Maria Ajaimy

The Clinical and Genomic Significance of Donor-Specific Antibody–Positive/C4d-Negative and Donor-Specific Antibody–Negative/C4d-Negative Transplant Glomerulopathy

BACKGROUND This study investigated the mechanisms involved in development of donor-specific antibody (DSA) and/or C4d-negative transplant glomerulopathy (TGP) by allograft gene expression profiles using microarrays. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS This cohort study was conducted in kidney transplant recipients. Patients were eligible for inclusion if they required a clinically indicated biopsy at any time point after their transplant. They were then classified according to their histopathology findings and DSA and C4d results. Eighteen chronic antibody-mediated rejection (CAMR), 14 DSA+/C4d- TGP, 25 DSA-/C4d- TGP, and 47 nonspecific interstitial fibrosis/tubular atrophy (IFTA) biopsy specimens were identified. In a subset of patients from the study population, biopsy specimens in each group and normal transplant kidney specimens were analyzed with Affymetrix Human Gene 1.0 ST Arrays. RESULTS The mean sum score of glomerulitis and peritubular capillaritis increased from 0.28±0.78 in IFTA specimens to 0.75±0.85 in DSA-/C4d- TGP specimens, 1.71±1.49 in DSA+/C4d-/TGP specimens, and 2.11±1.74 in CAMR specimens (P<0.001). During a median follow-up time of 2 (interquartile range, 1.4-2.8) years after biopsy, graft loss was highest in CAMR specimens (27.8%) compared to IFTA specimens (8.5%), DSA+/C4d- TGP specimens (14.3%), and DSA-/C4d- TGP specimens (16%) (P=0.01). With use of microarrays, comparison of the gene expression profiles of DSA-/C4d- TGP specimens with glomerulitis + peritubular capillaritis scores > 0 to normal and IFTA biopsy specimens revealed higher expression of quantitative cytotoxic T cell-associated transcripts (QCAT). However, both CAMR and DSA+/C4d- TGP specimens had higher expression of not only QCAT but also IFN-γ and rejection-induced, constitutive macrophage-associated, natural killer cell-associated, and DSA-selective transcripts. Endothelial cell-associated transcript expression was upregulated only in CAMR biopsy specimens. CONCLUSIONS These results suggested that DSA+/C4d- TGP biopsy specimens may be classified as CAMR. In contrast, DSA-/C4d- TGP specimens showed increased cytotoxic T cell-associated transcripts, suggesting T cell activation as a mechanism of injury.

The prevalence and clinical significance of C1q-binding donor-specific anti-HLA antibodies early and late after kidney transplantation.

We aimed to determine the prevalence and clinical significance of complement-binding donor-specific antibodies (DSA) detected up to 30 years after kidney transplantation. Group 1 patients included 284 consecutive DSA negative patients who underwent kidney transplantation after 1 May 2009. Group 2 included 405 patients transplanted before this date and followed at our center with functioning allografts. DSA were tested using Luminex Single Antigen and the C1q assay. In Group 1 patients, who were monitored prospectively, 31 (11%) developed de novo DSA during a median follow-up of 2.5 (1.9, 3.6) years. Of these, 11 (4%) had C1q+ and 20 (7%) had C1q negative DSA. In Group 2 patients, 77 (19%) displayed DSA. Among these, 33 (8%) had C1q+ and 44 (11%) had C1q negative DSA. The incidence of acute antibody-mediated rejection (AMR) was significantly higher in C1q+DSA patients in both Group 1 (45%) and Group 2 (15%) compared with C1q negative DSA (5% and 2%) and DSA negative patients (1% and 3%; P < 0.001 and P = 0.001). The incidence of chronic AMR was 36% (Group 1) and 51% (Group 2) in patients with C1q+DSA. In contrast, chronic AMR occurred in 5% and 25% of C1q negative DSA, and 2% and 6% of DSA negative Group 1 and 2 patients, respectively (P < 0.001). Although the graft survival was lower in Group 1 C1q+DSA patients (73%) compared with C1q negative DSA (95%) and DSA negative (94%) patients, the difference was not statistically significant by Kaplan-Meier survival analysis (P = 0.21). Our results indicated that the presence of C1q+ DSA was associated with acute and chronic AMR.

