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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.

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.

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.

Significance The bone marrow-derived CD11c+CD88+CD317+ myeloid cells within the central nervous system are associated with clinical experimental autoimmune encephalomyelitis. Transcriptional analyses identify ITGAX- (CD11c), C5AR1- (CD88), and BST2- (CD317) expressing cells as a distinct myeloid subset in human cerebrospinal fluid. The disease-propagating effects of these cells in experimental autoimmune encephalomyelitis can be effectively antagonized using anti-CD317 monoclonal antibody therapy., 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.

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 naive microglia expressed CD11c, CD88, and CD317. Finally, anti-CD317 treatment prior to clinical EAE substantially enhanced recovery in mice.

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., Gontu et al. conducted a longitudinal study in COVID patients in which they assessed the response trajectories of antibodies directed to the SARS-CoV-2 surface spike glycoprotein and in vitro SARS-CoV-2 live virus neutralizing titers. Their measurements demonstrate the presence of an optimum window for convalescent plasma donation as well as predictions of the most suitable donor type.

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.

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.

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 remains a global threat with few proven efficacious treatments. Transfusion of convalescent plasma collected from donors who have recovered from COVID-19 disease has emerged as a promising therapy and has been granted emergency use authorization by the U.S. Food and Drug Administration (FDA). 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 here present results from 60-day follow up of our cohort of 351 transfused hospitalized patients. Prospective determination of ELISA 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 (S/C) ratio of 24.0 for transfused units, a value far exceeding the recently FDA-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 post-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.

The optimal timeframe for donating convalescent plasma to be used for COVID-19 immunotherapy is unknown. To address this important knowledge deficit, we determinedin vitrolive-virus neutralizing capacity and persistence of IgM and IgG antibody responses against the receptor-binding domain and S1 ectodomain of the SARS-CoV-2 spike glycoprotein in 540 convalescent plasma samples obtained from 175 COVID-19 plasma donors for up to 142 days post-symptom onset. Robust IgM, IgG, and viral neutralization responses to SARS-CoV-2 persist, in the aggregate, for at least 100 days post-symptom onset. However, a notable acceleration in decline in virus neutralization titers ≥160, a value suitable for convalescent plasma therapy, was observed starting 60 days after first symptom onset. Together, these findings better define the optimal window for donating convalescent plasma useful for immunotherapy of COVID-19 patients and reveal important predictors of an ideal plasma donor, including age and COVID-19 disease severity score.One Sentence SummaryEvaluation of SARS-CoV-2 anti-spike protein IgM, IgG, and live-virus neutralizing titer profiles reveals that the optimal window for donating convalescent plasma for use in immunotherapy is within the first 60 days of symptom onset.

BackgroundNatalizumab, 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 CNS and ameliorate experimental autoimmune encephalomyelitis (EAE).MethodsWe generated CD11c.Cre+/-ITGA4fl/fl C57/Bl6 mice to selectively delete α4-integrin in CD11c+ cells. Active immunization and adoptive transfer EAE models were employed. Multi-parameter flow cytometry was utilized to immunophenotype leukocytes. Single-cell RNA sequencing (scRNA-seq) was used to profile individual cells.Resultsα4-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 EAE onset, CD11c+CD88+ cells accumulated in the CNS and expressed CD317+. In adoptive transfer experiments, CD11c.Cre+/-ITGA4fl/fl mice had ameliorated clinical disease associated with diminished numbers of CNS CD11c+CD88+CD317+ cells. The transcription profile of CD11c+CD88+CD317+ cells placed them within previously defined microglia-like cells in human CSF. We show that activated, but not naïve microglia expressed CD11c, CD88, and CD317. Finally, anti-CD317 treatment prior to clinical EAE substantially enhanced recovery.ConclusionCD11c+CD88+CD317+ cells in the CNS promote inflammatory damage. Transcriptional analysis identifies CD11c+CD88+CD317+ cells as a unique myeloid subset in human CSF. The disease-propagating effects of these cells can be antagonized using anti-CD317 mAb.

BackgroundCOVID-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.MethodsPatients (n=25) with severe and/or life-threatening COVID-19 disease were enrolled at the Houston Methodist hospitals from March 28 – 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.ResultsAt 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.ConclusionsThe 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.

