Prior immunization against an intracellular antigen enhances subsequent red blood cell alloimmunization in mice

Antibodies against red blood cell (RBC) alloantigens can increase morbidity and mortality among transfusion recipients. However, alloimmunization rates can vary dramatically, as some patients never generate alloantibodies after transfusion, whereas others not only become alloimmunized but may also be prone to generating additional alloantibodies after subsequent transfusion. Previous studies suggested that CD4 T-cell responses that drive alloantibody formation recognize the same alloantigen engaged by B cells. However, because RBCs express numerous antigens, both internally and externally, it is possible that CD4 T-cell responses directed against intracellular antigens may facilitate subsequent alloimmunization against a surface RBC antigen. Here, we show that B cells can acquire intracellular antigens from RBCs. Using a mouse model of donor RBCs expressing 2 distinct alloantigens, we demonstrate that immune priming to an intracellular antigen, which would not be detected by any currently used RBC compatibility assays, can directly influence alloantibody formation after exposure to a subsequent distinct surface RBC alloantigen. These findings suggest a previously underappreciated mechanism whereby transfusion recipient responders may exhibit an increased rate of alloimmunization because of prior immune priming toward intracellular antigens.

Storage differentially impacts alloimmunization to distinct red cell antigens following transfusion in mice

INTRODUCTION

The impact of blood storage on red blood cell (RBC) alloimmunization remains controversial, with some studies suggesting enhancement of RBC-induced alloantibody production and others failing to observe any impact of storage on alloantibody formation. Since evaluation of storage on RBC alloimmunization in patients has examined antibody formation against a broad range of alloantigens, it remains possible that different clinical outcomes reflect a variable impact of storage on alloimmunization to specific antigens.

METHODS

RBCs expressing two distinct model antigens, HEL-OVA-Duffy (HOD) and KEL, separately or together (HOD × KEL), were stored for 0, 8, or 14 days, followed by detection of antigen levels prior to transfusion. Transfused donor RBC survival was assessed within 24 h of transfusion, while IgM and IgG antibody production were assessed 5 and 14 days after transfusion.

RESULTS

Stored HOD or KEL RBCs retained similar HEL or KEL antigen levels, respectively, as fresh RBCs, but did exhibit enhanced RBC clearance with increased storage age. Storage enhanced IgG antibody formation against HOD, while the oppositive outcome occurred following transfusion of stored KEL RBCs. The distinct impact of storage on HOD or KEL alloimmunization did not appear to reflect intrinsic differences between HOD or KEL RBCs, as transfusion of stored HOD × KEL RBCs resulted in increased IgG anti-HOD antibody development and reduced IgG anti-KEL antibody formation.

CONCLUSIONS

These data demonstrate a dichotomous impact of storage on immunization to distinct RBC antigens, offering a possible explanation for inconsistent clinical experience and the need for additional studies on the relationship between RBC storage and alloimmunization.

Alloantigen Copy Number as a Critical Factor in RBC Alloimmunization

RBC alloimmunization remains a significant barrier to ongoing transfusion therapy leading to morbidity, and in extreme cases mortality, due to delayed or insufficient units of compatible RBCs. In addition, the monitoring and characterization of alloantibodies, often with multiple specificities in a single patient, consumes substantial health care resources. Extended phenotypic matching has mitigated, but not eliminated, RBC alloimmunization and is only logistically available for specialized populations. Thus, RBC alloimmunization remains a substantial problem. In recent decades it has become clear that mechanisms of RBC alloimmunization are distinct from other antigens and lack of mechanistic understanding likely contributes to the fact that there are no approved interventions to prevent RBC alloimmunization from transfusion. The combination of human studies and murine modeling have identified several key factors in RBC alloimmunization. In both humans and mice, immunogenicity is a function of alloantigen copy number on RBCs. Murine studies have further shown that copy number not only changes rates of immunization but the mechanisms of antibody formation. This review summarizes the current understanding of quantitative and qualitative effects of alloantigen copy number on RBC alloimmunization.

Joint consensus statement on the vaccination of adult and paediatric haematopoietic stem cell transplant recipients: Prepared on behalf of the British society of blood and marrow transplantation and cellular therapy (BSBMTCT), the Children's cancer and Leukaemia Group (CCLG), and British Infection Association (BIA)

Haematopoietic stem cell transplant (HSCT) recipients have deficiencies in their adaptive immunity against vaccine preventable diseases. National and International guidance recommends that HSCT recipients are considered 'never vaccinated' and offered a comprehensive course of revaccination. This position statement aims to draw upon the current evidence base and existing guidelines, and align this with national vaccine availability and licensing considerations in order to recommend a pragmatic and standardised re-vaccination schedule for adult and paediatric HSCT recipients in the UK.

Engineering a Therapeutic Protein to Enhance the Study of Anti-Drug Immunity

The development of anti-drug antibodies represents a significant barrier to the utilization of protein-based therapies for a wide variety of diseases. While the rate of antibody formation can vary depending on the therapeutic employed and the target patient population receiving the drug, the antigen-specific immune response underlying the development of anti-drug antibodies often remains difficult to define. This is especially true for patients with hemophilia A who, following exposure, develop antibodies against the coagulation factor, factor VIII (FVIII). Models capable of studying this response in an antigen-specific manner have been lacking. To overcome this challenge, we engineered FVIII to contain a peptide (323-339) from the model antigen ovalbumin (OVA), a very common tool used to study antigen-specific immunity. FVIII with an OVA peptide (FVIII-OVA) retained clotting activity and possessed the ability to activate CD4 T cells specific to OVA323-339 in vitro. When compared to FVIII alone, FVIII-OVA also exhibited a similar level of immunogenicity, suggesting that the presence of OVA323-339 does not substantially alter the anti-FVIII immune response. Intriguingly, while little CD4 T cell response could be observed following exposure to FVIII-OVA alone, inclusion of anti-FVIII antibodies, recently shown to favorably modulate anti-FVIII immune responses, significantly enhanced CD4 T cell activation following FVIII-OVA exposure. These results demonstrate that model antigens can be incorporated into a therapeutic protein to study antigen-specific responses and more specifically that the CD4 T cell response to FVIII-OVA can be augmented by pre-existing anti-FVIII antibodies.

Neutralizing Antibodies Against Factor VIII Can Occur Through a Non-Germinal Center Pathway

Humoral immunity to factor VIII (FVIII) represents a significant challenge for the treatment of patients with hemophilia A. Current paradigms indicate that neutralizing antibodies against FVIII (inhibitors) occur through a classical CD4 T cell, germinal center (GC) dependent process. However, clinical observations suggest that the nature of the immune response to FVIII may differ between patients. While some patients produce persistent low or high inhibitor titers, others generate a transient response. Moreover, FVIII reactive memory B cells are only detectable in some patients with sustained inhibitor titers. The determinants regulating the type of immune response a patient develops, let alone how the immune response differs in these patients remains incompletely understood. One hypothesis is that polymorphisms within immunoregulatory genes alter the underlying immune response to FVIII, and thereby the inhibitor response. Consistent with this, studies report that inhibitor titers to FVIII differ in animals with the same F8 pathogenic variant but completely distinct backgrounds; though, how these genetic disparities affect the immune response to FVIII remains to be investigated. Given this, we sought to mechanistically dissect how genetics impact the underlying immune response to FVIII. In particular, as the risk of producing inhibitors is weakly associated with differences in HLA, we hypothesized that genetic factors other than HLA influence the immune response to FVIII and downstream inhibitor formation. Our data demonstrate that FVIII deficient mice encoding the same MHC and F8 variant produce disparate inhibitor titers, and that the type of inhibitor response formed associates with the ability to generate GCs. Interestingly, the formation of antibodies through a GC or non-GC pathway does not appear to be due to differences in CD4 T cell immunity, as the CD4 T cell response to an immunodominant epitope in FVIII was similar in these mice. These results indicate that genetics can impact the process by which inhibitors develop and may in part explain the apparent propensity of patients to form distinct inhibitor responses. Moreover, these data highlight an underappreciated immunological pathway of humoral immunity to FVIII and lay the groundwork for identification of biomarkers for the development of approaches to tolerize against FVIII.

