A versatile CRISPR-Cas13d platform for multiplexed transcriptomic regulation and metabolic engineering in primary human T cells.

CRISPR technologies have begun to revolutionize T cell therapies; however, conventional CRISPR-Cas9 genome-editing tools are limited in their safety, efficacy, and scope. To address these challenges, we developed multiplexed effector guide arrays (MEGA), a platform for programmable and scalable regulation of the T cell transcriptome using the RNA-guided, RNA-targeting activity of CRISPR-Cas13d. MEGA enables quantitative, reversible, and massively multiplexed gene knockdown in primary human T cells without targeting or cutting genomic DNA. Applying MEGA to a model of CAR T cell exhaustion, we robustly suppressed inhibitory receptor upregulation and uncovered paired regulators of T cell function through combinatorial CRISPR screening. We additionally implemented druggable regulation of MEGA to control CAR activation in a receptor-independent manner. Lastly, MEGA enabled multiplexed disruption of immunoregulatory metabolic pathways to enhance CAR T cell fitness and anti-tumor activity in vitro and in vivo. MEGA offers a versatile synthetic toolkit for applications in cancer immunotherapy and beyond.

Inosine induces stemness features in CAR-T cells and enhances potency.

Adenosine (Ado) mediates immune suppression in the tumor microenvironment and exhausted CD8+ CAR-T cells express CD39 and CD73, which mediate proximal steps in Ado generation. Here, we sought to enhance CAR-T cell potency by knocking out CD39, CD73, or adenosine receptor 2a (A2aR) but observed only modest effects. In contrast, overexpression of Ado deaminase (ADA-OE), which metabolizes Ado to inosine (INO), induced stemness and enhanced CAR-T functionality. Similarly, CAR-T cell exposure to INO augmented function and induced features of stemness. INO induced profound metabolic reprogramming, diminishing glycolysis, increasing mitochondrial and glycolytic capacity, glutaminolysis and polyamine synthesis, and reprogrammed the epigenome toward greater stemness. Clinical scale manufacturing using INO generated enhanced potency CAR-T cell products meeting criteria for clinical dosing. These results identify INO as a potent modulator of CAR-T cell metabolism and epigenetic stemness programming and deliver an enhanced potency platform for cell manufacturing.

Inosine Induces Stemness Features in CAR T cells and Enhances Potency.

Adenosine (Ado) mediates immune suppression in the tumor microenvironment and exhausted CD8+ CAR T cells mediate Ado-induced immunosuppression through CD39/73-dependent Ado production. Knockout of CD39, CD73 or A2aR had modest effects on exhausted CAR T cells, whereas overexpression of Ado deaminase (ADA), which metabolizes Ado to inosine (INO), induced stemness features and potently enhanced functionality. Similarly, and to a greater extent, exposure of CAR T cells to INO augmented CAR T cell function and induced hallmark features of T cell stemness. INO induced a profound metabolic reprogramming, diminishing glycolysis and increasing oxidative phosphorylation, glutaminolysis and polyamine synthesis, and modulated the epigenome toward greater stemness. Clinical scale manufacturing using INO generated enhanced potency CAR T cell products meeting criteria for clinical dosing. These data identify INO as a potent modulator of T cell metabolism and epigenetic stemness programming and deliver a new enhanced potency platform for immune cell manufacturing.

Low Prevalence but High Impact of COVID-19 Positive Status in Adult Trauma Patients: A Multi-institutional Analysis of 28 904 Patients.

