Toxoplasma gondii-Induced Neutrophil Extracellular Traps Amplify the Innate and Adaptive Response.

Toxoplasmosis affects one-third of the human population worldwide. Humans are accidental hosts and are infected after consumption of undercooked meat and water contaminated with Toxoplasma gondii cysts and oocysts, respectively. Neutrophils have been shown to participate in the control of T. gondii infection in mice through a variety of effector mechanisms, such as reactive oxygen species (ROS) and neutrophil extracellular trap (NET) formation. However, few studies have demonstrated the role of neutrophils in individuals naturally infected with T. gondii. In the current study, we evaluated the activation status of neutrophils in individuals with acute or chronic toxoplasmosis and determined the role of T. gondii-induced NET formation in the amplification of the innate and adaptive immune responses. We observed that neutrophils are highly activated during acute infection through increased expression of CD66b. Moreover, neutrophils from healthy donors (HDs) cocultured with tachyzoites produced ROS and formed NETs, with the latter being dependent on glycolysis, succinate dehydrogenase, gasdermin D, and neutrophil elastase. Furthermore, we observed elevated levels of the chemokines (CXC motif) CXCL8 and (CC motif) CCL4 ligands in plasma from patients with acute toxoplasmosis and production by neutrophils from HDs exposed to T. gondii. Finally, we showed that T. gondii-induced NETs activate neutrophils and promote the recruitment of autologous CD4+ T cells and the production of interferon gamma (IFN-γ), tumor necrosis factor (TNF), interleukin 6 (IL-6), IL-17, and IL-10 by peripheral blood mononuclear cells. In conclusion, we demonstrated that T. gondii activates neutrophils and promotes the release of NETs, which amplify human innate and adaptive immune responses. IMPORTANCE Approximately one-third of the human population is estimated to be chronically infected with the obligate intracellular parasite Toxoplasma gondii. Humans are accidental hosts that are infected with T. gondii after consumption of undercooked meat or contaminated water. Neutrophils have been shown to control T. gondii growth by different mechanisms, including neutrophil extracellular traps (NETs). In the current study, we observed that neutrophils are highly activated during acute toxoplasmosis. We also determined that T. gondii-induced NETs are dependent on the energetic profile of neutrophils as well as the production of ROS and gasdermin D (GSDMD) cleavage. In addition, we showed that T. gondii-induced NETs activate neutrophils, promote the recruitment of autologous CD4+ T cells, and induce the production of cytokines by peripheral blood mononuclear cells, amplifying the innate and adaptive immune responses.

Aspectos morfológicos e ultraestruturais de células sanguíneas de Crotalus durissus terrificus / Morphological and ultrastructural aspects of Crotalus durissus terrificus blood cells

A avaliação hematológica, de importância comprovada como um meio auxiliar de diagnóstico ao clínico de pequenos animais domésticos, vem se tornando comum em animais selvagens não apenas para a clínica, mas para a avaliação do manejo e como estudo auxiliar para a fisiologia das várias espécies. Tendo em vista o aumento da demanda para a produção de várias drogas de importância farmacêutica, a criação de serpentes peçonhentas vem se tornando comum a ponto destes animais já serem reconhecidos como sendo de produção. O conhecimento do manejo e da clínica destes animais ainda é escasso e a mortalidade é elevada nos criatórios, tornando urgente a ampliação destes. Embora alguns estudos hematológicos já tenham sido realizados em cascavéis (Crotalus durissus) os dados analisados ainda são insipientes, notadamente em relação à caracterização das células do sangue e poucos estudos em microscopia eletrônica foram realizados em serpentes. Com o objetivo de caracterizar as células sanguíneas morfologicamente, sob microscopia óptica e ultraestrutural, foram coletadas amostras de sangue de 52 de indivíduos da subespécie Crotalus durissus terrificus para a realização de esfregaços sanguíneos e avaliação ultraestrutural. Concluiu-se que a coloração hematológica de Giemsa permite a avaliação morfológica e a diferenciação das células sanguíneas em serpentes assim como a visualização de hemoparasitos. A avaliação ultraestrutural permite evidenciar as organelas celulares e a diferenciação entre as células, inclusive entre os tipos leucocitários, porém ainda são necessários outros estudos para que seja elucidada a hipótese da existência dos eosinófilos na espécie estudada assim como é necessária melhor caracterização dos grânulos dos azurófilos para que se confirme uma possível diferença entre os monócitos típicos e os azurófilos.(AU)

Hematological evaluation, important for the diagnostic by the small domestic animal clinician, has become common in wildlife clinic, and for handling and study of the physiology of various species. Given the increased demand for drug production of pharmaceutical importance, the breeding of venomous snakes has become common and is already recognized as production. Knowledge of the management and clinics of snakes is still insufficient and their mortality is high. Although some hematological studies have already been conducted in the rattlesnake (Crotalus durissus), the analyzed data are still insufficient, especially with respect to the characterization of blood cells, and few electron microscopy studies have been performed on snakes. In order to characterize morphologically blood cells with light and ultrastructural microscopy, blood samples from 52 individuals of subspecies of Crotalus durissus terrificus were collected to perform blood smears and ultrastructural evaluation. It was concluded that hematologic Giemsa staining allows morphological evaluation and differentiation of the blood cells as well as of snake hemoparasites. The ultrastructural evaluation will highlight the cell organelles and differentiation between cells, including leukocyte types; although still further studies are needed to elucidate the hypothesis of eosinophils in the species studied as also is necessary a better characterization of azurophilic beads to confirm a possible difference between the typical monocyte and the azurophilic.(AU)

Development of ostrich thrombocytes and monocyte-derived macrophages in culture and the control of Toxoplasma gondii reproduction after macrophage activation.

Raising ostriches became an important economic activity after their products became commodities. The health of farm animals is of paramount importance, so assessing basic immunological responses is necessary to better understand health problems. We developed a method to obtain ostrich thrombocytes and macrophages. The thrombocytes died by apoptosis after 48 h in culture, and the macrophages expanded in size and increased the number of acidic compartments. Macrophages were activated by chicken interferon-γ, producing high levels of nitric oxide. Toxoplasma gondii was able to infect these macrophages, and activation controlled parasitic reproduction. T. gondii, however, persisted in these cells, and infection reduced the production of nitric oxide. These results are important for the future assessment of the basic cellular and immunobiology of ostriches and demonstrate T. gondii suppression of nitric oxide production.

Hematological parameters of Ameiva ameiva (Reptilia: Teiidae) naturally infected with hemogregarine: confirmation of monocytosis.

Little is known on how hematozoan infection changes reptile hematology. The lizard Ameiva ameiva is widely distributed in the Americas and is infected by hematozoan parasites. Previous studies on this lizard have shown that the parasite of monocytes causes a variety of ultrastructural changes in infected host cells. The present study reports that this infection does not cause any change to the erythrocytic values. However, a marked increase in the number of leukocytes (especially monocytes) was detected. This indicates that the hemogregarine not only modulates the infected monocyte, but also increases the blood pool of this leukocyte. A Plasmodium sp was also found infecting erythrocytes of one lizard.