Identification of Virulence Factors in <i>Leishmania infantum</i> Strains by a Proteomic Approach

Knowledge of <i>Leishmania</i> virulence is essential for understanding how the contact between the pathogen and host cells can lead to pathogenesis. Virulence in two <i>L. infantum</i> strains was characterized using macrophages and hamsters. Next, we used difference gel electrophoresis (DIGE) and mass spectrometry to identify the differentially expressed proteins. A total of 63 spots were identified corresponding to 36 proteins; 20 were up-regulated, in which 16 had been previously associated with <i>Leishmania</i> virulence. Considering our results and what has been reported before, we suggest the hypothesis that <i>L. infatum</i> virulence could be a result of the increased expression of KMP-11 and metallopeptidase, associated with an improved parasite–host interacting efficiency and degradation of the protective host proteins and peptides, respectively. Other factors are tryparedoxin peroxidase and peroxidoxin, which protect the parasite against the stress response, and 14-3-3 protein-like, which can prolong infected host cell lifetime. Proteins as chaperones and endoribonuclease L-PSP can increase parasite survival. Enolase is able to perform versatile functions in the cell, acting as a chaperone or in the transcription process, or as a plasminogen receptor or in cell migration events. As expected in more invasive cells with high replication rates, energy consumption and protein synthesis are higher, with up-regulation of Rieske iron–sulfur protein precursor, EF-2, <i>S</i>-adenosylhomocysteine, and phosphomannomutase.