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Leveraging mHealth and Patient Supporters for African Americans' and Latinxs' Engagement in HIV Care (LEAN): Protocol for a Randomized, Controlled, Effectiveness-Implementation Trial. JMIR Res Protoc 2023; 12:e42691. [PMID: 36787165 PMCID: PMC9975915 DOI: 10.2196/42691] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 11/02/2022] [Accepted: 11/18/2022] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Despite substantial investments in ending the HIV epidemic, disparities in HIV care persist, and there is an urgent need to evaluate novel and scalable approaches to improving HIV care engagement and viral suppression in real-world settings. OBJECTIVE This paper aims to describe a study protocol for a pragmatic type II hybrid effectiveness-implementation randomized controlled trial comparing existing standard of care clinic HIV linkage, adherence, and retention (LAR) protocols to a mobile health (mHealth)-enhanced linkage, adherence, and retention (mLAR) intervention. METHODS The study will enroll 450 participants from clinics in Baltimore City. Eligibility criteria include being ≥18 years of age, having a new HIV diagnosis or being HIV-positive and out of care, or being HIV-positive and deemed by clinic staff as someone who could benefit from linkage and retention services. Participants randomized to the intervention receive mHealth-supported patient navigation for 12 months. Participants in the control group receive the referring clinic's standard of care patient support. The primary outcome is HIV virologic suppression at 12 months. A subset of participants will be interviewed at 12 months to learn about their HIV care experiences and, for those in the intervention arm, their experiences with the mLAR intervention. This protocol was developed in collaboration with the Baltimore City Health Department (BCHD) and the Maryland Department of Health (MDH) and with input from a community advisory board. RESULTS Enrollment began on February 25, 2020. As of August 11, 2022, 411 of the 450 target participants had been enrolled. CONCLUSIONS Pragmatic implementation science trials designed with input from key stakeholders, including health departments and community members, can help evaluate the evidence for mHealth interventions to reduce HIV health disparities. TRIAL REGISTRATION ClinicalTrials.gov NCT03934437; https://clinicaltrials.gov/ct2/show/NCT03934437. INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID) DERR1-10.2196/42691.
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Evaluation of a competency based medical curriculum in a Sub-Saharan African medical school. BMC MEDICAL EDUCATION 2022; 22:724. [PMID: 36242004 PMCID: PMC9569118 DOI: 10.1186/s12909-022-03781-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/30/2022] [Revised: 09/16/2022] [Accepted: 09/30/2022] [Indexed: 05/12/2023]
Abstract
BACKGROUND Medical schools in Sub-Saharan Africa have adopted competency based medical education (CBME) to improve the quality of graduates trained. In 2015, Makerere University College of Health Sciences (MaKCHS) implemented CBME for the Bachelor of Medicine and Bachelor of Surgery (MBChB) programme in order to produce doctors with the required attributes to address community health needs. However, no formal evaluation of the curriculum has been conducted to determine whether all established competencies are being assessed. OBJECTIVE To evaluate whether assessment methods within the MBChB curriculum address the stated competencies. METHODS The evaluation adopted a cross-sectional study design in which the MBChB curriculum was evaluated using an Essential Course Evidence Form (ECEF) that was developed to collect information about each assessment used for each course. Information was collected on: (1) Assessment title, (2) Description, (3) Competency domain (4) Sub-competency addressed, (5) Student instructions, and (6) Grading method/details. Data were entered into a structured Access data base. In addition, face-to-face interviews were conducted with faculty course coordinators. RESULTS The MBChB curriculum consisted of 62 courses over 5 years, focusing on preclinical skills in years 1-2 and clinical skills in years 3-5. Fifty-nine competencies were identified and aggregated into 9 domains. Fifty-eight competencies were assessed at least one time in the curriculum. Faculty cited limited training in assessment as well as large student numbers as hindrances to designing robust assessments for the competencies. CONCLUSION CBME was successfully implemented evidenced by all but one of the 59 competencies within the nine domains established being assessed within the MBChB curriculum at MaKCHS. Faculty interviewed were largely aware of it, however indicated the need for more training in competency-based assessment to improve the implementation of CBME.
