Effectiveness of combined plasma cell therapy and costimulation blockade based desensitization regimen in heart transplant candidates.

BACKGROUND: Desensitization is one of the strategies to reduce antibodies and facilitate heart transplantation in highly sensitized patients. We describe our center's desensitization experience with combination of plasma cell (PC) depletion therapy (with proteasome inhibitor or daratumumab) and costimulation blockade (with belatacept). METHODS: We reviewed five highly sensitized patients who underwent desensitization therapy with plasma cell depletion and costimulation blockade. We evaluated the response to therapy by measuring the changes in cPRA, average MFI, and number of positive beads > 5000MFI. RESULTS: Five patients, mean age of 56 (37-66) years with average cPRA of 98% at 5000 MFI underwent desensitization therapy. After desensitization, mean cPRA decreased from 98% to 70% (p = .09), average number of beads > 5000 MFI decreased from 59 to 37 (p = .15), and average MFI of beads > 5000 MFI decreased from 16713 to 13074 (p = .26). CONCLUSION: Combined PC depletion and CoB could be a reasonable strategy for sustained reduction in antibodies in highly sensitized patients being listed for heart transplantation.

Exome Sequencing Implicates DGKZ , ESRRA , and GXYLT1 for Modulating Granuloma Formation in Crohn Disease.

Non-caseating granulomas may indicate a more aggressive phenotype of Crohn disease (CD). Genetic associations of granulomatous CD (GCD) may help elucidate disease pathogenesis. Whole-exome sequencing was performed on peripheral blood-derived DNA from 17 pediatric patients with GCD and 19 with non-GCD (NGCD), and from an independent validation cohort of 44 GCD and 19 NGCD cases. PLINK (a tool set for whole-genome association and population-based linkage analyses) analysis was used to identify single nucleotide polymorphisms (SNPs) differentiating between groups, and subgroup allele frequencies were also compared to a public genomic database (gnomAD). The Combined Annotation Dependent Depletion scoring tool was used to predict deleteriousness of SNPs. Human leukocyte antigen (HLA) haplotype findings were compared to a control group (n = 8496). PLINK-based analysis between GCD and NGCD groups did not find consistently significant hits. gnomAD control comparisons, however, showed consistent subgroup associations with DGKZ , ESRRA , and GXYLT1 , genes that have been implicated in mammalian granulomatous inflammation. Our findings may guide future research and precision medicine.

COVID-19 infection and vaccination rarely impact HLA antibody profile in waitlisted renal transplant candidates- a multicenter cohort.

Although rare, infection and vaccination can result in antibodies to human leukocyte antigens (HLA). We analyzed the effect of SARS-CoV-2 infection or vaccination on HLA antibodies in waitlisted renal transplant candidates. Specificities were collected and adjudicated if the calculated panel reactive antibodies (cPRA) changed after exposure. Of 409 patients, 285 (69.7 %) had an initial cPRA of 0 %, and 56 (13.7 %) had an initial cPRA > 80 %. The cPRA changed in 26 patients (6.4 %), 16 (3.9 %) increased, and 10 (2.4 %) decreased. Based on cPRA adjudication, cPRA differences generally resulted from a small number of specificities with subtle fluctuations around the borderline of the participating centers' cutoff for unacceptable antigen listing. All five COVID recovered patients with an increased cPRA were female (p = 0.02). In summary, exposure to this virus or vaccine does not increase HLA antibody specificities and their MFI in approximately 99 % of cases and 97 % of sensitized patients. These results have implications for virtual crossmatching at the time of organ offer after SARS-CoV-2 infection or vaccination, and these events of unclear clinical significance should not influence vaccination programs.

Deceased donor vein extension grafts for right living donor kidney transplantation.