Safety and Efficacy of Treatment of Hepatitis C in Kidney Transplant Recipients with Directly Acting Antiviral Agents.

Background With the development of all oral, interferon-free directly acting antiviral (DAA) medications, treatment of hepatitis C virus (HCV) infection in renal transplant recipients is possible, but limited data exists on its safety and efficacy. Methods We performed a retrospective cohort analysis of patients transplanted at our center with HCV who have been started on DAAs. Primary endpoints included sustained virologic response as defined as negative viral load at 12 weeks postcompletion of therapy and allograft function. Results A total of 31 patients met inclusion criteria. The most commonly used regimen was sofosbuvir and ledipasvir (n = 21). Of the treated patients, 100% had undetectable viral load at the completion of therapy. Of the 31 patients treated, 30 (97%) achieved sustained virologic response. Both graft and patient survivals at most recent follow-up was 100%. There was no significant change in glomerular filtration rate (GFR) before or after therapy (64.2 ± 16.5 mL/min per body surface area before vs. 58.9 ± 17.5 mL/min per body surface area after therapy; P = 0.22); however, 3 patients now have GFR less than 20. A total of 6 (19.3%) of 31 patients had worsening proteinuria during or shortly after therapy. Patients with more than 500 mg/g of proteinuria at the start of treatment were significantly more likely to develop worsening proteinuria than those with less than 500 mg/g of proteinuria at the start of therapy (P < 0.001). Retrospective review of 20 untreated HCV patients did not demonstrate worsening allograft function and proteinuria during a median follow-up time of 1386 days (range, 332–6254). Conclusions Our preliminary data demonstrate that DAAs can be used safely and effectively in patients after kidney transplantation. Patients with proteinuria or lower GFR should be monitored more closely.

Increased intragraft rejection-associated gene transcripts in patients with donor-specific antibodies and normal biopsies

We investigated why some donor-specific antibody-positive patients do not develop antibody-mediated rejection. Of 71 donor-specific antibody-positive patients, 46 had diagnosis of antibody-mediated rejection and 25 had normal biopsies. Fifty donor-specific antibody-negative patients with normal biopsies were used as a control group. A subgroup of 61 patients with available biopsy and 64 with blood samples were analyzed by microarrays. Both donor-specific antibody-positive/antibody-mediated rejection-positive and negative biopsies showed increased expression of gene transcripts associated with cytotoxic T cells, natural killer cells, macrophages, interferon-gamma, and rejection compared to donor-specific antibody-negative biopsies. Regulatory T-cell transcripts were upregulated in donor-specific antibody-positive/antibody-mediated rejection-positive and B-cell transcripts in donor-specific antibody-positive/antibody-mediated rejection-negative biopsies. Whole-blood gene expression analysis showed increased immune activity in only donor-specific antibody-positive/antibody-mediated rejection-positive but not negative patients. During a median follow-up of 36 months, 4 donor-specific antibody-positive/antibody-mediated rejection-negative patients developed antibody-mediated rejection, 12 continued to have donor-specific antibody, but 9 lost their donor-specific antibody. Gene expression profiles did not predict the development of antibody-mediated rejection or the persistence of donor-specific antibody. Thus, donor-specific antibody-positive/antibody-mediated rejection-negative patients had increased rejection-associated gene transcripts in their allografts despite no histologic findings of rejection but not in their blood. This was found in both biopsy and blood samples of donor-specific antibody-positive/antibody-mediated rejection-positive patients.

Pretransplant immunologic risk assessment of kidney transplant recipients with donor-specific anti-human leukocyte antigen antibodies.