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 differentin vitroassays 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, andin vitroVN 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.

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.CD11c.CreA significant reduction of α4-integrin expression among CD11cCre-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.

ObjectiveThe 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.MethodsWe generated CD19.Cre+/−α4-integrinfl/flmice. 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.ResultsA 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/flmice was unchanged during MOGp35-55-induced EAE. Adoptive transfer of purified CD19+B cells from CD19.Cre+/−α4-integrinfl/flmice or C57BL/6 wild-type (WT) control mice immunized with recombinant rMOG1-125or ovalbumin323-339into MOGp35-55-immunized CD19.Cre+/−α4-integrinfl/flmice 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.ConclusionsObservations made in CD19.Cre+/−α4-integrinfl/flmice 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.

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.

Background: Human leukocyte antigen (HLA) genes on chromosome 6p21 encode the major histocompatibility complex (MHC). MHC molecules are expressed on all nucleated cells and are essential to the immune system's ability to distinguish healthy native cells from foreign or abnormal ones. Specialized antigen presenting cells display MHC molecules loaded with foreign peptides to initiate T cell responses. HLA sequencing variability is critical to function; studies have shown even single allelic changes can alter the ability of MHC molecules to recognize cognate T cell receptors. Given the role of MHC molecules in identifying cells as "self", associations between HLA sequence variation and autoimmunity is a research focus. Like other autoimmune disorders, association between ITP and HLA genes has been investigated. Prior studies are limited by outdated HLA typing methods, genetically homogenous study populations, and lack of validation studies. Preexisting exome data has historically not been used to provide accurate HLA sequencing information given the polymorphic, highly repetitive sequence in this region. This study applied a novel bioinformatics pipeline, xHLA, to an existing set of whole exome sequencing in a cohort of chronic pediatric ITP patients. xHLA, reported by Xie et al. in 2017, yields high-resolution, two field HLA typing for HLA-A, -B, -C, -DQB1, -DPB1, and -DRB1. A prior genetic analysis of chronic ITP patient whole exome data identified a missense variant in BTNL2, a gene which plays a role in peripheral regulatory T cell induction. This variant (rs143211074) is upregulated in chronic ITP versus healthy controls (minor allele frequency= 4.17% in ITP v. 0.54% in controls, p=1.43x10-4). Linkage of rs143211074 and HLA alleles was examined in this study. Methods: Whole exome sequencing data for a cohort of 272 chronic ITP patients was processed using the xHLA method. In order to eliminate sequencing variability related to ethnicity alone, initial analyses were focused on Caucasians only (n=170), using Eigenvectors for principle components analysis. The frequency of individual HLA alleles and HLA haplotypes for Caucasians from the National Marrow Donor Program (NMDP) Be The Match Registry® were compared to the ITP cohort. HLA haplotypes were inferred using the NMDP HaploStats program. A chi-squared test was utilized to compare nonparametric categorical data using GraphPad Prism version 8.0.1 for Windows, GraphPad Software, San Diego, California, USA, www.graphpad.com. A Bonferroni correction was applied and a p-value of Results: 12 HLA alleles had increased frequency in the chronic ITP cohort versus controls. (Table 1) The BTNL2 variant, rs143211074, was found in linkage disequilibrium with the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype. Of the 10 patients heterozygous for the variant allele, 80% had the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype. Both patients homozygous for rs143211074 were also homozygous for the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype. In the entire cohort, this haplotype was identified in 3.63% of ITP patients, and only in 1.27% of controls. Our group recently published that a positive direct antiglobulin test is associated with chronic ITP and need for second line treatments. Of the patients with the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype with DAT testing performed (n=9), 66% had a positive DAT test and 33% had a negative DAT result. Of those without the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype who had DAT testing, 17.2% had a positive DAT and 82.8% had a negative test (p=0.0026). Conclusions: HLA alleles are seen at increased frequency in a cohort of Caucasian chronic ITP patients. The HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype is linked to a variant previously identified in BTNL2. Coupled with prior data suggesting that a positive DAT result is associated with chronic disease and use of second line agents, this presence of the HLA-DRB1*04:02, HLA-DQB1*03:02 haplotype may also be linked to refractory disease. Confirmation of the accuracy of the xHLA method in a cohort of patients with both exome data and traditional HLA typing is underway. In the future, a separate cohort of chronic and acute ITP patients will undergo next generation sequencing and have similar HLA typing performed as an independent validation set. Table 1 Disclosures Despotovic: Novartis: Research Funding; Amgen: Research Funding; Dova: Honoraria.