Clodronate inhibits alloimmunization against distinct red blood cell alloantigens in mice

BACKGROUND

Alloimmunization can be a significant barrier to red blood cell (RBC) transfusion. While alloantigen matching protocols hold promise in reducing alloantibody formation, transfusion-dependent patients can still experience RBC alloimmunization and associated complications even when matching protocols are employed. As a result, complementary strategies capable of actively preventing alloantibody formation following alloantigen exposure are warranted.

STUDY DESIGN AND METHODS

We examined whether pharmacological removal of macrophages using clodronate may provide an additional strategy to actively inhibit RBC alloimmunization using two preclinical models of RBC alloimmunization. To accomplish this, mice were treated with clodronate, followed by transfusion of RBCs expressing the HOD (HEL, OVA, and Duffy) or KEL antigens. On days 5 and 14 post transfusion, anti-HOD or anti-KEL IgM and IgG antibodies were evaluated.

RESULTS

Low dose clodronate effectively eliminated key marginal zone macrophage populations from the marginal sinus. Prior treatment with clodronate, but not empty liposomes, also significantly inhibited IgM and IgG anti-HOD alloantibody formation following transfusion of HOD RBCs. Similar exposure to clodronate inhibited IgM and IgG antibody formation following KEL RBC transfusion.

CONCLUSIONS

Clodronate can inhibit anti-HOD and anti-KEL antibody formation following RBC transfusion in preclinical models. These results suggest that clodronate may provide an alternative approach to actively inhibit or prevent the development of alloantibodies following RBC transfusion, although future studies will certainly be needed to fully explore this possibility.

Marginal zone B cells mediate a CD4 T-cell-dependent extrafollicular antibody response following RBC transfusion in mice

Red blood cell (RBC) transfusions can result in alloimmunization toward RBC alloantigens that can increase the probability of complications following subsequent transfusion. An improved understanding of the immune mechanisms that underlie RBC alloimmunization is critical if future strategies capable of preventing or even reducing this process are to be realized. Using the HOD (hen egg lysozyme [HEL] and ovalbumin [OVA] fused with the human RBC antigen Duffy) model system, we aimed to identify initiating immune factors that may govern early anti-HOD alloantibody formation. Our findings demonstrate that HOD RBCs continuously localize to the marginal sinus following transfusion, where they colocalize with marginal zone (MZ) B cells. Depletion of MZ B cells inhibited immunoglobulin M (IgM) and IgG anti-HOD antibody formation, whereas CD4 T-cell depletion only prevented IgG anti-HOD antibody development. HOD-specific CD4 T cells displayed similar proliferation and activation following transfusion of HOD RBCs into wild-type or MZ B-cell-deficient recipients, suggesting that IgG formation is not dependent on MZ B-cell-mediated CD4 T-cell activation. Moreover, depletion of follicular B cells failed to substantially impact the anti-HOD antibody response, and no increase in antigen-specific germinal center B cells was detected following HOD RBC transfusion, suggesting that antibody formation is not dependent on the splenic follicle. Despite this, anti-HOD antibodies persisted for several months following HOD RBC transfusion. Overall, these data suggest that MZ B cells can initiate and then contribute to RBC alloantibody formation, highlighting a unique immune pathway that can be engaged following RBC transfusion.

1097 Sleep Disturbances, Sleep Burden, And Depressive Symptoms In US Hispanics/Latinos: Results From The HCHS/SOL Sueño Study

Introduction

While sleep disturbances and depression often co-occur, these associations are understudied among Hispanics/Latinos. We examined the associations of sleep disturbances and sleep burden with depressive symptoms among Hispanic/Latino adults in the United States.

Methods

We used cross-sectional data from the Hispanic Community Health Study/Study of Latinos Sueño Ancillary study (2010-2013). The study enrolled 2072 adults (ages 18-64; 51.5% females) who completed one-week wrist-actigraphy and sleep questionnaires. Sleep burden was operationalized as the total count of sleep disturbances across six domains (duration, efficiency, midpoint, variability, insomnia, sleepiness). Depressive symptoms were assessed using the Center for Epidemiological Studies Depression scale (CESD-10). We used weighted survey linear regressions to evaluate the association of sleep disturbances and sleep burden with elevated depressive symptoms (CESD≥10) in individual models adjusted for age, gender, site, heritage, nativity, education, income, and employment. Sensitivity analyses further adjusted for behavioral health risk factors and apnea-hypopnea index.

Results

An estimated 28.3% had elevated depressive symptoms, 8.0% had short sleep duration (<6 hours of sleep), 10.9% had long sleep duration (>9 hours), 45.2% exhibited a later sleep midpoint (≥4:00AM), 38.4% had high sleep timing variability (upper third tertile for between day sleep midpoint), 15.3% had insomnia (ISI≥10), 17.3% had excessive daytime sleepiness (ESS ≥10), 21.5% had poor sleep efficiency (<85%), and 77.4% had a total sleep burden count of ≥0. Insomnia (ß=0.49,95%CI:.43,.56), later sleep timing (ß=0.10,95%CI:.04,.16), excessive daytime sleepiness (ß=0.19,95%CI:.11,.27), poor sleep efficiency (ß=0.09,95%CI:.02,.17), high variability (ß=0.07, 95%CI:.01,.12), and sleep burden (ß=0.11,95%CI:.09,.13), were each positively associated with elevated depressive symptoms in individual adjusted models and sensitivity analyses. Extreme sleep durations were not associated with elevated depressive symptoms.

Conclusion

Multiple inter-related sleep disturbances, particularly those pertaining to sleep quality and timing, are associated with depression and may be targets for future interventions aimed at improving mood among Hispanics/Latinos.

Support

HL127307, HL098927, HL125748

0357 CPAP Adherence is Lower in Minority Neighborhoods

Introduction

The effectiveness of continuous positive airway pressure (CPAP) in treating obstructive sleep apnea (OSA) is limited by adherence. Small, single-center studies have reported CPAP adherence is lower in racial minorities suggesting disparities in OSA care. We used nationally representative data to assess racial differences in CPAP adherence at a neighborhood level.

Methods

Telemonitoring data were obtained from a therapy database maintained by a CPAP manufacturer. Usage over the first 90 days in patients initiated on CPAP between 11/01/2015 and 10/31/2018 who had at least one usage session, age 18-90 years, and valid U.S. zip code were mapped to a zip code tabulation area (ZCTA). Age- and sex-adjusted CPAP usage was calculated for each ZCTA with greater than 10 CPAP users. Ecologic analyses were performed to model the association of the proportion of blacks and Hispanics in each ZCTA (obtained from the 2013-2017 American Community Survey) on CPAP usage controlling for proportion of adults with bachelor’s degree and proportion of adults with household income below the poverty line.

Results

Our analysis included 13,118 ZCTAs averaging data over 737,274 patients. In adjusted analyses, each 10% increase in the proportion of blacks and Hispanics was associated with a 0.12 (95% CI 0.11-0.12) hour and 0.14 (95% CI 0.14-0.15) hour decrease in nightly CPAP use, respectively. Mean usage in ZCTAs with <1%, 1-2.5%, 2.5-10%, 10-25%, and 25-100% blacks were 4.96, 4.81, 4.67, 4.56, and 4.14 hours respectively (p<0.001). Mean usage in ZCTAs with <1%, 1-2.5%, 2.5-10%, 10-25%, and 25-100% Hispanics were 4.87, 4.86, 4.75, 4.50, and 4.10 hours respectively (p<0.001).

