 24% in 2007, and 24% in 2008. Following the lung recruitment protocol, the arterial oxygen tension/fraction of inspired oxygen ratio increased to greater than 15% in more than 40% of donors. We were able to improve gas exchange sufficiently that as many as two-thirds of the lungs were suitable for transplantation. During the protocol, no complications were reported, and no patient became hemodynamically unstable, precluding organ procurement. We believe that optimization of multiorgan donor management with simple interventions may improve oxygenation, reducing the number of inadequate donor lungs and increasing the overall donor pool and organ availability.

Larch Seed Trees Sustain Arboreal Lichens and Encourage Recolonization of Regenerating Stands

In many areas Bryoria lichen is a major winter food for deer and caribou. We examined the role of western larch (Larix occidentalis) seed trees in retaining arboreal lichens and encouraging recolonization of regenerating stands by Bryoria. Although exposed to desiccation, Bryoria was sustained in significant amounts in larch seed trees. Other than a reduction near roads, apparently by alkaline road dust, arboreal forage lichens were relatively uniformly distributed throughout the regenerating stands. There was little difference in abundance up to 135 m from the source tree. The sorediate form of the lichens did better on lodgepole pine (Pinus contorta), and larger, nonsorediate fragments were more abundant on western larch. We attribute the difference to bark pH. Scattered western larch seed trees were effective at retaining lichens and facilitating recolonization of the regenerating stand.

Modifiable factors predicting patient survival in elderly kidney transplant recipients

BACKGROUND

Elderly transplant candidates represent an increasingly important group on the waiting list for kidney transplantation. Yet the factors that determine posttransplantation outcomes in this population remain poorly defined.

METHODS

We performed a population-based retrospective cohort study involving all patients aged 60 years or older who received a first cadaveric kidney transplantation between 1985 and 2000 in the province of Quebec. The main outcomes were patient survival, overall graft survival, and treatment failure (patient death or graft loss within the first posttransplant year). Survival analyses were performed using a Cox proportional hazard model. Logistic regression identified factors predicting treatment failure.

RESULTS

On multivariate analysis, the modifiable factors associated with patient survival were active smoking at transplantation [hazard ratio (HR) 2.09, 95% confidence interval (CI) 1.22-3.60)], body mass index (BMI) (HR 1.34 for a 5-point increase, 95% CI 1.05-1.67), and time on dialysis before transplantation (HR 1.10 for a 1-year increase, 95% CI 1.02-1.18). The only modifiable factor associated with graft survival was active smoking at transplantation (HR 2.04, 95% CI 1.24-3.30). Treatment failure was associated with time on dialysis before transplantation (odds ratio for dialysis >/=2 years 3.28, 95% CI 1.34-7.9).

CONCLUSION

Our results show that active smoking, obesity, and time on dialysis before transplantation are modifiable risk factors associated with an increased risk of mortality after transplantation in elderly recipients. They represent potential targets for interventions aimed at improving patient and graft survival in elderly patients.

Endothelin-1 levels and cardiovascular risk factors in renal transplant patients

OBJECTIVE

Circulating endothelin-1 (ET-1) levels have been reported to be associated with vascular complications and endothelial dysfunction in nontransplanted patients. The aim of this study was to investigate the relationship between ET-1 levels and major cardiovascular (CV) risk factors in renal transplant (RTX) patients with stable graft function.

METHODS

ET-1 levels were determined in 156 RTX patients and the relationship between circulating ET-1 levels and CV risk factors including age, gender, kidney function, blood lipids, diabetes, and hypertension was studied.

RESULTS

Circulating ET-1 levels were found to be positively correlated with creatinine (r = 0.25, p < 0.01) and systolic blood pressure (r = 0.20, p < 0.05) and inversely correlated with high-density lipoprotein cholesterol (HDL-C) levels (r = -0.27, p < 0.01). Patients with high and intermediate total cholesterol/HDL-C ratios (TC/HDL-C) had significantly higher ET-1 levels when compared to patients with low ratios (7.02 +/- 3.74, 6.79 +/- 2.67, and 5.37 +/- 3.04 pg/ml, respectively, p < 0.002). Only creatinine, HDL-C, and age >40 years were shown to be independent correlates for ET-1 levels according to multivariate analyses. Interestingly, ET-1 levels were significantly higher (+26%, p < 0.03) in RTX patients with documented CV disease, as compared to those without, when matched for age, gender, and presence of diabetes.

