A review of the evidence for use of thymoglobulin induction in renal transplantation

First-in-human Study With LIS1, a Next-generation Porcine Low Immunogenicity Antilymphocyte Immunoglobulin in Kidney Transplantation

BACKGROUND

Polyclonal rabbit antithymocyte globulins (ATGs) are commonly used in organ transplantation as induction. Anti- N -glycolylneuraminic acid carbohydrate antibodies which develop in response to rabbit carbohydrate antigens might lead to unwanted systemic inflammation. LIS1, the first new generation of antilymphocyte globulins (ALGs) derived from double knockout swine, lacking carbohydrate xenoantigens was already tested in nonhuman primates and rodent models.

METHODS

This open-label, single-site, dose escalation, first-in-human, phase 1 study evaluated the safety, T cell depletion, pharmacokinetics, and pharmacodynamics of LIS1. In an ascending dose cohort (n = 5), a primary kidney transplant recipient at low immunologic risk (panel reactive antibody [PRA] < 20%), received LIS1 for 5 d at either 0.6, 1, 3, 6, or 8 mg/kg. After each patient completed treatment, the data safety monitoring board approved respective dose escalation. In the therapeutic dose cohort (n = 5) in patients with PRA <50% without donor specific antibodies, 2 patients received 8 mg/kg and 3 patients 10 mg/kg.

RESULTS

CD3 + T cell depletion <100/mm 3 at day 2 was observed in all patients who received 6, 8, and 10 mg/kg of LIS1. The terminal half-life of LIS1 was 33.7 d with linearity in its disposition. Lymphocyte repopulation was fast and pretransplant lymphocyte subpopulation counts recovered within 2-4 wk. LIS1 was well tolerated, neither cytokine release syndrome nor severe thrombocytopenia or leukopenia were noticed. Antibodies to LIS1 were not detected.

CONCLUSIONS

In this first-in-human trial, genome-edited swine-derived polyclonal LIS1 ALG was well tolerated, did not elicit antidrug antibodies, and caused time-limited T cell depletion in low- and medium-risk kidney transplant recipients.

T-cell receptor sequencing reveals selected donor-reactive CD8+ T cell clones resist antithymocyte globulin depletion after kidney transplantation

High frequencies of donor-reactive memory T cells in the periphery of transplant candidates prior to transplantation are linked to the development of posttransplant acute rejection episodes and reduced allograft function. Rabbit antithymocyte globulin (rATG) effectively depletes naïve CD4+ and CD8+ T cells for >6 months posttransplant, but rATG's effects on human donor-reactive T cells have not been carefully determined. To address this, we performed T cell receptor β-chain sequencing on peripheral blood mononuclear cells aliquots collected pretransplant and serially posttransplant in 7 kidney transplant recipients who received rATG as induction therapy. We tracked the evolution of the donor-reactive CD4+ and CD8+ T cell repertoires and identified stimulated pretransplant, CTV-(surface dye)-labeled, peripheral blood mononuclear cells from each patient with donor cells or third-party cells. Our analyses showed that while rATG depleted CD4+ T cells in all tested subjects, a subset of donor-reactive CD8+ T cells that were present at high frequencies pretransplant, consistent with expanded memory cells, resisted rATG depletion, underwent posttransplant expansion and were functional. Together, our data support the conclusion that a subset of human memory CD8+ T cells specifically reactive to donor antigens expand in vivo despite induction therapy with rATG and thus have the potential to mediate allograft damage.

Machine Learning Model to Predict Graft Rejection After Kidney Transplantation

BACKGROUND

There are few predictive studies about early posttransplant outcomes taking into account baseline and posttransplant variables. The objective of this study was to create a predictive model for 30-day graft rejection using machine learning techniques.

METHODS

Retrospective study with 1255 patients undergoing transplant from living and deceased donors at a tertiary health service in Brazil. Recipient, donor, transplantation, and postoperative period data were collected from physical and electronic records. We split the data into derivation (training) and validation (test) datasets. Five supervised machine learning algorithms were developed with this subset of variables in the training set: Simple Logistic Regression, Lasso, Multilayer Perceptron, XGBoost, and Light GBM.

