Human polyomaviruses are associated with substantial morbidity in immunocompromised patients, including those with HIV/AIDS, recipients of bone marrow and kidney transplants, and individuals receiving immunomodulatory agents for autoimmune and inflammatory diseases. No effective antipolyomavirus agents are currently available, and no host determinants have been identified to predict susceptibility to polyomavirus-associated diseases. Using the mouse polyomavirus (MPyV) infection model, we recently demonstrated that perforin-granzyme exocytosis, tumor necrosis factor alpha (TNF-α), and Fas did not contribute to control of infection or virus-induced tumors. Gamma interferon (IFN-γ) was recently shown to inhibit replication by human BK polyomavirus in primary cultures of renal tubular epithelial cells. In this study, we provide evidence that IFN-γ is an important component of the host defense against MPyV infection and tumorigenesis. In immortalized and primary cells, IFN-γ reduces expression of MPyV proteins and impairs viral replication. Mice deficient for the IFN-γ receptor (IFN-γR−/−) maintain higher viral loads during MPyV infection and are susceptible to MPyV-induced tumors; this increased viral load is not associated with a defective MPyV-specific CD8+ T cell response. Using an acute MPyV infection kidney transplant model, we further show that IFN-γR−/− donor kidneys harbor higher MPyV levels than donor kidneys from wild-type mice. Finally, administration of IFN-γ to persistently infected mice significantly reduces MPyV levels in multiple organs, including the kidney, a major reservoir for persistent mouse and human polyomavirus infections. These findings demonstrate that IFN-γ is an antiviral effector molecule for MPyV infection.

Nephropathy associated with BK polyomavirus (BKV) causes kidney allograft dysfunction and failure. Understanding the pathogenesis of polyomavirus-associated allograft nephropathy (PVAN) is hampered by the species specificity of Polyomaviridae family members. Using a mouse polyomavirus (MPyV) kidney transplant model, we investigated clinically relevant variables that may contribute to PVAN. We found that the timing and source (i.e., donor versus recipient) of MPyV infection and the titer of the viral inoculum have significant effects on the extent of allograft injury, with acute infection of the recipient by high-titer MPyV inoculums producing the most profound PVAN. In contrast, altering the degree of MHC matching or increasing ischemia/reperfusion injury (IRI) by prolonging the cold ischemic time of the allograft did not affect the severity of PVAN. Survival correlated positively with serum creatinine levels, but not with viral loads in the kidney allograft. Using splenectomized aly/aly mice, which are unable to mount primary adaptive immune responses, we further demonstrate that persistent high viral loads in the kidney are not sufficient to cause advanced PVAN. These findings suggest that the mechanism of PVAN in mice is not a direct consequence of viral cytopathology, but rather involves interplay between viral infection and the recipient anti-donor immune response.

Migration to intestinal mucosa putatively depends on local activation because gastrointestinal lymphoid tissue induces expression of intestinal homing molecules, whereas skin-draining lymph nodes do not. This paradigm is difficult to reconcile with reports of intestinal T cell responses after alternative routes of immunization. We reconcile this discrepancy by demonstrating that activation within spleen results in intermediate induction of homing potential to the intestinal mucosa. We further demonstrate that memory T cells within small intestine epithelium do not routinely recirculate with memory T cells in other tissues, and we provide evidence that homing is similarly dynamic in humans after subcutaneous live yellow fever vaccine immunization. These data explain why systemic immunization routes induce local cell-mediated immunity within the intestine and indicate that this tissue must be seeded with memory T cell precursors shortly after activation.

Introduction: Cancer is an important outcome in kidney transplantation, but the scope and consistency of how cancer is defined and reported in trials involving kidney transplant recipients has not been evaluated. This study aimed to assess the range and variability of cancer outcomes in trials involving kidney transplant recipients. Methods: The ClinicalTrials.gov database was searched from February 2000 to July 2021 to identify all randomized controlled trials (RCTs) in adult kidney transplant recipients, and which included cancer as a specified outcome. The definition of cancer, types of cancer (if any), timepoint(s) of measurement and method of aggregation were extracted for each cancer outcome. Results: Of the 819 trials in kidney transplantation, only 84 (10%) included 1 or more cancer outcomes. Of these, 72 of 84 (86%) trials included cancer as a secondary outcome and 12 of 84 (14%) considered cancer as a primary outcome. The most frequent description of cancer was “malignancy” (n = 44, 43%), without reference to diagnostic criteria, histology, grade, or stage. The 2 most common cancer types were posttransplant lymphoproliferative disorder (PTLD) (n = 20, 20%) and nonmelanoma skin cancer (n = 10, 10%). Several methods of aggregation were identified, including incidence or rate (n = 47, 46%), frequency or proportion (n = 30, 29%), and time to event (n = 5, 5%). Approximately half the cancer outcomes were measured at a single time point (n = 44, 52%). Conclusion: Cancer is an infrequently reported outcome and is inconsistently defined in trials of kidney transplant recipients. Consistent reporting of cancer outcomes using standardized definitions would provide important information on the impact of cancer in patients after kidney transplantation.