CONCLUSIONS

Increased circulating ET-1 levels are associated with low HDL-C and documented CV disease in RTX. This is likely a reflection of vascular endothelial damage and dysfunction and therefore may represent an increased risk for atherosclerosis.

Seroprevalence of antibodies against human herpesvirus 8 in a population of renal transplant recipients at Hôtel-Dieu de Québec Hospital

We conducted a seroepidemiologic study to determine the prevalence of anti-human herpesvirus 8 antibodies in a renal transplant population at Hôtel-Dieu de Québec Hospital. Testing for immunoglobulin G antibodies against lytic and latent antigens was performed on serum samples from 150 renal transplant patients. Human immunodeficiency virus-positive patients with confirmed Kaposi's sarcoma were used as positive controls. None of the renal transplant patients tested positive.

Effects of prednisone withdrawal on the new metabolic triad in cyclosporine-treated kidney transplant patients

BACKGROUND

Cardiovascular disease is a major cause of morbidity and mortality after renal transplantation. Prednisone (Pred) maintenance therapy is associated with risk factors for atherosclerosis. Therefore, we were interested in quantifying the effects of Pred withdrawal on body weight and waist circumference as well as on metabolic markers of coronary heart disease risk.

METHODS

Twenty-six cyclosporine-treated renal transplant patients (13 men and 13 women) were evaluated before and after at least 11 months (16 +/- 2.9 months) of Pred withdrawal. A complete fasting lipoprotein-lipid profile as well as anthropometric measurements were obtained from each patient.

RESULTS

Pred withdrawal was associated with a 6.0% reduction of body weight (-4.34 +/- 5.40 kg; P < 0.05) and with a 7.7% decrease in waist girth (-7.13 +/- 5.75 cm; P < 0.005) in women, whereas no change in these variables were observed in men. In both genders, plasma low-density lipoprotein (LDL) cholesterol and triglyceride concentrations were unaffected by Pred withdrawal, whereas plasma high-density lipoprotein (HDL) cholesterol levels decreased by 14.0% in women (-0.22 +/- 0.22 mmol/L; P < 0.005) and 22.0% in men (-0.36 +/- 0.28 mmol/L; P < 0.005). Pred withdrawal was associated with a significant reduction in plasma apolipoprotein B concentrations in both women (-0.28 +/- 0.15 g/L; -24.6%; P < 0.0001) and men (-0.22 +/- 0.19 g/L; -20.5%; P < 0.005). A significant reduction in fasting insulin was observed in both women (-27.8 +/- 27.9 pmol/L; -25.3%; P < 0.005) and men (-25.0 +/- 32.8 pmol/L; -21.4%; P < 0.05), whereas the LDL peak particle size was unaffected by Pred withdrawal.

CONCLUSIONS

Pred withdrawal modifies several anthropometric and metabolic cardiovascular risk factors in renal transplant patients. Furthermore, female patients may derive further benefits of Pred withdrawal resulting from the concomitant loss of body weight and abdominal fat.

Mycophenolate mofetil, an alternative to cyclosporine A for long-term immunosuppression in kidney transplantation?

BACKGROUND

Mycophenolate-mofetil (MMF) is a nonnephrotoxic immunosuppressant most often used in combination with cyclosporine A (CsA) and prednisone (Pred). This study reports the outcome of 17 adult renal recipients whose immunosuppressive regimen was changed from CsA-Pred to MMF-Pred because of CsA nephrotoxicity.

METHODS

CsA nephrotoxicity was diagnosed in all patients based on suggestive histopathological lesions on a renal biopsy. Sixteen patients had deteriorating graft function and 1 had isolated persistent proteinuria. Immunosuppressive therapy was changed 57+/-32 months posttransplant.

RESULTS

After replacement of CsA by MMF, a reduction in serum creatinine was observed in all patients (mean 26+/-17%). This reduction was maintained 20+/-8 months after the change in therapy without any episodes of acute rejection. Serum lipids and blood pressure also decreased significantly.