RESULTS

There were 147 (12.48%) cases of graft rejection within 30 days of transplantation. The best model was XGBoost (accuracy, 0.839; receiver operating characteristic area under the curve, 0.715; precision, 0.900). The model showed that deceased donor transplantation, glomerulopathy as an underlying disease, and donor's use of vasoactive drugs had more than 20% importance as rejection risk factors. The variables with the greatest predictive values were thymoglobulin induction and delayed graft function.

CONCLUSIONS

We fitted a machine learning model to predict 30-day graft rejection after kidney transplantation that reaches a higher accuracy and precision. Machine learning models could contribute to predicting kidney survival using nontraditional approaches.

LIS1, a glyco-humanized swine polyclonal anti-lymphocyte globulin, as a novel induction treatment in solid organ transplantation

Anti-thymocyte or anti-lymphocyte globulins (ATGs/ALGs) are immunosuppressive drugs used in induction therapies to prevent acute rejection in solid organ transplantation. Because animal-derived, ATGs/ALGs contain highly immunogenic carbohydrate xenoantigens eliciting antibodies that are associated with subclinical inflammatory events, possibly impacting long-term graft survival. Their strong and long-lasting lymphodepleting activity also increases the risk for infections. We investigated here the in vitro and in vivo activity of LIS1, a glyco-humanized ALG (GH-ALG) produced in pigs knocked out for the two major xeno-antigens αGal and Neu5Gc. It differs from other ATGs/ALGs by its mechanism of action excluding antibody-dependent cell-mediated cytotoxicity and being restricted to complement-mediated cytotoxicity, phagocyte-mediated cytotoxicity, apoptosis and antigen masking, resulting in profound inhibition of T-cell alloreactivity in mixed leucocyte reactions. Preclinical evaluation in non-human primates showed that GH-ALG dramatically reduced CD4+ (p=0.0005,***), CD8+ effector T cells (p=0.0002,***) or myeloid cells (p=0.0007,***) but not T-reg (p=0.65, ns) or B cells (p=0.65, ns). Compared with rabbit ATG, GH-ALG induced transient depletion (less than one week) of target T cells in the peripheral blood (<100 lymphocytes/L) but was equivalent in preventing allograft rejection in a skin allograft model. The novel therapeutic modality of GH-ALG might present advantages in induction treatment during organ transplantation by shortening the T-cell depletion period while maintaining adequate immunosuppression and reducing immunogenicity.

Development of CMV-specific cytotoxic T cells (CMV-Tc) in pediatric renal transplant recipients with CMV viremia

BACKGROUND

Viral infections are controlled primarily by viral-specific T cells, raising concern for adequate T-cell response to clear CMV infection in transplant recipients receiving lymphocyte-depleting agents (LDA). We examined the rates of CMV viremia and clearance, seroconversion, and CMV-specific CD8+ T cell (CMV-Tc) activity with class of induction agent received.

METHODS

Retrospective review of 45 pediatric renal transplant recipients who received induction with LDA (n = 31) or non-LDA (NLDA; n = 14) received valganciclovir prophylaxis for 6 months post-transplant and CMV-PCR monitoring. CMV-Tc was measured by intracellular IFNγ flow cytometry, when possible, at baseline, 1 month after CMV viremia (>5 copies/PCR) and serially until CMV-Tc was positive (≥0.2%).

RESULTS

Viremia rates at 1, 2, and 4 years post-transplant were higher in LDA vs. NLDA (46.3% vs. 7.2%, 64.2% vs. 7.2%, and 64.2% vs. 7.2%, respectively; p = .002). Viremia rates at these time points in seronegative LDA (50.3%, 71.6%, 71.6%) were significantly or near significantly higher than seronegative NLDA (9.1%, 9.1%, 9.1%; p = .004), seropositive-LDA (22.3%, 22.3%, 22.3%; p = .07), or seropositive NLDA (0%, 0%, 0%; p = .07). Eleven of 17 (64.7%) viremic subjects required valganciclovir dose reduction during the prophylaxis period for leukopenia. All viremic LDA patients developed CMV-Tc. One viremic NLDA patient did not develop CMV-Tc. No patients developed CMV disease.

