P35 - Parasitología

Small extracellular vesicles from Trypanosoma cruzi-infected macrophages modulate early infection course in vivo

Poulakidas SN¹ - Vázquez ME¹ - Cosenza M² - Ramos F¹ - Acuña LA² - Pérez Brandán C¹ - Parodi CM¹ - Tekiel V² - Mesías AC¹

1) Instituto de Patología Experimental “Dr. Miguel Ángel Basombrío”, CONICET - Universidad Nacional de Salta, Salta, Argentina.
2) Instituto de Investigaciones Biotecnológicas, EByN, UNSAM-CONICET, San Martín, Buenos Aires, 1650, Argentina.
Contacto: sandrapoulakidas@gmail.com

Macrophages (Mφs) are key cells in the early stages of Trypanosoma cruzi infection, orchestrating innate and adaptive immune responses. Within the immune system, cell communication occurs simultaneously at multiple levels, and extracellular vesicles (EVs) play a significant part in this context. In fact, once Mφs become infected, they release increased amounts of host-derived EVs, impacting the surrounding environment. Here, we studied the role of small EVs in the context of acute in vivo infection, evaluating two distinct parasite strains: the virulent CL Brener and the attenuated TCC. EVs were isolated through an ultraconcentration and gradient ultracentrifugation protocol and subsequently, characterized by transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA), and Western blot to delineate the EV populations. In previous work, we observed that when internalized by naïve macrophages in vitro, small EVs derived from TCC-infected cells promoted an environment unfavorable to parasite spread, characterized by an M1-like cytokine profile. In contrast, EVs from cells infected with the virulent CL Brener strain fostered a more permissive environment, with higher phagocytic activity that could facilitate parasite entry and persistence. Also, these EVs caused a reduced migratory capacity, potentially hindering a timely immune response and favoring the establishment of a parasite replication niche. With this idea in mind, we conducted animal infections, administering small EVs from either CL Brener- or TCC-infected Mφs. Mice inoculated with small EVs derived from CL Brener-infected cells presented higher parasitemia values (p<0.05 at 21 days post- infection). Conversely, animals receiving EVs from Mφs infected with the attenuated strain showed a minor and retarded parasitemia peak, a finding also observed through analysis of the area under the curves. However, when analyzing parasite load by quantitative real-time PCR, we did not observe significant differences. Our results suggest that virulent strains may prompt immune cells to produce EVs carrying signals that facilitate early parasite dissemination, prior to the establishment of a robust adaptive response. In this context, host-derived EVs play a significant role in shaping the course of infection. However, they appear insufficient to trigger a response fully capable of controlling pathogen spread on their own.

Palabras clave: Enfermedad de Chagas, Trypanosoma cruzi, Macrófagos, Vesículas extracelulares