CONCLUSION

This study demonstrates that MMF-Pred can be an effective long-term immunosuppressive treatment alternative for renal transplant patients experiencing CsA nephrotoxicity. Such treatment may result in improved graft function, and better control of hypertension and hyperlipidemia.

Cytokine and cytotoxic molecule gene expression determined in peripheral blood mononuclear cells in the diagnosis of acute renal rejection

BACKGROUND

Prevention of acute rejection is the most prevalent measure used to reduce the long-term risk of chronic allograft rejection. Until now, biopsy was the only useful diagnostic tool for monitoring allograft acute rejection, but invasiveness of this procedure limits its use. The aim of this study was to investigate the implication of peripheral blood immune markers as a predictive diagnostic tool preceding biopsy in acute renal allograft rejection determination.

METHODS

Of the 61 patients studied, 13 had no rejection episodes, 8 had a proven acute rejection, and 40 were excluded for graft dysfunction causes. Mitogen-induced peripheral blood mononuclear cells were tested for interleukin- (IL) 2, IL-4, IL-5, IL-6, IL-10, IL-15, Interferon-gamma, Perforin, Granzyme B, and Fas L using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR). An up-regulated mRNA expression value was calculated in which a patient's sample was deemed positive if its differential expression value was equal or higher than the mean differential expression value calculated from the nonrejecting patients.

RESULTS

IL-4, IL-5, IL-6, Interferon-gamma, Perforin, and Granzyme B mRNA levels were associated with acute rejection. When at least two of these cytokine markers were up-regulated in a given patient, 75% of the rejecting recipients were identified against 15% of the nonrejecting patients.

CONCLUSIONS

We have shown that acute rejection episodes in renal transplant recipients were associated with an increase in mRNA expression of cytokines in mitogen-induced peripheral blood mononuclear cells. The evaluation of pro-inflammatory cytokines and cytotoxic molecules prove useful in the clinical identification of acutely rejecting transplant recipients and in the justification of concomitant antirejection therapy before histological diagnosis confirmation.

HDL cholesterol and TaqIB cholesteryl ester transfer protein gene polymorphism in renal transplant recipients

Decreased serum levels of high-density lipoprotein cholesterol (HDL-C) are a well-known risk factor for coronary heart disease (CHD) in the general population and have been suggested as one of the best predictor of CHD after renal transplantation. However, very heterogeneous HDL-C levels have been reported in renal transplant recipients. In this patient population, serum HDL-C levels are determined by complex interactions between hormonal, environmental (such as a high amount of abdominal adipose tissue), and genetic factors and drugs (particularly glucocorticoids). We, therefore, evaluated the effects of the cholesteryl ester transfer protein (CETP) gene TaqIB polymorphism as well as of abdominal obesity on HDL-C levels in 78 male renal transplant recipients who were receiving azathioprine and/or ciclosporin A in combination with prednisone as immunosuppression. The patients were classified into genotypic groups according to the presence or absence of the restriction site (B1 allele or B2 allele, respectively). The distribution of CETP genotypes was similar to that previously described in the general population. Overall, HDL-C levels were 19 and 26% higher in B1B2 and B2B2 patients as compared with B1B1 homozygotes (p < 0.05), even after control for other lipid measurements. Patients with abdominal obesity (waist girth >/=93 cm) showed reduced HDL-C levels as compared with lean (waist girth <93 cm) patients (1.20 +/- 0.28 vs. 1.42 +/- 0.41 mmol/l, respectively, p < 0.01). Moreover, the HDL-C levels were markedly affected by the CETP TaqIB polymorphism in lean patients (+28 and +41% in B1B2 and B2B2 as compared with B1B1 patients, p < 0.05), but no significant difference was observed among obese patients. Significantly lower total cholesterol:HDL-C ratios were obtained in lean B2B2 homozygotes, suggesting that these patients could be less susceptible to atherosclerosis than lean B1B1 homozygotes. In addition, patients with the B1B1 genotype had more documented CHD as compared with patients carrying at least one B2 allele, supporting the protective effect of the B2 allele against CHD. In conclusion, considerable variation in HDL-C levels appears to be explained by the CETP TaqIB gene polymorphism in male renal transplant recipients, but this potential protective gene effect appears strongly reduced by concomitant abdominal obesity.

