Human leukocyte antigen antibody sensitization, lung transplantation, and health equity

Assessment of Antimetabolite Intolerance in Older Lung Transplant Recipients

Introduction: Adverse effects from antimetabolites often lead to therapy adjustments; older patients may be more susceptible to these effects. Project Aims: Compare the intolerance of antimetabolites between older and younger lung transplant recipients. Design: A single-center, retrospective analysis of adult lung transplant recipients transplanted between January 1, 2019 and October 31, 2021 was conducted. Patients were stratified by age at the time of transplant (≥60 or <60 years) and assessed for the first year posttransplant. The primary outcome was the incidence of antimetabolite intolerance (defined as dose adjustment, agent/formulation change, or holding/discontinuation of agent). Secondary outcomes included reason for intolerance, safety (infection and leukopenia), and efficacy (rejection and patient/graft survival). Results: One hundred and nine recipients were included; 54 in the older (≥60 years) and 55 in the younger (<60 years) cohort. Most were initiated on azathioprine (74%) posttransplant. Antimetabolite intolerance occurred in 61% of older and 53% of younger recipients (P = 0.377). The most common reasons for intolerance were leukopenia followed by gastrointestinal side effects. Biopsy-proven acute rejection occurred more often in the older cohort (39% vs 18%, P = 0.017); this no longer remained significant when controlling for induction, indication, transplant type, gender, and antimetabolite intolerance (OR 0.36, 95% CI 0.11 to 1.15). There was no difference in the incidence of leukopenia, bacterial infection, or graft/patient survival within 1 year posttransplant. Conclusion: Antimetabolite intolerance between older and younger lung transplant recipients was similar. Most required modification to the initial antimetabolite regimen due to leukopenia and gastrointestinal side effects.

The Impact of Prelung Transplant HLA Antibodies on Post-transplant Outcomes in Recipients With Autoimmune Lung Disease

INTRODUCTION

Patients with advanced lung disease who have HLA antibodies against potential donors have reduced opportunities for transplant. Not all HLA antibodies, however, have the same impact on post-transplant outcomes. It is unknown whether HLA antibodies arising in the context of autoimmune lung disease are associated with increased antibody mediated rejection (AMR) or bronchiolitis obliterans stage 1 (BOS1)-free survival.

METHODS

This study used retrospective data from SRTR to examine BOS1-free survival and AMR among sensitized recipients with autoimmune ILD compared to sensitization recipients with nonautoimmune ILD, accounting for other sources of sensitization such as pregnancy and blood transfusions. This study did not use organs from prisoners and participants were neither coerced nor paid.

RESULTS

Sensitized recipients with autoimmune ILD did not have differences in BOS1-free survival when adjusting for sensitizing exposures (HR = 0.90, 95% CI: 0.70-1.16) or clinical covariates (HR = 0.96, 95% CI: 0.83-1.12). There was also no difference in AMR (OR = 1.92, 95% CI: 1.04-3.52).

CONCLUSIONS

HLA antibodies arising in the context of autoimmune ILD do not appear to have a differential impact on BOS1-free survival or AMR. This provides further evidence that patients sensitized via autoimmune lung diseases do not require separate decision-making regarding HLA antibody status compared to the overall sensitized population.

Intravenous Immunoglobulins Alone for the Desensitization of Lung Transplant Recipients with Preformed Donor Specific Antibodies and Negative Flow Cytometry Crossmatch

BACKGROUND

The lack of evidence regarding optimal desensitization strategies for lung transplant candidates with preformed donor specific anti-human leukocyte antigen antibodies (DSAs) has led to varying approaches among centers towards this patient group. Our institution's desensitization protocol for recipients with preformed DSAs and negative flow cytometry crossmatch (FCXM) consists of intravenous immunoglobulin (IVIG) as the sole therapy. The study aimed to determine outcomes using this approach.

METHODS

This retrospective study included adults who underwent lung-only transplantation for the first time between January 2015 and March 2022 at a single center. We excluded patients with positive or missing FCXM results. Transplant recipients with any DSA ≥ 1000 MFI on latest testing within three months of transplant were considered DSA-positive, while recipients with DSAs <1000 MFI and those without DSAs were assigned to the low-level/negative group. Graft survival (time to death/retransplantation) and chronic lung allograft dysfunction (CLAD)-free times were compared between groups using Cox proportional hazards models.

RESULTS

Thirty-six out of 167 eligible patients (22%) were DSA-positive. At least 50% of preformed DSAs had documented clearance (decrease to <1000 MFI) within the first 6 months of transplant. Multivariable Cox regression analyses did not detect a significantly increased risk of graft failure (aHR 1.04 95%CI 0.55-1.97) or chronic lung allograft dysfunction (aHR 0.71 95%CI 0.34-1.52) in DSA-positive patients compared to patients with low-level/negative DSAs. Incidences of antibody-mediated rejection (p = 1.00) and serious thromboembolic events (p = 0.63) did not differ between study groups.

CONCLUSION

We describe a single-center experience of administering IVIG alone to lung transplant recipients with preformed DSAs and negative FCXM. Further studies are required to confirm the efficacy of this strategy against other protocols.

The Highly Sensitized Recipient: Pretransplant and Posttransplant Considerations

Highly sensitized patients, who are often black and Hispanic women, are less likely to be listed for lung transplant and are at higher risk for prolonged waitlist time and waitlist death. In this review, the authors discuss strategies for improving access to transplant in this population, including risk stratification of crossing pretransplant donor-specific antibodies, based on antibody characteristics. The authors also review institutional protocols, such as perioperative desensitization, for tailoring transplant immunosuppression in the highly sensitized population. The authors conclude with suggestions for future research, including development of novel donor-specific antibody-directed therapeutics.

Addressing sex-based disparities in solid organ transplantation in the United States - a conference report

Solid organ transplantation provides the best treatment for end-stage organ failure, but significant sex-based disparities in transplant access exist. On June 25, 2021, a virtual multidisciplinary conference was convened to address sex-based disparities in transplantation. Common themes contributing to sex-based disparities were noted across kidney, liver, heart, and lung transplantation, specifically the existence of barriers to referral and wait listing for women, the pitfalls of using serum creatinine, the issue of donor/recipient size mismatch, approaches to frailty and a higher prevalence of allosensitization among women. In addition, actionable solutions to improve access to transplantation were identified, including alterations to the current allocation system, surgical interventions on donor organs, and the incorporation of objective frailty metrics into the evaluation process. Key knowledge gaps and high-priority areas for future investigation were also discussed.