CONCLUSION

CMV seronegative pediatric renal transplant patients receiving LDA are more likely to have valganciclovir prophylaxis dose reduction and develop subclinical CMV viremia; however, all developed CMV-Tc. Larger prospective studies are needed to further understand the effects of induction agents on CMV-Tc and CMV-Tc's role post-transplant.

Induction and Donor Specific Antibodies in Low Immunologic Risk Kidney Transplant Recipients

Background

Optimal induction for patients without pretransplant donor-specific antibodies (DSAs) is poorly defined. The goal of this study was to compare the incidence of de novo DSA (dnDSA) and graft outcomes between induction therapies in patients with a negative virtual crossmatch (VXM).

Methods

A retrospective chart review was performed, identifying 782 patients with a negative VXM who underwent kidney transplantation at a single, high-volume institution between January 2013 and May 2017. Kaplan-Meier analysis was used to assess the incidence of dnDSA and allograft survival between induction therapies in this group. dnDSA is defined as the development of new post-transplant DSA, at any MFI level.

Results

Induction therapy included alemtuzumab (N=87, 11%), basiliximab (N=522, 67%), and anti-thymocyte globulin (ATG; N=173, 22%). One-year graft survival was similar between groups (alemtuzumab, 100%; basiliximab, 98%; ATG, 99%). Incidence of acute rejection at 1 year was <2% and not different between the three groups. Alemtuzumab was associated with the highest incidence of dnDSA at 14%, compared with 5% and 8% in basiliximab and ATG groups, respectively, at 1 year (P=0.009). In multivariate regression analyses, alemtuzumab retained its significant association with a dnDSA HR of 2.5 (95% CI, 1.51 to 4.25; P=0.0004).

Conclusions

In summary, alemtuzumab was associated with a higher rate of dnDSA development in patients with a negative VXM; however, this finding was not associated with rejection or graft failure.

Severe Intraoperative Anaphylaxis Related to Thymoglobulin during Living Donor Kidney Transplantation

Anaphylaxis secondary to thymoglobulin (anti-thymocyte globulin) is a rare condition that can be life threatening. Thymoglobulin is a rabbit-derived T-cell depleting polyclonal immunoglobulin. It is commonly used for induction immunosuppression and/or for treatment of acute rejection in renal transplantation. We report a case of a living kidney transplant recipient who developed intraoperative anaphylactic shock secondary to thymoglobulin. The patient had a history of pet rabbit exposure. This case report highlights the importance of prompt identification and management of intraoperative anaphylaxis, which is key to a successful outcome. Induction immunosuppression selection based on patient characteristics is important. Communication between the anesthesia team and surgeons played a key role in stopping the donor surgery.

Benefits of multimodal enhanced recovery pathway in patients undergoing kidney transplantation

BACKGROUND

Use of enhanced recovery after surgery (ERAS) pathways to accelerate functional recovery and reduce length of stay (LOS) has rarely been investigated in kidney transplantation (KTX).

MATERIALS AND METHODS

Consecutive adult isolated KTXs between July 2015 and July 2016 (ERAS, n = 139) were compared with a historical cohort between January 2014 and July 2015 (HISTORIC, n = 95).

RESULTS

Enhanced recovery after surgery recipients were significantly more likely to receive kidneys that were non-local (56.1% vs 4.2%), higher Kidney Donor Profile Index (36-85, 58.4% vs 45.2%; >85, 15.2% vs 10.7%), cold ischemia time ≥30 h (62.4% vs 4.7%), induced with antithymocyte globulin (97.1% vs 87.4%), and to develop delayed graft function (46.4% vs 25.0%). LOS was shorter by 1 day among ERAS (mean 4.59) compared to HISTORIC patients (mean 5.65) predominantly due to a shift in discharges within 3 days (32.4% vs 4.2%); 30-day readmission to the hospital (27.3% vs 27.4%) or emergency room visit (9.4% vs 7.4%) was similar. There was one 30-day death in the ERAS group and none in the HISTORIC group. Return to bowel function and early meal consumption were significantly associated with ERAS, however, with somewhat higher diarrhea and emesis rates.