INTRODUCTION: In an effort to maximize living donor kidney utilization, we describe the use of deceased donor vein extension grafts for right-sided living donor kidneys and report our single-center experience using this technique. METHODS: A retrospective review of kidney transplant recipients (KTR) who received a right living donor kidney with deceased donor vein extension graft. Recipient demographics, postoperative graft function, and surgical complications were reviewed. Living donor nephrectomies were performed laparoscopically. Vein grafts were obtained from recent deceased donor procurements. End-to-end anastomosis of the graft to the renal vein was performed prior to implantation. RESULTS: Thirty-eight KTR received a right kidney transplant with deceased donor extension grafts. The median recipient age and BMI were 53.0 years and 29.3 kg/m2 . Total 71% were male. Ninety-five percent of grafts displayed immediate graft function, with two recipients requiring temporary dialysis due to anaphylaxis from induction therapy. Median serum creatinine at two weeks was 1.6 mg/dL and at three months was 1.5 mg/dL. There were no graft thromboses. CONCLUSION: Utilization of deceased donor extension grafts for short right renal veins is a simple technique that expands the donor pool for living donor renal transplantation. Our experience resulted in no technical complications and excellent early graft function.

Allogeneic, off-the-shelf, SARS-CoV-2-specific T cells (ALVR109) for the treatment of COVID-19 in high-risk patients.

Defects in T-cell immunity to SARS-CoV-2 have been linked to an increased risk of severe COVID-19 (even after vaccination), persistent viral shedding and the emergence of more virulent viral variants. To address this T-cell deficit, we sought to prepare and cryopreserve banks of virus-specific T cells, which would be available as a partially HLA-matched, off-the-shelf product for immediate therapeutic use. By interrogating the peripheral blood of healthy convalescent donors, we identified immunodominant and protective T-cell target antigens, and generated and characterized polyclonal virus-specific T-cell lines with activity against multiple clinically important SARS-CoV-2 variants (including 'delta' and 'omicron'). The feasibility of making and safely utilizing such virus-specific T cells clinically was assessed by administering partially HLA-matched, third-party, cryopreserved SARS-CoV-2-specific T cells (ALVR109) in combination with other antiviral agents to four individuals who were hospitalized with COVID-19. This study establishes the feasibility of preparing and delivering off-the-shelf, SARS-CoV-2-directed, virus-specific T cells to patients with COVID-19 and supports the clinical use of these products outside of the profoundly immune compromised setting (ClinicalTrials.gov number, NCT04401410).

Early humoral immune response to two doses of severe acute respiratory syndrome coronavirus 2 vaccine in a diverse group of solid organ transplant candidates and recipients.

Response to two doses of a nucleoside-modified messenger ribonucleic acid (mRNA) vaccine was evaluated in a large solid-organ transplant program. mRNA COVID-19 vaccine was administered to transplant candidates and recipients who met study inclusion criteria. Qualitative anti-SARS-CoV-2 Spike Total Immunoglobulin (Ig) and IgG-specific assays, and a semi-quantitative test for anti-SARS-CoV-2 Spike protein IgG were measured in 241 (17.2%) transplant candidates and 1163 (82.8%) transplant recipients; 55.2% of whom were non-Hispanic White and 44.8% identified as another race. Transplant recipients were a median (IQR) of 3.2 (1.1, 6.8) years from transplantation. Response differed by transplant status: 96.0% versus 43.2% by the anti-SARS-CoV-2 Total Ig (candidates vs. recipients, respectively), 93.5% versus 11.6% by the anti-SARS-CoV-2 IgG assay, and 91.9% versus 30.1% by anti-spike titers after two doses of vaccine. Multivariable analysis revealed candidates had higher likelihood of response versus recipients (odds ratio [OR], 14.6; 95 %CI 2.19, 98.11; P = .02). A slightly lower response was demonstrated in older patients (OR .96; 95 %CI .94, .99; P = .002), patients taking antimetabolites (OR, .21; 95% CI .08, .51; P = .001). Vaccination prior to transplantation should be encouraged.

Long-Term Follow-Up of Renal Transplant Recipients Treated With IVIG for De Novo Donor-Specific Antibodies.

