A influência da saliva do vetor Lutzomyia longipalpis na infecção de macrófagos por Leishmania infantum chagasi

Abstract

Parasitic protozoa of the genus Leishmania are transmitted when an infected sand fly takes a blood meal from a vertebrate host. During the blood-feeding process sand flies salivate into the host skin. Vector saliva presents active elements crucial for hematophagy that act directly on the host immune system, such as vasodilators, anticoagulants and chemotactic molecules. It is presumed that vector saliva exert influence on distinct phases throughout the Leishmania infectious cycle. Therefore, our objective was to evaluate the influence of Lutzomyia longipalpis vector saliva on Leishmania infantum chagasi infection in the macrophage cell line RAW 264.7. To obtain saliva, sand flies were collected from rural areas of Chapadinha County, province of Maranhão, Brasil, transported to the lab, sexed, and the non-blooded females placed in B.O.D. incubator at 27ºC. The salivary glands were dissected out under sterile phosphate-buffered saline (PBS) solution, sonicated, centrifuged and the supernatants collected and stored at -80ºC. For the in vitro experiments, RAW 264.7 macrophages were cultivated in chamber slides and stimulated with saliva at three stages of infection: before, during and post L. infantum chagasi infection in a 10:1 parasite: macrophage ratio. Subsequently, the chamber slides were incubated in 5% CO2 atmosphere at 37ºC, for 48 hours. Our findings showed that the salivastimulated cells before and during L. infantum chagasi infection showed the highest number of Leishmania-infected macrophages. It was observed that the salivastimulated macrophages produced high amount of nitric oxide at all stages of infection, expressly in the saliva-stimulated cells during Leishmania infection. Regarding the cytokine production, TNF-α was detected in the saliva-stimulated cells during and post Leishmania infection. However, the saliva-exposed macrophages produced more IL-6 before Leishmania infection than the other two stages. Furthermore, we show that saliva affects both Leishmania proliferation and infectivity. Therefore, saliva can modulate the immune response of macrophages and enhance Leishmania infection, crucial events for parasite survival.