CONCLUSION

ERAS following KTX correlated with lower LOS without change in readmissions or ER visits despite higher delayed graft function rates.

Cytolytic Induction Therapy Improves Clinical Outcomes in African-American Kidney Transplant Recipients

OBJECTIVE

Determine the impact of cytolytic versus IL-2 receptor antibody (IL-2RA) induction on acute rejection, graft loss and death in African-American (AA) kidney transplant (KTX) recipients.

BACKGROUND

AAs are underrepresented in clinical trials in transplantation; thus, there is controversy regarding the optimal choice of perioperative antibody induction in KTX to improve outcomes.

METHODS

National cohort study using US transplant registry data from January 1, 2000 to December 31, 2009 in adult solitary AA KTX recipients, with at least 5 years of follow-up. Multivariable logistic and Cox regression were utilized to assess the outcomes of acute rejection, graft loss, and mortality, with interaction terms to assess effect modification.

RESULTS

Twenty-five thousand eighty-four adult AAs receiving solitary KTX were included, 16,927 (67.5%) received cytolytic induction and 8157 (32.5%) received IL-2RA induction. After adjustment for recipient sociodemographics, donor, and transplant characteristics, the use of cytolytic induction therapy reduced the risk of acute rejection by 32% (OR 0.68, 0.62-0.75), graft loss by 9% (HR 0.91, 0.86-0.97), and death by 12% (HR 0.88, 0.83-0.94). There were a number of significant effect modifiers, including public insurance, panel reactive antibody, delayed graft function, and steroid withdrawal; in these groups, cytolytic induction substantially improved clinical outcomes.

CONCLUSIONS

These data demonstrate that cytolytic induction therapy, as compared with IL-2RA, reduces the risk of rejection, graft loss, and death in adult AA KTX recipients, particularly in those who are sensitized, receive public insurance, develop delayed graft function, or undergo steroid withdrawal.

Comparing Outcomes between Antibody Induction Therapies in Kidney Transplantation

Kidney transplant recipients often receive antibody induction. Previous studies of induction therapy were often limited by short follow-up and/or absence of information about complications. After linking Organ Procurement and Transplantation Network data with Medicare claims, we compared outcomes between three induction therapies for kidney recipients. Using novel matching techniques developed on the basis of 15 clinical and demographic characteristics, we generated 1:1 pairs of alemtuzumab-rabbit antithymocyte globulin (rATG) (5330 pairs) and basiliximab-rATG (9378 pairs) recipients. We used paired Cox regression to analyze the primary outcomes of death and death or allograft failure. Secondary outcomes included death or sepsis, death or lymphoma, death or melanoma, and healthcare resource utilization within 1 year. Compared with rATG recipients, alemtuzumab recipients had higher risk of death (hazard ratio [HR], 1.14; 95% confidence interval [95% CI], 1.03 to 1.26; P<0.01) and death or allograft failure (HR, 1.18; 95% CI, 1.09 to 1.28; P<0.001). Results for death as well as death or allograft failure were generally consistent among elderly and nonelderly subgroups and among pairs receiving oral prednisone. Compared with rATG recipients, basiliximab recipients had higher risk of death (HR, 1.08; 95% CI, 1.01 to 1.16; P=0.03) and death or lymphoma (HR, 1.12; 95% CI, 1.01 to 1.23; P=0.03), although these differences were not confirmed in subgroup analyses. One-year resource utilization was slightly lower among alemtuzumab recipients than among rATG recipients, but did not differ between basiliximab and rATG recipients. This observational evidence indicates that, compared with alemtuzumab and basiliximab, rATG associates with lower risk of adverse outcomes, including mortality.

An avoidable cause of thymoglobulin anaphylaxis

BACKGROUND

Thymoglobulin® (anti-thymocyte globulin [rabbit]) is a purified pasteurised, gamma immune globulin obtained by immunisation of rabbits with human thymocytes. Anaphylactic allergic reactions to a first injection of thymoglobulin are rare.