Characterization of two polymorphic sites in the human kinin B1 receptor gene: altered frequency of an allele in patients with a history of end-stage renal failure

On the basis of the genomic structure of the human B1 receptor (B1R) for kinins, the presence of possible allelic polymorphisms of this gene was investigated using restriction fragment-length polymorphism and single-strand conformation polymorphism. The frequencies of the found alleles were determined in healthy volunteers and in patients with a history of end-stage renal failure, because there is evidence for a nephroprotective action of the kallikrein-kinin system. An A1098-->G polymorphism has been identified in exon 3 in a minority of volunteer blood donors, and is located 35 nucleotides downstream from the stop codon and 14 nucleotides upstream from the polyadenylation signal. The frequency of the G allele is 4.4% in the control sample and not significantly altered in patients with a history of end-stage renal failure. A second and more frequent polymorphism (18.1% of the alleles in the control group, prevalence of 33.3%) consists of a single base substitution (G-699-->C) in the putative promoter region. This polymorphism is significantly less frequent in the population of renal failure patients (prevalence of 20.6%) and determines an increased activity of the promoter function in constructions involving a reporter gene. The altered prevalence of this allele was also found in some etiologic subgroups of uremic patients. This study confirms the mapping of the B1R gene to 14q32. Other investigators have mapped the bradykinin B2 receptor (B2R) gene to a close site on human chromosome 14. A previously described B2R polymorphism (exon 2, C181-->T) had an allele frequency of 9.7% in the control sample and appears to be clinically neutral. The polymorphism of the B1R promoter may be a marker of prognostic significance for the preservation of renal function in diseased individuals.

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

BACKGROUND

The CD8+CD38+ T-cell subset can predict progression to acquired immune deficiency syndrome among human immunodeficiency virus-positive subjects. This T-cell subset usually increases during other active viral infections (cytomegalovirus [CMV], Epstein Barr virus). We report on its usefulness in the early detection of CMV infection in kidney transplant recipients.

METHODS

Quantitation of CD8+CD38+ T cells was monitored by dual-color flow cytometry analysis on 77 patients during the posttransplantation period. Seventeen of the 52 patients at risk for CMV disease (33%) had primary infection or reactivation and three patients had herpes simplex virus infection only.

RESULTS

In every patient with CMV disease, high values for the CD8+CD38+ subset were detected with a 90% positive predictive value for the primary infections. Elevated values were observed at the very first clinical signs of the viral disease or within the few preceeding days. Acute rejection episodes did not provoke false-positive results.

CONCLUSION

This immunologic marker is sensitive and easily obtainable on a daily basis. It may help to direct therapy during rejection or serve as a tool for early detection of clinical viral diseases.

Structural analysis of gamma delta TCR using a novel set of TCR gamma and delta chain-specific monoclonal antibodies generated against soluble gamma delta TCR. Evidence for a specific conformation adopted by the J delta 2 region and for a V delta 1 polymorphism