CD4(+) T helper (Th) cells are critical for proper immune cell homeostasis and host defense, but are also major contributors to pathology of autoimmune and inflammatory diseases. Since the discovery of the Th1/Th2 dichotomy, many additional Th subsets were discovered, each with a unique cytokine profile, functional properties, and presumed role in autoimmune tissue pathology. This includes Th1, Th2, Th17, Th22, Th9, and Treg cells which are characterized by specific cytokine profiles. Cytokines produced by these Th subsets play a critical role in immune cell differentiation, effector subset commitment, and in directing the effector response. Cytokines are often categorized into proinflammatory and anti-inflammatory cytokines and linked to Th subsets expressing them. This article reviews the different Th subsets in terms of cytokine profiles, how these cytokines influence and shape the immune response, and their relative roles in promoting pathology in autoimmune and inflammatory diseases. Furthermore, we will discuss whether Th cell pathogenicity can be defined solely based on their cytokine profiles and whether rigid definition of a Th cell subset by its cytokine profile is helpful.

Immune surveillance of the CNS is critical for preventing infections; however, there is no accepted experimental model to assess the risk of infection when utilizing disease-modifying agents. We tested two approved agents for patients with multiple sclerosis (MS), glatiramer acetate and fingolimod, in an experimental model of CNS immune surveillance. C57BL/6 mice were infected with the ME49 strain of the neuroinvasive parasite Toxoplasma gondii (T. gondii) and then treated with GA and fingolimod. Neither treatment affected host survival; however, differences were observed in parasite load and in leukocyte numbers in the brains of infected animals. Here we demonstrate that this model could be a useful tool for analyzing immune surveillance.

Treatment of central nervous system (CNS) autoimmune disorders frequently involves the reduction, or depletion of immune-competent cells. Alternatively, immune cells are being sequestered away from the target organ by interfering with their movement from secondary lymphoid organs, or their migration into tissues. These therapeutic strategies have been successful in multiple sclerosis (MS), the most prevalent autoimmune inflammatory disorder of the CNS. However, many of the agents that are currently approved or in clinical development also have severe potential adverse effects that stem from the very mechanisms that mediate their beneficial effects by interfering with CNS immune surveillance. This review will outline the main cellular components of the innate and adaptive immune system that participate in host defense and maintain immune surveillance of the CNS. Their pathogenic role in MS and its animal model experimental autoimmune encephalomyelitis (EAE) is also discussed. Furthermore, an experimental model is introduced that may assist in evaluating the effect of therapeutic interventions on leukocyte homeostasis and function within the CNS. This model or similar models may become a useful tool in the repertoire of pre-clinical tests of pharmacological agents to better explore their potential for adverse events.

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

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., IMPORTANCE Klebsiella 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.

Aim Histocompatibility testing is used to predict the risk of hyperacute and accelerated-acute transplant rejection. The presence of HLA-specific antibodies, as detected by single antigen bead testing (SAB), are used in organ allocation through the calculated panel reactive antibody (cPRA) and by assessing the presence of donor HLA-specific antibodies (DSA). The presence of DSA and cPRA are considered in the algorithm for assigning patients to immunosuppression protocols. However, the interpretation of low level antibodies in SAB and DSA testing is challenging. Our aim was to look at antibodies below our current threshold of 2000 MFI but above our analytical threshold of 1000 MFI to determine if there is residual risk related to these antibodies. Methods Patient antibody screens were evaluated with 2000 MFI and 1000 MFI cutoff values. 181 patients were assessed for pre-transplant patient risk category and donor compatibility by determining: the change in cPRA, number of identified HLA specific antibodies between the thresholds, the presence of DSA identified between thresholds and the predicted change in immunosuppression protocols. Living donor kidney transplants with an average of 2 years of follow-up were reviewed. 81 recipients were scored for the presence of DSA and examined for the development of de novo DSA (dnDSA) post-transplant. Biopsy data was also reviewed on 40 living donor kidney transplant recipients to determine the incidence of biopsy-proven rejection. Results The reduction in antibody threshold was associated with an average increase in cPRA of 15% for HLA-Class I and 18% for HLA-Class II which corresponded to detection of 10 additional HLA specificities. We determined that using the 1000 MFI threshold, 15% of patients would have been considered higher risk based on transplant center protocols and would have necessitated increased immunosuppression. Changes in risk category were weakly associated with higher rates of dnDSA post-transplant and biopsy-proven rejection. Conclusions In this study, the development of biopsy-proven rejection was not associated with pre-transplant DSA or post-transplant dnDSA that were between 1000 and 2000 MFI.