Conclusion

CPAP adherence is lower in neighborhoods with higher proportions of black and Hispanic residents independent of differences in education or poverty. These differences lead to lower likelihood of meeting insurance coverage requirements for CPAP therapy, potentially exacerbating sleep health disparities.

Support

Philips Respironics, NIH R25HL130600 and K24HL127307.

0402 Impact of Various Actigraphic Editing Approaches on Sleep/Wake Outputs in Adults with Insomnia and Healthy Sleepers

Introduction

Actigraphy data can be edited using a variety of approaches. However, whether time-intensive manual editing provides different sleep/wake estimates compared to other approaches is unknown. The purpose of this study was to compare sleep/wake data obtained from a standardized editing approach that incorporates multiple inputs versus three other common approaches.

Methods

72 adults (33.8±11.1 y, 74% female, 71% white) provided 1022 nights of data for analysis; 45 were healthy sleepers (678 nights) and 27 met DSM-5 criteria for insomnia. Participants wore an Actiwatch Spectrum on their nondominant wrist and completed a sleep diary for 3-24 nights. Each night’s rest interval was set using four different approaches: (1) a standardized process based upon published guidelines (Patel et al., Sleep 2015) that incorporates a hierarchical order of multiple inputs (event marker, light, diary, activity; STANDARD); (2) software-provided automated algorithm (AUTO); (3) automated algorithm with incorporation of event markers (AUTOE); and (4) sleep diary (DIARY). We used linear mixed-effects models to evaluate whether sleep/wake parameters differed between the STANDARD and other editing approaches, accounting for patient status (healthy sleeper, insomnia) and the possibility that differences among editing approaches may be dependent on patient status.

Results

All results are expressed relative to the STANDARD approach. Bedtime was 36.1±5.1 min earlier (P<.0001) and morning out-of-bed time was 13.6±5.7 min later (P=.02) using the AUTO (P<.0001) approach. Time in bed was 42.3±4.7 min longer with AUTO (P<.0001). Sleep onset latency was 11.7±1.4 min and 2.8±1.4 min longer for AUTO (P<.0001) and DIARY (P=.05), respectively. Sleep duration was 22.5±4.4 min longer with AUTO (P<.0001). Wake after sleep onset was 6.8±1.2 min greater with AUTO (P<.0001). Similar patterns were observed for all sleep/wake measures among healthy sleepers and adults with insomnia.

Conclusion

A standardized approach to editing actigraphy data leads to different sleep/wake estimates compared to other common approaches, though the differences were often small in magnitude and not dependent upon sleep status. Most notably, reliance upon the automated algorithm yielded longer time in bed, sleep duration, sleep onset latency, and wake after sleep onset compared to the standardized approach.

Support

NIH K23HL118318

0677 Patient Preferences On Initiating Treatment With Continuous Positive Airway Pressure

Introduction

Clinical guidelines recommend continuous positive airway pressure (CPAP) therapy be initiated in patients with obstructive sleep apnea (OSA) either at home using an auto-titrating device or following manual titration in the sleep laboratory. Patient preference between these two options is unknown.

Methods

Patients newly prescribed CPAP therapy for the treatment of OSA at an academic sleep medicine clinic were surveyed by telephone within one month of initiating treatment. Data on demographics, disease severity and CPAP adherence were obtained from the medical record.

Results

A total of 75 participants (56% male, mean age 52±15 yrs, 48% moderate to severe OSA) were surveyed. Physicians prescribed home initiation of CPAP in 51%, lab initiation in 23%, and allowed the patient to choose in 27% of cases. Overall, 67% of participants (95% CI [56%-77%]) reported preference for home initiation. Preference for home initiation did not vary by age, sex, AHI, degree of sleepiness, or type of diagnostic study (home vs. lab sleep study) performed (p>0.10 for all). Convenience (44%) and starting treatment faster (44%) were the most common reasons provided for those favoring home initiation, while sleep technician availability (40%), optimization of pressure settings (32%), and ability to try multiple masks (28%) were cited by those favoring lab initiation. The prevalence of CPAP adherence at 90 days tended to be higher in those whose treatment was initiated aligned to preference (79% in those whose treatment initiation was concordant with preference vs. 64% in those whose treatment initiation was discordant, p=0.16).

Conclusion

Overall, two-thirds of patients with OSA prefer initiation of CPAP be done at home. This preference does not vary by demographics, OSA severity or diagnostic modality. Initiating treatment concordant with patient preference may lead to greater adherence.

Support

American Thoracic Society Academic Sleep Pulmonary Integrated Research/Clinical (ASPIRE) Fellowship, K24 HL127307

1144 Actigraphy-defined Sleep And Neurocognitive Decline In Middle-age Hispanic/Latino Adults

Introduction

Few studies have evaluated objective sleep measures and longitudinal neurocognitive decline, particularly in middle-age or Hispanic/Latino adults. We evaluated prospective associations between actigraphy-defined sleep and 7-year neurocognitive change among Hispanic/Latino adults. We hypothesized that sleep duration would be associated with neurocognitive decline.

Methods

We analyzed data from 1,036 adults 45-64 years of age from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), a multi-center prospective cohort study of diverse community-dwelling Hispanic/Latino adults. At Visit 1 (2008-2011), participants underwent neurocognitive assessments, 7-days of actigraphy, home sleep testing, and sleep questionnaires (including the Insomnia Severity Index). Seven years later, participants repeated neurocognitive assessments. The neurocognitive battery included the Six-Item Screener, Brief Spanish-English Verbal Learning Test, phonemic word fluency test, and Digit Symbol Subtest. Survey linear regression was used to evaluate prospective associations between actigraphy-defined or self-reported sleep variables and neurocognitive change. Final models adjusted for objectively-defined variables (age, body-mass index, Field Center, and time between neurocognitive assessments), and self-reported variables (sex, education, Hispanic/Latino background, alcohol consumption, physical activity, heart failure, cerebrovascular events, depression and anxiety symptoms, and antidepressant use).

Results

At Visit 1, the sample was 55% female and mean age was 54.9±2.2 years. The mean sleep duration was 402.6±27.6 minutes, mean sleep-onset latency was 11.3±9.7 minutes, mean number of days with naps of ≥ 15 minutes duration was 1.1±0.7, and mean sleep-time per nap was 51±14.1 minutes. Increased sleep-onset latency was associated with 7-year declines in global neurocognitive function (β=-0.0026, p<0.01), verbal learning (β=-0.0028, p<0.001) and verbal memory (β=-0.036, p<0.05). Increased sleep-time per nap predicted better verbal memory (β=0.0038, p<0.05). In contrast, sleep duration, sleep fragmentation, and self-reported sleep measures were not associated with neurocognitive change.

Conclusion

Among middle-age adults, sleep-onset latency and nap duration were associated with neurocognitive change. These findings may serve as targets for intervention of neurocognitive decline.

Support

This work is supported by the National Institute on Aging: R01AG048642, RF1AG054548, R01AG061022, R21AG056952, and R21HL140437 (AR).

0609 Sleep Phenotypes in Middle-Aged and Older Hispanics/Latinos. Results from the Hispanic Community Health Study/Study of Latinos (HCHS/SOL)

Introduction

Identifying sleep phenotypes in the diverse and understudied US Hispanic/Latino population is critical to developing interventions and mitigating distal clinical outcomes (e.g. dementias).

