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Safety and reactogenicity of a controlled human infection model of sand fly-transmitted cutaneous leishmaniasis

ABSTRACT: The leishmaniases are globally important parasitic diseases for which no human vaccines are currently available. To facilitate vaccine development, we conducted an open label observational study to establish a controlled human infection model of sand fly-transmitted cutaneous leishmaniasis caused by L. major. Between 24th January and 12th August 2022, we exposed 14 (8F, 6M) participants to infected sand flies. The primary objective was to demonstrate effectiveness (attack rate) and safety (absence of CL lesion at 12 months), whereas secondary and exploratory objectives included rate of lesion development, parasite load and analysis of local immune responses using immunohistology and spatial transcriptomics. We estimated a take rate for CL development of 64% (9/14) based on all participants, increasing to 82% (9/11) if only participants with confirmed bites are included. Lesion development was terminated by therapeutic biopsy in 10 participants with confirmed bites. 30% (3/10) had either one (2/10) or two (1/10) lesion recurrences between 4-8 months after biopsy that were treated successfully with cryotherapy. No severe or serious adverse events were recorded, but scarring was evident as expected. All participants were lesion-free at long-term (>12 month) follow up. We provide the first comprehensive map of immune cell distribution and cytokine/chemokine expression in human CL lesions, revealing discrete immune niches. This controlled human infection model offers opportunities for rapid vaccine candidate selection and a greater understanding of immune-mediated protection and pathology.

ORGANISM(S): Homo sapiens

PROVIDER: GSE263298 | GEO | 2024/04/30

REPOSITORIES: GEO

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Project description:Description: Experimental exposure to malaria parasites can lead to development of protective immunity, providing a foothold for the development of a malaria vaccine. The goal of this study is to investigate immune transcriptional profiles associated with malaria protective immune responses induced by experimental Chemo-Prophylaxis and Sporozoites (CPS) immunization of P. falciparum-naive human volunteers. Samples for this study were obtained from a CPS-immunization study conducted in 2011 (ClinicalTrials.gov Identifier: NCT01218893), where healthy volunteers received CPS-immunization with bites from different numbers of P. falciparum-infected mosquitoes (three times 15 (n=5), 10 (n=9) or 5 (n=10)). Five control subjects received uninfected mosquito bites under chloroquine prophylaxis. Fifteen weeks after discontinuation of chloroquine prophylaxis, all volunteers were challenged by exposure to infected mosquito bites. Study Design: A maximum of 30 volunteers were divided into four groups. All volunteers received weekly chloroquine prophylaxis for a period of 13 weeks (91 days). During these 13 weeks, on days 8, 36 and 64 they were exposed to the bites of 15 mosquitoes. Group 1 (n=5, positive control) received three CPS immunizations by 15 mosquitoes infected with P. falciparum sporozoites. Group 2 (n=10) received three times 10 bites from infected mosquitoes and 5 bites from uninfected mosquitoes. Group 3 (n=10) received three times 5 bites from infected mosquitoes and 10 bites from uninfected mosquitoes. Group 4 (n=5), the negative control, received three placebo immunizations with 15 bites of uninfected mosquitoes. Fifteen weeks after discontinuation of chloroquine prophylaxis, all 30 volunteers were challenged at day 196 by the bites of 5 infectious mosquitoes and followed for 21 days. All subjects were treated with chloroquine 21 days after challenge or whenever they had a positive thick smear during that period.

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Safety and reactogenicity of a controlled human infection model of sand fly-transmitted cutaneous leishmaniasis

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