Predictors of COVID-19 infection and hospitalization in group homes for individuals with intellectual and/or developmental disabilities.

BACKGROUND: More than seven million people with intellectual and/or developmental disabilities (ID/DD) live in the US and may face an elevated risk for COVID-19. OBJECTIVE: To identify correlates of COVID-19 and related hospitalizations among people with ID/DD in group homes in Massachusetts. METHODS: We collected data during March 1, 2020-June 30, 2020 (wave 1) and July 1, 2020-March 31, 2021 (wave 2) from the Massachusetts Department of Public Health and six organizations administering 206 group homes for 1035 residents with ID/DD. The main outcomes were COVID-19 infections and related hospitalizations. We fit multilevel Cox proportional hazards models to estimate associations with observed predictors and assess contextual home- and organizational-level effects. RESULTS: Compared with Massachusetts residents, group home residents had a higher age-adjusted rate of COVID-19 in wave 1 (incidence rate ratio [IRR], 12.06; 95 % confidence interval [CI], 10.51-13.84) and wave 2 (IRR, 2.47; 95 % CI, 2.12-2.88) and a higher age-adjusted rate of COVID-19 hospitalizations in wave 1 (IRR, 17.64; 95 % CI, 12.59-24.70) and wave 2 (IRR, 4.95; 95 % CI, 3.23-7.60). COVID-19 infections and hospitalizations were more likely among residents aged 65+ and in group homes with 6+ resident beds and recent infection among staff and residents. CONCLUSIONS: Aggressive efforts to decrease resident density, staff-to-resident ratios, and staff infections through efforts such as vaccination, in addition to ongoing access to personal protective equipment and COVID-19 testing, may reduce COVID-19 and related hospitalizations in people with ID/DD living in group homes.

Using simulation modeling to inform intervention and implementation selection in a rapid stakeholder-engaged hybrid effectiveness-implementation randomized trial.

BACKGROUND: Implementation research generally assumes established evidence-based practices and prior piloting of implementation strategies, which may not be feasible during a public health emergency. We describe the use of a simulation model of the effectiveness of COVID-19 mitigation strategies to inform a stakeholder-engaged process of rapidly designing a tailored intervention and implementation strategy for individuals with serious mental illness (SMI) and intellectual/developmental disabilities (ID/DD) in group homes in a hybrid effectiveness-implementation randomized trial. METHODS: We used a validated dynamic microsimulation model of COVID-19 transmission and disease in late 2020/early 2021 to determine the most effective strategies to mitigate infections among Massachusetts group home staff and residents. Model inputs were informed by data from stakeholders, public records, and published literature. We assessed different prevention strategies, iterated over time with input from multidisciplinary stakeholders and pandemic evolution, including varying symptom screening, testing frequency, isolation, contact-time, use of personal protective equipment, and vaccination. Model outcomes included new infections in group home residents, new infections in group home staff, and resident hospital days. Sensitivity analyses were performed to account for parameter uncertainty. Results of the simulations informed a stakeholder-engaged process to select components of a tailored best practice intervention and implementation strategy. RESULTS: The largest projected decrease in infections was with initial vaccination, with minimal benefit for additional routine testing. The initial level of actual vaccination in the group homes was estimated to reduce resident infections by 72.4% and staff infections by 55.9% over the 90-day time horizon. Increasing resident and staff vaccination uptake to a target goal of 90% further decreased resident infections by 45.2% and staff infections by 51.3%. Subsequent simulated removal of masking led to a 6.5% increase in infections among residents and 3.2% among staff. The simulation model results were presented to multidisciplinary stakeholders and policymakers to inform the "Tailored Best Practice" package for the hybrid effectiveness-implementation trial. CONCLUSIONS: Vaccination and decreasing vaccine hesitancy among staff were predicted to have the greatest impact in mitigating COVID-19 risk in vulnerable populations of group home residents and staff. Simulation modeling was effective in rapidly informing the selection of the prevention and implementation strategy in a hybrid effectiveness-implementation trial. Future implementation may benefit from this approach when rapid deployment is necessary in the absence of data on tailored interventions. TRIAL REGISTRATION: ClinicalTrials.gov NCT04726371.

COVID-19-Related Outcomes Among Group Home Residents with Serious Mental Illness in Massachusetts in the First Year of the Pandemic.