Methods

Using latent class analyses (LCA), we identify empirically derived and clinically meaningful sleep phenotypes using data on community dwelling middle-aged/older adults (ages ≥45-years) from the HCHS/SOL (2008-2011) - Investigation of Neurocognitive Aging (n=6,377). Sleep variables used included Apnea/Hypopnea Index (AHI), percent time SpO2<90%, Epworth Sleepiness Scale (ESS), Women’s Health Initiative Insomnia Rating Scale (WHIIRS), self-reported average sleep duration, restless legs symptoms, napping frequency, and sleep quality.

Results

Mean (M) age was 56.4±8.1 years, and 54.7% were female. Average AHI, ESS, WHIIRS, and sleep duration were 8.7±13.1, 6.0±5.0, 7.6±5.5, and 7.8±1.4, respectively, and 25.8% had zero percent time SpO2 <90%. Fit statistics indicated that a four-class solution provided the best data fit. The derived classes, adjusting for age, sex, income, and acculturation, corresponded with four clinically meaningful groups: (1) 28.8% were asymptomatic [(M) AHI=0.8; (M) ESS=5.6; (M)WHIIRS=7.6; (M) sleep duration=7.8; 0% SpO2<90%=74.1%], (2) 25.7 % were asymptomatic mild sleep apnea [(M) AHI=6.2; (M) ESS=3.8; (M) WHIIRS=2.9; (M) sleep duration=7.8; 0% SpO2<90%=8.8%], (3) 19.4% were symptomatic sleep apnea [(M) AHI=25.6; (M) ESS=8.5; (M) WHIIRS=7.2; (M) sleep duration=7.7; 0% SpO2<90%= 0.5%], and (4) 26.1% were insomnia [(M) AHI=5.7; (M) ESS=6.7; (M) WHIIRS=13.0; (M) sleep duration=7.8; 0% SpO2<90%=10.3%]. Classification into groups 3 and 4 were primarily driven by elevated AHI and WHIIRS scores, respectively. The distribution of scores in the derived groups suggest variations relative to current clinical thresholds.

Conclusion

We identified 4-groups using LCA in a community-based sample of diverse U.S. Hispanic/Latino adults. Better characterization of sleep phenotypes for Hispanics/Latinos can help in developing targeted interventions studies and ameliorate health disparities.

Support

5R01AG048642-05; R21AG056952; R21HL140437.

0607 Clinical Phenotypes of OSA in Diverse Hispanics/Latinos: Results from the Hispanic Community Health Study/Study of Latinos

Introduction

Recent work on US non-Latino Whites and Europeans from clinical samples used obstructive sleep apnea (OSA) symptoms to generate OSA phenotypes for individuals with moderate-severe OSA and proposed between 3-5 clusters. Validating these clusters in a diverse Hispanic/Latino community-based population with different biopsychosocial characteristics is crucial for early OSA identification and more personalized treatment.

Methods

This work is based on baseline data from The Hispanic Community Health Study/Study of Latinos (HCHS/SOL). HCHS/SOL is a prospective cohort study designed using a multisite (Bronx, NY, Chicago, IL, Miami, FL, San Diego, CA) multistage probability sample. The subpopulation of interest included adults 18-74 years (unweighted n=1,623) meeting criteria for moderate-severe OSA symptoms (≥15 Apnea-Hypopnea index (AHI) events per hour). We performed latent class analysis (LCA) using 15 common OSA symptoms to identify phenotype clusters.

Results

Average age was 52.4 ± 13.9 years and 34.1% were female. Mean AHI was 33.8 ± 22.5 events per hour. Fit statistics and clinical significance suggested that a three-class solution provided best fit to the data. The symptom profiles were consistent with (1) a Minimally Symptomatic group (46.8%), (2) a Disturbed Sleep group (38.1%), and (3) a Daytime Sleepiness group (15.1%). Validation analyses using alternative hierarchical and partitioning algorithms also suggested support for a three-class solution.

Conclusion

Sleep apnea phenotypes among diverse Hispanics/Latinos were consistent with recent findings from the Sleep Apnea Global Interdisciplinary Consortium. However, we found notable differences in the prevalence of these clusters relative to Whites. This suggests that other biopsychosocial factors may be contributing to OSA phenotypes among Hispanics/Latinos. Identification of OSA phenotypes in Hispanics/Latinos could inform better sleep interventions and therapeutics and help better align public health resources.

Support

5R01AG048642-05; R21AG056952; R21HL140437.

The Immune Response to the fVIII Gene Therapy in Preclinical Models

Neutralizing antibodies to factor VIII (fVIII), referred to as "inhibitors," remain the most challenging complication post-fVIII replacement therapy. Preclinical development of novel fVIII products involves studies incorporating hemophilia A (HA) and wild-type animal models. Though immunogenicity is a critical aspect of preclinical pharmacology studies, gene therapy studies tend to focus on fVIII expression levels without major consideration for immunogenicity. Therefore, little clarity exists on whether preclinical testing can be predictive of clinical immunogenicity risk. Despite this, but perhaps due to the potential for transformative benefits, clinical gene therapy trials have progressed rapidly. In more than two decades, no inhibitors have been observed. However, all trials are conducted in previously treated patients without a history of inhibitors. The current review thus focuses on our understanding of preclinical immunogenicity for HA gene therapy candidates and the potential indication for inhibitor treatment, with a focus on product- and platform-specific determinants, including fVIII transgene sequence composition and tissue/vector biodistribution. Currently, the two leading clinical gene therapy vectors are adeno-associated viral (AAV) and lentiviral (LV) vectors. For HA applications, AAV vectors are liver-tropic and employ synthetic, high-expressing, liver-specific promoters. Factors including vector serotype and biodistribution, transcriptional regulatory elements, transgene sequence, dosing, liver immunoprivilege, and host immune status may contribute to tipping the scale between immunogenicity and tolerance. Many of these factors can also be important in delivery of LV-fVIII gene therapy, especially when delivered intravenously for liver-directed fVIII expression. However, ex vivo LV-fVIII targeting and transplantation of hematopoietic stem and progenitor cells (HSPC) has been demonstrated to achieve durable and curative fVIII production without inhibitor development in preclinical models. A critical variable appears to be pre-transplantation conditioning regimens that suppress and/or ablate T cells. Additionally, we and others have demonstrated the potential of LV-fVIII HSPC and liver-directed AAV-fVIII gene therapy to eradicate pre-existing inhibitors in murine and canine models of HA, respectively. Future preclinical studies will be essential to elucidate immune mechanism(s) at play in the context of gene therapy for HA, as well as strategies for preventing adverse immune responses and promoting immune tolerance even in the setting of pre-existing inhibitors.

Mid-cervical interneuron networks following high cervical spinal cord injury

Spinal interneuron (IN) networks can facilitate respiratory motor recovery after spinal cord injury (SCI). We hypothesized that excitatory synaptic connectivity between INs located immediately caudal to unilateral cervical SCI would be most prevalent in a contra- to ipsilateral direction. Adult rats were studied following chronic C2 spinal cord hemisection (C2Hx) injury. Rats were anesthetized and ventilated and a multi-electrode array was used to simultaneously record INs on both sides of the C4-5 spinal cord. The temporal firing relationship between IN pairs was evaluated using cross-correlation with directionality of synaptic connections inferred based on electrode location. During baseline recordings, the majority of detectable excitatory IN connections occurred in a contra- to- ipsilateral direction. However, acute respiratory stimulation with hypoxia abolished this directionality, while simultaneously increasing the detectable inhibitory connections within the ipsilateral cord. We conclude that propriospinal networks caudal to SCI can display a contralateral-to-ipsilateral directionality of synaptic connections and that these connections are modulated by acute exposure to hypoxia.