BACKGROUND: Renal allograft survival is negatively affected by the development of de novo posttransplant donor-specific antibodies (dnDSA). We sought to determine whether treatment with intravenous immunoglobulin (IVIG) could remove or reduce the intensity of dnDSA. METHODS: A single-center study of 12 recipients with dnDSA and stable function who received IVIG 1 g/kg monthly for 6 months were compared with a contemporaneous cohort of 24 recipients with dnDSA who did not receive IVIG. RESULTS: The median time to first dnDSA was 6 months (interquartile range [IQR], 1-12), and follow-up was 83 months (IQR, 58-94) posttransplant. Resolution of dnDSA occurred in 27% of IVIG vs 46% of control recipients (P = .48). Fifty-eight percent of recipients in both cohorts demonstrated a reduction in the intensity of the dominant DSA at last follow-up (P =1.0). A reduction in the number of dnDSAs occurred in 58% vs 62% of the IVIG and control cohorts, respectively (P = .81). Post-dnDSA, acute rejection occurred in 8% of the IVIG vs 42% in the control group (P = .06). Forty-two percent of IVIG-treated vs 49% of control recipients had a deterioration in function from first dnDSA until most recent follow-up (P = .81). Actuarial graft survivals were equivalent between groups. CONCLUSIONS: IVIG treatment of dnDSA in recipients with stable graft function had no impact on DSA clearance or MFI reduction, but this outcome may also be owing to sample size. Larger studies or alternate dosing regimens may be required to determine if there is any role for the use of IVIG as a treatment for dnDSA.

CD11c+CD88+CD317+ myeloid cells are critical mediators of persistent CNS autoimmunity.

Natalizumab, a humanized monoclonal antibody (mAb) against α4-integrin, reduces the number of dendritic cells (DC) in cerebral perivascular spaces in multiple sclerosis (MS). Selective deletion of α4-integrin in CD11c+ cells should curtail their migration to the central nervous system (CNS) and ameliorate experimental autoimmune encephalomyelitis (EAE). We generated CD11c.Cre+/-ITGA4fl/fl C57BL/6 mice to selectively delete α4-integrin in CD11c+ cells. Active immunization and adoptive transfer EAE models were employed and compared with WT controls. Multiparameter flow cytometry was utilized to immunophenotype leukocyte subsets. Single-cell RNA sequencing was used to profile individual cells. α4-Integrin expression by CD11c+ cells was significantly reduced in primary and secondary lymphoid organs in CD11c.Cre+/-ITGA4fl/fl mice. In active EAE, a delayed disease onset was observed in CD11c.Cre+/-ITGA4fl/fl mice, during which CD11c+CD88+ cells were sequestered in the blood. Upon clinical EAE onset, CD11c+CD88+ cells appeared in the CNS and expressed CD317+ In adoptive transfer experiments, CD11c.Cre+/-ITGA4fl/fl mice had ameliorated clinical disease phenotype associated with significantly diminished numbers of CNS CD11c+CD88+CD317+ cells. In human cerebrospinal fluid from subjects with neuroinflammation, microglia-like cells display coincident expression of ITGAX (CD11c), C5AR1 (CD88), and BST2 (CD317). In mice, we show that only activated, but not naïve microglia expressed CD11c, CD88, and CD317. Finally, anti-CD317 treatment prior to clinical EAE substantially enhanced recovery in mice.

Limited window for donation of convalescent plasma with high live-virus neutralizing antibody titers for COVID-19 immunotherapy.

Millions of individuals who have recovered from SARS-CoV-2 infection may be eligible to participate in convalescent plasma donor programs, yet the optimal window for donating high neutralizing titer convalescent plasma for COVID-19 immunotherapy remains unknown. Here we studied the response trajectories of antibodies directed to the SARS-CoV-2 surface spike glycoprotein and in vitro SARS-CoV-2 live virus neutralizing titers (VN) in 175 convalescent donors longitudinally sampled for up to 142 days post onset of symptoms (DPO). We observed robust IgM, IgG, and viral neutralization responses to SARS-CoV-2 that persist, in the aggregate, for at least 100 DPO. However, there is a notable decline in VN titers ≥160 for convalescent plasma therapy, starting 60 DPO. The results also show that individuals 30 years of age or younger have significantly lower VN, IgG and IgM antibody titers than those in the older age groups; and individuals with greater disease severity also have significantly higher IgM and IgG antibody titers. Taken together, these findings define the optimal window for donating convalescent plasma useful for immunotherapy of COVID-19 patients and reveal important predictors of an ideal plasma donor.

Significantly Decreased Mortality in a Large Cohort of Coronavirus Disease 2019 (COVID-19) Patients Transfused Early with Convalescent Plasma Containing High-Titer Anti-Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Spike Protein IgG.