We recently showed that secretion of non-chimeric disulfide-linked human gamma delta TCR ('soluble' TCR, sTCR) comprising V gamma 9 and V delta 2 regions could be achieved by simply introducing translational termination codons upstream from the sequences encoding TCR transmembrane region. Here we extended these findings by demonstrating efficient secretion and heterodimerization of gamma delta sTCR comprising V gamma 8, V delta 1 and V delta 3 regions, obtained via the same strategy. After immunization against immunoaffinity-purified soluble TCR, several hundreds of TCR-specific monoclonal antibodies (mAb) were generated, which fell in at least seven groups. One set of mAb was directed against a V gamma 8-specific epitope. Strikingly, despite the high degree of sequence homology between V gamma 8 and other V gamma I domains, none of these mAb were crossreactive with other members of the V gamma I family. Three other sets of mAbs were shown to recognize delta chains comprising V delta 1, V delta 2 and V delta 3 regions respectively, regardless of their junctional sequence or of the gamma chain to which they were paired. Among the V delta 1-specific mAb, some specifically recognized V delta 1D delta J delta C delta chains while others reacted with both V delta 1 D delta J delta C delta and V delta 1J alpha C alpha chains, which suggested V domain conformational alterations induced by the C region. Moreover, reactivity of one V delta 1-specific mAb (#R6.11) was affected by a polymorphic residue located on the predicted CDR4 loop of the V delta region. Two delta chain-specific mAb (#178 and #515) showed a highly unusual reactivity, which was negatively affected by particular V delta and J delta sequences: (i) mAb #515 and #178 recognized all TCR delta chains except those comprising V delta 1 or V delta 2 regions, respectively and (ii) within TCR delta chains carrying 'permissive' V delta regions, none of those comprising the J delta 2 region were recognized by #515 and/or #178 mAbs, which suggested a highly specific conformation adopted by this particular J delta sequence. Apart from its usefulness in TCR structural studies, this novel set of mAb represents an important tool for the characterization and isolation of gamma delta T cells expressing particular combinations of V gamma/V delta regions and for analysis of V alpha/V delta usage by alpha beta T cells. Moreover, since our present data strongly suggest that gamma delta TCR are easier to obtain in a soluble form than alpha beta TCR, an efficient strategy for the generation of V alpha region-specific mAb might be to immunize with chimeric gamma delta sTCR comprising particular V alpha regions.

Repertoire analysis of human peripheral blood lymphocytes using a human V delta 3 region-specific monoclonal antibody. Characterization of dual T cell receptor (TCR) delta-chain expressors and alpha beta T cells expressing V delta 3J alpha C alpha-encoded TCR chains

V delta 3 usage and combinatorial expression of V gamma and V delta regions was studied on peripheral T cells with a novel V delta 3-specific mAb (p11.10b), generated against a soluble V gamma 9V delta 3 TCR. V delta 3+ cells represented the vast majority of V delta 1/V delta 2- gamma delta T cells within peripheral blood and mucosal lymphocytes. No preferential V gamma region expression was noted within V delta 3+ cells, but the frequency of V gamma 9+ cells was significantly lower among V delta 3+ than among V delta 1+ or V delta 2+ PBL. Phenotypic analysis of cultured V delta 3+ cells sorted with p11.10b mAb revealed the presence of T lymphocytes with unusual phenotypes. First, cells carrying two distinct surface TCR delta-chains, recognized by both V delta 1- and V delta 3-specific mAbs, were detected in most T cell lines, though at frequencies much lower than that of dual gamma expressors, indicating that allelic exclusion of delta genes is more tightly regulated than that of gamma genes. Moreover, a significant fraction of V delta 3+ cells were recognized by C beta- but not C delta-specific mAbs. Molecular analysis of V delta 3+C beta+ clones revealed the presence of V delta 3J alpha C alpha transcripts in all of them. Given the peculiar location of the V delta 3 gene between the delta Rec/psi J alpha elements, those observations formally demonstrate that activation of rearrangements with J alpha elements is not necessarily preceded by a delta Rec/psi J alpha-mediated deletion of the delta locus on the same chromosome.

Repertoire analysis of human peripheral blood lymphocytes using a human V delta 3 region-specific monoclonal antibody. Characterization of dual T cell receptor (TCR) delta-chain expressors and alpha beta T cells expressing V delta 3J alpha C alpha-encoded TCR chains