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Addressing the global burden of hepatitis B virus while developing long-acting injectables for the prevention and treatment of HIV. Lancet HIV 2019; 7:e443-e448. [PMID: 31870675 DOI: 10.1016/s2352-3018(19)30342-x] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Revised: 08/05/2019] [Accepted: 08/13/2019] [Indexed: 12/23/2022]
Abstract
The first long-acting formulations of HIV drugs are undergoing regulatory review for use in maintenance of viral suppression in people with HIV. Although these novel drug formulations could contribute greatly to HIV treatment and prevention efforts, their lack of activity against hepatitis B virus (HBV) could limit their global impact, particularly in populations with high burdens of both HIV and HBV. An urgent need for greater investment in research and development of long-acting drugs with dual activity against HIV and HBV exists. Access to long-acting HIV drug formulations with dual activity against HBV would be transformative and have a great impact on efforts to prevent, treat, and eradicate both of these important global epidemics.
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Evaluation of miLINC to shorten time to treatment for rifampicin-resistant Mycobacterium tuberculosis. Int J Tuberc Lung Dis 2019; 23:980-988. [PMID: 31615604 DOI: 10.5588/ijtld.18.0503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND: Achieving the 90-90-90 targets for tuberculosis (TB) will require interventions that enhance diagnosis, linkage, treatment and adherence to care. As a first step in the process, our team designed a suite of smartphone applications known as miLINC to improve time from diagnosis to treatment initiation in drug-resistant TB patients.SETTING: Three clinical locations in a large, peri-urban district in KwaZulu-Natal, South Africa.OBJECTIVE: To assess the acceptability, feasibility and impact of the miLINC mobile health applications as a solution to reducing the time from presentation to treatment initiation of rifampicin-resistant (RR) TB patients.METHODS: We used a prospective, observational quality improvement evaluation of miLINC's impact among newly diagnosed patients with RR-TB.RESULTS: A convenience sample comprising details of 6341 patients with presumptive TB were entered into miLINC. Of the 631 TB-positive sputum specimens, 41 (6.5%) were found to be RR-TB. The mean time from clinical presentation to RR-TB treatment initiation was 3 days, 21 h, 17 min.CONCLUSION: This is the first study to suggest that the time from presentation to diagnosis and to treatment initiation for patients with RR-TB can be significantly improved using an integrated approach combining technology with appropriate human resources.
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Long-acting or extended-release antiretroviral products for HIV treatment and prevention in infants, children, adolescents, and pregnant and breastfeeding women: knowledge gaps and research priorities. Lancet HIV 2019; 6:e552-e558. [PMID: 31307946 PMCID: PMC7152795 DOI: 10.1016/s2352-3018(19)30147-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2018] [Revised: 03/14/2019] [Accepted: 04/04/2019] [Indexed: 12/31/2022]
Abstract
Antiretroviral agents with long-acting properties have potential to improve treatment outcomes substantially for people living with HIV. In November 2017, the Long acting/Extended Release Antiretroviral Resource Program (LEAP) convened a workshop with the aim of shaping the research agenda and promoting early development of long-acting or extended release products for key populations: pregnant and lactating women, children aged up to 10 years, and adolescents aged 10-19 years. Goals included strategies and principles to ensure that the needs of children, adolescents, and pregnant and lactating women are considered when developing long-acting formulations. Research should focus not only on how best to transition long-acting products to these populations, but also on early engagement across sectors and among stakeholders. A parallel rather than sequential approach is needed when establishing adult, adolescent, and paediatric clinical trials and seeking regulatory approval. Pregnant and lactating women should be included in adult clinical trials. Adolescent-friendly trial design is needed to improve recruitment and retention of young people.
