Faculty Bibliography

BACKGROUND:Porcine genome editing has revolutionized xenotransplantation, recently enabling the first pig-to-human heart xenotransplants. However, the xeno-immune response in heart xenografts remains largely unexplored. This study aimed to precisely characterize the xeno-immune response and injury in two heart xenografts, transplanted from 10-gene-edited pigs into brain-dead human recipients. METHODS:We analyzed xenograft biopsies at 66-hour post-reperfusion using a multimodal phenotyping approach combining: morphological evaluation, immunophenotyping, ultrastructural assessment, automated quantification of multiplex immunofluorescence staining and gene expression profiling. Xenografts before implantation and wild-type pig hearts with and without ischemia reperfusion injury and brain death were used as controls. RESULTS:Both xenografts showed evidence of endothelial activation and mild microvascular inflammation without capillary C4d deposition. Immune infiltrates were mainly composed of CD15+ and CD68+ innate immune cells. Ultrastructural assessment showed endothelial swelling with occasional intravascular leucocytes. Deep-learning based automated multiplex immunofluorescence analysis confirmed that microvascular inflammation was primarily associated with CD15+ and CD68+ innate immune cells. Both xenografts showed increased expression of genes and pathways associated with monocyte/macrophage activation, neutrophil activation, interferon-gamma response, natural killer cell burden, endothelial activation, apoptosis and injury repair. This phenotype was absent in all control pig hearts, independently from ischemia reperfusion injury and brain death. CONCLUSIONS:Multimodal phenotyping of pig-to-human heart xenografts revealed early signs of xeno-immune response, characterized by mild innate microvascular inflammation, endothelial activation, and molecular signature characteristic of antibody-mediated rejection. Developing such precision diagnostic system could improve graft monitoring in future clinical settings.

Xenotransplantation of genetically-modified pig kidneys offers a solution to the scarcity of organs for end-stage renal disease patients.¹ We performed a 61-day alpha-Gal knock-out pig kidney and thymic autograft transplant into a nephrectomized brain-dead human using clinically approved immunosuppression, without CD40 blockade or additional genetic modification. Hemodynamic and electrolyte stability and dialysis independence were achieved. Post-operative day (POD) 10 biopsies revealed glomerular IgM and IgA deposition, activation of early complement components and mesangiolysis with stable renal function without proteinuria, a phenotype not seen in allotransplantation. On POD 33, an abrupt increase in serum creatinine was associated with antibody-mediated rejection and increased donor-specific IgG. Plasma exchange, C3/C3b inhibition and rabbit anti-thymocyte globulin (rATG), completely reversed xenograft rejection. Pre-existing donor-reactive T cell clones expanded progressively in the circulation post-transplant, acquired an effector transcriptional profile and were detected in the POD 33 rejecting xenograft prior to rATG treatment. This study provides the first long-term physiologic, immunologic, and infectious disease monitoring of a pig-to-human kidney xenotransplant and indicates that pre-existing xenoreactive T cells and induced antibodies to unknown epitope(s) present a major challenge, despite significant immunosuppression. It also demonstrates that a minimally gene-edited pig kidney can support long-term life-sustaining physiologic functions in a human.

The scarcity of transplantable organs represents a worldwide public health crisis, and as a result, thousands of people with end-stage kidney disease (ESKD) die waiting for a transplant each year. Xenotransplantation involves transplanting organs from an animal source into humans, offering a potential solution to this significant unmet need. Indeed, if there is a limitless supply of organs, many more patients who do not meet the current criteria for transplant eligibility could also be considered candidates. While there are examples of attempts to transplant animal tissues or organs into humans dating back over 300 years, none were successful due to cross-species immunologic incompatibility. Even so, significant advances in genetic engineering and the emergence of novel immunosuppressive agents have spurred impressive improvements in xenograft survival in preclinical studies involving nonhuman primates. Furthermore, recent reports of genetically modified pig kidney and heart xenotransplants in human decedents and living recipients on a compassionate use basis have provided impetus to advancing the field towards first-in-human trials. However, studies in nonhuman primates and humans thus far have described adaptive as well as innate immune-mediated xenograft injury. Understanding the mechanistic aspects of these responses at the cellular and molecular levels is critical to the development of targeted genetic modifications and innovative therapeutic strategies aimed at preventing rejection and inducing tolerance. Moreover, the physiological components of the bidirectional communication between the human host and pig xenograft must also be understood and manipulated. Here, we review the breakthroughs in renal xenotransplantation in the past few decades and highlight the immunologic hurdles that have yet to be overcome.