CASE PRESENTATION

We report a case of serious anaphylactic reaction occurring after a first intraoperative injection of thymoglobulin during renal transplantation in a patient with undiagnosed respiratory allergy to rabbit allergens.

CONCLUSIONS

This case report reinforces the importance of identifying rabbit allergy by a simple combination of clinical interview followed by confirmatory skin testing or blood tests of all patients prior to injection of thymoglobulin, which is formally contraindicated in patients with a history of hypersensitivity to rabbit proteins.

Targeted preemptive therapy according to perceived risk of CMV infection after kidney transplantation

Background

Methods

Results

Conclusion

Incidence and differential characteristics of culture-negative fever following pancreas transplantation with anti-thymocyte globulin induction

BACKGROUND

Limited data are available on the incidence and characteristics of culture-negative fever following pancreas transplantation (PTx) with anti-thymocyte globulin (ATG) induction. Our study aims to better define the features of culture-negative fever, so it can be delineated from infectious fever, hopefully helping clinicians to guide antibiotic therapy in this high-risk patient population.

METHODS

We performed a retrospective cohort study of postoperative fever among 198 consecutive patients undergoing PTx at our center between August 1, 2004 and December 31, 2014. Fever was classified as culture-negative if there was neither a positive culture nor a documented clinical diagnosis of infection.

RESULTS

Fever was identified in 113 patients; 66 were deemed to be infectious, 39 were culture-negative, and 8 were indeterminate. High body mass index of recipient (odds ratio 1.87, 95% confidence interval: 1.15-3.03, P = 0.011) was a significant factor associated with culture-negative fever in multivariate analysis. No patients with culture-negative fever were diagnosed with infiltrates or effusion on chest radiography. In addition, an increase in white blood cell count, C-reactive protein, and serum amylase was less prominent in culture-negative fever. Culture-negative fever developed most frequently at postoperative 7 or 14 days, showing a biphasic curve.

CONCLUSION

Culture-negative fever develops in a substantial proportion of patients early after PTx. The awareness of the possibility and clinical features of post-transplant culture-negative fever might help clinicians to guide antibiotic therapy in this high-risk patient population, especially following ATG induction and early steroid withdrawal.

Rabbit antithymocyte globulin-induced serum sickness disease and human kidney graft survival

BACKGROUND

Rabbit-generated antithymocyte globulins (ATGs), which target human T cells, are widely used as immunosuppressive agents during treatment of kidney allograft recipients. However, ATGs can induce immune complex diseases, including serum sickness disease (SSD). Rabbit and human IgGs have various antigenic differences, including expression of the sialic acid Neu5Gc and α-1-3-Gal (Gal), which are not synthesized by human beings. Moreover, anti-Neu5Gc antibodies have been shown to preexist and be elicited by immunization in human subjects. This study aimed to assess the effect of SSD on long-term kidney allograft outcome and to compare the immunization status of grafted patients presenting with SSD following ATG induction treatment.

METHODS

We analyzed data from a cohort of 889 first kidney graft recipients with ATG induction (86 with SSD [SSD(+)] and 803 without SSD [SSD(-)]) from the Données Informatisées et Validées en Transplantation data bank. Two subgroups of SSD(+) and SSD(-) patients that had received ATG induction treatment were then assessed for total anti-ATG, anti-Neu5Gc, and anti-Gal antibodies using ELISA assays on sera before and after transplantation.

RESULTS

SSD was significantly associated with long-term graft loss (>10 years, P = 0.02). Moreover, SSD(+) patients exhibited significantly elevated titers of anti-ATG (P = 0.043) and anti-Neu5Gc (P = 0.007) IgGs in late post-graft samples compared with SSD(-) recipients.

CONCLUSION

In conclusion, our data indicate that SSD is a major contributing factor of late graft loss following ATG induction and that anti-Neu5Gc antibodies increase over time in SSD(+) patients.

