RESUMO
Objectives: Decellularized homograft valves (DHV) appear to elicit an immune response despite efficient donor cell removal. Materials and methods: A semiquantitative Dot-Blot analysis for preformed and new recipient antibodies was carried out in 20 patients following DHV implantation on days 0, 1, 7, and 28 using secondary antihuman antibodies. Immune reactions were tested against the implanted DHV as well as against the stored samples of 5 non-implanted decellularized aortic (DAH) and 6 pulmonary homografts (DPH). Results: In this study, 20 patients (3 female and 17 male patients) were prospectively included, with a median age of 18 years and an IQR of 12-30 years. Six patients received DPH and 14 received DAH. The amount of antibody binding, averaged for all patients, decreased on post-operative days 1 and 7 compared to pre-operative values; and on day 28, antibody binding reached close to pre-operative levels (16.8 ± 2.5 on day 0, 3.7 ± 1.9 on day 1, 2.3 ± 2.7 on day 7, and 13.2 ± 3.7 on day 28). In comparison with the results in healthy controls, there was a higher amount of antibody binding to DAH than to DPH. The mean number of arbitrary units was 18.4 ± 3.1 in aortic and 12.9 ± 4.5 in pulmonary DHV (p = 0.140). Male patients exhibited higher antibody binding to aortic DHV than female patients (19.5 ± 2.1 vs. 1.6 ± 6.7). The p-value calculation was limited, as only two female patients received DAH. There was no correlation between the amount of overall antibody binding to DHV with respect to donor age (Kruskal-Wallis test p = 0.550). DHV recipients with a sex mismatch to the donor showed significantly less antibody binding (6.5 ± 1.8 vs. 13.7 ± 1.8; p = 0.003). Our main finding was an increase in antibody binding in younger patients receiving decellularized aortic allografts. This increase was higher in patients with early degeneration signs but was not specific to the individual DHV implanted nor previous DHV implantation. Antibody binding toward explanted DHV was significantly increased in implicating antibody-mediated DHV degeneration. Conclusion: Serial assessment of tissue-specific antibody binding revealed an increase in some patients within 4 weeks after surgery, who subsequently developed early signs of allograft degeneration. Further studies with larger sample sizes are needed to confirm the prognostic relevance of increased antibody activity in addition to targeted research efforts to identify the molecular agents triggering this type of antibody response.
RESUMO
OBJECTIVES: Decellularized homograft valves (DHVs) have shown promising clinical results, particularly in the treatment of congenital heart disease. However, DHV appears to elicit an immune response in a subset of young patients, indicated by early valve degeneration. As the decellularization process is quality controlled for each DHV, we hypothesized that there may be residual immunogenicity within the extracellular matrix of DHV. METHODS: A semi-quantitative dot blot analysis was established to screen for preformed recipient antibodies using secondary anti-human antibodies. Fifteen DHV samples (7 aortic, 8 pulmonary) were solubilized and exposed to serum from 20 healthy controls. RESULTS: The sera from young controls (n = 10, 18-25 years) showed significantly stronger binding of preformed antibodies than sera from older individuals (n = 10, 48-73 years). The difference between the means of arbitrary units was 15.1 ± 6.5 (P = 0.0315). There was high intraindividual variance in the mean amounts of arbitrary units of antibody binding with some healthy controls showing >10 times higher antibody binding towards 2 different DHV. The amount of preformed antibodies bound to DHVs was higher in aortic than in pulmonary DHVs. The mean number of antibody binding (in arbitrary units) was 17.2 ± 4.5 in aortic and 14.5 ± 4.7 in pulmonary DHV (P = 0.27). The amount of preformed antibodies bound to pulmonary DHVs was statistically significantly higher in the sera of healthy males (n = 10) than in the sera of healthy females (n = 10). The mean number of arbitrary units was 17.2 ± 4.2 in male and 11.7 ± 5.3 in female sera (P = 0.036). Antibody binding to aortic DHV was also higher in males, but not significant (18.8 ± 5.0 vs 15.6 ± 4.0). Blood group (ABO) incompatibility between the serum from controls and DHV showed no impact on antibody binding, and there was no age-related impact among DHV donors. CONCLUSIONS: Residual immunogenicity of decellularized homografts appears to exist despite almost complete cell removal. The established dot blot method allows a semi-quantitative assessment of the individual immune response towards extracellular DHV components and potentially the possibility of preoperative homograft matching.