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Internal Medicine Residents' Knowledge and Practice of Pulmonary Tuberculosis Diagnosis. Open Forum Infect Dis 2018; 5:ofy152. [PMID: 30046640 PMCID: PMC6054198 DOI: 10.1093/ofid/ofy152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2018] [Accepted: 06/26/2018] [Indexed: 01/31/2023] Open
Abstract
Background Internal medicine physicians are often the first providers to encounter patients with a new diagnosis of tuberculosis. Given the public health risks of missed tuberculosis cases, assessing internal medicine residents’ ability to diagnose tuberculosis is important. Methods Internal medicine resident knowledge and practice patterns in pulmonary tuberculosis diagnosis at 7 academic hospitals were assessed utilizing (a) a 10-item validated pulmonary tuberculosis diagnosis assessment tool and (b) a retrospective chart review of 343 patients who underwent a pulmonary tuberculosis evaluation while admitted to a resident-staffed internal medicine or infectious disease service. Our primary outcomes were the mean score and percentage of correct responses per assessment tool question, and the percentage of patients who had Centers for Disease Control and Prevention–recommended tuberculosis diagnostic tests obtained. Results Of the 886 residents who received the assessment, 541 responded, yielding a response rate of 61%. The mean score on the assessment tool (SD) was 4.4 (1.6), and the correct response rate was 57% (311/541) or less on 9 of 10 questions. On chart review, each recommended test was obtained for ≤43% (148/343) of patients, other than chest x-ray (328/343; 96%). A nucleic acid amplification test was obtained for 18% (62/343) of patients, whereas 24% (83/343) had only 1 respiratory sample obtained. Twenty patients were diagnosed with tuberculosis. Conclusions Significant knowledge and practice gaps exist in internal medicine residents’ abilities to diagnose tuberculosis. As residents represent the future providers who will be evaluating patients with possible tuberculosis, such deficiencies must be addressed.
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Leveraging information technology to bridge the health workforce gap. Bull World Health Organ 2013; 91:890-2. [PMID: 24347719 PMCID: PMC3853951 DOI: 10.2471/blt.13.118737] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2013] [Revised: 08/04/2013] [Accepted: 08/06/2013] [Indexed: 11/27/2022] Open
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A novel educational strategy targeting health care workers in underserved communities in Central America to integrate HIV into primary medical care. PLoS One 2012; 7:e46426. [PMID: 23115628 PMCID: PMC3480350 DOI: 10.1371/journal.pone.0046426] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 08/30/2012] [Indexed: 11/24/2022] Open
Abstract
Background Current educational strategies to integrate HIV care into primary medical care in Central America have traditionally targeted managers or higher-level officials, rather than local health care workers (HCWs). We developed a complementary online and on-site interactive training program to reach local HCWs at the primary care level in underserved communities. Methods The training program targeted physicians, nurses, and community HCWs with limited access to traditional onsite training in Panama, Nicaragua, Dominican Republic, and Guatemala. The curriculum focused on principles of HIV care and health systems using a tutor-supported blended educational approach of an 8-week online component, a weeklong on-site problem-solving workshop, and individualized project-based interventions. Results Of 258 initially active participants, 225 (225/258 = 87.2%) successfully completed the online component and the top 200 were invited to the on-site workshop. Of those, 170 (170/200 = 85%) attended the on-site workshop. In total, 142 completed all three components, including the project phase. Quantitative and qualitative evaluation instruments included knowledge assessments, reflexive essays, and acceptability surveys. The mean pre and post-essay scores demonstrating understanding of social determinants, health system organization, and integration of HIV services were 70% and 87.5%, respectively, with an increase in knowledge of 17.2% (p<0.001). The mean pre- and post-test scores evaluating clinical knowledge were 70.9% and 90.3%, respectively, with an increase in knowledge of 19.4% (p<0.001). A survey of Likert scale and open-ended questions demonstrated overwhelming participant satisfaction with course content, structure, and effectiveness in improving their HIV-related knowledge and skills. Conclusion This innovative curriculum utilized technology to target HCWs with limited access to educational resources. Participants benefited from technical skills acquired through the process, and could continue working within their underserved communities while participating in the online component and then implement interventions that successfully converted theoretical knowledge to action to improve integration of HIV care into primary care.
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Evaluation of a multimodal, distance learning HIV management course for clinical care providers in India. ACTA ACUST UNITED AC 2012; 11:277-82. [PMID: 22802357 DOI: 10.1177/1545109712451330] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Distance learning is an important tool for training HIV health workers. However, there is limited evidence on design and evaluation of distance learning HIV curricula and tools. We therefore designed, implemented, and evaluated a distance learning course on HIV management for clinical care providers in India. After course completion, participant scores rose significantly from a pretest (78.4% mean correct) compared with the posttest (87.5%, P < .001). After course completion, participants were more likely to be confident in starting an initial antiretroviral (ARV) regimen, understanding ARV toxicities, encouraging patient adherence, diagnosing immune reconstitution syndrome, and monitoring patients on ARV medications (P ≤ .05). All participants (100%) strongly agreed/agreed that they would recommend this course to others, and most of them (96%) strongly agreed/agreed that they would take a course in this format again. A pragmatic approach to HIV curriculum development and evaluation resulted in reliable learning outcomes, as well as learner satisfaction and improvement in knowledge.