V delta 3 usage and combinatorial expression of V gamma and V delta regions was studied on peripheral T cells with a novel V delta 3-specific mAb (p11.10b), generated against a soluble V gamma 9V delta 3 TCR. V delta 3+ cells represented the vast majority of V delta 1/V delta 2- gamma delta T cells within peripheral blood and mucosal lymphocytes. No preferential V gamma region expression was noted within V delta 3+ cells, but the frequency of V gamma 9+ cells was significantly lower among V delta 3+ than among V delta 1+ or V delta 2+ PBL. Phenotypic analysis of cultured V delta 3+ cells sorted with p11.10b mAb revealed the presence of T lymphocytes with unusual phenotypes. First, cells carrying two distinct surface TCR delta-chains, recognized by both V delta 1- and V delta 3-specific mAbs, were detected in most T cell lines, though at frequencies much lower than that of dual gamma expressors, indicating that allelic exclusion of delta genes is more tightly regulated than that of gamma genes. Moreover, a significant fraction of V delta 3+ cells were recognized by C beta- but not C delta-specific mAbs. Molecular analysis of V delta 3+C beta+ clones revealed the presence of V delta 3J alpha C alpha transcripts in all of them. Given the peculiar location of the V delta 3 gene between the delta Rec/psi J alpha elements, those observations formally demonstrate that activation of rearrangements with J alpha elements is not necessarily preceded by a delta Rec/psi J alpha-mediated deletion of the delta locus on the same chromosome.

Close correlation between Daudi and mycobacterial antigen recognition by human gamma delta T cells and expression of V9JPC1 gamma/V2DJC delta-encoded T cell receptors

Recent studies have demonstrated that a large fraction of human gamma delta PBL recognize Ag of prokaryotic and eukaryotic origins, respectively found in hydrosoluble mycobacterial extracts and on the Daudi Burkitt's lymphoma cells. The structural basis of the recognition of these Ag have been presently studied in detail, through analysis of a large panel of thymus- and peripheral blood-derived gamma delta T-cell clones. Our results suggest that Daudi and mycobacteria-reactive gamma delta subsets are strictly overlapping and hence that gamma delta T-cell responses against these two Ag are closely related. Daudi cells and mycobacteria were recognized by V gamma 9+V delta 2+, but not by V gamma 9+V delta 2-, V gamma 9-V delta 2+, or V gamma 9-V delta 2- PBL clones. However, not all V gamma 9+V delta 2+ clones were reactive and, in particular: 1) the proportion of Ag-reactive lymphocytes was much lower among thymus- than PBL-derived clones (respectively 24/36 vs 72/73); 2) none of the V gamma 9+V delta 2+ clones expressing a V9J2C2 gamma chain (n = 4) were reactive to Daudi or mycobacteria, indicating that expression of a disulfide-linked TCR is probably a prerequisite for recognition of these Ag; and 3) among V gamma 9+V delta 2+ clones bearing disulfide-linked TCR, almost all (50/53) clones expressing a V9JPC1 gamma chain were reactive, whereas a large fraction (6/10) of those expressing a V9J1C1 gamma chain were weakly or nonreactive. Together, these observations suggest that germline residues specific to V gamma 9, V delta 2, and J gamma P elements directly contribute to recognition of Daudi and mycobacterial Ag. Furthermore, these findings may provide an explanation for coordinate use of these gene elements by a large fraction of gamma delta PBL, through peripheral selection events mediated by ligands identical or structurally related to the above Ag.

Close correlation between Daudi and mycobacterial antigen recognition by human gamma delta T cells and expression of V9JPC1 gamma/V2DJC delta-encoded T cell receptors

Recent studies have demonstrated that a large fraction of human gamma delta PBL recognize Ag of prokaryotic and eukaryotic origins, respectively found in hydrosoluble mycobacterial extracts and on the Daudi Burkitt's lymphoma cells. The structural basis of the recognition of these Ag have been presently studied in detail, through analysis of a large panel of thymus- and peripheral blood-derived gamma delta T-cell clones. Our results suggest that Daudi and mycobacteria-reactive gamma delta subsets are strictly overlapping and hence that gamma delta T-cell responses against these two Ag are closely related. Daudi cells and mycobacteria were recognized by V gamma 9+V delta 2+, but not by V gamma 9+V delta 2-, V gamma 9-V delta 2+, or V gamma 9-V delta 2- PBL clones. However, not all V gamma 9+V delta 2+ clones were reactive and, in particular: 1) the proportion of Ag-reactive lymphocytes was much lower among thymus- than PBL-derived clones (respectively 24/36 vs 72/73); 2) none of the V gamma 9+V delta 2+ clones expressing a V9J2C2 gamma chain (n = 4) were reactive to Daudi or mycobacteria, indicating that expression of a disulfide-linked TCR is probably a prerequisite for recognition of these Ag; and 3) among V gamma 9+V delta 2+ clones bearing disulfide-linked TCR, almost all (50/53) clones expressing a V9JPC1 gamma chain were reactive, whereas a large fraction (6/10) of those expressing a V9J1C1 gamma chain were weakly or nonreactive. Together, these observations suggest that germline residues specific to V gamma 9, V delta 2, and J gamma P elements directly contribute to recognition of Daudi and mycobacterial Ag. Furthermore, these findings may provide an explanation for coordinate use of these gene elements by a large fraction of gamma delta PBL, through peripheral selection events mediated by ligands identical or structurally related to the above Ag.