Background Patients with pretransplantation strong donor-specific anti–human leukocyte antigen (HLA) antibodies (DSA) are at higher risk for rejection. We aimed to study the safety of kidney transplantation in patients with lower strength DSAs in a prospective cohort study. Methods Three hundred and seventy-three consecutive adult kidney transplant recipients with (DSA+; n=66) and without (DSA−; n=307) DSA were evaluated. Anti-HLA antibodies with mean fluorescence intensity values over 5,000 for HLA-A, HLA-B, and HLA-DR and more than 10,000 for HLA-DQ were reported as unacceptable antigens. Patients received transplant if flow cytometry T-cell and B-cell cross-match channel shift values were less than 150 and 250, respectively, with antithymocyte globulin and intravenous immunoglobulin induction treatment. Results Patients had a mean number of 1.6±0.8 DSAs with a mean fluorescence intensity value of 2,815±2,550. Twenty-seven percent were flow cytometry cross-match positive with T-cell and B-cell channel shift values of 129±49 and 159±52, respectively. During a median follow-up of 24 months (range, 6–50), there were no statistically significant differences in patient (99% vs. 95%) and graft survival (88% vs. 90%) rates between DSA+ and DSA− groups, respectively. Cumulative acute rejection rates of 11% in the DSA+ group and 12% in the DSA− group were similar. Two DSA+ (3%) and five DSA− (2%) patients developed chronic antibody-mediated rejection (3%). The mean serum creatinine levels were identical between the two groups (1.4±0.6 mg/dL). Conclusion Similar patient and graft survival, and acute rejection rates can be achieved in DSA+ patients compared to DSA− patients with pretransplantation immunologic risk assessment.

Clinical and molecular significance of microvascular inflammation in transplant kidney biopsies.

The diagnostic criteria for antibody-mediated rejection (AMR) are continuously evolving. Here we investigated the clinical and molecular significance of different Banff microvascular inflammation (MVI) scores in transplant kidney biopsies. A total of 356 patients with clinically indicated kidney transplant biopsies were classified into three groups based on MVI scores of 0, 1, 2, or more for Groups 1-3, respectively. Gene expression profiles were assessed using arrays on a representative subset of 93 patients. The incidence of donor-specific anti-HLA antibodies was increased from 25% in Group 1 to 36% in Group 2 and to 54% in Group 3. Acute and chronic AMR were significantly more frequent in Group 3 (15% and 35%) compared with the Group 2 (3% and 15%) and Group 1 (0% and 5%), respectively. Gene expression profiles showed increased interferon-γ and rejection-induced, cytotoxic and regulatory T-cell, natural killer cell-associated and donor-specific antibody (DSA)-selective transcripts in Group 3 compared with Groups 1 and 2. There was no significant difference in gene expression profiles between the Groups 1 and 2. Increased intragraft expression of DSA-selective transcripts was found in the biopsies of C4d- Group 3 patients. Thus, an MVI score of 2 or more was significantly associated with a histological diagnosis of acute and chronic antibody-mediated rejection. Hence, increased intragraft DSA-selective gene transcripts may be used as molecular markers for AMR, especially in C4d- biopsies.

Genomics of BK viremia in kidney transplant recipients.

Background This study aimed to investigate global gene expression profiles of BK viremia and nephropathy (BKVN) samples using microarrays to investigate the immunologic response to BK virus. Methods Patients were monitored for BK viremia in the blood monthly for 6 months, then at 9 and 12 months after kidney transplantation. BKVN and normal transplant kidney biopsy samples, and whole blood samples of patients with and without BK viremia were analyzed by Affymetrix Human Gene 1.0 ST Arrays. Results During a mean follow-up of 917±325 days, 61 of the 289 patients (21%) developed BK viremia at a median 149 (27, 1,113) days after transplantation with a median peak PCR titers of 35,900 (1,000, 2,677,000). The only significant risk factor for development of BK viremia was induction with anti-thymocyte globulin (P=0.03). Only four patients developed BKVN (1.3%). Pathogenesis-based transcript analysis revealed a significant increased expression of interferon-gamma and rejection induced (GRIT), quantitative cytotoxic T-cell (QCAT), quantitative constitutive and alternate macrophage, B-cell and natural killer cell–associated transcripts (NKAT), indicating an active inflammatory immune response in BKVN biopsies (n=3) compared to normal transplant kidney biopsies with (n=3) and without BK viremia (n=11). The whole blood gene expression profiles of 19 BK viremia patients revealed significant increased expression of GRIT, QCAT, and NKAT compared to 14 patients without viremia. Conclusions The results showed increased activity of cytotoxic T cells and natural killer cells in BKVN and viremia samples resembling acute rejection and suggested the involvement of both adaptive and innate immunity.