Antibody-mediated immunosuppression can result from RBC antigen loss independent of Fcγ receptors in mice

BACKGROUND

Anti-RhD administration can prevent de novo anti-RhD formation following RhD+ red blood cell (RBC) exposure, termed antibody-mediated immunosuppression (AMIS). Recent studies suggest that AMIS may occur through target antigen alterations, known as antigen modulation. However, studies suggest that AMIS may occur independent of antigen modulation. In particular, AMIS to RBCs that transgenically express the fusion hen egg lysozyme-ovalbumin-Duffy (HOD) antigen have been shown to occur independent of activating Fcγ receptors (FcγRs) thought to be required for antigen modulation. Therefore, we sought to determine the mechanism behind AMIS following HOD RBC exposure.

STUDY DESIGN AND METHODS

Following transfer of HOD RBCs into wild-type or FcγR-chain knockout recipients in the presence or absence of monoclonal anti-hen egg lysozyme (HEL) antibody, individually or in combination, HOD antigen levels and anti-HOD antibody formation were examined.

RESULTS

Our results demonstrate that anti-HEL antibodies individually or in combination suppressed anti-HOD IgM, which correlated with the rate of detectable decrease in HEL on HOD RBCs. Furthermore, exposure to anti-HEL antibodies alone or in combination equally suppressed anti-HOD IgG formation. Unexpectedly, combination or individual anti-HEL antibodies induced AMIS and antigen modulation in an FcγR-independent manner. Pre-exposure of HOD RBCs to anti-HEL antibodies reduced antigen levels and suppressed anti-HOD antibody formation following HOD RBC exposure.

CONCLUSION

These results suggest that antibody-mediated antigen modulation may reflect a mechanism of AMIS that can occur independent of activating FcγRs and may provide a surrogate to identify antibodies capable of inducing AMIS against different RBC antigens.

Marginal Zone B Cells Induce Alloantibody Formation Following RBC Transfusion

Red blood cell (RBC) alloimmunization represents a significant immunological challenge for some patients. While a variety of immune constituents likely contribute to the initiation and orchestration of alloantibodies to RBC antigens, identification of key immune factors that initiate alloantibody formation may aid in the development of a therapeutic modality to minimize or prevent this process. To define the immune factors that may be important in driving alloimmunization to an RBC antigen, we determined the specific immune compartment and distinct cells that may initially engage transfused RBCs and facilitate subsequent alloimmunization. Our findings demonstrate that the splenic compartment is essential for formation of anti-KEL antibodies following KEL RBC transfusion. Within the spleen, transfused KEL RBCs are found within the marginal sinus, where they appear to specifically co-localize with marginal zone (MZ) B cells. Consistent with this, removal of MZ B cells completely prevented alloantibody formation following KEL RBC transfusion. While MZ B cells can mediate a variety of key downstream immune pathways, depletion of follicular B cells or CD4 T cells failed to similarly impact the anti-KEL antibody response, suggesting that MZ B cells may play a key role in the development of anti-KEL IgM and IgG following KEL RBC transfusion. These findings highlight a key contributor to KEL RBC-induced antibody formation, wherein MZ B cells facilitate antibody formation following RBC transfusion.

Complement serves as a switch between CD4+ T cell-independent and -dependent RBC antibody responses

RBC alloimmunization represents a significant immunological challenge for patients requiring lifelong transfusion support. The majority of clinically relevant non-ABO(H) blood group antigens have been thought to drive antibody formation through T cell-dependent immune pathways. Thus, we initially sought to define the role of CD4+ T cells in formation of alloantibodies to KEL, one of the leading causes of hemolytic transfusion reactions. Unexpectedly, our findings demonstrated that KEL RBCs actually possess the ability to induce antibody formation independent of CD4+ T cells or complement component 3 (C3), two common regulators of antibody formation. However, despite the ability of KEL RBCs to induce anti-KEL antibodies in the absence of complement, removal of C3 or complement receptors 1 and 2 (CR1/2) rendered recipients completely reliant on CD4+ T cells for IgG anti-KEL antibody formation. Together, these findings suggest that C3 may serve as a novel molecular switch that regulates the type of immunological pathway engaged following RBC transfusion.

Antibody-mediated immune suppression by antigen modulation is antigen-specific

Alloantibodies developing after exposure to red blood cell (RBC) alloantigens can complicate pregnancy and transfusion therapy. The only method currently available to actively inhibit RBC alloantibody formation is administration of antigen-specific antibodies, a phenomenon termed antibody-mediated immune suppression (AMIS). A well-known example of AMIS is RhD immune globulin prophylaxis to prevent anti-D formation in RhD- individuals. However, whether AMIS is specific or impacts alloimmunization to other antigens on the same RBC remains unclear. To evaluate the specificity of AMIS, we passively immunized antigen-negative recipients with anti-KEL or anti-hen egg lysozyme (HEL) antibodies, followed by transfusion of murine RBC expressing both the HEL-ovalbumin-Duffy (HOD) and human KEL antigens (HOD × KEL RBC). Significant immunoglobulin G deposition on transfused HOD × KEL RBC occurred in all passively immunized recipients. Complement deposition and antigen modulation of the KEL antigen occurred on transfused RBC only in anti-KEL-treated recipients, whereas HEL antigen levels decreased only in the presence of anti-HEL antibodies. Western blot analysis confirmed the specificity of antigen loss, which was not attributable to RBC endocytosis and appears distinct for the 2 antigens. Specifically, removal of KEL was attenuated by clodronate treatment, whereas loss of HEL was unaffected by clodronate in vivo but sensitive to protease treatment in vitro. Antigen-specific modulation correlated with antigen-specific AMIS, with anti-KEL treated recipients forming antibodies to the HOD antigen and anti-HEL-treated recipients developing antibodies to the KEL antigen. Together, these results demonstrate that passively administered antibodies can selectively inhibit the immune response to a specific antigen.

Complement Component 3 Negatively Regulates Antibody Response by Modulation of Red Blood Cell Antigen

Red blood cell (RBC) alloimmunization can make it difficult to procure compatible RBCs for future transfusion, directly leading to increased morbidity and mortality in transfusion-dependent patients. However, the factors that regulate RBC alloimmunization remain incompletely understood. As complement has been shown to serve as a key adjuvant in the development of antibody (Ab) responses against microbes, we examined the impact of complement on RBC alloimmunization. In contrast to the impact of complement component 3 (C3) in the development of an immune response following microbial exposure, transfusion of C3 knockout (C3 KO) recipients with RBCs expressing KEL (KEL RBCs) actually resulted in an enhanced anti-KEL Ab response. The impact of C3 appeared to be specific to KEL, as transfusion of RBCs bearing another model antigen, the chimeric HOD antigen (hen egg lysozyme, ovalbumin and Duffy), into C3 KO recipients failed to result in a similar increase in Ab formation. KEL RBCs experienced enhanced C3 deposition and loss of detectable target antigen over time when compared to HOD RBCs, suggesting that C3 may inhibit Ab formation by impacting the accessibility of the target KEL antigen. Loss of detectable KEL on the RBC surface did not reflect antigen masking by C3, but instead appeared to result from actual removal of the KEL antigen, as western blot analysis demonstrated complete loss of detectable KEL protein. Consistent with this, exposure of wild-type B6 or C3 KO recipients to KEL RBCs with reduced levels of detectable KEL antigen resulted in a significantly reduced anti-KEL Ab response. These results suggest that C3 possesses a unique ability to actually suppress Ab formation following transfusion by reducing the availability of the target antigen on the RBC surface.