Historically, liver transplant (LT) candidates with human immunodeficiency virus (HIV) have experienced high waitlist mortality. Since the HIV Organ Policy Equity (HOPE) Act expands access to organs from donors with HIV, we assessed the impact of HOPE on LT rate and wait time for this population. We linked data from a multicenter HOPE in Action study to Scientific Registry of Transplant Recipients (February 21, 2019 to June 1, 2024) and used Poisson regression to compare transplant rates among 99 candidates willing to accept HOPE donors (HOPE candidates) to 13 495 candidates with or without HIV not listed as willing to accept HOPE donors (non-HOPE candidates) matched on transplant center. The median time to any deceased donor liver transplant (DDLT) was 2.3 months for HOPE and 1.1 years for non-HOPE candidates. Within 2 years of listing, 90.9% of HOPE versus 58.5% of non-HOPE candidates received a DDLT (P < .001). HOPE was associated with an overall 3.11-fold higher DDLT incident rate ratio (95% CI 2.48-3.88, P < .001). Stratified by model for end-stage liver disease score categories 6 to 14, 15 to 24, 25 to 34, and 35 to 40/status 1; HOPE candidates had 10.12-fold, 5.31-fold, 1.41-fold and 2.90-fold higher DDLT rates, respectively. Willingness to accept livers from donors with HIV improves access to liver transplantation for candidates with HIV.

Transplantation of kidneys from donors with HIV to recipients with HIV (HIV D+/R+) has been shown to be safe and effective, but there is a unique risk of donor-derived HIV-superinfection (HIV-SI) in these recipients. Recipients from a multicenter observational HIV D+/R+ study were examined for HIV-SI using site-directed next-generation sequencing (Illumina). Eighteen HIV D+/R+ kidney transplant recipients had both baseline and follow-up samples that successfully amplified. One recipient was confirmed to have experienced donor-derived HIV-SI at week 26, but did not experience any clinically significant changes. HIV-SI in HIV D+/R+ transplant recipients is rare, and the clinical ramifications appear negligible.

Kidney transplantation from donors with HIV has recently become standard clinical practice, but the plasma inflammatory profile is not well characterized. Thirty-two cytokines and chemokines were evaluated among donors with HIV (n = 63) and without HIV (n = 41). Wilcoxon rank sum test was used to compare cytokines between groups. Donors with and without HIV were generally similar in terms of characteristics, except those with HIV had a non-significantly lower kidney donor profile index, reflecting better graft survival, creatinine, and body mass index. Most cytokine and chemokine levels were similar between groups. However, median IL-8 levels were higher (p < 0.0015) in donors without HIV (32.6 pg/mL, IQR = 13.8-394.9) compared to donors with HIV (15.1 pg/mL, IQR = 8.4-35.5). There were no significant correlations between cytokine and chemokine concentrations and CD4 counts or HIV viral load. In summary, inflammatory profiles were similar or lower among donors with HIV compared to donors without HIV supporting the safety of this emerging kidney transplantation practice.