FUNDING

This study was funded by Société d'Accélération du Transfert de Technologies Ouest Valorisation, the European FP7 "Translink" research program, the French National Agency of Research, Labex Transplantex, the Natural Science and Engineering Research Council of Canada, and the Canadian Foundation for Innovation.

Circulating biomarkers of tolerance

On the basis of reviewed literature here we describe models of tolerance and summarize the evidence of circulating biomarkers suitable for the assessment of immunological risk in organ transplantation. We focused on results of evaluation of specific peripheral immune cell populations and transcripts in peripheral blood of operationally tolerant liver and kidney transplant recipients. Validation of described markers to define potentially tolerant patients before their use in clinical trials is critical.

Antithymocyte antibody-induced coagulopathy in renal transplant recipients

BACKGROUND

Antithymocyte antibody (ATA) remains the most commonly used induction immunosuppressive agent in renal transplantation (RT). To date, few case reports of ATA-induced coagulopathy exist.

METHODS

We performed a single-center, retrospective analysis of renal transplant recipients (RTRs) who underwent RT followed by ATA therapy between 2007 and 2011. The protocol used for deceased donor and unrelated living donor recipient immunosuppression was Thymoglobulin (TMG), methylprednisolone, Cellcept, Prograf, and Rapamune. In related living donor recipients, Simulect (SIM) was substituted for TMG. The international normalized ratio (INR) was routinely checked on days 0 and 2, and thereafter at the discretion of the surgeon. RTRs were transfused packed red blood cells (PRBCs) or fresh frozen plasma (FFP) at the discretion of the surgeon.

RESULTS

During the study period, 257 RTs were performed at our institution. The following 18 RTR were excluded: simultaneous kidney and pancreas transplant recipients (4), RTRs on warfarin at the time of admission (2), RTRs who received OKT3 (2), and RTRs with INR ≥ 1.2 at the time of admission (10). Of the remaining 239 RTR, 208 (87%) underwent TMG induction therapy; 31 RTR (13%) underwent SIM induction therapy. The mean INR peaked in both groups on day 4 but was higher in TMG recipients (TMG 1.35, SIM 1.20). FFP was transfused in 65 TMG (31%) and 3 SIM (10%) recipients (P = .01); PRBCs were transfused in 88 TMG (44%) and 6 SIM (19%) recipients (P = .02). No patients returned to the operating room for bleeding complications within 7 days of RT. Patient age, gender, ethnicity, and diabetes status were not statistically significant factors in the development of coagulopathy.

CONCLUSION

TMG administration is associated with coagulopathy. Using an INR screening protocol and an aggressive transfusion protocol, bleeding complications associated with coagulopathy can be avoided in this higher-risk group.

A surgeons' guide to renal transplant immunopathology, immunology, and immunosuppression

The response to allografting involves adaptive and innate immune mechanisms. In the adaptive system, activated T cells differentiate to cytotoxic effectors that attack the graft and trigger B cells to differentiation to plasma cells that produce anti-HLA antibodies. The innate immune system recognizes antigens in a non-specific manner and recruits immune cells to the graft through the productions of chemotactic factors, and activation of cytokines and the complement cascade. In the kidney the tubules and the endothelium are the targets of the rejection response. Immune suppression is effective in modulating the adaptive immune system effect on graft histology.

Kidney Transplantation in the United States: Economic Burden and Recent Trends Analysis

Objective

As kidney transplant is the preferred mode of management of advanced kidney disease and economic trends for kidney transplant procedures are not well known, data were analyzed to assess these trends.

Data Source

Annual data for 1998 to 2008 from the Nationwide Inpatient Sample, Healthcare Cost and Utilization Project, Agency for Healthcare Research and Quality were used to analyze characteristics of patients discharged from hospitals in the United States with kidney transplant as the primary procedure.

Data Synthesis/Results

The population more than 65 years old had the most significant increase in hospitalizations for kidney transplant procedures (P < .01). The mean length of stay decreased by 2.8 days over the period studied ( P = .02). Mean hospital charge increased despite a decrease in length of stay resulting in a 225% increase in charge per day of hospitalization, from $6907 in 1998 to $22484 in 2008. The national aggregate hospital charges for kidney transplant procedures rose from $0.9 billion in 1998 to $3.1 billion in 2008. Kidney transplant was overall ranked sixth by mean cost per hospitalization and ranked seventh by mean charge per hospitalization among the Clinical Classification Software's Services and Procedures in this database in 2008.