BACKGROUND: Few large investigations have addressed the prevalence of COVID-19 infection among trauma patients and impact on providers. The purpose of this study was to quantify the prevalence of COVID-19 infection among trauma patients by timing of diagnosis, assess nosocomial exposure risk, and evaluate the impact of COVID-19 positive status on morbidity and mortality. METHODS: Registry data from adults admitted 4/1/2020-10/31/2020 from 46 level I/II trauma centers were grouped by: timing of first positive status (Day 1, Day 2-6, or Day ≥ 7); overall Positive/Negative status; or Unknown if test results were unavailable. Groups were compared on outcomes (Trauma Quality Improvement Program complications) and mortality using univariate analysis and adjusted logistic regression. RESULTS: There were 28 904 patients (60.7% male, mean age: 56.4, mean injury severity score: 10.5). Of 13 274 (46%) patients with known COVID-19 status, 266 (2%) were Positive Day 1, 119 (1%) Days 2-6, 33 (.2%) Day ≥ 7, and 12 856 (97%) tested Negative. COVID-19 Positive patients had significantly worse outcomes compared to Negative; unadjusted comparisons showed longer hospital length of stay (10.98 vs 7.47;P < .05), higher rates of intensive care unit (57.7% vs 45.7%; P < .05) and ventilation use (22.5% vs 16.9%; P < .05). Adjusted comparisons showed higher rates of acute respiratory distress syndrome (1.7% vs .4%; P < .05) and death (8.1% vs 3.4%; P < .05). CONCLUSIONS: This multicenter study conducted during the early pandemic period revealed few trauma patients tested COVID-19 positive, suggesting relatively low exposure risk to care providers. COVID-19 positive status was associated with significantly higher mortality and specific morbidity. Further analysis is needed with consideration for care guidelines specific to COVID-19 positive trauma patients as the pandemic continues.

Enhanced safety and efficacy of protease-regulated CAR-T cell receptors.

Regulatable CAR platforms could circumvent toxicities associated with CAR-T therapy, but existing systems have shortcomings including leakiness and attenuated activity. Here, we present SNIP CARs, a protease-based platform for regulating CAR activity using an FDA-approved small molecule. Design iterations yielded CAR-T cells that manifest full functional capacity with drug and no leaky activity in the absence of drug. In numerous models, SNIP CAR-T cells were more potent than constitutive CAR-T cells and showed diminished T cell exhaustion and greater stemness. In a ROR1-based CAR lethality model, drug cessation following toxicity onset reversed toxicity, thereby credentialing the platform as a safety switch. In the same model, reduced drug dosing opened a therapeutic window that resulted in tumor eradication in the absence of toxicity. SNIP CARs enable remote tuning of CAR activity, which provides solutions to safety and efficacy barriers that are currently limiting progress in using CAR-T cells to treat solid tumors.

Hyperglycemia in nondiabetic adult trauma patients is associated with worse outcomes than diabetic patients: An analysis of 95,764 patients.

BACKGROUND: The adverse impact of acute hyperglycemia is well documented but its specific effects on nondiabetic trauma patients are unclear. The purpose of this study was to analyze the differential impact of hyperglycemia on outcomes between diabetic and nondiabetic trauma inpatients. METHODS: Adults admitted 2018 to 2019 to 46 Level I/II trauma centers with two or more blood glucose tests were analyzed. Diabetes status was determined from International Classification of Diseases-10th Rev.-Clinical Modification, trauma registry, and/or hemoglobin A1c greater than 6.5. Patients with and without one or more hyperglycemic result >180 mg/dL were compared. Logistic regression examined the effects of hyperglycemia and diabetes on outcomes, adjusting for age, sex, Injury Severity Score, and body mass index. RESULTS: There were 95,764 patients: 54% male; mean age, 61 years; mean Injury Severity Score, 10; diabetic, 21%. Patients with hyperglycemia had higher mortality and worse outcomes compared with those without hyperglycemia. Nondiabetic hyperglycemic patients had the highest odds of mortality (diabetic: adjusted odds ratio, 3.11; 95% confidence interval, 2.8-3.5; nondiabetics: adjusted odds ratio, 7.5; 95% confidence interval, 6.8-8.4). Hyperglycemic nondiabetics experienced worse outcomes on every measure when compared with nonhyperglycemic nondiabetics, with higher rates of sepsis (1.1 vs. 0.1%, p < 0.001), more SSIs (1.0 vs. 0.1%, p < 0.001), longer mean hospital length of stay (11.4 vs. 5.0, p < 0.001), longer mean intensive care unit length of stay (8.5 vs. 4.0, p < 0.001), higher rates of intensive care unit use (68.6% vs. 35.1), and more ventilator use (42.4% vs. 7.3%). CONCLUSION: Hyperglycemia is associated with increased odds of mortality in both diabetic and nondiabetic patients. Hyperglycemia during hospitalization in nondiabetics was associated with the worst outcomes and represents a potential opportunity for intervention in this high-risk group. LEVEL OF EVIDENCE: Therapeutic/care management; Level III.

Affordable IgY-based antiviral prophylaxis for resource-limited settings to address epidemic and pandemic risks.