BACKGROUND:Due to high prevalence of Kaposi Sarcoma (KS)-Associated Herpesvirus (KSHV) among people with HIV, KSHV-associated disease (KAD) may be increased after kidney transplantation from donors with HIV (HIV D+) to recipients with HIV (HIV R+). METHODS:Anti-KSHV antibodies were measured in HIV R+ and donors with and without HIV (HIV D-) using a 30-antigen multiplex assay within three multicenter kidney transplantation studies. KSHV seropositivity was defined as reactivity to conventional KSHV antigens (≥1 ORF73 or K8.1); reactivity to expanded 5-antigen and 30-antigen panels were also reported. Risk factors were identified using modified Poisson regression. Recipients were monitored for post-transplant anti-KSHV antibody changes and KAD. RESULTS:KSHV seroprevalence was 40.6% (143/352) among HIV R+, 25.2% (33/131) among HIV D+, and 7.5% (4/53) among HIV D-. In the multivariable model, only men who have sex with men (MSM) was associated with KSHV seropositivity: relative risk 1.51 (95% confidence interval [CI] 1.07-2.14) in recipients and 2.39 (95%CI 1.03-5.53) in donors. Among 418 HIV R+ (215 HIV D+/R+, 203 HIV D-/R+), there were 5 KAD cases (incidence 0.63 cases/100 person-years, 95%CI 0.26-1.52): 3 skin-only KS, 1 multicentric Castleman disease, 1 allograft KS. The allograft KS occurred in a female HIV D+/R+ and was likely donor-derived. Remaining KAD cases occurred in male HIV D-/R+ and were likely recipient KSHV reactivation or acquisition. CONCLUSIONS:In the United States, KSHV seroprevalence in donors and recipients with HIV was high, particularly among MSM. Reassuringly, KSHV-associated disease was rare, and primarily attributed to recipient rather than donor-derived KSHV.

BACKGROUND:Kidney transplantation from donors with human immunodeficiency virus (HIV) to recipients with HIV is an emerging practice. It has been performed since 2016 under the U.S. congressional HIV Organ Policy Equity Act and is currently approved for research only. The Department of Health and Human Services is considering expanding the procedure to clinical practice, but data are limited to small case series that did not include donors without HIV as controls. METHODS:In an observational study conducted at 26 U.S. centers, we compared transplantation of kidneys from deceased donors with HIV and donors without HIV to recipients with HIV. The primary outcome was a safety event (a composite of death from any cause, graft loss, serious adverse event, HIV breakthrough infection, persistent failure of HIV treatment, or opportunistic infection), assessed for noninferiority (margin for the upper bound of the 95% confidence interval, 3.00). Secondary outcomes included overall survival, survival without graft loss, rejection, infection, cancer, and HIV superinfection. RESULTS:We enrolled 408 transplantation candidates, of whom 198 received a kidney from a deceased donor; 99 received a kidney from a donor with HIV and 99 from a donor without HIV. The adjusted hazard ratio for the composite primary outcome was 1.00 (95% confidence interval [CI], 0.73 to 1.38), which showed noninferiority. The following secondary outcomes were similar whether the donor had HIV or not: overall survival at 1 year (94% vs. 95%) and 3 years (85% vs. 87%), survival without graft loss at 1 year (93% vs. 90%) and 3 years (84% vs. 81%), and rejection at 1 year (13% vs. 21%) and 3 years (21% vs. 24%). The incidence of serious adverse events, infections, surgical or vascular complications, and cancer was similar in the groups. The incidence of HIV breakthrough infection was higher among recipients of kidneys from donors with HIV (incidence rate ratio, 3.14; 95%, CI, 1.02 to 9.63), with one potential HIV superinfection among the 58 recipients in this group with sequence data and no persistent failures of HIV treatment. CONCLUSIONS:In this observational study of kidney transplantation in persons with HIV, transplantation from donors with HIV appeared to be noninferior to that from donors without HIV. (Funded by the National Institute of Allergy and Infectious Diseases; ClinicalTrials.gov number, NCT03500315.).

PURPOSE OF REVIEW/OBJECTIVE:Strongyloides stercoralis infection remains of concern due to its high associated morbidity among solid organ transplant recipients (SOTR) and the risk of donor-derived infection (DDI). We review key aspects of epidemiology to inform screening for and treatment of chronic infection among organ transplant candidates to reduce the risk of infectious complications in the posttransplant setting. RECENT FINDINGS/RESULTS:In this work, we offer guidance regarding the optimal management of Strongyloides hyperinfection syndrome and disseminated infection and offer recommendations regarding posttreatment surveillance and the potential need for repeat treatment during subsequent periods of augmented immunosuppression. This review also provides updated recommendations for screening of deceased and living donors as recently proposed by the Organ Procurement and Transplantation Network's Ad Hoc Disease Transmission Advisory Committee. SUMMARY/CONCLUSIONS:Risk reduction of Strongyloides infection in the SOTR population can be further enhanced by optimized treatment of infection, posttreatment surveillance during at-risk periods and recent proposed policy shifts to universal donor screening.