CD4 Depletion or CD40L Blockade Results in Antigen-Specific Tolerance in a Red Blood Cell Alloimmunization Model

Approximately 3–10% of human red blood cell (RBC) transfusion recipients form alloantibodies to non-self, non-ABO blood group antigens expressed on donor RBCs, with these alloantibodies having the potential to be clinically significant in transfusion and pregnancy settings. However, the majority of transfused individuals never form detectable alloantibodies. Expanding upon observations that children initially transfused with RBCs at a young age are less likely to form alloantibodies throughout their lives, we hypothesized that “non-responders” may not only be ignorant of antigens on RBCs but instead tolerized. We investigated this question in a reductionist murine model, in which transgenic donors express the human glycophorin A (hGPA) antigen in an RBC-specific manner. Although wild-type mice treated with poly IC and transfused with hGPA RBCs generated robust anti-hGPA IgG alloantibodies that led to rapid clearance of incompatible RBCs, those transfused in the absence of an adjuvant failed to become alloimmunized. Animals depleted of CD4⁺ cells or treated with CD40L blockade prior to initial hGPA RBC exposure, in the presence of poly IC, failed to generate detectable anti-hGPA IgG alloantibodies. These non-responders to a primary transfusion remained unable to generate anti-hGPA IgG alloantibodies upon secondary hGPA exposure and did not prematurely clear transfused hGPA RBCs even after their CD4 cells had returned or their CD40L blockade had resolved. This observed tolerance was antigen (hGPA) specific, as robust IgG responses to transfused RBCs expressing a third-party antigen occurred in all studied groups. Experiments completed in an RBC alloimmunization model that allowed evaluation of antigen-specific CD4⁺ T-cells (HOD (hen egg lysozyme, ovalbumin, and human duffy^b)) demonstrated that CD40L blockade prevented the expansion of ovalbumin 323-339 specific T-cells after HOD RBC transfusion and also prevented germinal center formation. Taken together, our data suggest that recipients may indeed become tolerized to antigens expressed on RBCs, with the recipient’s immune status upon initial RBC exposure dictating future responses. Although questions surrounding mechanism(s) and sustainability of tolerance remain, these data lay the groundwork for future work investigating RBC immunity versus tolerance in reductionist models and in humans.

Antigen Density Dictates Immune Responsiveness following Red Blood Cell Transfusion

Although RBC transfusion can result in the development of anti-RBC alloantibodies that increase the probability of life-threatening hemolytic transfusion reactions, not all patients generate anti-RBC alloantibodies. However, the factors that regulate immune responsiveness to RBC transfusion remain incompletely understood. One variable that may influence alloantibody formation is RBC alloantigen density. RBC alloantigens exist at different densities on the RBC surface and likewise exhibit distinct propensities to induce RBC alloantibody formation. However, although distinct alloantigens reside on the RBC surface at different levels, most alloantigens also represent completely different structures, making it difficult to separate the potential impact of differences in Ag density from other alloantigen features that may also influence RBC alloimmunization. To address this, we generated RBCs that stably express the same Ag at different levels. Although exposure to RBCs with higher Ag levels induces a robust Ab response, RBCs bearing low Ag levels fail to induce RBC alloantibodies. However, exposure to low Ag-density RBCs is not without consequence, because recipients subsequently develop Ag-specific tolerance. Low Ag-density RBC-induced tolerance protects higher Ag-density RBCs from immune-mediated clearance, is Ag specific, and occurs through the induction of B cell unresponsiveness. These results demonstrate that Ag density can potently impact immune outcomes following RBC transfusion and suggest that RBCs with altered Ag levels may provide a unique tool to induce Ag-specific tolerance.

Coupling multielectrode array recordings with silver labeling of recording sites to study cervical spinal network connectivity

Midcervical spinal interneurons form a complex and diffuse network and may be involved in modulating phrenic motor output. The intent of the current work was to enable a better understanding of midcervical "network-level" connectivity by pairing the neurophysiological multielectrode array (MEA) data with histological verification of the recording locations. We first developed a method to deliver 100-nA currents to electroplate silver onto and subsequently deposit silver from electrode tips after obtaining midcervical (C3-C5) recordings using an MEA in anesthetized and ventilated adult rats. Spinal tissue was then fixed, harvested, and histologically processed to "develop" the deposited silver. Histological studies verified that the silver deposition method discretely labeled (50-μm resolution) spinal recording locations between laminae IV and X in cervical segments C3-C5. Using correlative techniques, we next tested the hypothesis that midcervical neuronal discharge patterns are temporally linked. Cross-correlation histograms produced few positive peaks (5.3%) in the range of 0-0.4 ms, but 21.4% of neuronal pairs had correlogram peaks with a lag of ≥0.6 ms. These results are consistent with synchronous discharge involving mono- and polysynaptic connections among midcervical neurons. We conclude that there is a high degree of synaptic connectivity in the midcervical spinal cord and that the silver-labeling method can reliably mark metal electrode recording sites and "map" interneuron populations, thereby providing a low-cost and effective tool for use in MEA experiments. We suggest that this method will be useful for further exploration of midcervical network connectivity.NEW & NOTEWORTHY We describe a method that reliably identifies the locations of multielectrode array (MEA) recording sites while preserving the surrounding tissue for immunohistochemistry. To our knowledge, this is the first cost-effective method to identify the anatomic locations of neuronal ensembles recorded with a MEA during acute preparations without the requirement of specialized array electrodes. In addition, evaluation of activity recorded from silver-labeled sites revealed a previously unappreciated degree of connectivity between midcervical interneurons.

Innate immunity against molecular mimicry: Examining galectin-mediated antimicrobial activity

Adaptive immunity provides the unique ability to respond to a nearly infinite range of antigenic determinants. Given the inherent plasticity of the adaptive immune system, a series of tolerance mechanisms exist to reduce reactivity toward self. While this reduces the probability of autoimmunity, it also creates an important gap in adaptive immunity: the ability to recognize microbes that look like self. As a variety of microbes decorate themselves in self-like carbohydrate antigens and tolerance reduces the ability of adaptive immunity to react with self-like structures, protection against molecular mimicry likely resides within the innate arm of immunity. In this review, we will explore the potential consequences of microbial molecular mimicry, including factors within innate immunity that appear to specifically target microbes expressing self-like antigens, and therefore provide protection against molecular mimicry.

Bridging channel dendritic cells induce immunity to transfused red blood cells

Calabro et al. show that 33D1⁺ dendritic cells present in the bridging channel of the spleen are essential for alloantibody response to transfused red blood cells.

Red blood cell (RBC) transfusion is a life-saving therapeutic tool. However, a major complication in transfusion recipients is the generation of antibodies against non-ABO alloantigens on donor RBCs, potentially resulting in hemolysis and renal failure. Long-lived antibody responses typically require CD4⁺ T cell help and, in murine transfusion models, alloimmunization requires a spleen. Yet, it is not known how RBC-derived antigens are presented to naive T cells in the spleen. We sought to answer whether splenic dendritic cells (DCs) were essential for T cell priming to RBC alloantigens. Transient deletion of conventional DCs at the time of transfusion or splenic DC preactivation before RBC transfusion abrogated T and B cell responses to allogeneic RBCs, even though transfused RBCs persisted in the circulation for weeks. Although all splenic DCs phagocytosed RBCs and activated RBC-specific CD4⁺ T cells in vitro, only bridging channel 33D1⁺ DCs were required for alloimmunization in vivo. In contrast, deletion of XCR1⁺CD8⁺ DCs did not alter the immune response to RBCs. Our work suggests that blocking the function of one DC subset during a narrow window of time during RBC transfusion could potentially prevent the detrimental immune response that occurs in patients who require lifelong RBC transfusion support.

