RABBIT ANTITHYMOCYTE GLOBULIN AS INDUCTION IMMUNOTHERAPY FOR PEDIATRIC DECEASED DONOR KIDNEY TRANSPLANTATION

0022-5347/05/1742-0703/0 THE JOURNAL OF UROLOGY® Copyright © 2005 by AMERICAN UROLOGICAL ASSOCIATION

Vol. 174, 703–707, August 2005 Printed in U.S.A.

DOI: 10.1097/01.ju.0000164752.37118.9c

RABBIT ANTITHYMOCYTE GLOBULIN AS INDUCTION IMMUNOTHERAPY FOR PEDIATRIC DECEASED DONOR KIDNEY TRANSPLANTATION M. HAMDI KAMEL, P. MOHAN, D. M. LITTLE, A. AWAN

AND

D. P. HICKEY*

From the Department of Urology and Transplantation (MHK, PM, DML, DPH), Beaumont Hospital, and Temple Street Hospital for Sick Children (AA), Dublin, Ireland

ABSTRACT

Purpose: There is scant literature describing the long-term outcome of the use of antithymocyte globulin induction immunotherapy in pediatric deceased donor kidney transplants. We retrospectively studied the long-term results and safety of antithymocyte globulin as induction immunotherapy in all children undergoing transplantation at our institution since 1991. Materials and Methods: A total of 120 kidney transplants were performed in 95 patients 18 years or younger between January 1986 and December 1998. Patients were divided into 2 groups. The control group (63 patients) received cyclosporine, azathioprine and prednisolone, while the treatment group (59 patients) received rabbit antithymocyte globulin (RATG) induction immunotherapy for 6 to 10 days, combined with cyclosporine, azathioprine and prednisolone. Results: Actuarial patient survival rates at 1, 3, 5 and 10 years were 96%, 95%, 95% and 90%, respectively. Actuarial graft survival rates at 1, 3, 5 and 10 years were 76%, 69%, 64% and 49%, respectively. The 1, 3, 5 and 10-year graft survival rates in the control group were 62%, 57%, 51% and 36%, respectively, compared to 90%, 82%, 79% and 69%, respectively, in the RATG group (p ⫽ 0.001). There was a significant difference in the incidence of graft loss secondary to acute cellular rejection between the control and RATG groups (19.7% vs 3.3%, p ⫽ 0.008). There was no difference in infectious complications between the control and RATG groups (13% vs 20%, p ⫽ 0.33), and there was no case of post-transplant lymphoproliferative disorder encountered in either group. Conclusions: The use of rabbit antithymocyte globulin in pediatric deceased donor kidney transplant recipients resulted in significant improvement in graft survival and was relatively safe. KEY WORDS: antilymphocyte serum, kidney transplantation, graft rejection, immunotherapy

Kidney transplantation is accepted as the treatment of choice for children with end stage renal failure. Current success in pediatric kidney transplantation is attributed to improvements in immunosuppressive therapy, better cross matching techniques, refinement of surgical technique and the provision of age appropriate clinical care.1 Children are known to have a more active immune system than adults, and graft loss secondary to acute cellular rejection is reportedly higher among this age group.2 Since 1991, we have adopted a quadruple immunosuppressive protocol including rabbit antithymocyte globulin (RATG) as induction immunotherapy in all children undergoing transplantation at our institution. This study is a retrospective analysis of the long-term results and safety of RATG in this group of patients. PATIENTS AND METHODS

A total of 120 consecutive kidney transplants were performed in 95 pediatric recipients between January 1, 1986 and December 31, 1998. These patients consisted of 53 males and 42 females, and mean age at transplantation was 12.4 years (range 2 to 17). Patients were divided into 2 groups, controls (61 patients) and RATG treatment arm (59). Average time on the waiting list was 11 months. Table 1 summa-

