Human cytomegalovirus and Epstein-Barr virus infections occurring early after transplantation are risk factors for antibody-mediated rejection in heart transplant recipients

Clinical Features and Treatment of Antibody-Mediated Rejection After Liver Transplantation: A Largest Single Center Experience in China

Antibody-mediated rejection (AMR) is frequently observed in renal transplantation but remains rare and less understood in liver transplantation (LT). This study summarizes the clinical features of AMR in liver transplant patients at our center from August 2020 to October 2023. Thirteen patients were identified as having AMR, including 11 pediatric cases with a median age of 16.2 months. The median interval from transplantation to AMR diagnosis was 54.13 months. Most patients exhibited mild elevation in liver function. A notable decrease in CD4+ T cells was found in acute AMR patients, alongside reduced complement C3 in chronic cases. PRA was positive in 92.31% of patients, all of whom had elevated class II DSA. Additionally, many patients experienced infections with non-hepatotropic viruses. Following intensified immunosuppression and other therapies, 92.31% of patients achieved normal liver function, including five chronic AMR cases with characteristic histological features and seven acute AMR cases that showed no inflammation or centrilobular fibrosis on biopsy. These findings indicate that AMR patients may not exhibit significant liver function abnormalities, emphasizing the critical role of PRA and DSA in diagnosis. The observed reduction in CD4+ T cells and complement C3 may provide valuable insights into the pathogenesis of AMR.

Pre-Transplant Immunophenotyping in Pediatric Heart Transplant: A Role for the Immunologist?

BACKGROUND

Pediatric heart transplant recipients are at risk for complications from prolonged exposure to immunosuppressive drugs, possibly worsened due to over-immune suppression in patients with pre-existing immune abnormalities.

METHODS

This was a retrospective, single-center pediatric cohort study and review of baseline immune evaluation in patients referred for heart transplant. Referrals included were from January 1, 2021, to June 31, 2022.

RESULTS

Fifty-one patients were referred during the time period with a median age of 5 years (ranging 1 month-20 years). Twenty-seven total patients were transplanted. Given a lack of standardized immune evaluation, results were focused on lymphocyte quantitation, functional testing when available, and T-cell subsets. Outcome measures focused on the number of infections and episodes of rejection requiring treatment. In total, 44.4% of patients experienced rejection, and the mean number of infections in the first 12 months post-heart transplant was 2.1 (range 0-7 total infections).

CONCLUSIONS

Baseline immune evaluation showed general T and B cell lymphopenia, without a clear connection between outcome differences for the number of infections or episodes of rejection requiring treatment. This small study demonstrated some differences in immune function in patients prior to heart transplant but was inadequately powered to draw conclusions about the effects of immunosuppression on post-transplant outcomes.

Mechanistic Understanding of EBV+Lymphoproliferative Disease Development After Transplantation

Posttransplant lymphoproliferative disorders (PTLDs) are among the most common malignant complications after transplantation, leading to a drastic reduction in patient survival rates. The majority of PTLDs are tightly linked to Epstein-Barr virus (EBV+PTLDs) and are the result of an uncontrolled proliferation of EBV-infected cells. However, although EBV infections are a common finding in transplant recipients, most patients with high EBV loads will never develop EBV+PTLD. Natural killer cells and EBV-specific CD8+ T lymphocytes are critical for controlling EBV-infected cells, and the impairment of these cytotoxic immune responses facilitates the unfettered proliferation of EBV-infected cells. Recent years have seen a considerable increase in available literature aiming to describe novel risk factors associated with the development of EBV+PTLD, which may critically relate to the strength of EBV-specific natural killer cell and EBV-CD8+ T lymphocyte responses. The accumulation of risk factors and the increased risk of developing EBV+PTLD go hand in hand. On the one hand, most of these risk factors, such as the level of immunosuppression or the EBV donor and recipient serologic mismatch, and distinct genetic risk factors are host related and affect cytotoxic EBV-specific immune responses. On the other hand, there is growing evidence that distinct EBV variants may have an increased malignant potential and are thus more likely to induce EBV+PTLD. Here, we aim to review, from a mechanistic point of view, the risk factors for EBV+PTLD in the host and the infecting EBV variants that may explain why only a minority of transplant recipients develop EBV+PTLD.

Cytomegalovirus infection is associated with impaired myocardial flow reserve after heart transplantation

BACKGROUND

Cardiac allograft vasculopathy (CAV) limits long-term survival after heart transplantation (HT). This study evaluates the relationship between clinically significant cytomegalovirus infection (CS-CMVi) and CAV using cardiac positron emission tomography (PET).

METHODS

We retrospectively evaluated HT patients from 2005 to 2019 who underwent cardiac PET for CAV evaluation. Multivariable linear and logistic regression models were used to evaluate the association between CS-CMVi and myocardial flow reserve (MFR). Kaplan-Meier and Cox regression analyses were used to assess the relationship between CS-CMV, MFR, and clinical outcomes.

RESULTS

Thirty-two (31.1%) of 103 HT patients developed CS-CMVi at a median 9 months after HT. Patients with CS-CMVi had a significantly lower MFR at year 1 and 3, driven by reduction in stress myocardial blood flow. Patients with CS-CMVi had a faster rate of decline in MFR compared to those without infection (-0.10 vs -0.06 per year, p < 0.001). CS-CMVi was an independent predictor of abnormal MFR (<2.0) (odds ratio: 3.8, 95% confidence intervals (CI): 1.4-10.7, p = 0.001) and a lower MFR (β = -0.39, 95% CI: -0.63 to -0.16, p = 0.001) at year 3. In adjusted survival analyses, both abnormal MFR (log-rank p < 0.001; hazard ratio [HR]: 5.7, 95% CI: 4.2-7.2) and CS-CMVi (log-rank p = 0.028; HR: 3.3, 95% CI: 1.8-4.8) were significant predictors of the primary outcome of all-cause mortality, retransplantation, heart failure hospitalization, and acute coronary syndrome.

CONCLUSIONS

CS-CMVi is an independent predictor of reduced MFR following HT. These findings suggest that CMV infection is an important risk factor in the development and progression of CAV.