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

Abstract

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.

Figure 4. Longitudinal analysis of anti-ATG and anti-Neu5Gc IgG serum levels in SSD⁺ patients from cohort B.

T0, T1, and T2 samples for each patient in the SSD⁺ group were assessed for (A and B) anti-ATG and (C and D) anti-Neu5Gc antibody levels. Antibody levels were quantified using ELISA assays, with median and interquartile range shown for each group. Comparisons between time points for one patient were performed using a Wilcoxon paired test. (A) Anti-ATG IgGs in T0 (mean 9.99 ± SD 10.96 ng/μl) and T1 (15.06 ± 12.78 ng/μl) samples (n = 9 patients at T1, NS). (B) Anti-ATGs in T0 (mean 7.04 ± SD 1.93 ng/μl) and T2 (16.89 ± 12.83 ng/μl) samples (n = 12 patients at T2, P = 0.001). (C) Anti-Neu5Gc IgGs in T0 (mean 0.74 ± SD 0.91 ng/μl) and T1 (2.46 ± 2.92 ng/μl) samples (n = 9 patients at T1, P = 0.047). (D) Anti-Neu5Gc in T0 (mean 1.41 ± SD 1.91 ng/μl) and T2 (9.78 ± 19.82 ng/μl) samples, n = 12 patients at T2, P = 0.054. Similar analysis in the SSD^– group did not yield significant differences (data not shown).

Figure 3. Cross-sectional analysis of anti-ATG, anti-Neu5Gc, and anti-Gal IgG serum levels in SSD⁺ and SSD^– patients from cohort B.

Results are expressed as mean ± SEM of the ΔT1 or ΔT2 values. Comparisons between SSD⁺ and SSD^– matched patients were performed using a Wilcoxon paired test. (A) In SSD⁺ patients, anti-ATG levels increased from a mean of 9.49 ± 9.02 ng/μl in T0 sera to 17.41 ± 13.74 ng/μl in T1 sera, while SSD^– patients had T0 levels of 10.33 ± 4.95 ng/μl and T1 levels of 13.85 ± 11.90 ng/μl (ΔT1, NS). (B) In SSD⁺ patients, anti-Neu5Gc levels increased from 1.3 ± 1.87 ng/μl (T0 sera) to 2.28 ± 3.08 ng/μl in T1 sera, in comparison with SSD^– patients (T0 = 12.10 ± 29.22 ng/μl vs. T1 = 6.91 ± 14.64 ng/μl, ΔT1, NS). (C) In SSD⁺ patients, anti-Gal levels remained stable (5.62 ± 5.24 ng/μl in T0 sera vs. 5.78 ± 7.33 ng/μl in T1 sera), in comparison with SSD^– patients (T0 = 5.83 ± 3.89 ng/μl vs. T1 = 3.13 ± 2.48 ng/μl, ΔT1, NS). (D) In SSD⁺ patients, anti-ATG levels increased from a mean of 9.49 ± 9.02 ng/μl in T0 sera to 16.48 ± 12.99 ng/μl in T2 sera, while SSD^– patients had T0 levels of 10.33 ± 4.95 ng/μl and T2 levels of 13.85 ± 19.33 ng/μl (ΔT2, P = 0.04). (E) In SSD⁺ patients, anti-Neu5Gc levels significantly increased from 1.3 ± 1.87 ng/μl to 9.85 ± 19.8 ng/μl in T2 sera, in comparison with SSD^– patients (T0 = 12.10 ± 29.22 ng/μl vs. T2 = 4.55 ± 13.54 ng/μl, ΔT2, P = 0.007). (F) In SSD⁺ patients, anti-Gal levels remained stable (5.62 ± 5.24 ng/μl in T0 sera vs. 5.5 ± 5.41 ng/μl in T2 sera), in comparison with SSD^– patients (T0 = 5.83 ± 3.89 ng/μl vs. T1 = 4.42 ± 3.02 ng/μl, ΔT2, NS).

Figure 2. Death-censored graft survival curves estimated from cohort A, according to SSD status.

The SSD⁺ and SSD^– populations have different rates of late graft survival (P = 0.02). The median follow-up was 9.0 years (interquartile range, from 3.4 to 16.5 years).

Figure 1. Flow chart of the study cohorts.

(A) Cohorts A and (B) B are shown, along with the selection of the SSD⁺ group and the control SSD^– group matched for five clinical variables. See “Patients” for details on the selection procedure.