Malek Trimèche Poster 2025

Dr Malek Trimèche

Institut Pasteur de Tunis, Tunisia

Effect of Phlebotomus papatasi Salivary Gland on the Development of Zoonotic Cutaneous Leishmaniasis in the Balb/c Mice Model

Poster Abstract

Sandfly saliva, co-inoculated with Leishmania (L.) parasites during a blood meal, has been shown to exacerbate L. major infection, leading to zoonotic cutaneous leishmaniasis (ZCL). However, pre-sensitization with salivary glands (SG) has provided significant protection. Therefore, we intended to evaluate the potential protective effect of immunization with sandfly SGs against L. major infection in BALB/c mice by testing different immunization and/or challenge models: (1) The sandfly colony used for the preparation of the salivary gland homogenate (SGH) administered during immunization or infection. (2) The dose of SGH used (2 or 0.2 pairs). (3) The challenge route (intradermal injection in the ear or subcutaneous injection in the footpad).

Lesion size was measured weekly for mice belonging to the different studied groups.

Parasite load at the infection site was also evaluated. Sera were collected before the L. major challenge (Day0) and at different time points post-infection (Weeks 1, 10, 13, 20) to assess the kinetics of total IgG, IgG1 and IgG2a, anti-SGH and anti-Leishmania antibodies.

No protection was observed in BALB/c mice infected via subcutaneous inoculation with 106 parasites associated with 2 or 0.2 pairs of SGH from different generations (F0, F4, or F20). SG from all generations seem to exacerbate ZCL lesions, even in immunized groups, with the most significant effect seen in the SG of the older generation. Additionally, specific humoral responses to SGH and Leishmania suggested a Th2-type immunological profile, characterized by lesion exacerbation and a high parasite load. However, only immunization with SG from the F4 generation induced the production of IgG2a in addition to IgG1, suggesting a mixed anti-SGH response. In contrast, ear challenge of BALB/c mice with a low dose of SGH (0.2 pairs) co-inoculated with Leishmania parasites (1.000), conferred protection against ZCL in mice immunized with SGH from different generations.

Keywords: Phlebotomus papatasi; Salivary Gland; Zoonotic Cutaneous Leishmaniasis; BALB/c

Biography

Dr Malek Trimèche is a post-doctoral researcher working on the development of an mRNA vaccine against zoonotic cutaneous leishmaniasis. She is interested in evaluating the immunogenicity and efficacy of various candidate vaccines for cutaneous leishmaniasis.

During her doctoral research, she studied the effect of the saliva on the development of zoonotic cutaneous leishmaniasis in a mouse model following immunization with homogenized salivary glands from different generations of Phlebotomus papatasi. She is also involved in other projects that assess sandfly vaccines as a strategy for controlling hematophagous vectors.