Secretion of disulfide-linked human T-cell receptor gamma delta heterodimers

The availability of soluble forms of T-cell antigen receptors (sTCR) should be of great use in the detailed characterization of their interactions with ligands, for the generation of anti-TCR monoclonal antibodies (mAb), and for the eventual determination of their three-dimensional structures by x-ray crystallography. Here, we show that efficient secretion of nonchimeric disulfide-linked human gamma delta TCR could be achieved by simply introducing translational termination codons upstream from the sequences encoding TCR chain transmembrane regions. This recombinant protein appeared to be correctly folded, as judged by its reactivity with a panel of anti-gamma and anti-delta mAbs, and proved to be a powerful immunogen, allowing generation of mAb that are able to recognize both soluble- and membrane-bound gamma delta TCR. While variable and constant domains of gamma delta sTCR seem to be folded into compact conformations, the extreme sensitivity of its interchain disulfide bridge to digestion with papain suggests that sTCR C-terminal portions are in a more extended configuration than the corresponding region in immunoglobulins. Finally, the gamma delta heterodimer remains stable even after removal of the interchain disulfide link, suggesting the existence of strong noncovalent forces holding the two chains together.

Surface expression of two distinct functional antigen receptors on human gamma delta T cells

Lymphocytes recognize antigens with highly variable heterodimeric surface receptors. Although four distinct antigen receptors could in principle be produced by any lymphocyte, only one functional combination of receptor chains has thus far been found expressed on their surface. Examination of human gamma delta T cells revealed a population that violated this rule by expressing on their surface two distinct functional gamma delta T cell receptors (TCRs) that used different TCR gamma gene alleles. Thus, current models for T cell clonal selection may need modification, and a possible escape mechanism for autoreactive TCRs is suggested.

Peripheral selection of antigen receptor junctional features in a major human gamma delta subset

Recent studies demonstrating the existence of murine gamma delta T cell subsets with structurally identical T cell receptors (TcR) suggest that unlike alpha beta T cells, some gamma delta T cells are specialized in the recognition of a limited number of monomorphic antigens. However, this question still remains open in humans, since the TcR structural diversity of their peripheral gamma delta T cells was shown to be extensive. Here we have analyzed in detail the TcR chain genes expressed by human V gamma 9+V delta 2+ peripheral blood lymphocytes (PBL), a major peripheral gamma delta T cell subset in adults and present evidence for an antigen-driven peripheral selection of both TcR gamma and delta junctional motifs among these cells. First, it is shown that the proportion of V gamma 9+V delta 2+ cells expressing the V9JPC1 gamma chain is much higher among PBL than among thymus-derived clones, indicating that preferential use of this J gamma segment is not due to pairing or combinatorial constraints. Second, analysis of V9JPC1 gamma transcripts derived from V gamma 9+V delta 2+ PBL clones revealed a high prevalence of a unique V9JP gamma sequence with limited "N" nucleotide additions and VJ trimming, which could not be accounted for by enzymatic or antigen-independent structural limitations. Third, the TcR delta chain expressed by most V gamma 9+V delta 2+ PBL clones, though diverse in amino acid composition and length, carried a highly distinctive junctional motif, found at a much lower frequency among V2DJ delta sequences derived from V gamma 9-V delta 2+ PBL or V gamma 9+V delta 2+ thymocytes. Together, these results which demonstrate shared gamma and delta junctional features by cells using unique V gamma and V delta genes, suggest that in vivo selection of V gamma 9+V delta 2+ lymphocytes is mediated by a highly restricted number of nominal ligands.