Coronavirus disease 2019 (COVID-19) convalescent plasma has emerged as a promising therapy and has been granted Emergency Use Authorization by the US Food and Drug Administration for hospitalized COVID-19 patients. We recently reported results from interim analysis of a propensity score-matched study suggesting that early treatment of COVID-19 patients with convalescent plasma containing high-titer anti-spike protein receptor binding domain (RBD) IgG significantly decreases mortality. We herein present results from a 60-day follow-up of a cohort of 351 transfused hospitalized patients. Prospective determination of enzyme-linked immunosorbent assay anti-RBD IgG titer facilitated selection and transfusion of the highest titer units available. Retrospective analysis by the Ortho VITROS IgG assay revealed a median signal/cutoff ratio of 24.0 for transfused units, a value far exceeding the recent US Food and Drug Administration-required cutoff of 12.0 for designation of high-titer convalescent plasma. With respect to altering mortality, our analysis identified an optimal window of 44 hours after hospitalization for transfusing COVID-19 patients with high-titer convalescent plasma. In the aggregate, the analysis confirms and extends our previous preliminary finding that transfusion of COVID-19 patients soon after hospitalization with high-titer anti-spike protein RBD IgG present in convalescent plasma significantly reduces mortality.

Treatment of Coronavirus Disease 2019 Patients with Convalescent Plasma Reveals a Signal of Significantly Decreased Mortality.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, has spread globally, and proven treatments are limited. Transfusion of convalescent plasma collected from donors who have recovered from COVID-19 is among many approaches being studied as potentially efficacious therapy. We are conducting a prospective, propensity score-matched study assessing the efficacy of COVID-19 convalescent plasma transfusion versus standard of care as treatment for severe and/or critical COVID-19. We present herein the results of an interim analysis of 316 patients enrolled at Houston Methodist hospitals from March 28 to July 6, 2020. Of the 316 transfused patients, 136 met a 28-day outcome and were matched to 251 non-transfused control COVID-19 patients. Matching criteria included age, sex, body mass index, comorbidities, and baseline ventilation requirement 48 hours from admission, and in a second matching analysis, ventilation status at day 0. Variability in the timing of transfusion relative to admission and titer of antibodies of plasma transfused allowed for analysis in specific matched cohorts. The analysis showed a significant reduction (P = 0.047) in mortality within 28 days, specifically in patients transfused within 72 hours of admission with plasma with an anti-spike protein receptor binding domain titer of ≥1:1350. These data suggest that treatment of COVID-19 with high anti-receptor binding domain IgG titer convalescent plasma is efficacious in early-disease patients.

Relationship between Anti-Spike Protein Antibody Titers and SARS-CoV-2 In Vitro Virus Neutralization in Convalescent Plasma.

Newly emerged pathogens such as SARS-CoV-2 highlight the urgent need for assays that detect levels of neutralizing antibodies that may be protective. We studied the relationship between anti-spike ectodomain (ECD) and anti-receptor binding domain (RBD) IgG titers, and SARS-CoV-2 virus neutralization (VN) titers generated by two different in vitro assays using convalescent plasma samples obtained from 68 COVID-19 patients, including 13 who donated plasma multiple times. Only 23% (16/68) of donors had been hospitalized. We also studied 16 samples from subjects found to have anti-spike protein IgG during surveillance screening of asymptomatic individuals. We report a strong positive correlation between both plasma anti-RBD and anti-ECD IgG titers, and in vitro VN titer. Anti-RBD plasma IgG correlated slightly better than anti-ECD IgG titer with VN titer. The probability of a VN titer ≥160 was 80% or greater with anti-RBD or anti-ECD titers of ≥1:1350. Thirty-seven percent (25/68) of convalescent plasma donors lacked VN titers ≥160, the FDA-recommended level for convalescent plasma used for COVID-19 treatment. Dyspnea, hospitalization, and disease severity were significantly associated with higher VN titer. Frequent donation of convalescent plasma did not significantly decrease either VN or IgG titers. Analysis of 2,814 asymptomatic adults found 27 individuals with anti-RBD or anti-ECD IgG titers of ≥1:1350, and evidence of VN ≥1:160. Taken together, we conclude that anti-RBD or anti-ECD IgG titers can serve as a surrogate for VN titers to identify suitable plasma donors. Plasma anti-RBD or anti-ECD titer of ≥1:1350 may provide critical information about protection against COVID-19 disease.