This study examined COVID-19 infection and hospitalizations among people with serious mental illness who resided in residential care group homes in Massachusetts during the first year of the COVID-19 pandemic. The authors analyzed data on 2261 group home residents and COVID-19 data from the Massachusetts Department of Public Health. Outcomes included positive COVID-19 tests and COVID-19 hospitalizations March 1, 2020-June 30, 2020 (wave 1) and July 1, 2020-March 31, 2021 (wave 2). Associations between hazard of outcomes and resident and group home characteristics were estimated using multi-level Cox frailty models including home- and city-level frailties. Between March 2020 and March 2021, 182 (8%) residents tested positive for COVID-19, and 51 (2%) had a COVID-19 hospitalization. Compared with the Massachusetts population, group home residents had age-adjusted rate ratios of 3.0 (4.86 vs. 1.60 per 100) for COVID infection and 13.5 (1.99 vs. 0.15 per 100) for COVID hospitalizations during wave 1; during wave 2, the rate ratios were 0.5 (4.55 vs. 8.48 per 100) and 1.7 (0.69 vs. 0.40 per 100). In Cox models, residents in homes with more beds, higher staff-to-resident ratios, recent infections among staff and other residents, and in cities with high community transmission risk had greater hazard of COVID-19 infection. Policies and interventions that target group home-specific risks are needed to mitigate adverse communicable disease outcomes in this population.Clinical Trial Registration Number This study provides baseline (i.e., pre-randomization) data from a clinical trial study NCT04726371.

Group Home Staff Experiences With Work and Health in the COVID-19 Pandemic in Massachusetts.

Importance: Direct reports of the experiences of staff working in group homes for people with serious mental illness (SMI) and/or intellectual or developmental disabilities (ID/DD) are rarely reported. Hearing from workers about their experiences in the COVID-19 pandemic may inform future workforce and public policy. Objective: To gather baseline data on worker experience with the perceived effects of COVID-19 on health and work in the pandemic prior to initiating an intervention to mitigate the spread of COVID-19 and to measure differences in worker experience by gender, race, ethnicity, education, and resident population served (persons with SMI and/or IDD/DD). Design, Setting, and Participants: This mixed-mode, cross-sectional survey study was conducted using online then paper-based self-administration from May to September 2021 at the end of the first year of the pandemic. Staff working in 415 group homes that provided care within 6 Massachusetts organizations serving adults aged 18 years or older with SMI and/or ID/DD were surveyed. The eligible survey population included a census of staff who were currently employed in participating group homes during the study period. A total of 1468 staff completed or partially completed surveys. The overall survey response rate was 44% (range by organization, 20% to 52%). Main Outcomes and Measures: Self-reported experiential outcomes were measured in work, health, and vaccine completion. Bivariate and multivariate analyses explore experiences by gender, race, ethnicity, education, trust in experts and employers, and population served. Results: The study population included 1468 group home staff (864 [58.9%] women; 818 [55.7%] non-Hispanic Black; 98 [6.7%] Hispanic or Latino). A total of 331 (22.5%) group home staff members reported very serious perceived effects on health; 438 (29.8%) reported very serious perceived effects on mental health; 471 (32.1%) reported very serious perceived effects on health of family and friends; and 414 reported very serious perceived effects (28.2%) on access to health services, with statistically significant differences observed by race and ethnicity. Vaccine acceptance was higher among persons with higher educational attainment and trust in scientific expertise and lower among persons who self-reported as Black or Hispanic/Latino. A total of 392 (26.7%) respondents reported needing support for health needs, and 290 (19.8%) respondents reported needing support for loneliness or isolation. Conclusions and Relevance: In this survey study, approximately one-third of group home workers reported serious personal health and access to health care barriers during the first year of the COVID-19 pandemic in Massachusetts. Addressing unmet health needs and access to health and mental health services, including inequities and disparities by race, ethnicity, and education, should benefit staff health and safety, as well as that of the individuals with disabilities who rely on them for support and care.

Cost-Effectiveness of Routine Screening for Autoimmune Encephalitis in Patients With First-Episode Psychosis in the United States.

