Non-HLA donor-recipient (D-R) genetic mismatches contribute to kidney allograft injury and long-term graft loss, but their clinical use is limited by the unavailability of donor DNA after transplantation. We tested whether non-invasively obtained, recipient-derived samples could be used to infer donor genotype and D-R mismatches. Genomic DNA (g-DNA) of 11 unselected kidney transplant recipients and donors underwent whole-exome sequencing (100x). Additional customized probes were added for intronic coverage (300x) of 55 targeted non-HLA genes of reported clinical relevance. Variants identified from sequencing results were compared with plasma cell-free DNA (cfDNA), urine cell-pellet DNA (U-DNA) obtained from the same recipients. Genome-wide-, exonic-, or non-synonymous exonic- mismatches in transmembrane or secreted proteins, and mismatches within target genes were benchmarked using donor g-DNA to generate mismatch scores for each D-R pair. Within each of these genomic scales of mismatch, U-DNA identified D-R mismatches significantly better than the corresponding cfDNA (P<0.001 for each comparison). U-DNA also identified gene-level mismatches in the LIMS1 gene, and correctly inferred established donor-origin risk alleles, including SHROOM3 and APOL1 . Our findings demonstrate proof-of-concept that U-DNA in tandem with recipient genome, can non-invasively infer relevant non-HLA loci/mismatches circumventing the need for the donor's genomic DNA.

Background: There is no standard definition for "HLA incompatible " transplants. For the first time, we systematically assessed how HLA incompatibility was defined in contemporary peer-reviewed publications and its prognostic implication to transplant outcomes. Methods: We combined 2 independent searches of MEDLINE, EMBASE, and the Cochrane Library from 2015 to 2019. Content-expert reviewers screened for original research on outcomes of HLA-incompatible transplants (defined as allele or molecular mismatch and solid-phase or cell-based assays). We ascertained the completeness of reporting on a predefined set of variables assessing HLA incompatibility, therapies, and outcomes. Given significant heterogeneity, we conducted narrative synthesis and assessed risk of bias in studies examining the association between death-censored graft failure and HLA incompatibility. Results: Of 6656 screened articles, 163 evaluated transplant outcomes by HLA incompatibility. Most articles reported on cytotoxic/flow T-cell crossmatches (n = 98). Molecular genotypes were reported for selected loci at the allele-group level. Sixteen articles reported on epitope compatibility. Pretransplant donor-specific HLA antibodies were often considered (n = 143); yet there was heterogeneity in sample handling, assay procedure, and incomplete reporting on donor-specific HLA antibodies assignment. Induction (n = 129) and maintenance immunosuppression (n = 140) were frequently mentioned but less so rejection treatment (n = 72) and desensitization (n = 70). Studies assessing death-censored graft failure risk by HLA incompatibility were vulnerable to bias in the participant, predictor, and analysis domains. Conclusions: Optimization of transplant outcomes and personalized care depends on accurate HLA compatibility assessment. Reporting on a standard set of variables will help assess generalizability of research, allow knowledge synthesis, and facilitate international collaboration in clinical trials.

Introduction: A recent case report in a patient awaiting living donor kidney transplant demonstrated vaccination against SARS CoV-2 with resulted in B-cell activation causing emergence of DSA. This raises the questions as to whether vaccination against SARS CoV-2 should be considered a sensitizing event and warrant increased testing of sera for anti-HLA antibodies in patients awaiting kidney transplant. Methods: We sought to anwer this question by reviewing anti-HLA antibody testing results in sensitized and unsensitized patients before and after vaccination against SARS CoV-2. Patients were selected on the basis of having received at least two doses of either the Pfizer or Moderna SARS CoV-2 vaccine and have sera tested before and after receiving the vaccinations. 12 sensitized and 10 unsensitized who met criteria were indentified. Sera was tested using Luminex single antigen bead platforms per protocol. Results included anti-HLA antibody specificity as well as MFI ranges. cPRA was calculated from these values. Results: In 11/12 sensitized patients vaccination against SARS CoV-2 did not result in production of new anti-HLA antibodies nor appreciaciably change the MFI of exisiting antibodies. One sensitized patient did have an increased number of both class I and class II antibodies after vaccination but this patient also stopped immunsuppression prior to receiving the vaccine. Thus this patient’s results are likely attributable to alterations in immunosuppression and not from vaccination (Figure 1). In unsensitized patients, there was no de novo development of anti-HLA antibodies after vaccination. Conclusion: Vaccination against SARS CoV-2 did not result in de novo development of anti-HLA antibodies in unsensitized patients and did not alter the specificity nor the MFI’s of existing anti-HLA antibodies in sensitized patients. This indicates that there is no braod need for increased testing of sera in patients awaiting kidney transplant after SARS CoV-2 vaccination.