Human mesenchymal stromal cells suppress T-cell proliferation independent of heme oxygenase-1

Mesenchymal stromal cells deploy immune suppressive properties amenable for use as cell therapy for inflammatory disorders. It is now recognized that mesenchymal stromal cells necessitate priming with an inflammatory milieu, in particular interferon-γ, to exert augmented immunosuppressive effects. It has been recently suggested that the heme-catabolizing enzyme heme oxygenase-1 is an essential component of the mesenchymal stromal cell-driven immune suppressive response. Because mesenchymal stromal cells upregulate indoleamine 2,3-dioxygenase expression on interferon-γ priming and indoleamine 2,3-dioxygenase requires heme as a cofactor for optimal catabolic function, we investigated the potential antagonism of heme oxygenase-1 activity on indoleamine 2, 3-dioxygenase and the impact on mesenchymal stromal cell immune plasticity. We herein sought to evaluate the molecular genetic effect of cytokine priming on human mesenchymal stromal cell heme oxygenase-1 expression and its functional role in differentially primed mesenchymal stromal cells. Contrary to previous reports, messenger RNA and protein analyses demonstrated that mesenchymal stromal cells derived from normal subjects (n = 6) do not express heme oxygenase-1 at steady state or after interferon-γ, tumor necrosis factor-α, and/or transforming growth factor-β priming. Pharmacological inhibition of heme oxygenase-1 with the use of tin protoporphyrin did not significantly abrogate the ability of mesenchymal stromal cells to suppress T-cell proliferation in vitro. Overall, these results unequivocally demonstrate that under steady state and after cytokine priming, human mesenchymal stromal cells immunoregulate T-cell proliferation independent of heme oxygenase-1.

The effect of hypercapnia on the sensitivity to flicker defined stimuli

BACKGROUND/AIMS

To investigate the effect of increased CO2 levels on flicker defined stimuli.

METHODS

The sensitivity of two flicker defined tasks was measured in nine healthy, trained observers using the Flicker Defined Form (FDF) stimulus of the Heidelberg Edge Perimeter (HEP; Heidelberg Engineering) and Frequency Doubling Technology (FDT) stimulus of the Matrix perimeter (Carl Zeiss Meditec) during normoxia and 15% hypercapnia (end-tidal CO2 increased by 15% relative to baseline). HEP-FDF and Matrix-FDT sensitivities were analysed for the global field, superior and inferior hemifields and at specific matched eccentricities, using repeated measures analysis of variance. The main effect of hypercapnia on flicker sensitivity was analysed using regression models.

RESULTS

Higher flicker sensitivity outcomes with increasing CO2 values were found for HEP-FDF and Matrix-FDT with a statistically significant main effect for HEP-FDF global, superior and inferior hemifields (p<0.01 for all) as well as 6°, 18°, 12° and 24° eccentricities (p=0.03, 0.04, 0.01, 0.05, respectively). When comparing mean sensitivity values between normocapnia and hypercapnia conditions, no statistically significantly different results were found for HEP-FDF and Matrix-FDT (p>0.05).

CONCLUSIONS

As CO2 levels were increased in healthy young individuals, there was an associated increase in visual sensitivity that was only significant for HEP-FDF stimuli, highlighting the different mechanisms involved in processing each of HEP-FDF and Matrix-FDT stimuli. Mean visual sensitivity outcomes were found to be similar for normocapnia and hypercapnia suggesting that a capability to compensate for a mild and stable increase in systemic CO2 levels may exist.

Transfusion-induced bone marrow transplant rejection due to minor histocompatibility antigens

Traditionally, alloimmunization to transfused blood products has focused exclusively on recipient antibodies recognizing donor alloantigens present on the cell surface. Accordingly, the immunologic sequelae of alloimmunization have been antibody mediated effects (ie, hemolytic transfusion reactions, platelet refractoriness, anti-HLA and anti-HNA effects, etc). However, in addition to the above sequelae, there is also a correlation between the number of antecedent transfusions in humans and the rate of bone marrow transplant (BMT) rejection-under reduced intensity conditioning with HLA-matched or HLA-identical marrow. Bone marrow transplant of this nature is the only existing cure for a series of nonmalignant hematologic diseases (eg, sickle cell disease, thalassemias, etc); however, rejection remains a clinical problem. It has been hypothesized that transfusion induces subsequent BMT rejection through immunization. Studies in animal models have observed the same effect and have demonstrated that transfusion-induced BMT rejection can occur in response to alloimmunization. However, unlike traditional antibody responses, sensitization in this case results in cellular immune effects, involving populations such as T cell or natural killer cells. In this case, rejection occurs in the absence of alloantibodies and would not be detected by existing immune-hematologic methods. We review human and animal studies in light of the hypothesis that, for distinct clinical populations, enhanced rejection of BMT may be an unappreciated adverse consequence of transfusion, which current blood bank methodologies are unable to detect.

Helicobacter pylori downregulates expression of human β-defensin 1 in the gastric mucosa in a type IV secretion-dependent fashion

Helicobacter pylori establishes a chronic lifelong infection in the human gastric mucosa, which may lead to peptic ulcer disease or gastric adenocarcinoma. The human beta-defensins (hβDs) are antimicrobial peptides, hβD1 being constitutively expressed in the human stomach. We hypothesized that H. pylori may persist, in part, by downregulating gastric hβD1 expression. We measured hβD1 and hβD2 expression in vivo in relation to the presence, density and severity of H. pylori infection, investigated differential effects of H. pylori virulence factors, and studied underlying signalling mechanisms in vitro. Significantly lower hβD1 and higher hβD2 mRNA and protein concentrations were present in gastric biopsies from infected patients. Those patients with higher-level bacterial colonization and inflammation had significantly lower hβD1 expression, but there were no differences in hβD2. H. pylori infection of human gastric epithelial cell lines also downregulated hβD1. Using wild-type strains and isogenic mutants, we showed that a functionalcag pathogenicity island-encoded type IV secretion system induced this downregulation. Treatment with chemical inhibitors or siRNA revealed that H. pylori usurped NF-κB signalling to modulate hβD1 expression. These data indicate that H. pylori downregulates hβD1 expression via NF-κB signalling, and suggest that this may promote bacterial survival and persistence in the gastric niche.

Comparative efficacy of two standard methods for determination of iron and zinc in fruits, pulses and cereals

Micronutrients are essential elements needed in small amounts for adequate human nutrition and include the elements iron and zinc. Both of these minerals are essential to human well-being and an adequate supply of iron and zinc help to prevent iron deficiency anaemia and zinc deficiency, two prevalent health concerns of the developing world. The levels of zinc and, iron were measured in the Banana, Papaya, Rice, Finger millet, Soybean and Urdbean. Standard Atomic absorption spectroscopy (AAS) method was also applied to all the samples for zinc and iron analysis and compared with inductively coupled plasma mass spectroscopy (ICP-MS). It was observed that there was no matrix interference affecting the determination of both elements interested in all the samples analyzed. Average concentration relative standard deviation and standard deviation were used for the statistical evaluation of the results for both elements. Correlation coefficient was used as statistical model to compare both the techniques.

Democratizing molecular diagnostics: the GeneXpert(®) enterovirus assay

BACKGROUND

Few clinical scenarios are as diagnostically demanding as the workup of acute meningitis in the emergency room setting. In humans, most cases of meningitis are due to enteroviral infection, which usually resolves with supportive care and does not generally require hospitalization. The difficulty in evaluating meningitis is often related to its nonspecific presentation; rapid identification of the underlying etiologic agent is critical to selection of the most appropriate course of therapy.