Patients tolerant to a kidney graft display a specific blood cell transcriptional pattern but results from five different studies were inconsistent, raising the question of relevance for future clinical application. To resolve this, we sought to identify a common gene signature, specific functional and cellular components, and discriminating biomarkers for tolerance following kidney transplantation. A meta-analysis of studies identified a robust gene signature involving proliferation of B and CD4 T cells, and inhibition of CD14 monocyte related functions among 96 tolerant samples. This signature was further supported through a cross-validation approach, yielding 92.5% accuracy independent of the study of origin. Experimental validation, performed on new tolerant samples and using a selection of the top-20 biomarkers, returned 91.7% of good classification. Beyond the confirmation of B-cell involvement, our data also indicated participation of other cell subsets in tolerance. Thus, the use of the top 20 biomarkers, mostly centered on B cells, may provide a common and standardized tool towards personalized medicine for the monitoring of tolerant or low-risk patients among kidney allotransplant recipients. These data point to a global preservation of genes favoring the maintenance of a homeostatic and ‘healthy’ environment in tolerant patients and may contribute to a better understanding of tolerance maintenance mechanisms.

Background. Gaps in our knowledge of long-term outcomes affect decision making for potential living kidney donors. Methods. The Scientific Registry of Transplant Recipients was asked to determine the feasibility of a candidate registry. Results. Ten living kidney donor programs evaluated 2107 consecutive kidney donor candidates; 2099 of 2107 (99.6%) completed evaluations, 1578 of 2099 (75.2%) had a decision, and 790 of 1578 (50.1%) were approved to donate as of March 12, 2020. By logistic regression, candidates most likely to be approved were married or had attended college or technical school; those least likely to be approved had ≥1 of the following characteristics: Black race, history of cigarette smoking, and higher blood pressure, higher triglycerides, or higher urine albumin-to-creatinine ratios. Reasons for 617 candidates not being approved included medical issues other than chronic kidney disease risk (25.3%), chronic kidney disease risk (18.5%), candidate withdrawal (15.2%), recipient reason (13.6%), anatomical risk to the recipient (10.3%), noneconomic psychosocial (10.3%), economic (0.5%), and other reasons (6.4%). Conclusions. These results suggest that a comprehensive living donor registry is both feasible and necessary to assess long-term outcomes that may inform decision making for future living donor candidates. There may be socioeconomic barriers to donation that require more granular identification so that active measures can address inequities. Some candidates who did not donate may be suitable controls for discerning the appropriateness of acceptance decisions and the long-term outcomes attributable to donation. We anticipate that these issues will be better identified with modifications to the data collection and expansion of the registry to all centers over the next several years.

In a phase 2 multicenter open-label randomized trial sponsored by the National Institutes of Health, simultaneous pancreas-kidney (SPK) recipients were randomized to a calcineurin inhibitor (CNI)–based immunosuppressive regimen (tacrolimus) (n = 21), or an investigational arm using low-dose CNI plus costimulation blockade (belatacept) with intended CNI withdrawal (n = 22). Both arms included induction therapy with rabbit ATG, mycophenolate sodium, or mycophenolate mofetil and rapid withdrawal of steroids. Enrollment and CNI withdrawal were stopped after 43/60 planned subjects had been enrolled. At that time, the rate of biopsy-proven acute rejection (BPAR) of the pancreas was low in both groups until CNI was withdrawn, with four of the five pancreas rejections occurring during or after CNI withdrawal. The rate of BPAR of kidney allografts was low in both control (9.5%) and investigational (9.1%) arms. Pancreas graft survival at 52 weeks, defined by insulin independence, was 21 (100%) in the control group and 19 (86%) in the investigational arm. One subject in the investigational arm died with functioning pancreas and kidney grafts. Renal function at week 52 was similar in both arms. Costimulation blockade with belatacept did not provide sufficient immunosuppression to reliably prevent pancreas rejection in SPK transplants undergoing CNI withdrawal.

