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Signal regulatory protein α (SIRPα) is an immunoreceptor expressed in myeloid innate immune cells that signals for inhibition of both phagocytosis and inflammatory response. Malaria parasites have evolutionarily selected multiple mechanisms that allow them to evade host immune defenses, including the modulation of cells belonging to innate immunity. Notwithstanding, little attention has been given to SIRPα in the context of immunosuppressive states induced by malaria. The present study attempted to investigate if malaria parasites are endowed with the capacity of modulating the expression of SIRPα on cells of innate immune system. Human peripheral blood mononuclear cells (PBMC) from healthy individuals were incubated in the presence of lipopolysaccharide (LPS) or crude extracts of P. falciparum or P. vivax and then, the expression of SIRPα was evaluated by flow cytometry. As expected, LPS showed an inhibitory effect on the expression of SIRPα in the population of monocytes, characterized by cell morphology in flow cytometry analysis, while Plasmodium extracts induced a significant positive modulation. Additional phenotyping of cells revealed that the modulatory potential of Plasmodium antigens on SIRPα expression was restricted to the population of monocytes (CD14+CD11c+), as no effect on myeloid dendritic cells (CD14−CD11c+) was observed. We hypothesize that malaria parasites explore inhibitory signaling of SIRPα to suppress antiparasitic immune responses contributing to the establishment of infection. Nevertheless, further studies are still required to better understand the role of SIRPα modulation in malaria immunity and pathogenesis.

The aim of this study was to determine the occurrence of emerging arthropod-borne pathogens Anaplasma, Ehrlichia and Rickettsia infection in ticks (Acari: Ixodidae) and fleas (Insecta: Siphonaptera) collected from dogs and horses within municipality of Itaboraí, Rio de Janeiro State, Southern Brazil. Samples from 280 ticks and two fleas were subjected to family or/and genus specific PCR for Anaplasmataceae, Ehrlichia and Rickettsia, followed by DNA sequencing to ensure pathogen identity. In ticks Rhipicephalus sanguineus collected from dogs the DNAof Anaplasma platys and Ehrlichia canis was detected in 6.8% and 2.2% samples respectively. In two R. sanguineus confection with two pathogens was observed. In Dermacentor nitens ticks, collected from horses Francisella-like endosymbiont was found in 42.8% samples. DNA of Rickettsia felis and Wolbachia pipetens was detected in fleas Ctenocephalides canis fleas. No DNA of Rickettsia was found in tested ticks. The findings contribute to our knowledge of tick-borne bacteria, ticks and endosymbionts distribution in Brazil.

In the present study, we investigated the genetic diversity of Plasmodium vivax metacaspase 1 ( Pv MCA1) catalytic domain in two municipalities of the main malaria hotspot in Brazil, i.e., the Juruá Valley, and observed complete sequence identity among all P. vivax field isolates and the Sal-1 reference strain. Analysis of Pv MCA1 catalytic domain in different P. vivax genomic sequences publicly available also revealed a high degree of conservation worldwide, with very few amino acid substitutions that were not related to putative histidine and cysteine catalytic residues, whose involvement with the active site of protease was herein predicted by molecular modeling. The genetic conservation presented by Pv MCA1 may contribute to its eligibility as a druggable target candidate in vivax malaria.