Conclusion

Despite shorter hospital stays, the economic burden of kidney transplants increased from 1998 to 2008.

Anti-CD2 producing pig xenografts effect localized depletion of human T cells in a huSCID model

BACKGROUND

We investigated whether graft produced anti-human CD2, mediated by adenovirus (Adv) transduction of pig neonatal islet cell clusters (pNICC), would protect xenografts in a humanized mouse model from immune attack and whether such immunosuppression would remain local.

METHODS

A mouse anti-human CD2 Ab (CD2hb11) previously generated by us was genetically engineered to produce chimeric and humanized versions. The three forms of CD2hb11 were named dilimomab (mouse), diliximab (chimeric) and dilizumab (humanized). All 3 forms of CD2hb11 Ab were tested for their ability to bind CD3(+) human T cells and to inhibit a human anti-pig xenogeneic mixed lymphocyte reaction (MLR). They were administered systemically in a humanized mouse model in order to test their ability to deplete human CD3(+) T cells and whether they induced a cytokine storm. An adenoviral vector expressing diliximab was generated for transduction of pNICC. Humanized mice were transplanted with either control-transduced pNICC or diliximab-transduced pNICC and human T cells within grafts and spleens were enumerated by flow cytometry.

RESULTS

Dilimomab and diliximab inhibited a human anti-pig xenogeneic response but dilizumab did not. All 3 forms of CD2hb11 Ab bound human T cells in vitro though dilimomab and diliximab exhibited 300-fold higher avidity than dilizumab. All 3 anti-CD2 Abs could deplete human CD3(+) T cells in vivo in a humanized mouse model without inducing upregulation of activation markers or significant release of cytokines. Humanized mice transplanted with diliximab-transduced pNICC afforded depletion of CD3(+) T cells at the graft site leaving the peripheral immune system intact.

CONCLUSIONS

Local production of a single Ab against T cells can reduce graft infiltration at the xenograft site and may reduce the need for conventional, systemic immunosuppression.

Severe anaphylactoid reaction to thymoglobulin in a pediatric renal transplant recipient

Intraoperative administration of thymoglobulin is an integral part of the anti-rejection regimen during organ transplantation. However, its administration may be associated with complications. An anaphylactoid reaction that occurred in a pediatric recipient of a living-related renal transplant, on initiating an intravenous infusion of thymoglobulin, is presented.

A CD3+ count-based thymoglobulin induction regimen permits delayed introduction of calcineurin inhibitors in kidney transplantation

BACKGROUND

Withholding calcineurin inhibitors (CNIs) can be considered when graft function is inadequate following kidney transplantation (KT). Thymoglobulin (rATG) can be used to prevent acute rejection while CNIs are being withheld. Here, we report our results of a novel CNI-sparing induction protocol, which utilizes a CD3+ cell count-based rATG treatment regimen when delayed graft function (DGF) develops in the immediate postoperative period.

METHODS

In a cohort of 153 consecutive deceased-donor KT recipients, all received a single intraoperative dose of basiliximab; 84 subsequently developed DGF and therefore received rATG (rATG+ group), while 69 demonstrated immediate graft function and received CNIs (rATG- group).

RESULTS

In the rATG+ group, mean duration of therapy was 8.5±6.0 d, permitting CNI initiation to be delayed until postoperative day 10.3±6.2. Cumulative dose of rATG was only 5.1±4.5 mg/kg while targeting CD3+ counts of ≤30 cells/mm3. CD3+ counts were reduced to a mean of 16.7±17.0 cells/mm3 during therapy. At one yr, patient and graft survival rates were 97.6% and 92.9%, respectively, while the frequency of infections and malignancies were not significantly increased compared to the rATG- group.

