Evaluation of the Immunostimulant Effect of Microvesicles of <i>Lactobacillus acidophilus</i> Isolated from Wild Rats

Lactic acid bacteria are components of the gastrointestinal tract microbiota in both humans and animals and are widely used as probiotics. Lactobacillus is the most related genus to probiotic activity and is able to release membrane microvesicles (MVs), which primary functions include to carry and transmit antigens to host tissues and modulate host defense responses. In the present study, MVs were isolated from Lactobacillus acidophilus resident in the ileum of free-living rats, and its immunostimulant effect was evaluated in two biological models. MVs were characterized using SDS-PAGE electrophoresis, electron microscopy, and nanoparticle tracking analysis. In the first model, the immunostimulant effect of MVs was evaluated on ovine abomasal explants, previously stimulated with MVs and challenged with third-stage larvae of Haemonchus contortus, demonstrating a decrease in the percentage of larvae association, and favoring the migration of inflammatory cells to the infection site. In the second model, macrophage cell line (RAW 264.7) was stimulated with MVs to evaluate the expression of transcripts coding for IL-1β and TNF-α. In both cases, the immunostimulatory effect of MVs was verified, demonstrating that MVs can carry important antigens that could be considered in a formulation to promote the intestinal health in livestock production.