OBJECTIVE

To develop a rapid, automated polymerase chain reaction-based test for enteroviral meningitis that can be run on demand, and to make the test easy enough to operate that most hospital laboratories can offer it on an immediate basis in order to provide maximum medical impact.

METHODS

A sensitive and specific test on the GeneXpert was developed for detection of enteroviral RNA in cerebrospinal fluid. The automated test was carried out in a disposable GeneXpert cartridge, which conducts the steps of nucleic acid purification, amplification and detection of enteroviral genomic RNA in ∼ 2 h. Preclinical and clinical studies showed sensitivities of 97.1 and 98%, respectively, and specificities of 100 and 97.1%, respectively. In February 2006, the test received FDA clearance as an aid in the diagnosis of viral meningitis.

CONCLUSIONS

Rapid and accurate molecular diagnostic testing for enterovirus infection provides clinicians with information they need to make the best patient decisions in managing patients with meningitis. The GeneXpert enterovirus assay features on-demand availability and a level of simplicity that allows nearly any hospital laboratory to offer a sophisticated test that was once the exclusive domain of reference laboratories.

Mechanisms of alloimmunization and subsequent bone marrow transplantation rejection induced by platelet transfusion in a murine model

For many nonmalignant hematological disorders, HLA-matched bone marrow transplantation (BMT) is curative. However, due to lack of neoplasia, the toxicity of stringent conditioning regimens is difficult to justify, and reduced intensity conditioning is used. Unfortunately, current reduced intensity regimens have high rates of BMT rejection. We have recently reported in a murine model that mHAs on transfused platelet products induce subsequent BMT rejection. Most nonmalignant hematological disorders require transfusion support prior to BMT and the rate of BMT rejection in humans correlates with the number of transfusions given. Herein, we perform a mechanistic analysis of platelet transfusion-induced BMT rejection and report that unlike exposure to alloantigens during transplantation, platelet transfusion primes alloimmunity but does not stimulate full effector function. Subsequent BMT is itself an additional and distinct immunizing event, which does not induce rejection without antecedent priming from transfusion. Both CD4(+) and CD8(+) T cells are required for priming during platelet transfusion, but only CD8(+) T cells are required for BMT rejection. In neither case are antibodies required for rejection to occur.

CTLA4-Ig prevents alloantibody production and BMT rejection in response to platelet transfusions in mice

BACKGROUND

Platelet (PLT) transfusions can induce humoral and cellular alloimmunity. HLA antibodies can render patients refractory to subsequent transfusion, and both alloantibodies and cellular alloimmunity can contribute to subsequent bone marrow transplant (BMT) rejection. Currently, there are no approved therapeutic interventions to prevent alloimmunization to PLT transfusions other than leukoreduction. Targeted blockade of T-cell costimulation has shown great promise in inhibiting alloimmunity in the setting of transplantation, but has not been explored in the context of PLT transfusion.

STUDY DESIGN AND METHODS

We tested the hypothesis that the costimulatory blockade reagent CTLA4-Ig would prevent alloreactivity against major and minor alloantigens on transfused PLTs. BALB/c (H-2(d)) mice and C57BL/6 (H-2(b)) mice were used as PLT donors and transfusion recipients, respectively. Alloantibodies were measured by indirect immunofluorescence using BALB/c PLTs and splenocytes as targets. BMTs were carried out under reduced-intensity conditioning using BALB.B (H-2(b) ) donors and C57BL/6 (H-2(b)) recipients to model HLA-identical transplants. Experimental groups were given CTLA4-Ig (before or after PLT transfusion) with control groups receiving isotype-matched antibody.

RESULTS

CTLA4-Ig abrogated both humoral alloimmunization (H-2(d) antibodies) and transfusion-induced BMT rejection. Whereas a single dose of CTLA4-Ig at time of transfusion prevented alloimmunization to subsequent PLT transfusions, administration of CTLA4-Ig after initial PLT transfusion was ineffective. Delaying treatment until after PLT transfusion failed to prevent BMT rejection.

CONCLUSIONS

These findings demonstrate a novel strategy using an FDA-approved drug that has the potential to prevent the clinical sequelae of alloimmunization to PLT transfusions.

Phase II Study of Paclitaxel in Patients With Soft Tissue Sarcomas

Purpose. Patients with soft tissue sarcoma (STS) who have previously received standard chemotherapy including adriamycin (doxorubicin), ifosfamide, cyclophosphamide and DTIC (dacarbazine) have very limited therapeutic options. It is important to identify new drugs with some activity in this disease and we therefore undertook this trial to determine the antitumor activity of paclitaxel (Taxol).Methods. We conducted a phase II study of paclitaxel in patients with STS who had received prior standard chemotherapy. Paclitaxel was administered at a starting dose of 200 mg m(-2) as a 24-h infusion with STS premedication, every 21 days or upon hematologic recovery (absolute granulocyte count (AGC) >/= 1500/mul, platelets >/= 100 000/mul). Neupogen was not used routinely. The study was conducted based on a two-stage design proposed by Simon. Responses were assessed radiographically using standard criteria.Results. Nineteen eligible patients were treated in the first stage of the study. The median age was 50 years (range 20-68 years), and there were nine females and 10 males with Zubrod performance status of 1 or 2. One patient achieved a minor response. Median AGC nadir was 0.1/mul on day 12 with absolute neutropenia lasting 5 days. Median platelet nadir was 171 000/mul on day 9. There were no grade 3/4 non-hematologic toxicities and no deaths related to treatment.Discussion. Paclitaxel, at this dose and schedule, is well tolerated but inactive in this patient population.

Identification of patient safety improvement targets in successful vascular and endovascular procedures: analysis of 251 hours of complex arterial surgery

OBJECTIVES

To investigate failures in patient safety for patients undergoing vascular and endovascular procedures to guide future quality and safety interventions.

DESIGN

Single centre prospective observational study.

METHODS

66 procedures (17 thoracoabdominal and 23 abdominal aortic aneurysms, 4 carotid and 22 limb procedures) were observed prospectively over a 9-month period (251 h operating time) by two trained observers. Event logs were recorded for each procedure. Two blinded experts identified and independently categorised failures into 22 types (using a validated category tool) and severity (5-point scale). Data are expressed as median (range). Statistical analysis was performed using Mann-Whitney U, Kruskal-Wallis and Spearman's Rank tests.

RESULTS

1145 failures were identified with good inter-assessor reliability (Cronbach's alpha 0.844). The commonest failure types related to equipment (including unavailability, configuration and other failures) (269/1145 [23.5%]) and communication (240/1145 [21.0%]). A comparatively lower number of technical and psychomotor failures were identified (103 [9.0%]). The number of failures correlated with procedure duration (rho = 0.695, p < 0.001) but not anatomical site of the procedure or pathology of the disease process. Failure rate was higher in patients undergoing combined surgical/endovascular procedures compared to open surgery (median 5.7/h [IQR 4.2-8.1] vs 3.0/h [2.5-3.5]; p < 0.001). The severity of failures was similar (1.5/5 [1-2] vs 1/5 [1-2] respectively; p = 0.095). For combined procedures, failure rates were significantly higher during the endovascular phase (9.6/h [7.5-13.7]) compared to the non-endovascular phase (3.0/h [1.0-5.0]; p < 0.001).

CONCLUSIONS

Failures in patient safety are common during complex arterial procedures. Few failures were severe, although minor failures during critical stages and accumulation of multiple minor failures may potentially be important. Failures occurred especially during the endovascular phase and were often related to equipment or communication aspects. Interventions to improve procedural safety and quality of care should primarily target these specific areas.