Background: The COVID-19 pandemic caused by SARS-CoV-2 exposed a global problem, as highly effective vaccines are challenging to produce and distribute, particularly in regions with limited resources and funding. As an alternative, immunoglobulins produced in eggs of immunized hens (IgY) can be a simple and inexpensive source for a topical and temporary prophylaxis. Here, we developed a method to extract and purify IgY antibodies from egg yolks of hens immunized against viral pathogen-derived proteins using low-cost, readily available materials, for use in resource-limited settings. Methods: Existing protocols for IgY purification and equipment were modified, including extraction from yolks and separation of water-soluble IgY using common household reagents and tools. A replacement for a commercial centrifuge was developed, using a home food processor equipped with a 3D printed adapter to enable IgY precipitation. IgY purification was verified using standard gel electrophoresis and Western blot analyses. Results: We developed a step-by-step protocol for IgY purification for two settings in low- and middle-income countries (LMIC): a local laboratory, where commercial centrifuges are available, or a more rural setting, where an alternative for expensive centrifuges can be used. Gel electrophoresis and Western blot analyses confirmed that the method produced highly enriched IgY preparation; each commercial egg produced ~ 90 mg of IgY. We also designed a kit for IgY production in these two settings and provided a cost estimate of the kit. Conclusion: IgY purified from eggs of immunized local hens can offer a fast and affordable prophylaxis, provided that purification can be performed in a resource-limited setting. Here, we created a low-cost method that can be used anywhere where electricity is available using inexpensive, readily available materials in place of costly, specialized laboratory equipment and chemicals. This procedure can readily be used now to make an anti-SARS-CoV-2 prophylaxis in areas where vaccines are unavailable, and can be modified to combat future threats from viral epidemics and pandemics.

The public health burden of geriatric trauma: Analysis of 2,688,008 hospitalizations from Centers for Medicare and Medicaid Services inpatient claims.

BACKGROUND: Geriatric trauma care (GTC) represents an increasing proportion of injury care, but associated public health research on outcomes and expenditures is limited. The purpose of this study was to describe GTC characteristics, location, diagnoses, and expenditures. METHODS: Patients at short-term nonfederal hospitals, 65 years or older, with ≥1 injury International Classification of Diseases, Tenth Revision, were selected from 2016 to 2019 Centers for Medicare and Medicaid Services Inpatient Standard Analytical Files. Trauma center levels were linked to Inpatient Standard Analytical Files data via American Hospital Association Hospital ID and fuzzy string matching. Demographics, care location, diagnoses, and expenditures were compared across groups. RESULTS: A total of 2,688,008 hospitalizations (62% female; 90% White; 71% falls; mean Injury Severity Score, 6.5) from 3,286 hospitals were included, comprising 8.5% of all Medicare inpatient hospitalizations. Level I centers encompassed 7.2% of the institutions (n = 236) but 21.2% of hospitalizations, while nontrauma centers represented 58.5% of institutions (n = 1,923) and 37.7% of hospitalizations. Compared with nontrauma centers, patients at Level I centers had higher Elixhauser scores (9.0 vs. 8.8) and Injury Severity Score (7.4 vs. 6.0; p < 0.0001). The most frequent primary diagnosis at all centers was hip/femur fracture (28.3%), followed by traumatic brain injury (10.1%). Expenditures totaled $32.9 billion for trauma-related hospitalizations, or 9.1% of total Medicare hospitalization expenditures and approximately 1.1% of the annual Medicare budget. The overall mortality rate was 3.5%. CONCLUSION: Geriatric trauma care accounts for 8.5% of all inpatient GTC and a similar percentage of expenditures, the most common injury being hip/femur fractures. The largest proportion of GTC occurs at nontrauma centers, emphasizing their vital role in trauma care. Public health prevention programs and GTC guidelines should be implemented by all hospitals, not just trauma centers. Further research is required to determine the optimal role of trauma systems in GTC, establish data-driven triage guidelines, and define the impact of trauma centers and nontrauma centers on GTC mortality. LEVEL OF EVIDENCE: Therapeutic/care management, Level III.

A guide for concurrent TMS-fMRI to investigate functional brain networks.