rizes patient demographics. Table 2 outlines causes of end stage renal disease in both groups. Maintenance immunosuppression for the 2 groups consisted of cyclosporine, azathioprine and prednisolone. Cyclosporine dose was 500 mg/m2 for children younger than 6 years, administered in 3 divided doses, and 15 mg/kg for older children, administered in 2 divided doses. The dose of cyclosporine was adjusted to maintain a trough level of 250 to 300 ng/ml during the first post-transplant month and a trough level of 150 to 200 ng/ml thereafter. Azathioprine was given as a maintenance drug in a dose of 2 mg/kg daily, with dose adjustment based on white cell counts. Prednisolone was tapered during a 3-month period following transplantation until the children were maintained on 5 mg alternate day dosing. Rabbit antithymocyte globulin was given as 5 mg/kg intravenously (IV) for 4 hours once every 24 hours for 2 doses, followed by a dose of 2.5 mg/kg IV once every 24 hours for 6 to 10 doses. RATG dose was subsequently adjusted to maintain an absolute lymphocyte count of 0.1 ⫻ 109/l. Adjustment of RATG dose in the range of 20% was done if the desired absolute lymphocytic count was not achieved. In all patients RATG was administered via a central line. Patients receiving RATG with cytomeglo virus (CMV) antibody positive donor recipient combinations (D⫹/R-, D-/R⫹, D⫹/R⫹) received CMV prophylaxis of 2.5 mg/kg ganciclovir IV every 12 hours. Subsequently, patients continued on oral CMV prophylaxis, which consisted of 400 mg acyclovir orally per day for 3 months. Antifungal medication consisting of 3

Submitted for publication November 14, 2004. * Correspondence: Beaumont Hospital, Dublin 9, Ireland (telephone: 00353 1 8093000; FAX: 00353 1 8093962; e-mail: [email protected]). 703

704

RABBIT ANTITHYMOCYTE GLOBULIN FOR DECEASED DONOR KIDNEY TRANSPLANTATION TABLE 1. Patient demographics Variables

Controls

RATG Pts

61

59

6 55

5 54

35 26

34 25

15 31 14 2.54 ⫾ 1.26 21.46 ⫾ 5.69 21.05 ⫾ 13.29 10.32 ⫾ 19.9

16 25 19 2.78 ⫾ 1.04 21.537 ⫾ 0.07 25.90 ⫾ 11.66 15.94 ⫾ 26

No. Mean pt age: Younger than 5 yrs 5 Yrs or older

p Value 0.52 0.56

No. males No. females No. renal replacement therapy: Hemodialysis Continuous ambulatory peritoneal dialysis Preemptive Mean human leukocytic antigen mismatch ⫾ SD Mean cold ischemia time (hrs) ⫾ SD Mean donor age (yrs) ⫾ SD Mean % panel reactive antibodies ⫾ SD

0.44

mg/kg fluconazole was given as prophylaxis and continued for the duration of therapy. Bacterial and Pneumocystis carinii pneumonia prophylaxis was achieved with trimethoprim-sulfamethoxazole, pediatric suspension 240 mg/5 ml in young children or tablets in older ones, for 6 months. The cost of each day of RATG treatment added approximately $120 to the overall cost of pediatric kidney transplantation at our department. Assessment of acute rejection as well as chronic allograft nephropathy was based on clinical features, biochemical parameters and biopsy of the transplanted kidney. Reversal of acute rejection episodes was by steroid boost of 10 mg/kg methylprednisolone IV per 24 hours, for 3 to 5 days. Steroid resistant rejection was treated with monoclonal antibody OKT3. Median hospital stay was 13 days (range 3 to 31) for the control group and 15 days (7 to 32) for the RATG group (p ⫽ 0.49). Statistical methods. Demographic and clinical characteristics were compared for the 2 groups using nonparametric Wilcoxon rank sum and Fisher’s exact tests. Kaplan-Meier methods were used to construct survivor functions, and group comparisons for survival outcomes were analyzed using the Wilcoxon (Breslow) test. All statistical analysis was conducted using Stata® version 8.0.

