Assessing the effects of Leishmania (Leishmania) infantum and L. (L.) amazonensis infections in macrophages using a quantitative proteome approach.

Leishmania (Leishmania) infantum is the causative agent of visceral leishmaniasis, while L. (L.) amazonensis is associated with localized cutaneous and diffuse leishmaniasis, which can affect different organ tissues leading to visceral manifestations in some hosts. The wide range of clinical manifestations of leishmaniasis depends on host factors such as the immune response and on the species of Leishmania involved in the infection. Macrophages are the main infected cells in the vertebrate host, and proteins play a pivotal role in Leishmania-macrophage interactions. Here, we performed difference gel electrophoresis (DIGE) and shotgun quantitative mass spectrometry-based proteomics by means of tandem mass tags (TMT) isobaric peptide labeling followed by LC-MS/MS to investigate differentially abundant proteins in BALB/c macrophages infected with these Leishmania species. Using DIGE for comparison, we found that 2.34% spots (29/1240) were differentially intense in infected murine macrophages. Leishmania (L.) infantum and L. (L.) amazonensis induced similar changes in the host cells; 11 spots were selected as differentially intense in each species and seven in the uninfected control group. Using TMT, 5939 Mus musculus proteins were identified, of which 410 and 433 were differentially abundant in L. (L.) infantum and L. (L.) amazonensis infections, respectively, while 170 proteins were commonly regulated by both the species. Gene ontology enrichment analysis indicated that Leishmania infection interfered with apoptotic mechanisms in macrophages and induced epigenetic changes that may affect gene transcription. Moreover, downregulation of proteins such as PYCARD and MyD88 seemed to influence the inflammatory process in L. (L.) amazonensis infection, whereas upregulation of TAP1 and ERAP1 was involved in the adaptive immune response in L. (L.) infantum infection. Differentially abundant proteins identified in this study may contribute to a better understanding of the factors that determine the course of infection. Our results suggest several possible targets for vaccines, drugs, and diagnosis of leishmaniasis.

Assessing the composition of the plasma membrane of Leishmania (Leishmania) infantum and L. (L.) amazonensis using label-free proteomics.

Protozoan parasites of the genus Leishmania are causative agents of leishmaniasis, a wide range of diseases affecting 12 million people worldwide. The species L. infantum and L. amazonensis are etiologic agents of visceral and cutaneous leishmaniasis, respectively. Most proteome analyses of Leishmania have been carried out on whole-cell extracts, but such an approach tends to underrepresent membrane-associated proteins due to their high hydrophobicity and low solubility. Considering the relevance of this category of proteins in virulence, invasiveness and the host-parasite interface, this study applied label-free proteomics to assess the plasma membrane sub-proteome of L. infantum and L. amazonensis. The number of proteins identified in L. infantum and L. amazonensis promastigotes was 1168 and 1455, respectively. After rigorous data processing and mining, 157 proteins were classified as putative plasma membrane-associated proteins, of which 56 proteins were detected in both species, six proteins were detected only in L. infantum and 39 proteins were exclusive to L. amazonensis. The quantitative analysis revealed that two proteins were more abundant in L. infantum, including the glucose transporter 2, and five proteins were more abundant in L. amazonensis. The identified proteins associated with distinct processes and functions. In this regard, proteins of L. infantum were linked to metabolic processes whereas L. amazonensis proteins were involved in signal transduction. Moreover, transmembrane transport was a significant process among the group of proteins detected in both species and members of the superfamily of ABC transporters were highly represented. Interestingly, some proteins of this family were solely detected in L. amazonensis, such as ABCA9. GP63, a well-known virulence factor, was the only GPI-anchored protein identified in the membrane preparations of both species. Finally, we found several proteins with uncharacterized functions, including differentially abundant ones, highlighting a gap in the study of Leishmania proteins. Proteins characterization could provide a better biological understanding of these parasites and deliver new possibilities regarding the discovery of therapeutic targets, drug resistance and vaccine candidates.