Transcranial Magnetic Stimulation (TMS) allows for the direct activation of neurons in the human neocortex and has proven to be fundamental for causal hypothesis testing in cognitive neuroscience. By administering TMS concurrently with functional Magnetic Resonance Imaging (fMRI), the effect of cortical TMS on activity in distant cortical and subcortical structures can be quantified by varying the levels of TMS output intensity. However, TMS generates significant fluctuations in the fMRI time series, and their complex interaction warrants caution before interpreting findings. We present the methodological challenges of concurrent TMS-fMRI and a guide to minimize induced artifacts in experimental design and post-processing. Our study targeted two frontal-striatal circuits: primary motor cortex (M1) projections to the putamen and lateral prefrontal cortex (PFC) projections to the caudate in healthy human participants. We found that TMS parametrically increased the BOLD signal in the targeted region and subcortical projections as a function of stimulation intensity. Together, this work provides practical steps to overcome common challenges with concurrent TMS-fMRI and demonstrates how TMS-fMRI can be used to investigate functional brain networks.

Applicability, safety, and biological activity of regulatory T cell therapy in liver transplantation.

Regulatory T cells (Tregs) are a lymphocyte subset with intrinsic immunosuppressive properties that can be expanded in large numbers ex vivo and have been shown to prevent allograft rejection and promote tolerance in animal models. To investigate the safety, applicability, and biological activity of autologous Treg adoptive transfer in humans, we conducted an open-label, dose-escalation, Phase I clinical trial in liver transplantation. Patients were enrolled while awaiting liver transplantation or 6-12 months posttransplant. Circulating Tregs were isolated from blood or leukapheresis, expanded under good manufacturing practices (GMP) conditions, and administered intravenously at either 0.5-1 million Tregs/kg or 3-4.5 million Tregs/kg. The primary endpoint was the rate of dose- limiting toxicities occurring within 4 weeks of infusion. The applicability of the clinical protocol was poor unless patient recruitment was deferred until 6-12 months posttransplant. Thus, only 3 of the 17 patients who consented while awaiting liver transplantation were dosed. In contrast, all six patients who consented 6-12 months posttransplant received the cell infusion. Treg transfer was safe, transiently increased the pool of circulating Tregs and reduced anti-donor T cell responses. Our study opens the door to employing Treg immunotherapy to facilitate the reduction or complete discontinuation of immunosuppression following liver transplantation.

Pulsed dye laser repurposed: Treatment of refractory molluscum contagiosum in renal transplant patient.

We present a case of a 15-year-old girl with an allogenic renal transplant secondary to chronic glomerulonephritis of unknown etiology who presented with treatment refractory molluscum contagiosum of the lower extremities and perineum. Treatment of mollusca with pulsed dye laser resulted in a clinically significant and sustained response. To our knowledge, this is the first report of a successful treatment of molluscum contagiosum with pulsed dye laser in the setting of a renal transplant.

Hb Penang [ß78(EF2)Leu→Pro, HBB: c.236T>C]: a Novel ß-Globin Variant.

We report a novel hemoglobin (Hb) variant with a ß chain amino acid substitution at codon 78 (CTG>CCG) (HBB: c.236T>C), detected through prenatal screening via capillary electrophoresis (CE) in an otherwise healthy and asymptomatic 38-year-old female of Southeast Asian ancestry. The variant, named Hb Penang after the proband's Malaysian city of origin, underwent further characterization through high performance liquid chromatography (HPLC), reversed phase HPLC, Sanger sequencing, isopropanol stability testing and isoelectric focusing (IEF).

Antiviral activity of pyrrole-imidazole polyamides against SV40 and BK polyomaviruses.

The ability of antiviral polyamides (AVP) to act upon polyomaviruses (PyV) was evaluated. Initial studies found that a single treatment of AVP protected SV40-infected BSC-1 cells from cytopathic effect (CPE) for as long as 11 days p.i.. AVP substantially suppressed SV40 genome copy numbers over the duration of the experiment. Immunofluorescence analysis of ataxia-telangiectasia mutated (ATM) activation and large T antigen (LTag) expression clearly demonstrated that AVP treatment at day 1 p.i. delayed the onset of productive SV40 replication by approximately 3 days, and substantially limited the infection relative to vehicle-treated controls. AVP dose-response experiments recorded IC50s in the low nM range that were similar to IC50s previously reported for HPV16. The ability of AVPs to act on BKPyV was next examined. Again, IC50s in the low nM range were obtained with the exception of an AVP (PA1) that gave an IC50 of 437 nM against the BKPyV Dunlop strain. The Mre11 inhibitor Mirin substantially reduced the AVP IC50 against SV40 demonstrating that Mre11 protects PyV genomes from AVP action as previously shown for HPV. Together these experiments show that AVPs are potent antiviral agents for PyV that act via a mechanism with similarities to that found for HPV. The results demonstrate that AVPs are useful tools for controlling and studying PyV biology. The potential use of these agents against BKPyV and other PyV pathogens also has clinical implications.