0.39 0.5 0.953 0.59

RESULTS

Patient survival. Minimum followup was 6 years (range 6 to 18). Actuarial 1, 3, 5 and 10-year survival rates for all patients were 96%, 95%, 95% and 90%, respectively. Actuarial 1, 3, 5 and 10-year survival rates for the control group were 92%, 90%, 90% and 87%, respectively, compared to 100%, 100%, 100% and 92%, respectively, for the RATG group (fig. 1, p ⫽ 0.1). Cause of death. There were 7 mortalities overall (5.8%), 5 in the control group and 2 in the RATG group. Causes of death in the control group were cerebrovascular accident in 2 patients, sepsis in 1, hyperkalemia in 1 and unknown in 1. Causes of death in the RATG group were complications following bone marrow transplantation for hypogammaglobulinemia in 1 patient and unknown in 1. Graft survival. Actuarial 1, 3, 5 and 10-year graft survival rates for the 120 grafts were 76%, 69%, 64% and 49%, respectively. Actuarial 1, 3, 5 and 10-year graft survival rates were 62%, 57%, 51% and 36%, respectively, for the control group, compared to 90%, 82%, 79% and 69%, respectively, for the RATG group (fig. 2, p ⫽ 0.001). Cause of graft failure. Causes of failure in each group are summarized in table 3. A striking difference was noted in

TABLE 2. Causes of end stage renal disease Causes Glomerulonephritis (32 pts): Focal segmental glomerulosclerosis IgA nephropathy Membranoproliferative glomerulonephritis Rapidly progressing glomerulonephritis Unspecified Reflux nephropathy (26 pts) Neurogenic bladder (14 pts) Nephrotic syndrome (4 pts) Congenital and hereditary conditions (32 pts): Medullary cystic disease Cystinosis Renal dysplasia Multicystic kidneys Bardet-Biedl syndrome Potter’s syndrome Familial nephropathy Polycystic kidney disease Miscellaneous (12 pts): Wilms tumor Renovascular disease Hemolytic uremic syndrome Systemic lupus erythematosus Unknown Totals

No. Controls

No. RATG Pts

Totals

6 1 5

7 1 1

13 2 6

3

3

6

5 17 6 0

— 9 8 4

5 26 14 4

0 2 6 1 2 0 2 1

2 0 11 0 0 1 1 3

2 2 17 1 2 1 3 4

0 0 2 1 4

2 1 1 0 1

2 1 3 1 5

64

56

120

FIG. 1. Patient survival in both groups. RATG, rabbit antithymocyte globulin.

705

RABBIT ANTITHYMOCYTE GLOBULIN FOR DECEASED DONOR KIDNEY TRANSPLANTATION

86 mmol/l (40 to 396) in the RATG group. This difference did not reach statistical significance (p ⫽ 0.12). At a minimum followup of 13 years median serum creatinine in controls with functioning grafts was 139.5 mmol/l (range 53 to 278). By comparison, at a minimum followup of 6 years median serum creatinine in RATG patients with functioning grafts was 106 mmol/l (range 53 to 333, p ⫽ 0.007). Complications. Infectious complications in each group are summarized in table 5. In all 6 patients with development of CMV infection after transplant the donor was CMV positive while the recipient was CMV negative. There was no case of post-transplantation lymphoproliferative disorder (PTLD) in either group. However, we did not specifically look at donorrecipient Epstein-Barr virus mismatch, and we did not deny transplantation in any patient based on such mismatch. DISCUSSION

FIG. 2. Graft survival in both groups. RATG, rabbit antithymocyte globulin.

TABLE 3. Causes of graft failure

Rejection: Acute Chronic Renal vein thrombosis Primary disease recurrence Primary nonfunctioning kidney Hemolytic uremic syndrome Unknown Death with functioning graft Totals

No. Controls

No. RATG Pts

12 12 5 2 3 — 2 2

2 8 — 1 — 1 — 1

38

13

p Value p ⫽ 0.008 p ⫽ 0.002

renal vein thrombosis as a cause of graft loss between the 2 groups (9.3% in controls vs 0% in RATG patients, p ⫽ 0.002). Details regarding patients with renal vein thrombosis in relation to common risk factors for the condition are listed in table 4. Acute rejection rate. Acute rejection occurred in 47 grafts in the control group (75%), compared to 14 (24%) in the RATG group (p ⫽ 0.04). Graft loss secondary to acute rejection occurred in 12 grafts in controls (19%), compared to 2 grafts (3%) in RATG patients (p ⫽ 0.008). Renal function. At 3 months after kidney transplantation median serum creatinine for the remaining functioning grafts was 97 mmol/l (range 50 to 398) in the control group vs