Clinical, Histological, and Molecular Markers Associated With Allograft Loss in Transplant Glomerulopathy Patients.

Background We aimed to investigate the clinical, histopathological, and molecular factors associated with allograft loss in transplant glomerulopathy (TGP) patients. Methods Of the 525 patients who underwent clinically indicated kidney biopsies, 52 (10%) had diagnosis of TGP. Gene expression profiles of 28 TGP and 11 normal transplant kidney biopsy samples were analyzed by Affymetrix HuGene 1.0 ST expression arrays. Results Over a median follow up of 23 months (1-46 months) after the diagnosis of TGP by biopsy, 17 patients (32%) lost their allografts at a median of 16 months (1-44 months). There was no difference between the 2 groups in terms of any demographic variables, serum creatinine, panel reactive antibody levels, donor-specific antibody frequency, or mean fluorescence intensity values. Patients who lost their allograft had a significantly higher median spot protein to creatinine ratio 2.81 (1.20-6.00) compared to no graft loss patients 1.16 (0.15-2.53), (P < 0.01), and a trends toward a higher mean chronic glomerulopathy (cg) score (1.65 ± 0.93 vs 1.11 ± 0.93) (P = 0.05). There was also no difference in microvascular inflammation or any other Banff injury scores between the 2 groups. Although 117 gene transcripts were upregulated in both groups, 86 and 57 were upregulated in graft loss and functioning allograft groups, respectively. There were significantly increased levels of intragraft endothelial cell–associated transcripts, gene transcripts associated with complement cascade, interleukins and their receptors and granulysin in graft loss patients compared to patients with a functioning allograft. Conclusion Our results demonstrate differential intragraft gene expression profiles in TGP patients with allograft loss.

A pathogenesis-based transcript signature in donor-specific antibody-positive kidney transplant patients with normal biopsies

Affymetrix Human Gene 1.0-ST arrays were used to assess the gene expression profiles of kidney transplant patients who presented with donor-specific antibodies (DSAs) but showed normal biopsy histopathology and did not develop antibody-mediated rejection (AMR). Biopsy and whole-blood profiles for these DSA-positive, AMR-negative (DSA +/AMR−) patients were compared to both DSA-positive, AMR-positive (DSA +/AMR +) patients as well as DSA-negative (DSA −) controls. While individual gene expression changes across sample groups were relatively subtle, gene-set enrichment analysis using previously identified pathogenesis-based transcripts (PBTs) identified a clear molecular signature involving increased rejection-associated transcripts in AMR − patients. Results from this study have been published in Kidney International (Hayde et al., 2014 [1]) and the associated data have been deposited in the GEO archive and are accessible via the following link: http://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE50084

Reimbursement for living kidney donor follow-up care: how often does donor insurance pay?

Background Currently, many transplantation centers do not follow former living kidney donors on a long-term basis. Several potential barriers have been identified to provide this follow-up of former living kidney donors, including concerns that donor insurance will not reimburse transplantation centers or primary care physicians for this care. Here, we report the rates at which different insurance companies reimbursed our transplantation center for follow-up visits of living donors. Methods We collected data on all yearly follow-up visits of living donors billed from January 1, 2007, to December 31, 2010, representing 82 different donors. Concurrent visits of their recipients were available for 47 recipients and were used as a control group. Results We find that most bills for follow-up visits of living kidney donors were paid by insurance companies, at a rate similar to the reimbursement for recipient follow-up care. Conclusions Our findings suggest that, for former donors with insurance, inadequate reimbursement should not be a barrier in providing follow-up care.