Intro: Angiotensin-II (Ang-II) plays an important role in the pathophysiology of various cardiovascular disorders, including cardiomyopathy and hypertension. Angiotensin II type 1 receptor (AT1R) mediates the deleterious effects of Ang-II and can cause vasoconstriction, vascular and cardiac remodeling, and cell death. Animal models have shown that the AT1R signal is obligatory for the development of virus-induced myocardial injury through the proinflammatory action of Ang-II. Data from animal studies and human case studies showed AT1R autoantibodies (AT1R A) were a novel mediator of vasomotor changes and LV dysfunction related to acute myocarditis and that blocking AT1R can be effective. Hypothesis: Little is known whether patients on immune checkpoint inhibitors (ICI) develop AT1R A and whether this can worsen the severity of ICI myocarditis. We measured AT1R A in 9 hospitalized patients who were diagnosed with ICI induced myocarditis. We describe this cohort, the course of their illness and their response to steroids. Methods: This was a prospective study. Quantitative antibodies to AT1R at the time of hospitalization were measured by an Enzyme Linked Immunosorbent Assay (ELISA) (One Lambda) and classified as positive (>17U/mL); at risk (10-17 U/mL) and negative (<10 U/mL). Results: Demographic and co-morbidity details are shown (Table 1). 5/9 patients (55%) were either positive or at risk for AT1R A elevation. 4/9 patients (45%) were AT1R A negative. 4/5 (80%) of the AT1R A positive/at risk required increased immunosuppression whereas 1/4 (25%) of the AT1R A negative required increased immunosuppression for myocarditis. Conclusions: AT1R autoantibodies may worsen the severity of ICI myocarditis. A larger cohort study and comparisons of AT1R A levels in non-ICI patients are underway. If trends hold true, testing for AT1R A and treating with an angiotensin receptor blocker may be a potential strategy to reduce ICI myocarditis severity.

Despite significant improvement in the rates of acute allograft rejection, proportionate improvements in kidney allograft longevity have not been realized, and are a source of intense research efforts. Emerging translational data and natural history studies suggest a role for anti-donor immune mechanisms in a majority of cases of allograft loss without patient death, even when overt evidence of acute rejection is not identified. At the level of the donor and recipient genome, differences in highly polymorphic HLA genes are routinely evaluated between donor and recipient pairs as part of organ allocation process, and utilized for patient-tailored induction and maintenance immunosuppression. However, a growing body of data have characterized specific variants in donor and recipient genes, outside of HLA loci, that induce phenotypic changes in donor organs or the recipient immune system, impacting transplant outcomes. Newer mechanisms for "mismatches" in these non-HLA loci have also been proposed during donor-recipient genome interactions with transplantation. Here, we review important recent data evaluating the role of non-HLA genetic loci and genome-wide donor-recipient mismatches in kidney allograft outcomes.

The Banff antibody-mediated rejection (ABMR) classification is vulnerable to misinterpretation, but the reasons are unclear. To better understand this vulnerability, we evaluated how ABMR is diagnosed in practice. To do this, the Banff Antibody-Mediated Injury Workgroup electronically surveyed an international cohort of nephrologists/surgeons (n = 133) and renal pathologists (n = 99). Most providers (97%) responded that they use the Banff ABMR classification at least sometimes, but DSA information is often not readily available. Only 41.1% (55/133) of nephrologists/surgeons and 19.2% (19/99) of pathologists reported that they always have DSA results when the biopsy is available. Additionally, only 19.6% (26/133) of nephrologists/surgeons responded that non-HLA antibody or molecular transcripts are obtained when ABMR histologic features are present but DSA is undetected. Several respondents agreed that histologic features concerning for ABMR in the absence of DSA and/or C4d are not well accounted for in the current classification [31.3% (31/99) pathologists and 37.6% (50/133) nephrologist/surgeons]. The Banff ABMR classification appears widely accepted, but efforts to improve the accessibility of DSA information for the multidisciplinary care team are needed. Further clarity is also needed in Banff ABMR nomenclature to account for the spectrum of ABMR and for histologic features suspicious for ABMR when DSA is absent.