Young children appear to have a heightened nonspecific immune reactivity compared to older children and adults. The immunological defects often observed in adult dialysis patients are absent in children.2 Children younger than 6 years receiving dialysis have higher indices of nonspecific cellular immune responsiveness than older children or young adults. These indices include spontaneous blastogenesis, number of total T lymphocytes, B lymphocytes and immature activated lymphocytes, and increased CD4⫹ to CD8⫹ ratio.3 These findings suggest that young children may be at higher risk for immunological rejection than older children and may require more intensive immunosuppression.4 RATG is an antihuman thymocyte immunoglobulin widely used in the prevention and treatment of acute rejection in organ transplantation. The mechanism of action involves impairment of the proliferative response of circulating T cells, and this effect persists after cessation of treatment. This continued effect may result from the generation of nonspecific suppressor T cells.5 Merion et al reported a significant in vitro decrease in inflammatory cytokines such as interleukin (IL)-2 contributing to the immunosuppressive effect of antithymocyte globulin (ATG).6 Suthanthiran and Strom reported the role of IL-2, IL-10 and cytotoxic molecules displayed on cell surface during acute rejection.7 They clearly showed the important role of polyclonal antibodies directed at the aforementioned molecules, preventing the T cell activation cascade that ultimately ends in acute allograft rejection. It is accepted that one of the major determinants of longterm graft survival is the absence of acute rejection episodes in the early post-transplant period.8 Since the early 1980s, ATG has been observed to decrease the incidence and severity of acute rejection episodes.9 Brennan et al reported a 1-year 95% rejection-free rate in patients receiving RATG induction immunotherapy and cyclosporine maintenance therapy.10 In the North American Pediatric Renal Transplant Cooperative Study (NAPRTCS) database one of the factors associated with improved outcome was the use of an antilymphocyte preparation as induction therapy.11 Graft survival and renal function were better in children receiving

TABLE 4. Details of renal vein thrombosis in control group Pt No.

Donor Age (yrs)

Recipient Age (yrs)

Dialysis Type

Acute Cellular Rejection

Cold Ischemia Time (hrs)

1

13

2

No

Not available

2

27

9

No

20

3 4

1 59

4 15

Yes Yes

Not available 17

5

40

18

Continuous ambulatory peritoneal dialysis Continuous ambulatory peritoneal dialysis Preemptive Continuous ambulatory peritoneal dialysis Continuous ambulatory peritoneal dialysis

No

26

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RABBIT ANTITHYMOCYTE GLOBULIN FOR DECEASED DONOR KIDNEY TRANSPLANTATION TABLE 5. Complications in both groups Infections

No. Controls

No. RATG Pts

p Value

Cytomegalovirus Epstein-Barr virus Pneumonia (bacterial) Wound Urinary tract Hepatitis C

2 — 1

0.43

5 —

4 1 1 1 4 1

8

12

0.33

Totals

either polyclonal or monoclonal antibody preparation during the first post-transplant month. NAPRTCS data revealed that there was a 31% increased risk of graft failure when an antibody preparation was not used in the first posttransplant month. In this study patients receiving RATG had a statistically significant decrease in acute cellular rejection rate and graft loss secondary to acute rejection (p ⫽ 0.04 and p ⫽ 0.008, respectively). This outcome translated into an improved graft survival in the RATG group of 90% at 1 year. This survival advantage was durable at 3 and 5 years. Similarly, Ault et al reported a 0% rate of acute cellular rejection in children receiving RATG.12 The most recent median serum creatinine level in the remaining functioning grafts was better in the RATG group than in the control group (106 vs 139 mmol/l, p ⫽ 0.007). It is noteworthy that the minimum followup for patients in the RATG group was 6 years. No patient in the RATG group in our series had development of renal vein thrombosis. The protective role of polyclonal antibody preparations against renal vein thrombosis in children has been reported previously. In a regression analysis model of 4,392 transplants Singh et al reported that the risk factors for vascular thrombosis in living related donor pediatric recipients were previous transplantation and absence of antilymphocyte globulin prophylaxis, while the risk factors for deceased donor recipients were a cold ischemia time of more than 24 hours, absence of antilymphocyte globulin prophylaxis, donor age less than 5 years and recipient age less than 2 years.13 In our study, in addition to the use of polyclonal antibodies in the RATG group, mean cold ischemia time was 21.5 hours, mean donor age was 21.9 years and only 5 recipients were younger than 5 years. Ismail et al reported an association between renal vein thrombosis in children and acute rejection.14 The RATG group in our study had statistically significant decreased rates of acute rejection and graft loss secondary to acute rejection. Among the 5 kidneys that were lost due to renal vein thrombosis in the control group we noted that 4 children were receiving peritoneal dialysis. The NAPRTCS group reported a link between the development of renal vein thrombosis in children and pre-transplant peritoneal dialysis.15 One criticism of the use of RATG was the marked increase in post-transplant infections. This result has been reported by Dharnidharka et al.16 However, one of the great advances in transplantation medicine has been the efficacy of the newer agents such as ganciclovir, which is used as an antiviral treatment and as prophylaxis. The efficacy of ganciclovir, particularly as prophylaxis for Epstein-Barr virus infection and PTLD, in patients receiving antilymphocyte antibody preparation has been reported previously. In a series of 198 kidney transplant recipients receiving ATG and antiviral ganciclovir prophylaxis Darenkov et al reported that only 1 patient (0.5%) had development of PTLD.17 Hardinger et al conducted a double-blind, randomized, prospective, controlled trial comparing RATG (thymoglobulin) to equine antithymocyte globulin.18 At 5-year followup none of the patients who had undergone kidney transplantation and RATG induction immunotherapy had development of PTLD. Similarly, Beaufigeau et al did not report PTLD in 117 children receiving heart transplants with