Background Two coding risk variants in the Apo L1 gene (APOL1) underlie most of the excess risk for kidney diseases in recent African ancestry patients. Strength and consistency of the relationship between APOL1 high-risk genotypes and the risk of chronic kidney diseases (CKD) and end-stage renal disease (ESRD) are not uniform. Objective To conduct a systematic review and meta-analysis of prospective studies assessing the association of APOL1 genotypes and the risk of developing CKD, ESRD, and CKD to ESRD in adults. Methods Systematic search of MEDLINE, EMBASE, and Google Scholar was performed for prospective studies assessing the associations between APOL1 genotypes and CKD, ESRD, and progression from CKD to ESRD. Secondary analyses were to evaluate the annual kidney function change by APOL1 gene status. Random effects models were used to estimate pooled risk ratios (RRs) and weighted mean differences for outcomes of interest. Results The search yield 10 prospective during a follow-up period ranging from 4.4 to 25 years. The high-risk APOL1 genotype was associated with the incidence of CKD (RR:1.41[95% CI: 1.14–1.75]), the progression from CKD to ESRD (RR: 1.70[95% CI:1.44; 2.01]) compared with the low-risk APOL1 genotype. There was no appreciable association between high-risk APOL1 genotype with the incidence of ESRD. Furthermore, high-risk APOL1 genotype was associated with a marginal decrement in the annual eGFR decline (−0.55[95% CI: −0.94 to −0.16]) mL/min/1.73m2 compared with low-risk APOL1 genotype status. Conclusion In summary, African Americans carrying APOL1 high-risk genotypes are at increased risk of developing CKD and ESRD. Given that the APOL1 risk alleles are common among individuals with African ancestry, with ~18% of African Americans carrying high-risk alleles, these findings highlight the potential identification of subgroups of patients who may benefit from APOL1 screening and developing culturally-appropriate interventions.

Belatacept, a T cell costimulation blocker, demonstrated superior renal function, lower cardiovascular risk, and improved graft and patient survival in renal transplant recipients. Despite the potential benefits, adoption of belatacept has been limited in part due to concerns regarding higher rates and grades of acute rejection in clinical trials. Since July 2011, we have utilized belatacept-based immunosuppression regimens in clinical practice. In this retrospective analysis of 745 patients undergoing renal transplantation at our center, we compared patients treated with belatacept (n = 535) with a historical cohort receiving a tacrolimus-based protocol (n = 205). Patient and graft survival were equivalent for all groups. An increased rate of acute rejection was observed in an initial cohort treated with a protocol similar to the low-intensity regimen from the BENEFIT trial versus the historical tacrolimus group (50.5% vs. 20.5%). The addition of a transient course of tacrolimus reduced rejection rates to acceptable levels (16%). Treatment with belatacept was associated with superior estimated GFR (belatacept 63.8 mL/min vs. tacrolimus 46.2 mL/min at 4 years, p < 0.0001). There were no differences in serious infections including rates of cytomegalovirus or BK viremia. We describe the development of a costimulatory blockade-based strategy that ultimately allows renal transplant recipients to achieve calcineurin inhibitor–free immunosuppression.

BACKGROUND: The interplay between viral infection and alloimmunity is known to influence the fate of transplanted organs. Clarifying how local virus-associated inflammation/injury and antiviral immunity can alter host alloimmune responses in transplantation remains a critical question. METHODS: We used a mouse model of polyomavirus (PyV) infection and kidney transplantation to investigate the roles of direct viral pathology, the antiviral immune response, and alloimmunity in the pathogenesis of PyV-associated allograft injury. We have previously shown that an effective primary T cell response is required in PyV-associated graft injury. RESULTS: Here we show that the transfer of primed antidonor, but not antiviral, T cells results in PyV-associated allograft injury. In further studies, we use a surrogate minor antigen model (ovalbumin) and show that only antidonor specific T cells and not antiviral specific T cells are sufficient to mediate injury. Lastly, we demonstrate that local but not systemic virus-mediated inflammation and injury within the graft itself are required. CONCLUSIONS: These data suggest that in this mouse model, the predominant mechanism of allograft injury in PyV-associated injury is due to an augmented alloimmune T cell response driven by virus-induced inflammation/injury within the graft. These studies highlight the important interplay between viral infection and alloimmunity in a model system.