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Parkash V, Ashwin H, Sadlova J, Vojtkova B, Jones G, Martin N, Greensted E, Allgar V, Kamhawi S, Valenzuela JG, Layton AM, Jaffe CL, Volf P, Kaye PM, Lacey CJN. A clinical study to optimise a sand fly biting protocol for use in a controlled human infection model of cutaneous leishmaniasis (the FLYBITE study). Wellcome Open Res 2021; 6:168. [PMID: 34693027 PMCID: PMC8506224 DOI: 10.12688/wellcomeopenres.16870.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2021] [Indexed: 02/02/2023] Open
Abstract
Background: Leishmaniasis is a globally important yet neglected parasitic disease transmitted by phlebotomine sand flies. With new candidate vaccines in or near the clinic, a controlled human challenge model (CHIM) using natural sand fly challenge would provide a method for early evaluation of prophylactic efficacy. Methods : We evaluated the biting frequency and adverse effects resulting from exposure of human volunteers to bites of either Phlebotomus papatasi or P. duboscqi, two natural vectors of Leishmania major. 12 healthy participants were recruited (mean age 40.2 ± 11.8 years) with no history of significant travel to regions where L. major-transmitting sand flies are prevalent. Participants were assigned to either vector by 1:1 allocation and exposed to five female sand flies for 30 minutes in a custom biting chamber. Bite frequency was recorded to confirm a bloodmeal was taken. Participant responses and safety outcomes were monitored using a visual analogue scale (VAS), clinical examination, and blood biochemistry. Focus groups were subsequently conducted to explore participant acceptability. Results: All participants had at least one successful sand fly bite with none reporting any serious adverse events, with median VAS scores of 0-1/10 out to day 21 post-sand fly bite. Corresponding assessment of sand flies confirmed that for each participant at least 1/5 sand flies had successfully taken a bloodmeal (overall mean 3.67±1.03 bites per participant). There was no significant difference between P. papatasi and P. duboscqi in the number of bites resulting from 5 sand flies applied to human participants (3.3±0.81 vs 3.00±1.27 bites per participant; p=0.56) . In the two focus groups (n=5 per group), themes relating to positive participant-reported experiences of being bitten and the overall study, were identified. Conclusions: These results validate a protocol for achieving successful sand fly bites in humans that is safe, well-tolerated and acceptable for participants. Clinicaltrials.gov registration: NCT03999970 (27/06/2019).
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Affiliation(s)
- Vivak Parkash
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
- Department of Infection and Tropical Medicine, Sheffield Teaching Hospitals NHS Foundation Trust, Sheffield, UK
| | - Helen Ashwin
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Jovana Sadlova
- Department of Parasitology, Charles University, Prague, Czech Republic
| | - Barbora Vojtkova
- Department of Parasitology, Charles University, Prague, Czech Republic
| | - Georgina Jones
- School of Social Sciences, Leeds Beckett University, Leeds, UK
| | - Nina Martin
- School of Social Sciences, Leeds Beckett University, Leeds, UK
| | - Elizabeth Greensted
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Victoria Allgar
- Peninsula Medical School, University of Plymouth, Plymouth, UK
| | - Shaden Kamhawi
- Laboratory of Malaria and Vector Research, National Institutes of Health, Rockville, MD, USA
| | - Jesus G. Valenzuela
- Laboratory of Malaria and Vector Research, National Institutes of Health, Rockville, MD, USA
| | - Alison M. Layton
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Charles L. Jaffe
- Department of Microbiology and Molecular Genetics, The Hebrew University – Hadassah Medical School, Jerusalem, Israel
| | - Petr Volf
- Department of Parasitology, Charles University, Prague, Czech Republic
| | - Paul M. Kaye
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
| | - Charles J. N. Lacey
- York Biomedical Research Institute, Hull York Medical School, University of York, York, N.Yorks, YO10 5DD, UK
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Walsh GM, Annunziato L, Frossard N, Knol K, Levander S, Nicolas JM, Taglialatela M, Tharp MD, Tillement JP, Timmerman H. New insights into the second generation antihistamines. Drugs 2001; 61:207-36. [PMID: 11270939 DOI: 10.2165/00003495-200161020-00006] [Citation(s) in RCA: 76] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Second generation antihistamines are recognised as being highly effective treatments for allergy-based disease and are among the most frequently prescribed and safest drugs in the world. However, consideration of the therapeutic index or the benefit/risk ratio of the H1 receptor antagonists is of paramount importance when prescribing this class of compounds as they are used to treat non-life threatening conditions. There are many second generation antihistamines available and at first examination these appear to be comparable in terms of safety and efficacy. However, the newer antihistamines in fact represent a heterogeneous group of compounds, having markedly differing chemical structures, adverse effects, half-life, tissue distribution and metabolism, spectrum of antihistaminic properties, and varying degrees of anti-inflammatory effects. With regard to the latter, there is growing awareness that some of these compounds might represent useful adjunct medications in asthma therapy. In terms of safety issues, the current second generation grouping includes compounds with proven cardiotoxic effects and others with the potential for adverse drug interactions. Moreover, some of the second generation H1 antagonists have given cause for concern regarding their potential to cause a degree of somnolence in some individuals. It can be argued, therefore, that the present second generation grouping is too large and indistinct since this was based primarily on the concept of separating the first generation sedating compounds from nonsedating H1 antagonists. Although it is too early to talk about a third generation grouping of antihistamines, future membership of such a classification could be based on a low volume of distribution coupled with a lack of sedating effects, drug interactions and cardiotoxicity.
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Affiliation(s)
- G M Walsh
- Department of Medicine and Therapeutics, University of Aberdeen Medical School, Scotland.
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