antithymocyte globulin induction immunotherapy and effective antiviral prophylaxis.19 Our effective use of antiviral and Pneumocystis carinii pneumonia prophylaxis resulted in similar rates of posttransplant infections in both patient groups (13% in controls vs 20% in RATG group). There was no CMV related death or graft loss in the RATG group. The high incidence of PTLD reported by Swinnen et al20 and the increased risk of CMV infections with OKT3 predated the use of ganciclovir, and were generally seen in patients who received a second course of OKT3 for refractory rejection. It is true that RATG may have increased the transplant cost initially but this increase was easily offset by the decrease in the overall immunosuppressive and rehospitalization costs following the significant reduction of the acute rejection rate. We did not find a difference in length of hospital stay between the 2 groups (p ⫽ 0.49). Finally, we acknowledge the retrospective and consecutive nature of the 2 groups, and the improvement in overall pediatric transplantation management at our department during the 2 periods studied. Indeed, such improvement in overall patient care may yield enhanced results, particularly in the more recently treated RATG group. However, it is our contention that the decrease in acute cellular rejection, which was related to RATG administration, was a significant factor in the improvement in graft survival. CONCLUSIONS

We believe that the use of RATG as induction therapy is efficacious and safe. The decrease in acute rejection rate and improvement in graft survival were achieved without any increased infection or mortality risk. Reversal of acute rejection episodes involves steroid boluses and occasionally antilymphocytic agents. This therapy results in increased total immunosuppressive load for the recipient with a concomitant increase in infection risk, patient mortality and treatment costs, and poorer long-term graft survival. Induction RATG therapy with appropriate antiviral, antifungal, antiprotozoal and antibacterial prophylaxis resulted in a decrease in rejection rates and ultimately less use of immunosuppressive medication. Our results support its continued use in pediatric transplantation. REFERENCES

1. Al-Akash, S. I. and Ettenger, R. B.: Kidney transplantation in children. In: Handbook of Kidney Transplantation, 3rd ed. Edited by G. M. Danovitch. Philadelphia: Lippincott Williams & Wilkins, chapt. 15, pp. 332–364, 2001 2. Drachman, R. B., Schlesinger, M., Shapira, H. and Dukker, A.: The immune status of uraemic children /adolescents with chronic renal failure and renal replacement therapy. Pediatr Nephrol, 3: 305, 1989 3. Ettenger, R. B., Blifeld, C., Prince, H., Gradus, D. B., Cho, S., Sekiya, N., Salusky, I. B. et al: The pediatric nephrologist’s dilemma: growth after renal transplantation and its interaction with age as a possible immunologic variable. J Pediatr, 111: 1022, 1987 4. Ettenger, R., Marik, J. and Rosenthal, J. T.: Sequential therapy in pediatric cadaveric renal transplantation: a critical analysis. J Am Soc Nephrol, suppl., 2: S304, 1992 5. Thomas, J. M., Carver, F. M., Haisch, C. E., Fahrenbruch, G., Deepe, R. M. and Thomas, F. T.: Suppressor cells in rhesus monkeys treated with antithymocyte globulin. Transplantation, 34: 83, 1982 6. Merion, R. M., Howell, T. and Bromberg, J. S.: Partial T-cell activation and anergy induction by polyclonal antithymocyte globulin. Transplantation, 65: 1481, 1998 7. Suthanthiran, M. and Strom, T. B.: Mechanisms and management of acute renal allograft rejection. Surg Clin North Am, 78: 77, 1998 8. Opelz, G.: Critical evaluation of the association of acute with chronic graft rejection in kidney and heart transplant recipients. The Collaborative Transplant Study. Transplant Proc, 29: 73, 1997