OBJECTIVE: Autoimmune encephalitis (AE) is a highly treatable neurologic condition that can cause psychosis. Screening for AE is not currently recommended in routine workup for first-episode psychosis (FEP), owing partly to the high cost of testing for AE-associated neuronal autoantibodies. METHODS: This study used a decision-analytic model to estimate the cost-effectiveness of routine serum screening for AE compared with clinically targeted screening in patients with FEP. Model parameters drawn from prior published literature included the prevalence of neuronal autoantibodies in FEP (4.5%), serum autoantibody panel cost (US $291), remission probability with antipsychotics (0.58), and remission probability with immunotherapy for patients diagnosed with AE (0.85). Outcomes included quality-adjusted life-years (QALYs), costs, and incremental cost-effectiveness ratios (ICERs), assessed over a 5-year horizon from the US health care sector and societal perspectives. ICER thresholds of $50,000/QALY to $150,000/QALY were used to define cost-effectiveness. The analysis was conducted between June 2018 and January 2020. RESULTS: Routine screening led to mean QALY gains of 0.008 among all patients and 0.174 among the subgroup of patients with neuronal autoantibodies. Mean costs increased by $780 from a societal perspective and $1,150 from a health care sector perspective, resulting in ICERs of $99,330/QALY and $147,460/QALY, respectively. Incorporating joint input data uncertainty, the likelihood routine screening has an ICER ≤ $150,000/QALY was 55% from a societal perspective and 37% from a health care sector perspective. The model parameter with the greatest contribution to overall uncertainty was the effectiveness of immunotherapy relative to antipsychotics. CONCLUSIONS: Routine screening for AE in patients with FEP may be cost-effective in the United States. As further immunotherapy effectiveness data become available, a more definitive recommendation to perform routine screening could be warranted.

Pediatric Consultation-Liaison Psychiatry: An Update and Review.

Background: In recent years, there has been an increasing burden of child and adolescent mental illness recognized in the United States, and the need for pediatric mental health care is growing. Pediatric consultation-liaison (C-L) psychiatrists are increasingly playing a role in the management of medical and psychiatric disease for pediatric patients. The field is a fast-moving one, with understanding of new neuropsychiatric disease entities; reformulation of prior disease entities; and new interdisciplinary treatments and models of care. Methods: In this study, we aim to review recent advances in the field of pediatric C-L psychiatry, including new diagnostic entities, updated management of frequently encountered clinical presentations, and developments in systems of care. Conclusion: The advances in pediatric C-L psychiatry are broad and serve to promote more streamlined, evidence-based care for the vulnerable population of psychiatrically ill pediatric medical patients. More work remains to determine the most effective interventions for the wide array of presentations seen by pediatric C-L psychiatrists.

Registration, results reporting, and publication bias of clinical trials supporting FDA approval of neuropsychiatric drugs before and after FDAAA: a retrospective cohort study.

BACKGROUND: Mandatory trial registration, and later results reporting, were proposed to mitigate selective clinical trial publication and outcome reporting. The Food and Drug Administration (FDA) Amendments Act (FDAAA) was enacted by Congress on September 27, 2007, requiring the registration of all non-phase I clinical trials involving FDA-regulated medical interventions and results reporting for approved drugs. The association between FDAAA enactment and the registration, results reporting, and publication bias of neuropsychiatric trials has not been studied. METHODS: We conducted a retrospective cohort study of all efficacy trials supporting FDA new drug approvals between 2005 to 2014 for neuropsychiatric indications. Trials were categorized as pre- or post-FDAAA based on initiation and/or completion dates. The main outcomes were the proportions of trials registered and reporting results in ClinicalTrials.gov, and the degree of publication bias, estimated using the relative risks pre- and post-FDAAA of both the publication of positive vs non-positive trials, as well as of publication of positive vs non-positive trials without misleading interpretations. Registration and results reporting proportions were compared pre- and post-FDAAA using the two-tailed Fisher exact test, and the degrees of publication bias were compared by calculating the ratio of relative risks (RRR) for each period. RESULTS: The FDA approved 37 new drugs for neuropsychiatric indications between 2005 and 2014 on the basis of 142 efficacy trials, of which 101 were pre-FDAAA and 41 post-FDAAA. Post-FDAAA trials were significantly more likely to be registered (100% vs 64%; p < 0.001) and report results (100% vs 10%; p < 0.001) than pre-FDAAA trials. Pre-FDAAA, positive trials were more likely to be published (relative risk [RR] = 1.52; 95% confidence interval [CI] = 1.17-1.99; p = 0.002) and published without misleading interpretations (RR = 2.47; CI = 1.57-3.73; p < 0.001) than those with non-positive results. In contrast, post-FDAAA positive trials were equally likely to have been published (RR = 1; CI = 1-1, p = NA) and published without misleading interpretations (RR = 1.20; CI = 0.84-1.72; p = 0.30). The likelihood of publication bias pre-FDAAA vs post-FDAAA was greater for positive vs non-positive trials (RRR = 1.52; CI = 1.16-1.99; p = 0.002) and for publication without misleading interpretations (RRR = 2.06, CI = 1.17-3.61, p = 0.01). CONCLUSIONS: The enactment of FDAAA was followed by significantly higher proportions of trials that were registered and reporting results on ClinicalTrials.gov and significantly lower degrees of publication bias among trials supporting recent FDA approval of drugs for neuropsychiatric indications.