Treatment of COVID-19 Patients with Convalescent Plasma in Houston, Texas.

BACKGROUND: COVID-19 disease, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread globally, and no proven treatments are available. Convalescent plasma therapy has been used with varying degrees of success to treat severe microbial infections for more than 100 years. METHODS: Patients (n=25) with severe and/or life-threatening COVID-19 disease were enrolled at the Houston Methodist hospitals from March 28 to April 14, 2020. Patients were transfused with convalescent plasma obtained from donors with confirmed SARS-CoV-2 infection and had been symptom free for 14 days. The primary study outcome was safety, and the secondary outcome was clinical status at day 14 post-transfusion. Clinical improvement was assessed based on a modified World Health Organization 6-point ordinal scale and laboratory parameters. Viral genome sequencing was performed on donor and recipient strains. RESULTS: At baseline, all patients were receiving supportive care, including anti-inflammatory and anti-viral treatments, and all patients were on oxygen support. At day 7 post-transfusion with convalescent plasma, nine patients had at least a 1-point improvement in clinical scale, and seven of those were discharged. By day 14 post-transfusion, 19 (76%) patients had at least a 1-point improvement in clinical status and 11 were discharged. No adverse events as a result of plasma transfusion were observed. The whole genome sequencing data did not identify a strain genotype-disease severity correlation. CONCLUSIONS: The data indicate that administration of convalescent plasma is a safe treatment option for those with severe COVID-19 disease. Randomized, controlled trials are needed to determine its efficacy.

Treatment of Coronavirus Disease 2019 (COVID-19) Patients with Convalescent Plasma.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2, has spread globally, and no proven treatments are available. Convalescent plasma therapy has been used with varying degrees of success to treat severe microbial infections for >100 years. Patients (n = 25) with severe and/or life-threatening COVID-19 disease were enrolled at the Houston Methodist hospitals from March 28, 2020, to April 14, 2020. Patients were transfused with convalescent plasma, obtained from donors with confirmed severe acute respiratory syndrome coronavirus 2 infection who had recovered. The primary study outcome was safety, and the secondary outcome was clinical status at day 14 after transfusion. Clinical improvement was assessed on the basis of a modified World Health Organization six-point ordinal scale and laboratory parameters. Viral genome sequencing was performed on donor and recipient strains. At day 7 after transfusion with convalescent plasma, nine patients had at least a one-point improvement in clinical scale, and seven of those were discharged. By day 14 after transfusion, 19 (76%) patients had at least a one-point improvement in clinical status, and 11 were discharged. No adverse events as a result of plasma transfusion were observed. Whole genome sequencing data did not identify a strain genotype-disease severity correlation. The data indicate that administration of convalescent plasma is a safe treatment option for those with severe COVID-19 disease.

Limitations of cell-lineage-specific non-dynamic gene recombination in CD11c.Cre+ITGA4fl/fl mice.

BACKGROUND: The Cre-lox system is a non-dynamic method of gene modification and characterization. Promoters thought to be relatively cell-specific are utilized for generation of cell-lineage-specific gene modifications. METHODS: CD11c.Cre+ITGA4fl/fl mice were generated to abolish the expression of ITGA (α4-integrin) in CD11c+ cells. Ex vivo flow cytometry studies were used to assess the expression of cellular surface markers in different lymphoid compartments and leukocytes subsets after Cre-mediated recombination. RESULTS: A significant reduction of α4-integrin expression among CD11c+- cells was achieved in CD11c.Cre+ITGA4fl/fl mice in primary and secondary lymphoid tissues. A similar reduction in the expression of α4-integrin was also observed in CD11c- cells. CONCLUSION: Cre-lox-mediated cell lineage-specific gene deletion is limited by the transient expression of recombination regulating sequences in hematopoietic cell lines. These methodological issues indicate the need to consider when to employ non-dynamic DNA recombination models in animal models of CNS autoimmunity. An experimental algorithm to address the biological complexities of non-dynamic gene recombination is provided.

α4-integrin deficiency in B cells does not affect disease in a T-cell-mediated EAE disease model.

