Posttransplant monitoring of pediatric lung transplant recipients

T-cell immune monitoring in organ transplantation

PURPOSE OF REVIEW

Chronic injury and late allograft loss remain major causes of morbidity in clinical transplantation. Biomarkers that can reliably assess the risk of posttransplant complications are required to direct and individualize therapy aimed at prolonging graft survival and improving patient health. The purpose of this review is to provide a framework for understanding how to use biomarkers in the context of clinical transplantation and to summarize current data on available noninvasive cellular-based immune monitoring methods to predict transplant outcome.

RECENT FINDINGS

New microarray and gene profiling data reveal peripheral blood cell gene expression patterns that identify operational tolerance, raising the possibility that the measurements can be used to direct immunosuppression withdrawal. Additional data support the use of selective urine gene products and soluble CD30 measurements in serum as reliable biomarkers of acute graft injury. Finally, recent studies demonstrate that measurement of T-cell alloimmunity by cytokine enzyme-linked immunospot is a promising, supplementary pretransplant risk assessment tool.

SUMMARY

Recently published studies in organ transplantation suggest that results derived from assays focused on markers of T-cell immunity can segregate transplant candidates or recipients into high and low-risk subgroups for posttransplant graft injury. Larger prospective studies are needed, however, before any proposed biomarker can be incorporated into the transplant physicians' armamentarium to guide individualized therapeutic decision-making.

Assessing immunologic function through CD4 T-lymphocyte ahenosine triphosphate levels by ImmuKnow assay in Chinese patients following renal transplantation

OBJECTIVE

Balancing immunosuppression to prevent rejection while minimizing infection/drug toxicity risk is a challenge in organ transplantation. Drug monitoring alone or with functional monitoring is inadequate to measure the immune response after transplantation. The Food and Drug Administration (FDA)-approved immune monitoring assay, ImmuKnow, offers an noninvasive method to assess the immune status of transplanted patients by measuring adenosine triphosphate (ATP) released from CD4 T cells. Herein, we have evaluated ATP levels reflecting the immune responses of Chinese kidney transplant recipients as a monitoring parameter to guide treatment after transplantation.

METHODS

From October 2008 to March 2010, we recruited 259 kidney transplant patients who were divided into four groups: stable (n = 174), postoperative infection (n = 32), postoperative rejection (n = 16), and high-dose corticosteroid treatment (n = 33). The ImmuKnow assay was performed to measure CD4 T-cell ATP levels. No prisoners or organs from prisoners were used in the study.

RESULTS

Receiver operating characteristics measurements indicated an ATP predictive range of 238 to 497 ng/mL to monitor immune responses after transplantation and immunosuppressive therapy. To identify patients with infection, we used a cutoff ATP value of 238 ng/mL with 100% specificity and positive predictive value and 92.9% sensitivity. To identify patients with rejection, we used a value of 497 ng/mL with 91.5% sensitivity. Compared with the 225 to 525 ng/mL ATP levels recommended by the FDA, our target values showed similar or better diagnostic accuracy.

CONCLUSION

We provide additional data to monitor immunosupressant treatment of Chinese kidney transplant patients.

[Lung transplantation and rejection. Basic principles, clinical aspects and histomorphology]

Lung transplantation is the ultimate therapeutical approach for the treatment of both children and adults with terminal congenital or acquired lung disease. In contrast to survival rates during the first year following transplantation, the long-term survival for patients after lung transplantation has not significantly improved in the past. In addition to other complications, acute cellular rejection constitutes a major cause for diminished function of pulmonary grafts, and can, among other factors, be causative for chronic rejection (bronchiolitis obliterans syndrome, BOS). In 2006, the International Society for Heart and Lung Transplantation (ISHLT) provided a revised version of the grading system for acute and chronic rejection of pulmonary grafts.

The impact of intercurrent EBV infection on ATP levels in CD4+ T cells of pediatric kidney transplant recipients

ImmuKnow measures ATP (ng/mL) in PHA-activated CD4+ T cells from patient's whole blood. According to published reports, median ImmuKnow is 258 ng/mL in stable pediatric kidney transplant (PKT) recipients > or =12 yr, and 165 ng/mL in those <12 yr. However, data on the effect of infection or AR on ImmuKnow are scarce. We studied the effect of Epstein-Barr virus (EBV) viremia on ImmuKnow in PKT with GD. Twenty-eight PKT with GD were reviewed. Group 1 has 19 PKT > or =12 yr, and group 2 has nine PKT <12 yr. Mean follow-up was 19.4 +/- 12 months. All ImmuKnow values discussed in this study were measured during GD +/- fever. None had ImmuKnow pretransplant. EBV DNA was isolated from patient blood by real-time PCR. Group 1 has eight boys and 11 girls (mean age = 16.6 +/- 2.4 yr). Group 2 has two boys and seven girls (mean age = 6 +/- 3.1 yr). Median ImmuKnow was 292 ng/mL in group 1, and 370 ng/mL in group 2. Nine children developed EBV viremia: two in group 1 (median ImmuKnow = 273 ng/mL), and seven in group 2 (median ImmuKnow = 475 ng/mL). Overall mean ImmuKnow in the nine EBV viremic patients was higher than that in the 19 non-viremic ones (422 +/- 176 ng/mL, and 302 +/- 113 ng/mL, respectively, unequal variance t-test, p = 0.08). Eight children developed AR (all in G1, median ImmuKnow = 272 ng/mL). In group 1, one patient developed concurrent EBV viremia and rejection, while another patient developed EBV viremia six months following a rejection episode. In group 2, none developed simultaneous AR, CMV, or BK virus infection with EBV viremia. None developed post-transplant lymphoproliferative disease. In summary, EBV viremia was paradoxically associated with high ImmuKnow in PKT <12 yr. This suggests strong co-stimulation of PHA-activated CD4+ T cells by EBV-transformed B cells.

Assessment of CD4 T-lymphocyte reactivity by the Cylex ImmuKnow assay in patients following allogeneic hematopoietic SCT

After allogeneic hematopoietic SCT (alloHSCT), immunosuppressed patients are susceptible to opportunistic infections, and uncontrolled function of the graft can result in GVHD. Accurate immune monitoring may help early detection and treatment of these severe complications. Between October 2005 and November 2007, a total of 170 blood samples were collected from 40 patients after alloHSCT in the Hadassah Hebrew University Medical Center and from 13 healthy controls. We utilized the Cylex ImmuKnow assay for CD4 ATP levels to compare known clinically immunocompromised vs immunocompetent patients after alloHSCT. We also compared the reconstitution of WBC count to the ImmuKnow results and clinical status. The patients' clinical course correlated with the stratification of immune response established by the ImmuKnow assay for solid organ transplantation (immunocompetent vs immunocompromised), and this often differed from their WBC count. On the basis of our observations, we conclude that the ImmuKnow assay is a simple and fast immune-monitoring technique for patients undergoing alloHSCT, with potential to predict clinical course and facilitate prompt management of post-HSCT complications. The assay should be evaluated prospectively in clinical trials.