Immune response profiles from humans experimentally exposed to Phlebotomus duboscqi bites

• Published in: Frontiers in immunology Vol. 15; p. 1335307
• Main Authors: de Araujo, Fernanda Fortes, Abdeladhim, Maha, Teixeira, Clarissa, Hummer, Kelly, Wilkerson, Matthew D, Ressner, Roseanne, Lakhal-Naouar, Ines, Ellis, Michael W, Meneses, Claudio, Nurmukhambetova, Saule, Gomes, Regis, Tolbert, W David, Turiansky, George W, Pazgier, Marzena, Oliveira, Fabiano, Valenzuela, Jesus G, Kamhawi, Shaden, Aronson, Naomi
• Format: Journal Article
• Language: English
• Published: Switzerland Frontiers Media S.A 03.04.2024
• Subjects: Animals; antigen; Antigens; Humans; immune response; Immunity, Cellular; Immunoglobulin G; Immunology; Insect Bites and Stings; Leukocytes, Mononuclear; P. duboscqi; Phlebotomus - parasitology; saliva; Salivary Proteins and Peptides; vaccine; saliva; vaccine; P. duboscqi; antigen; immune response
• ISSN: 1664-3224; 1664-3224
• DOI: 10.3389/fimmu.2024.1335307

Cutaneous leishmaniasis is a neglected vector-borne parasitic disease prevalent in 92 countries with approximately one million new infections annually. Interactions between vector saliva and the human host alter the response to infection and outcome of disease. To characterize the human immunological responses developed against saliva of , a vector, we repeatedly exposed the arms of 14 healthy U.S volunteers to uninfected bites. Blood was collected a week after each exposure and used to assess total IgG antibodies against the proteins of salivary gland homogenate (SGH) and the levels of IFN-gamma and IL-10 from peripheral blood mononuclear cells (PBMCs) stimulated with SGH or recombinant sand fly proteins. We analyzed skin punch biopsies of the human volunteer arms from the insect bite site and control skin site after multiple exposures (four volunteers) using immunohistochemical staining. A variety of immediate insect bite skin reactions were observed. Late skin reactions to insect bites were characterized by macular hyperpigmentation and/or erythematous papules. Hematoxylin and eosin staining showed moderate mononuclear skin infiltrate with eosinophils in those challenged recently (within 2 months), eosinophils were not seen in biopsies with recall challenge (6 month post bites). An increase in plasma antigen-specific IgG responses to SGH was observed over time. Western Blot results showed strong plasma reactivity to five salivary proteins. Importantly, volunteers developed a cellular immunity characterized by the secretion of IFN-gamma upon PBMC stimulation with SGH and recombinant antigens. Our results demonstrate that humans mounted a local and systemic immune response against salivary proteins. Specifically, PduM02/SP15-like and PduM73/adenosine deaminase recombinant salivary proteins triggered a Th1 type immune response that might be considered in future development of a potential vaccine.