Objective: The goal of this study was to investigate the role of CD 19+ B cells within the brain and spinal cord during CNS autoimmunity in a peptide-induced, primarily T-cell-mediated experimental autoimmune encephalomyelitis (EAE) model of MS. We hypothesized that CD19+ B cells outside the CNS drive inflammation in EAE. Methods: We generated CD19.Cre+/- α4-integrinfl/fl mice. EAE was induced by active immunization with myelin oligodendrocyte glycoprotein peptide (MOGp35-55). Multiparameter flow cytometry was used to phenotype leukocyte subsets in primary and secondary lymphoid organs and the CNS. Serum cytokine levels and Ig levels were assessed by bead array. B-cell adoptive transfer was used to determine the compartment-specific pathogenic role of antigen-specific and non-antigen-specific B cells. Results: A genetic ablation of α4-integrin in CD19+/- B cells significantly reduced the number of CD19+ B cells in the CNS but does not affect EAE disease activity in active MOGp35-55-induced disease. The composition of B-cell subsets in the brain, primary lymphoid organs, and secondary lymphoid organs of CD19.Cre+/- α4-integrinfl/fl mice was unchanged during MOGp35-55-induced EAE. Adoptive transfer of purified CD19+ B cells from CD19.Cre+/- α4-integrinfl/fl mice or C57BL/6 wild-type (WT) control mice immunized with recombinant rMOG1-125 or ovalbumin323-339 into MOGp35-55-immunized CD19.Cre+/- α4-integrinfl/fl mice caused worse clinical EAE than was observed in MOGp35-55-immunized C57BL/6 WT control mice that did not receive adoptively transferred CD19+ B cells. Conclusions: Observations made in CD19.Cre+/- α4-integrinfl/fl mice in active MOGp35-55-induced EAE suggest a compartment-specific pathogenic role of CD19+ B cells mostly outside of the CNS that is not necessarily antigen specific.

Presenilin1 regulates Th1 and Th17 effector responses but is not required for experimental autoimmune encephalomyelitis.

Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) where pathology is thought to be regulated by autoreactive T cells of the Th1 and Th17 phenotype. In this study we sought to understand the functions of Presenilin 1 (PSEN1) in regulating T cell effector responses in the experimental autoimmune encephalomyelitis (EAE) murine model of MS. PSEN1 is the catalytic subunit of γ-secretase a multimolecular protease that mediates intramembranous proteolysis. γ-secretase is known to regulate several pathways of immune importance. Here we examine the effects of disrupting PSEN1 functions on EAE and T effector differentiation using small molecule inhibitors of γ-secretase (GSI) and T cell-specific conditional knockout mice (PSEN1 cKO). Surprisingly, blocking PSEN1 function by GSI treatment or PSEN1 cKO had little effect on the development or course of MOG35-55-induced EAE. In vivo GSI administration reduced the number of myelin antigen-specific T cells and suppressed Th1 and Th17 differentiation following immunization. In vitro, GSI treatment inhibited Th1 differentiation in neutral but not IL-12 polarizing conditions. Th17 differentiation was also suppressed by the presence of GSI in all conditions and GSI-treated Th17 T cells failed to induce EAE following adoptive transfer. PSEN cKO T cells showed reduced Th1 and Th17 differentiation. We conclude that γ-secretase and PSEN1-dependent signals are involved in T effector responses in vivo and potently regulate T effector differentiation in vitro, however, they are dispensable for EAE.

The detrimental impact of persistent vs an isolated occurrence of de novo donor-specific antibodies on intermediate-term renal transplant outcomes.

BACKGROUND: De novo donor-specific antibodies (dnDSA) after renal transplant are associated with acute rejection (AR) and graft loss, yet most recipients with dnDSA have stable function and no AR. We assessed whether the persistence of dnDSA increased the risk of a detrimental outcome. METHODS: A single-center review of renal transplant recipients monitored for dnDSA at multiple time points post-transplant. An Isolated dnDSA was defined as one positive dnDSA and no additional positive tests, whereas ≥2 positive dnDSA was defined as persistent dnDSA. RESULTS: Of 708 recipients, 22% developed dnDSA, of whom 64% had persistent dnDSA. At median follow-up of 35 (range 12-74) months, there were fewer episodes of AR in the isolated dnDSA vs the persistent dnDSA group (2% vs 22%; P<.001,) and fewer graft losses with isolated dnDSA vs persistent dnDSA (0% vs 10%; P=.03). Within the persistent dnDSA group, recipients with dnDSA ≥60% of time points, had more AR (32% vs 16%, P=.10) and more graft losses (21% vs 2%; P=.003) than those with dnDSA<60%. CONCLUSIONS: Persistence of dnDSA resulted in more AR and graft failure than a single positive value. Recipients with longer duration of dnDSA persistence had an additional increased risk of AR and graft failure.