Patterns and predictors of off-label prescription of psychiatric drugs.

Off-label prescribing of psychiatric drugs is common, despite lacking strong scientific evidence of efficacy and potentially increasing risk for adverse events. The goal of this study was to characterize prevalence of off-label prescriptions of psychiatric drugs and examine patient and clinician predictors of off-label use. This manuscript presents a retrospective, cross-sectional study using data from the 2012 and 2013 National Ambulatory Medical Care Surveys (NAMCS). The study examined all adult outpatient visits to psychiatric practices for chronic care management with a single listed visit diagnosis in which at least one psychiatric drug was prescribed. The main outcome measure was off-label prescribing of at least one psychiatric drug, defined as prescription for a condition for which it has not been approved for use by the FDA. Among our sample representative of 1.85 billion outpatient visits, 18.5 million (1.3%) visits were to psychiatrists for chronic care management in which at least one psychiatric drug was prescribed. Overall, the rate of off-label use was 12.9% (95% CI: 12.2-15.7). The most common off-label uses were for manic-depressive psychosis treated with citalopram and primary insomnia treated with trazodone. Several patient and clinician characteristics were positively associated with off-label prescribing, including seeing a psychiatrist (OR: 1.06, 95% CI, 1.01-1.12; p = 0.03) instead of another type of clinician, the office visit taking place in the Western region of the country (OR: 1.09, 95% CI, 1.01-1.17; p = 0.02), and the patient having 3 or more chronic conditions (OR: 1.12, 95% CI, 1.02-1.14; p = 0.003). In contrast, having Medicare coverage (OR: 0.93, 95% CI, 0.84-0.97; p = 0.04) and receiving payment assistance from a medical charity (OR: 0.91, 95% CI, 0.88-0.96; p = 0.03) instead of private insurance were negatively associated with off-label prescribing. These results suggest that certain classes of psychiatric medications are being commonly prescribed to treat conditions for which they have not been determined by the FDA to be clinically efficacious and/or safe.

The lifetime medical cost savings from preventing HIV in the United States.

OBJECTIVE: Enhanced HIV prevention interventions, such as preexposure prophylaxis for high-risk individuals, require substantial investments. We sought to estimate the medical cost saved by averting 1 HIV infection in the United States. METHODS: We estimated lifetime medical costs in persons with and without HIV to determine the cost saved by preventing 1 HIV infection. We used a computer simulation model of HIV disease and treatment (CEPAC) to project CD4 cell count, antiretroviral treatment status, and mortality after HIV infection. Annual medical cost estimates for HIV-infected persons, adjusted for age, sex, race/ethnicity, and transmission risk group, were from the HIV Research Network (range, $1854-$4545/mo) and for HIV-uninfected persons were from the Medical Expenditure Panel Survey (range, $73-$628/mo). Results are reported as lifetime medical costs from the US health system perspective discounted at 3% (2012 USD). RESULTS: The estimated discounted lifetime cost for persons who become HIV infected at age 35 is $326,500 (60% for antiretroviral medications, 15% for other medications, 25% nondrug costs). For individuals who remain uninfected but at high risk for infection, the discounted lifetime cost estimate is $96,700. The medical cost saved by avoiding 1 HIV infection is $229,800. The cost saved would reach $338,400 if all HIV-infected individuals presented early and remained in care. Cost savings are higher taking into account secondary infections avoided and lower if HIV infections are temporarily delayed rather than permanently avoided. CONCLUSIONS: The economic value of HIV prevention in the United States is substantial given the high cost of HIV disease treatment.