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Building a global health education network for clinical care and research. The benefits and challenges of distance learning tools. Lessons learned from the Hopkins Center for Clinical Global Health Education. Infect Dis Clin North Am 2011; 25:385-98. [PMID: 21628053 DOI: 10.1016/j.idc.2011.02.006] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Expanding the capacity for clinical care and health research is a global priority and a global challenge. The Johns Hopkins Center for Clinical Global Health Education (CCGHE) was established in 2005 to provide access to high-quality training to health care providers in resource-limited settings. The CCGHE made a strategic decision to develop, use, and evaluate distance learning platforms to achieve its mission. In the initial years of this new program, several lessons have been learned that may be helpful to other programs considering the use of distance learning programs to expand global health clinical and research capacity.
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A comparison of online versus on-site training in health research methodology: a randomized study. BMC MEDICAL EDUCATION 2011; 11:37. [PMID: 21682858 PMCID: PMC3141795 DOI: 10.1186/1472-6920-11-37] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2010] [Accepted: 06/17/2011] [Indexed: 05/23/2023]
Abstract
BACKGROUND Distance learning may be useful for building health research capacity. However, evidence that it can improve knowledge and skills in health research, particularly in resource-poor settings, is limited. We compared the impact and acceptability of teaching two distinct content areas, Biostatistics and Research Ethics, through either on-line distance learning format or traditional on-site training, in a randomized study in India. Our objective was to determine whether on-line courses in Biostatistics and Research Ethics could achieve similar improvements in knowledge, as traditional on-site, classroom-based courses. SUBJECTS Volunteer Indian scientists were randomly assigned to one of two arms. INTERVENTION Students in Arm 1 attended a 3.5-day on-site course in Biostatistics and completed a 3.5-week on-line course in Research Ethics. Students in Arm 2 attended a 3.5-week on-line course in Biostatistics and 3.5-day on-site course in Research Ethics. For the two course formats, learning objectives, course contents and knowledge tests were identical. MAIN OUTCOME MEASURES Improvement in knowledge immediately and 3-months after course completion, compared to baseline. RESULTS Baseline characteristics were similar in both arms (n = 29 each). Median knowledge score for Biostatistics increased from a baseline of 49% to 64% (p < 0.001) 3 months after the on-site course, and from 48% to 63% (p = 0.009) after the on-line course. For the on-site Research Ethics course, median score increased from 69% to 83% (p = 0.005), and for the on-line Research Ethics course from 62% to 80% (p < 0.001). Three months after the course, median gains in knowledge scores remained similar for the on-site and on-line platforms for both Biostatistics (16% vs. 12%; p = 0.59) and Research Ethics (17% vs. 13%; p = 0.14). CONCLUSION On-line and on-site training formats led to marked and similar improvements of knowledge in Biostatistics and Research Ethics. This, combined with logistical and cost advantages of on-line training, may make on-line courses particularly useful for expanding health research capacity in resource-limited settings.