Early clearance vs persistence of de novo donor-specific antibodies following lung transplantation.

BACKGROUND: The natural history of de novo donor-specific antibodies (dnDSA) after lung transplantation is not well-described. We sought to determine the incidence and risk factors associated with dnDSA and compare outcomes between recipients with transient (or isolated) vs persistent dnDSA after transplantation. METHODS: A single-center review of all lung transplants from 1/2009-7/2013. DSAs were tested eight times in the first year and every 4 months thereafter. Outcomes examined included acute rejection and graft failure. RESULTS: Median follow-up was 18 months (range: 1-61 months), and 24.6% of 333 first-time lung-only transplant recipients developed a dnDSA. Ethnicity, HLA-DQ mismatches, post-transplantation platelet transfusion and Lung Allocation Score >60 were associated with dnDSA (P<.05). Overall graft survival was worse for dnDSA-positive vs negative recipients (P=.025). Of 323 recipients with 1-year follow-up, 72 (22.2%) developed dnDSA, and in 25 (34.7%), the dnDSA was transient and cleared. Recipients with transient dnDSA were less likely to develop acute rejection than those with persistent dnDSA (P=.007). CONCLUSIONS: Early post-lung transplantation, dnDSA occurred in 1/4 of recipients, was associated with peri-transplant risk factors and resulted in decreased survival. Spontaneous clearance of dnDSA, seen in one-third of recipients, was associated with a lower risk of acute rejection.

Population Genomic Analysis of 1,777 Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Isolates, Houston, Texas: Unexpected Abundance of Clonal Group 307.

Klebsiella pneumoniae is a major human pathogen responsible for high morbidity and mortality rates. The emergence and spread of strains resistant to multiple antimicrobial agents and documented large nosocomial outbreaks are especially concerning. To develop new therapeutic strategies for K. pneumoniae, it is imperative to understand the population genomic structure of strains causing human infections. To address this knowledge gap, we sequenced the genomes of 1,777 extended-spectrum beta-lactamase-producing K. pneumoniae strains cultured from patients in the 2,000-bed Houston Methodist Hospital system between September 2011 and May 2015, representing a comprehensive, population-based strain sample. Strains of largely uncharacterized clonal group 307 (CG307) caused more infections than those of well-studied epidemic CG258. Strains varied markedly in gene content and had an extensive array of small and very large plasmids, often containing antimicrobial resistance genes. Some patients with multiple strains cultured over time were infected with genetically distinct clones. We identified 15 strains expressing the New Delhi metallo-beta-lactamase 1 (NDM-1) enzyme that confers broad resistance to nearly all beta-lactam antibiotics. Transcriptome sequencing analysis of 10 phylogenetically diverse strains showed that the global transcriptome of each strain was unique and highly variable. Experimental mouse infection provided new information about immunological parameters of host-pathogen interaction. We exploited the large data set to develop whole-genome sequence-based classifiers that accurately predict clinical antimicrobial resistance for 12 of the 16 antibiotics tested. We conclude that analysis of large, comprehensive, population-based strain samples can assist understanding of the molecular diversity of these organisms and contribute to enhanced translational research.IMPORTANCEKlebsiella pneumoniae causes human infections that are increasingly difficult to treat because many strains are resistant to multiple antibiotics. Clonal group 258 (CG258) organisms have caused outbreaks in health care settings worldwide. Using a comprehensive population-based sample of extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae strains, we show that a relatively uncommon clonal type, CG307, caused the plurality of ESBL-producing K. pneumoniae infections in our patients. We discovered that CG307 strains have been abundant in Houston for many years. As assessed by experimental mouse infection, CG307 strains were as virulent as pandemic CG258 strains. Our results may portend the emergence of an especially successful clonal group of antibiotic-resistant K. pneumoniae.