Development, calibration and performance of an HIV transmission model incorporating natural history and behavioral patterns: application in South Africa.

Understanding HIV transmission dynamics is critical to estimating the potential population-wide impact of HIV prevention and treatment interventions. We developed an individual-based simulation model of the heterosexual HIV epidemic in South Africa and linked it to the previously published Cost-Effectiveness of Preventing AIDS Complications (CEPAC) International Model, which simulates the natural history and treatment of HIV. In this new model, the CEPAC Dynamic Model (CDM), the probability of HIV transmission per sexual encounter between short-term, long-term and commercial sex worker partners depends upon the HIV RNA and disease stage of the infected partner, condom use, and the circumcision status of the uninfected male partner. We included behavioral, demographic and biological values in the CDM and calibrated to HIV prevalence in South Africa pre-antiretroviral therapy. Using a multi-step fitting procedure based on Bayesian melding methodology, we performed 264,225 simulations of the HIV epidemic in South Africa and identified 3,750 parameter sets that created an epidemic and had behavioral characteristics representative of a South African population pre-ART. Of these parameter sets, 564 contributed 90% of the likelihood weight to the fit, and closely reproduced the UNAIDS HIV prevalence curve in South Africa from 1990-2002. The calibration was sensitive to changes in the rate of formation of short-duration partnerships and to the partnership acquisition rate among high-risk individuals, both of which impacted concurrency. Runs that closely fit to historical HIV prevalence reflect diverse ranges for individual parameter values and predict a wide range of possible steady-state prevalence in the absence of interventions, illustrating the value of the calibration procedure and utility of the model for evaluating interventions. This model, which includes detailed behavioral patterns and HIV natural history, closely fits HIV prevalence estimates.

Clinical impact and cost-effectiveness of expanded voluntary HIV testing in India.

BACKGROUND: Despite expanding access to antiretroviral therapy (ART), most of the estimated 2.3 to 2.5 million HIV-infected individuals in India remain undiagnosed. The questions of whom to test for HIV and at what frequency remain unclear. METHODS: We used a simulation model of HIV testing and treatment to examine alternative HIV screening strategies: 1) current practice, 2) one-time, 3) every five years, and 4) annually; and we applied these strategies to three population scenarios: 1) the general Indian population ("national population"), i.e. base case (HIV prevalence 0.29%; incidence 0.032/100 person-years [PY]); 2) high-prevalence districts (HIV prevalence 0.8%; incidence 0.088/100 PY), and 3) high-risk groups (HIV prevalence 5.0%; incidence 0.552/100 PY). Cohort characteristics reflected Indians reporting for HIV testing, with a median age of 35 years, 66% men, and a mean CD4 count of 305 cells/µl. The cost of a rapid HIV test was $3.33. Outcomes included life expectancy, HIV-related direct medical costs, incremental cost-effectiveness ratios (ICERs), and secondary transmission benefits. The threshold for "cost-effective" was defined as 3x the annual per capita GDP of India ($3,900/year of life saved [YLS]), or for "very cost-effective" was <1x the annual per capita GDP ($1,300/YLS). RESULTS: Compared to current practice, one-time screening was very cost-effective in the national population (ICER: $1,100/YLS), high-prevalence districts (ICER: $800/YLS), and high-risk groups (ICER: $800/YLS). Screening every five years in the national population (ICER: $1,900/YLS) and annual screening in high-prevalence districts (ICER: $1,900/YLS) and high-risk groups (ICER: $1,800/YLS) were also cost-effective. Results were most sensitive to costs of care and linkage-to-care. CONCLUSIONS: In India, voluntary HIV screening of the national population every five years offers substantial clinical benefit and is cost-effective. Annual screening is cost-effective among high-risk groups and in high-prevalence districts nationally. Routine HIV screening in India should be implemented.

Could early antiretroviral therapy entail more risks than benefits in sub-Saharan African HIV-infected adults? A model-based analysis.