CONCLUSION

A unique induction regimen successfully delayed CNI initiation by using modest doses of rATG to deplete CD3+ cells, while yielding excellent long-term graft outcome without increased risk of infection or malignancy.

Anti-thymocyte globulin for conditioning in matched unrelated donor hematopoietic cell transplantation provides comparable outcomes to matched related donor recipients

Rabbit anti-thymocyte globulin (ATG) is used as prophylaxis against GVHD following allogeneic hematopoietic cell transplantation (HCT). At our institution, ATG is exclusively used in the conditioning of matched unrelated donor (URD) transplant recipients. A total of 50 URD HCT recipients who received ATG (ATG group) were retrospectively compared with 48 matched related donor (MRD) HCT recipients who did not receive ATG (no ATG group). There were no significant differences between the groups in rates of day 100 mortality, acute GVHD or relapse. Chronic GVHD incidence was significantly lower in the ATG group (P = 0.007). At a median follow-up of 36 months in the entire cohort, 50% patients are alive in the ATG group and 63% of the patients are alive in the no ATG group (P = 0.13). We conclude that the administration of ATG to patients undergoing URD HCT preserves the anti-leukemia benefit of the transplant, while reducing the risk of developing GVHD, resulting in OS rates that are comparable to MRD HCT recipients.

A simplified immune suppression scheme leads to persistent micro-dystrophin expression in Duchenne muscular dystrophy dogs

Highly abbreviated micro-dystrophin genes have been intensively studied for Duchenne muscular dystrophy (DMD) gene therapy. Following adeno-associated virus (AAV) gene transfer, robust microgene expression is achieved in murine DMD models in the absence of immune suppression. Interestingly, a recent study suggests that AAV gene transfer in dystrophic dogs may require up to 18 weeks' immune suppression using a combination of three different immune-suppressive drugs (cyclosporine, mycophenolate mofetil, and anti-dog thymocyte globulin). Continued immune suppression is not only costly but also may cause untoward reactions. Further, some of the drugs (such as anti-dog thymocyte globulin) are not readily available. To overcome these limitations, we developed a novel 5-week immune suppression scheme using only cyclosporine and mycophenolate mofetil. AAV vectors (either AV.RSV.AP that expresses the heat-resistant human alkaline phosphatase gene, or AV.CMV.μDys that expresses the canine R16-17/H3/ΔC microgene) at 2.85×10(12) vg particles were injected into adult dystrophic dog limb muscles under the new immune suppression protocol. Sustained transduction was observed for nearly half year (the end of the study). The simplified immune suppression strategy described here may facilitate preclinical studies in the dog model.

Low-dose rabbit antithymocyte globulin induction therapy results in prolonged selective lymphocyte depletion irrespective of maintenance immunosuppression

Rabbit antithymocyte globulin therapy (rATG) is a potent lymphocyte-depleting agent commonly used following renal transplantation to reduce the risk of acute rejection. Standard doses (7-10 mg/kg) of rATG result in profound lymphopenia and predispose patients to infection and malignancy. The effects of lower doses of rATG (LoD-rATG, 3-5 mg/kg) on peripheral blood lymphocytes (PBL) are as yet unknown. In this prospective clinical trial, PBL subsets were characterized by flow cytometry over 12 months following LoD-rATG therapy. All patients were initially treated with standard doses of tacrolimus, mycophenolic acid, and prednisone. At 3 months, patients were randomized to either lower doses of tacrolimus or sirolimus to examine the effects of maintenance immunosuppression on PBL reemergence. LoD-rATG therapy resulted in prolonged suppression of CD19+ B cells, total CD3+ T cells, as well as naïve and memory CD4+ T cell and CD4/CD25/Foxp3+ T-regulatory subsets irrespective of chronic immunosuppressive therapy. Selective depletion was only noted in the CD4CD45RA+ naïve T-cell subset resulting in an altered memory/naïve CD4+ ratio. LoD-rATG failed to deplete CD8+ T cells, which increased their relative contribution to the total CD3+ pool. All other lymphocyte subsets maintained near normal proportions. Thus, LoD-rATG therapy may lessen the adverse effects of full dose rATG while maintaining overall efficacy.