Phenotypic and molecular characterization of a serum-free miniature erythroid differentiation system suitable for high-throughput screening and single-cell assays.

In vitro erythroid differentiation systems are used to study the mechanisms underlying normal and abnormal erythropoiesis and to test the effects of various extracellular factors on erythropoiesis. The use of serum or conditioned medium in liquid cultures and the seeding of cultures with heterogeneous peripheral blood mononuclear cells confound the reproducibility of these systems. Newer erythroid differentiation culture systems have overcome some of these limitations by using a fully defined, serum-free medium and initiating cultures using purified CD34+ cells. Although widely used in bulk cultures, these protocols have not been rigorously tested in high-throughput or single-cell assays. Here, we describe a serum-free erythroid differentiation system suitable for small-scale and single-cell experiments. This system generates large numbers of terminally differentiated erythroid cells of very high purity. Here we have adapted this culture system to a 96-well format and have developed a protocol to grow erythroid colonies from single erythroid progenitors in minute culture volumes.

The ATM and Rad3-Related (ATR) Protein Kinase Pathway Is Activated by Herpes Simplex Virus 1 and Required for Efficient Viral Replication.

The ATM and Rad3-related (ATR) protein kinase and its downstream effector Chk1 are key sensors and organizers of the DNA damage response (DDR) to a variety of insults. Previous studies of herpes simplex virus 1 (HSV-1) showed no evidence for activation of the ATR pathway. Here we demonstrate that both Chk1 and ATR were phosphorylated by 3 h postinfection (h.p.i.). Activation of ATR and Chk1 was observed using 4 different HSV-1 strains in multiple cell types, while a specific ATR inhibitor blocked activation. Mechanistic studies point to early viral gene expression as a key trigger for ATR activation. Both pATR and pChk1 localized to the nucleus within viral replication centers, or associated with their periphery, by 3 h.p.i. Significant levels of pATR and pChk1 were also detected in the cytoplasm, where they colocalized with ICP4 and ICP0. Proximity ligation assays confirmed that pATR and pChk1 were closely and specifically associated with ICP4 and ICP0 in both the nucleus and cytoplasm by 3 h.p.i., but not with ICP8 or ICP27, presumably in a multiprotein complex. Chemically distinct ATR and Chk1 inhibitors blocked HSV-1 replication and infectious virion production, while inhibitors of ATM, Chk2, and DNA-dependent protein kinase (DNA-PK) did not. Together our data show that HSV-1 activates the ATR pathway at early stages of infection and that ATR and Chk1 kinase activities play important roles in HSV-1 replication fitness. These findings indicate that the ATR pathway may provide insight for therapeutic approaches.IMPORTANCE Viruses have evolved complex associations with cellular DNA damage response (DDR) pathways, which sense troublesome DNA structures formed during infection. The first evidence for activation of the ATR pathway by HSV-1 is presented. ATR is activated, and its downstream target Chk1 is robustly phosphorylated, during early stages of infection. Both activated proteins are found in the nucleus associated with viral replication compartments and in the cytoplasm associated with viral proteins. We also demonstrate that both ATR and Chk1 kinase activities are important for viral replication. The findings suggest that HSV-1 activates ATR and Chk1 during early stages of infection and utilizes the enzymes to promote its own replication. The observation may be exploitable for antiviral approaches.

Editing an α-globin enhancer in primary human hematopoietic stem cells as a treatment for ß-thalassemia.