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.

BACKGROUND:Aquaporin 4 (AQP4) is considered a putative autoantigen in patients with Neuromyelitis optica (NMO), an autoinflammatory disorder of the central nervous system (CNS). HLA haplotype analyses of patients with NMO suggest a positive association with HLA-DRB1* 03:01. We previously showed that the human (h) AQP4 peptide 281-300 is the dominant immunogenic determinant of hAQP4 in the context of HLA-DRB1*03:01. This immunogenic peptide stimulates a strong Th1 and Th17 immune response. AQP4281-300-specific encephalitogenic CD4+ T cells should initiate CNS inflammation that results in a clinical phenotype in HLA-DRB1*03:01 transgenic mice. METHODS:Controlled study with humanized experimental animals. HLA-DRB1*03:01 transgenic mice were immunized with hAQP4281-300, or whole-length hAQP4 protein emulsified in complete Freund's adjuvant. Humoral immune responses to both antigens were assessed longitudinally. In vivo T cell frequencies were assessed by tetramer staining. Mice were followed clinically, and the anterior visual pathway was tested by pupillometry. CNS tissue was examined histologically post-mortem. Flow cytometry was utilized for MHC binding assays and to immunophenotype T cells, and T cell frequencies were determined by ELISpot assay. RESULTS:Immunization with hAQP4281-300 resulted in an in vivo expansion of antigen-specific CD4+ T cells, and an immunoglobulin isotype switch. HLA-DRB1*03:01 TG mice actively immunized with hAQP4281-300, or with whole-length hAQP4 protein were resistant to developing a neurological disease that resembles NMO. Experimental mice show no histological evidence of CNS inflammation, nor change in pupillary responses. Subsequent analysis reveals that a single amino acid substitution from aspartic acid in hAQP4 to glutamic acid in murine (m)AQP4 at position 290 prevents the recognition of hAQP4281-300 by the murine T cell receptor (TCR). CONCLUSION:Induction of a CNS inflammatory autoimmune disorder by active immunization of HLA-DRB1*03:01 TG mice with human hAQP4281-300 will be complex due to a single amino acid substitution. The pathogenic role of T cells in this disorder remains critical despite these observations.

The single antigen bead assay is a widely-used platform for the detection of human leukocyte antigen (HLA)-specific antibodies in both pre- and post-transplant patients. Our regional organ procurement organization recommends a cutoff value of 2000 mean fluorescence intensity (MFI) for the detection of HLA antibodies using the Luminex single antigen bead assay. This cutoff has proven effective for the prevention of HLA-mediated hyperacute rejection; however, this cutoff may be too lenient for the detection of post-transplant donor-specific antibodies. Indeed, we hypothesize that some patients have donor-specific HLA antibody-mediated organ allograft rejection even with a MFI of To define a clinically-relevant DSA MFI cutoff, we analyzed MFI values of 75 runs of a commercially available negative control serum and MFI values of 75 post-transplant patients with negative DSAs. After normalizing the data by log-transformation, we found that the negative control runs had a mean + 3 standard deviation cutoff of 328, and the post-transplant negative DSA patients had a mean + 3 standard deviation cutoff of 969, suggesting that a cutoff of 1000 MFI would be adequate to capture approximately 99% of all negative DSA patients. We applied the 1000 MFI cutoff to the six cases with findings suggestive of ABMR but with no DSAs identified. We found that the highest MFI for donor-specific antigens in these patients was well below the 1000 MFI cutoff. Using a cutoff of 1000 would not have changed the DSA result to positive in these patients. The overall findings suggest that a cutoff of 2000 MFI has been adequate to capture all cases of HLA-mediated antibody-mediated rejection over the period analyzed at our institution.