Immunostimulatory effect of low molecular weight fraction from Bothrops jararacussu venom

With the development of biotechnology, vaccines changed from whole attenuated microorganisms to purified or recombinant subunits, or fragments of nucleic acids, bringing the need of immunostimulatory molecules to ensure immunogenicity. Pro-inflammatory molecules that activate antigen-presenting cells (APCs) are potential candidates for the development of new immunostimulatory molecules. Due to its pro-inflammatory properties, Bothrops venoms are a likely source of these molecules. Herein, we obtained seven fractions of Bothrops jararacussu (B. jararacussu) venom, which were tested in cultures of murine peritoneal macrophages. All the fractions exerted significant immunostimulatory effect for at least one cytokine analyzed, but the low molecular weight fraction (Fr7) was the only one that increased the production of the pro-inflammatory mediators tumor necrosis factor (TNF), interleukin (IL)-6, monocyte chemoattractant protein-1 (MCP-1) and IL-1β, at a low sub-toxic concentration (5 μg/mL). This fraction was selected to evaluate whether it would be able to modulate murine peritoneal cells in vivo. Fr7 recruited activated APCs in vivo, including macrophages and subpopulations of dendritic cells and B1 cells, and also promoted the expansion and/or activation of adaptive immune cells, including TCD4, TCD8 and B2 lymphocytes. The molecular content of Fr7 was preliminary investigated by MALDI-TOF analysis, with molecular masses compatible with peptides and phospholipases A₂. Initial steps of purification were also performed using HPLC. Two subfractions provided interesting results that deserve further investigation, aiming to obtain a purified molecule with immunostimulatory effects and to explore its mechanism of action.