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Upregulation of FcepsilonRI on human basophils by IgE antibody is mediated by interaction of IgE with FcepsilonRI. J Allergy Clin Immunol 1999; 104:492-8. [PMID: 10452777 DOI: 10.1016/s0091-6749(99)70399-4] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
BACKGROUND IgE is now known to upregulate the expression of FcepsilonRI on human basophils. It is not known which receptor on basophils mediates this process of upregulation. OBJECTIVE We sought to determine whether galectin-3, FcepsilonRII (CD23), or FcepsilonRI were involved in the upregulation of FcepsilonRI by IgE. METHODS The role of galectin-3 was examined by measuring the influence of alpha-lactose on upregulation. Basophils were examined for expression of FcepsilonRII (CD23) by flow cytometry and messenger (m)RNA expression. Functional discrimination between binding to FcepsilonRII or FcepsilonRI was examined through the use of mutant IgE-Fc fragments or anti-FcepsilonRII antibody. RESULTS Upregulation of FcepsilonRI on basophils in the presence of IgE was not altered by coincubation with alpha-lactose, eliminating a role for galectin-3. Basophils were not found to express FcepsilonRII, as determined by flow cytometry with enriched basophil preparations or RT-PCR with highly purified basophil preparations. A mutant of the Fc fragment of IgE (IgE-Fc), which binds to FcepsilonRI with a greater than 10-fold lower affinity than IgE or wild-type IgE-Fc but exhibits no change in affinity for FcepsilonRII, allowed us to distinguish between the functions of the two Fc receptors. The mutant (R334S; Henry et al 1997) was required at about 30-fold higher concentration than the wild-type IgE-Fc for the same stimulation of FcepsilonRI expression on basophils, thus excluding a role for FcepsilonRII in the response. In addition, treatment of basophils with anti-FcepsilonRII antibody (MHM6), which is known to be competitive with IgE, had no effect on the expression of FcepsilonRI or the ability of IgE to upregulate expression of FcepsilonRI. CONCLUSION Collectively, these data indicate that IgE interacts with FcepsilonRI to upregulate its expression on human basophils.
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In vitro regulation of FcepsilonRIalpha expression on human basophils by IgE antibody. Blood 1998; 91:1633-43. [PMID: 9473229] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In vivo studies suggested the possibility of an IgE-dependent regulation of high-affinity (FcepsilonRI) IgE receptor expression on basophils. The current studies extend these observations to in vitro cultures of human basophils. Incubation of basophils for 3 to 4 weeks resulted in a slow dissociation of IgE antibody, during which time FcepsilonRI expression decreased, as measured by flow cytometry using the anti-FcepsilonRIalpha monoclonal antibody, 22E7, or by measuring FcRIalpha mass by Western blotting of whole-cell lysates. Culture of basophils with IgE resulted in upregulation of FcepsilonRIalpha expression by both flow cytometry and Western blotting of whole-cell lysates. Upregulation followed a linear time course during 2 weeks of culture. The relative increase in FcepsilonRIalpha density depended on the starting density; with starting densities of FcepsilonRIalpha of 10,000 to 170,000 per basophil, the upregulation varied 20- to 1.1-fold, respectively. Upregulation occurred in high-purity basophils, was not influenced by IgG at concentrations up to 1 mg/mL, and was inhibited by dimeric IgE. Heat-inactivated IgE was less effective and the monoclonal antibody CGP51901 that prevents IgE binding to FcepsilonRIalpha blocked the ability of IgE to induce upregulation. The dose-response curve for IgE-induced upregulation had an effective concentration50 of 230 ng/mL. Although the receptor through which IgE induces this upregulation is not yet known, several characteristics suggest that the upregulation is mediated by IgE interacting through FcepsilonRIalpha itself.
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Down-regulation of Fc(epsilon)RI expression on human basophils during in vivo treatment of atopic patients with anti-IgE antibody. THE JOURNAL OF IMMUNOLOGY 1997. [DOI: 10.4049/jimmunol.158.3.1438] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Abstract
Treatment of allergic disease by decreasing circulating IgE with anti-IgE Abs is currently under clinical study. Based on previous unrelated studies, it appeared likely that Fc(epsilon)RI expression on basophils and mast cells might also be regulated by levels of circulating IgE Ab. Therefore, the expression of IgE and Fc(epsilon)RI on human basophils was examined in 15 subjects receiving humanized anti-IgE mAb intravenously. Treatment with the anti-IgE mAb decreased free IgE levels to 1% of pretreatment levels and also resulted in a marked down-regulation of Fc(epsilon)RI on basophils. Median pretreatment densities of Fc(epsilon)RI were approximately 220,000 receptors per basophil and after 3 mo of treatment, the densities had decreased to a median of 8,300 receptors per basophil. Flow cytometric studies, conducted in parallel, showed similar results and also showed in a subset of 3 donors that receptors decreased with a t1/2 of approximately 3 days. The responsiveness of the cells to IgE-mediated stimulation using anti-IgE Ab was marginally decreased (approximately 40%) while the response of the same cells to stimulation with dust mite Ag, Dermatophagoides farinae, was reduced by approximately 90%. One possible explanation for these results is that Fc(epsilon)RI density is directly or indirectly regulated by plasma-free IgE levels.