ß-Thalassemia is one of the most common inherited anemias, with no effective cure for most patients. The pathophysiology reflects an imbalance between α- and ß-globin chains with an excess of free α-globin chains causing ineffective erythropoiesis and hemolysis. When α-thalassemia is co-inherited with ß-thalassemia, excess free α-globin chains are reduced significantly ameliorating the clinical severity. Here we demonstrate the use of CRISPR/Cas9 genome editing of primary human hematopoietic stem/progenitor (CD34+) cells to emulate a natural mutation, which deletes the MCS-R2 α-globin enhancer and causes α-thalassemia. When edited CD34+ cells are differentiated into erythroid cells, we observe the expected reduction in α-globin expression and a correction of the pathologic globin chain imbalance in cells from patients with ß-thalassemia. Xenograft assays show that a proportion of the edited CD34+ cells are long-term repopulating hematopoietic stem cells, demonstrating the potential of this approach for translation into a therapy for ß-thalassemia.ß-thalassemia is characterised by the presence of an excess of α-globin chains, which contribute to erythrocyte pathology. Here the authors use CRISP/Cas9 to reduce α-globin expression in hematopoietic precursors, and show effectiveness in xenograft assays in mice.

The chromatin remodelling factor ATRX suppresses R-loops in transcribed telomeric repeats.

ATRX is a chromatin remodelling factor found at a wide range of tandemly repeated sequences including telomeres (TTAGGG)n ATRX mutations are found in nearly all tumours that maintain their telomeres via the alternative lengthening of telomere (ALT) pathway, and ATRX is known to suppress this pathway. Here, we show that recruitment of ATRX to telomeric repeats depends on repeat number, orientation and, critically, on repeat transcription. Importantly, the transcribed telomeric repeats form RNA-DNA hybrids (R-loops) whose abundance correlates with the recruitment of ATRX Here, we show loss of ATRX is also associated with increased R-loop formation. Our data suggest that the presence of ATRX at telomeres may have a central role in suppressing deleterious DNA secondary structures that form at transcribed telomeric repeats, and this may account for the increased DNA damage, stalling of replication and homology-directed repair previously observed upon loss of ATRX function.

Hepcidin detects iron deficiency in Sri Lankan adolescents with a high burden of hemoglobinopathy: A diagnostic test accuracy study.

Anemia affects over 800 million women and children globally. Measurement of hepcidin as an index of iron status shows promise, but its diagnostic performance where hemoglobinopathies are prevalent is unclear. We evaluated the performance of hepcidin as a diagnostic test of iron deficiency in adolescents across Sri Lanka. We selected 2273 samples from a nationally representative cross-sectional study of 7526 secondary schoolchildren across Sri Lanka and analyzed associations between hepcidin and participant characteristics, iron indices, inflammatory markers, and hemoglobinopathy states. We evaluated the diagnostic accuracy of hepcidin as a test for iron deficiency with estimation of the AUCROC , sensitivity/specificity at each hepcidin cutoff, and calculation of the Youden Index to find the optimal threshold. Hepcidin was associated with ferritin, sTfR, and hemoglobin. The AUCROC for hepcidin as a test of iron deficiency was 0.78; hepcidin outperformed Hb and sTfR. The Youden index-predicted cutoff to detect iron deficiency (3.2 ng/mL) was similar to thresholds previously identified to predict iron utilization and identify deficiency in African populations. Neither age, sex, nor α- or ß-thalassemia trait affected diagnostic properties of hepcidin. Hepcidin pre-screening would prevent most iron-replete thalassemia carriers from receiving iron whilst still ensuring most iron deficient children were supplemented. Our data indicate that the physiological relationship between hepcidin and iron status transcends specific populations. Measurement of hepcidin in individuals or populations could establish the need for iron interventions. Am. J. Hematol. 92:196-203, 2017. © 2016 Wiley Periodicals, Inc.

The evolutionary and clinical implications of the uneven distribution of the frequency of the inherited haemoglobin variants over short geographical distances.

Studies of the frequency of heterozygous carriers for common inherited diseases of haemoglobin in over 7500 adolescent children in 25 districts in Sri Lanka have disclosed a highly significant variation over very short geographical distances. A further analysis of these findings, including their relationship to the past frequency and distribution of malaria, climatic variation, altitude, ethnic origin and consanguinity rates, have provided evidence regarding the evolutionary basis for the variable distribution of these conditions over short distances. It is likely that the complex interplay between malaria and the environment, together with related ethnic and social issues, exists in many countries across the tropical belt. Hence, these observations emphasise the importance of micromapping heterozygote distributions in high-frequency countries in order to define their true burden and the facilities required for the prevention and management of the homozygous and compound heterozygous disorders that result from their interaction.