BACKGROUND: Initiation of antiretroviral therapy (ART) in all HIV-infected adults, regardless of CD4⁺ T-cell count, is a proposed strategy for reducing HIV transmission. We investigated the conditions under which starting ART early could entail more risks than benefits for patients with high CD4⁺ T-cell counts. METHODS: We used a simulation model to compare ART initiation upon entry to care ('immediate ART') to initiation at CD4⁺ T-cell count ≤ 350 cells/µl ('WHO 2010 ART') in African adults with CD4⁺ T-cell counts >500 cells/µl. We varied inputs to determine the combination of parameters (population characteristics, conditions of care, treatment outcomes) that would result in higher 15-year mortality with immediate ART. RESULTS: The 15-year mortality was 56.7% for WHO 2010 ART and 51.8% for immediate ART. In one-way sensitivity analysis, lower 15-year mortality was consistently achieved with immediate ART unless the rate of fatal ART toxicity was >1.0/100 person-years, the rate of withdrawal from care was >1.2-fold higher or the rate of ART failure due to poor adherence was >4.3-fold higher on immediate than on WHO 2010 ART. In multi-way sensitivity analysis, immediate ART led to higher mortality when moderate rates of fatal ART toxicity (0.25/100 person-years) were combined with rates of withdrawal from care >1.1-fold higher and rates of treatment failure >2.1-fold higher on immediate than on WHO 2010 ART. CONCLUSIONS: In sub-Saharan Africa, ART initiation at entry into care would improve long-term survival of patients with high CD4⁺ T-cell counts, unless it is associated with increased withdrawal from care and decreased adherence. In early ART trials, a focus on retention and adherence will be crucial.

Cost-effectiveness analysis of UGT1A1 genetic testing to inform antiretroviral prescribing in HIV disease.

BACKGROUND: Homozygosity for UGT1A1*28/*28 has been reported to be associated with atazanavir-associated hyperbilirubinaemia and premature atazanavir discontinuation. We assessed the potential cost-effectiveness of UGT1A1 testing to inform the choice of an initial protease-inhibitor-containing regimen in antiretroviral therapy (ART)-naive individuals. METHODS: We used the Cost-Effectiveness of Preventing AIDS Complications computer simulation model to project quality-adjusted life years (QALYs) and lifetime costs (2009 USD) for atazanavir-based ART with or without UGT1A1 testing, using darunavir rather than atazanavir when indicated. We assumed the UGT1A1-associated atazanavir discontinuation rate reported in the Swiss HIV Cohort Study (a *28/*28 frequency of 14.9%), equal efficacy and cost of atazanavir and darunavir and a genetic assay cost of $107. These parameters, as well as the effect of hyperbilirubinaemia on quality of life and loss to follow up, were varied in sensitivity analyses. Costs and QALYs were discounted at 3% annually. RESULTS: Initiating atazanavir-based ART at CD4(+) T-cell counts <500 cells/µl without UGT1A1 testing had an average discounted life expectancy of 16.02 QALYs and $475,800 discounted lifetime cost. Testing for UGT1A1 increased QALYs by 0.49 per 10,000 patients tested and was not cost-effective (>$100,000/QALY). Testing for UGT1A1 was cost-effective (<$100,000/QALY) if assay cost decreased to $10, or if avoiding hyperbilirubinaemia by UGT1A1 testing reduced loss to follow-up by 5%. If atazanavir and darunavir differed in cost or efficacy, testing for UGT1A1 was not cost-effective under any scenario. CONCLUSIONS: Testing for UGT1A1 may be cost-effective if assay cost is low and if testing improves retention in care, but only if the comparator ART regimens have the same drug cost and efficacy.

Peripheral antigen display by lymph node stroma promotes T cell tolerance to intestinal self.

The intestinal epithelium functions to absorb nutrients and to protect the organism against microbes. To prevent autoimmune attack on this vital tissue, T cell tolerance to intestinal self-antigens must be established. Central tolerance mechanisms involve medullary thymic epithelial cells (mTECs), which use endogenously expressed peripheral-tissue antigens (PTAs) to delete self-reactive thymocytes. The prevailing model for the induction of peripheral tolerance involves cross-presentation of tissue antigens by quiescent dendritic cells. Here we show that lymph node stromal cells present endogenously expressed PTAs to T cells. Moreover, antigen presentation by lymph node stroma is sufficient to induce primary activation and subsequent tolerance among CD8(+) T cells. Thus, lymph node stromal cells are functionally akin to mTECs and provide a direct strategy for purging the peripheral repertoire of self-reactive T cells.