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Down-regulation of Fc(epsilon)RI expression on human basophils during in vivo treatment of atopic patients with anti-IgE antibody. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 1997; 158:1438-45. [PMID: 9013989] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Treatment of allergic disease by decreasing circulating IgE with anti-IgE Abs is currently under clinical study. Based on previous unrelated studies, it appeared likely that Fc(epsilon)RI expression on basophils and mast cells might also be regulated by levels of circulating IgE Ab. Therefore, the expression of IgE and Fc(epsilon)RI on human basophils was examined in 15 subjects receiving humanized anti-IgE mAb intravenously. Treatment with the anti-IgE mAb decreased free IgE levels to 1% of pretreatment levels and also resulted in a marked down-regulation of Fc(epsilon)RI on basophils. Median pretreatment densities of Fc(epsilon)RI were approximately 220,000 receptors per basophil and after 3 mo of treatment, the densities had decreased to a median of 8,300 receptors per basophil. Flow cytometric studies, conducted in parallel, showed similar results and also showed in a subset of 3 donors that receptors decreased with a t1/2 of approximately 3 days. The responsiveness of the cells to IgE-mediated stimulation using anti-IgE Ab was marginally decreased (approximately 40%) while the response of the same cells to stimulation with dust mite Ag, Dermatophagoides farinae, was reduced by approximately 90%. One possible explanation for these results is that Fc(epsilon)RI density is directly or indirectly regulated by plasma-free IgE levels.
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Pharmacologic control of histamine release from human basophils induced by platelet-activating factor. Int Arch Allergy Immunol 1993; 102:383-90. [PMID: 7694703 DOI: 10.1159/000236587] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
We studied the effect of several compounds that influence different cell activation steps on platelet-activating factor (PAF)-induced basophil histamine secretion. Isobutylmethylxanthine (1-100 microM), dimaprit (1-100 microM) and dibutyryl adenosine 3',5'-cyclic phosphate (cAMP; 0.01-1 mM), that increase intracellular cAMP levels, concentration-dependently inhibited PAF-elicited histamine release. Rolipram (phosphodiesterase, PDE, isotype IV inhibitor; 0.1 nM-10 microM) potently inhibited histamine secretion activated by PAF, whereas SKF95654 (PDE III inhibitor; 0.01-10 microM) was ineffective. The kinase inhibitor, staurosporine (0.1-100 nM), enhanced PAF-induced basophil histamine release, whereas the G-protein inhibitor, pertussis toxin (1 microgram/ml), had an inhibitory effect. The specific lipoxygenase inhibitor, AA-861 (0.1-10 microM), inhibited PAF-activated histamine release, while the leukotriene A4 hydrolase inhibitor, bestatin (100 microM), had only a marginal effect. Finally, the Ca2+ channel entry blockers, verapamil (3-30 microM) and zinc (1.5-50 microM), inhibited PAF-induced histamine release. These results suggest that PAF is a unique secretagogue for human basophils unlike antigen, anti-IgE or univalent stimuli.
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Abstract
The effects of a putatively specific 5-lipoxygenase inhibitor, 2(12-hydroxydodeca-5,10-dinyl)-3,5,6-trimethyl-1,4-benzoquin one (AA-861), and its major metabolite, M-I, were assessed using anti-IgE activated human basophils, lung mast cells and skin mast cells. In basophils and lung mast cells, no effects on histamine release were observed, whereas leukotriene C4 (LTC4) production was inhibited (IC50 values less than 1 microM). In addition, prostaglandin D2 (PGD2) production was inhibited in lung mast cells (IC50 congruent to 5 microM). In contrast, in skin mast cells both histamine release and PGD2 production were reduced by AA-861 and M-I, with IC50 values of congruent to 5 and 0.4 microM for histamine and PGD2, respectively. These data reveal biochemical heterogeneity among human histamine-containing cells and underscore the necessity of assessing a pharmacologic agonist in relevant cell systems.
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