Rabbit Antithymocyte Globulin Induction in Heart Transplant Recipients at High Risk for Rejection

Background: Induction with lymphocyte-depleting antibodies may improve allograft outcomes in heart transplant recipients who are at high immunologic risk for rejection.

Methods: We conducted a single-center retrospective cohort study that compared outcomes between adult patients receiving rabbit antithymocyte globulin (rATG) induction vs no induction from 2011 through 2017. Key exclusion criteria were patients who did not receive tacrolimus and mycophenolate and patients who did not meet high immunologic risk criteria.

Results: A total of 50 patients were included in the analysis. At 1 year, the composite primary outcome of ≥2R rejection as defined by the International Society for Heart and Lung Transplantation, any treated rejection, development of cardiac allograft vasculopathy, or graft loss was not different between groups (P=0.474). Serious infections were also similar between groups (P=0.963). In accordance with institutional guidelines, prednisone exposure was decreased in the rATG induction group at 1 month (24.04 mg ± 13.74 vs 35.18 mg ± 16.95; P=0.014).

Conclusion: These results suggest that while rATG induction does not improve heart allograft outcomes, it may enable reducing early corticosteroid exposure in patients at high immunologic risk.

Usefulness of a systematic approach at listing for vaccine prevention in solid organ transplant candidates

Solid organ transplant (SOT) candidates may not be immune against potentially vaccine-preventable diseases because of insufficient immunizations and/or limited vaccine responses. We evaluated the impact on vaccine immunity at transplant of a systematic vaccinology workup at listing that included (1) pneumococcal with and without influenza immunization, (2) serology-based vaccine recommendations against measles, varicella, hepatitis B virus, hepatitis A virus, and tetanus, and (3) the documentation of vaccines and serology tests in a national electronic immunization registry (www.myvaccines.ch). Among 219 SOT candidates assessed between January 2014 and November 2015, 54 patients were transplanted during the study. Between listing and transplant, catch-up immunizations increased the patients' immunity from 70% to 87% (hepatitis A virus, P = .008), from 22% to 41% (hepatitis B virus, P = .008), from 77% to 91% (tetanus, P = .03), and from 78% to 98% (Streptococcus pneumoniae, P = .002). Their immunity at transplant was significantly higher against S. pneumoniae (P = .006) and slightly higher against hepatitis A virus (P = .07), but not against hepatitis B virus, than that of 65 SOT recipients transplanted in 2013. This demonstrates the value of a systematic multimodal serology-based approach of immunizations of SOT candidates at listing and the need for optimized strategies to increase their hepatitis B virus vaccine responses.

New frontiers in immunosuppression

Immunosuppressive therapy is arguably the most important component of medical care after lung transplantation. The goal of immunosuppression is to prevent acute and chronic rejection while maximizing patient survival and long-term allograft function. However, the benefits of immunosuppressive therapy must be balanced against the side effects and major toxicities of these medications. Immunosuppressive agents can be classified as induction agents, maintenance therapies, treatments for acute rejection and chronic rejection and antibody directed therapies. Although induction therapy remains an area of controversy in lung transplantation, it is still used in the majority of transplant centers. On the other hand, maintenance immunosuppression is less contentious; but, unfortunately, since the creation of three-drug combination therapy, including a glucocorticoid, calcineurin inhibitor and anti-metabolite, there have been relatively modest improvements in chronic maintenance immunosuppressive regimens. The presence of HLA antibodies in transplant candidates and development of de novo antibodies after transplantation remain a major therapeutic challenge before and after lung transplantation. In this chapter we review the medications used for induction and maintenance immunosuppression along with their efficacy and side effect profiles. We also review strategies and evidence for HLA desensitization prior to lung transplantation and management of de novo antibody formation after transplant. Finally, we review immune tolerance and the future of lung transplantation to limit the toxicities of conventional immunosuppressive therapy.

Induction regimen and survival in simultaneous heart-kidney transplant recipients

BACKGROUND

Induction therapy in simultaneous heart-kidney transplantation (SHKT) is not well studied in the setting of contemporary maintenance immunosuppression consisting of tacrolimus (TAC), mycophenolic acid (MPA), and prednisone (PRED).

METHODS

We analyzed the Organ Procurement and Transplant Network registry from January 1, 2000, to March 3, 2015, for recipients of SHKT (N = 623) maintained on TAC/MPA/PRED at hospital discharge. The study cohort was further stratified into 3 groups by induction choice: induction (n = 232), rabbit anti-thymoglobulin (r-ATG; n = 204), and interleukin-2 receptor-α (n = 187) antagonists. Survival rates were estimated using the Kaplan-Meier estimator. Multivariable inverse probability weighted Cox proportional hazard regression models were used to assess hazard ratios associated with post-transplant mortality as the primary outcome. The study cohort was censored on March 4, 2016, to allow at least 1-year of follow-up.

RESULTS

During the study period, the number of SHKTs increased nearly 5-fold. The Kaplan-Meier survival curve showed superior outcomes with r-ATG compared with no induction or interleukin-2 receptor-α induction. Compared with the no-induction group, an inverse probability weighted Cox proportional hazard model showed no independent association of induction therapy with the primary outcome. In sub-group analysis, r-ATG appeared to lower mortality in sensitized patients with panel reactive antibody of 10% or higher (hazard ratio, 0.19; 95% confidence interval, 0.05-0.71).

CONCLUSION

r-ATG may provide a survival benefit in SHKT, especially in sensitized patients maintained on TAC/MPA/PRED at hospital discharge.