RABBIT ANTITHYMOCYTE GLOBULIN FOR DECEASED DONOR KIDNEY TRANSPLANTATION 9. Crosnier, J., Kreis, H., Descamps, J. M. and Mansouri, R.: Are there non-steroid-dependent rejection episodes? Proc Eur Dial Transplant Assoc, 17: 391, 1980 10. Brennan, D. C., Flavin, K., Lowell, J. A., Howard, T. K., Shenoy, S., Burgess, S. et al: A randomized, double-blind comparison of Thymoglobulin versus Atgam for induction immunosuppressive therapy in adult renal transplant recipients. Transplantation, 67: 1011, 1999 11. Warady, B. A., Hebert, D., Sullivan, E. K., Alexander, S. R. and Tejani, A.: Renal transplantation, chronic dialysis, and chronic renal insufficiency in children and adolescents. The 1995 Annual Report of the North American Pediatric Renal Transplant Cooperative Study. Pediatr Nephrol, 11: 49, 1997 12. Ault, B. H., Honaker, M. R., Osama Gaber, A., Jones, D. P., Duhart, B. T., Jr., Powell, S. L. et al: Short-term outcomes of Thymoglobulin induction in pediatric renal transplant recipients. Pediatr Nephrol, 17: 815, 2002 13. Singh, A., Stablein, D. and Tejani, A.: Risk factors for vascular thrombosis in pediatric renal transplantation: a special report of the North American Pediatric Renal Transplant Cooperative Study. Transplantation, 63: 1263, 1997 14. Ismail, H., Kalicinski, P., Drewniak, T., Smirska, E., Kaminski, A., Prokurat, A. et al: Primary vascular thrombosis after renal transplantation in children. Pediatr Transplant, 1: 43, 1997 15. McDonald, R. A., Smith, J. M., Stablein, D. and Harmon, W. E.:

16.

17.

18.

19.

20.

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Pretransplant peritoneal dialysis and graft thrombosis following pediatric kidney transplantation: a NAPRTCS report. Pediatr Transplant, 7: 204, 2003 Dharnidharka, V. R., Stablein, D. M. and Harmon, W. E.: Posttransplant infections now exceed acute rejection as cause for hospitalization: a report of the NAPRTCS. Am J Transplant, 4: 384, 2004 Darenkov, I. A., Marcarelli, M. A., Basadonna, G. P., Friedman, A. L., Lorber, K. M., Howe, J. G. et al: Reduced incidence of Epstein-Barr virus-associated posttransplant lymphoproliferative disorder using preemptive antiviral therapy. Transplantation, 64: 848, 1997 Hardinger, K. L., Schnitzler, M. A., Miller, B., Lowell, J. A., Shenoy, S., Koch, M. J. et al: Five-year follow up of thymoglobulin versus ATGAM induction in adult renal transplantation. Transplantation, 78: 136, 2004 Beaufigeau, M., Dumesnil, D., Carrier, M., White, M. and Pellitier, G. B.: Seven year experience with rabbit antithymocyte globulin after cardiac transplantation at the Montreal Heart Institute. Transplant Proc, 64: 848, 1997 Swinnen, L. J., Costanzo-Nordin, M. R., Fisher, S. G., O’Sullivan, E. J., Johnson, M. R., Heroux, A. L. et al: Increased incidence of lymphoproliferative disorder after immunosuppression with the monoclonal antibody OKT3 in cardiactransplant recipients. N Engl J Med, 323: 1723, 1990