Inflammation events occurring upon bacterial infection in Mytilus galloprovincialis

Bivalves, and in particular the Mediterranean Mytilus galloprovincialis are important sources of food in several countries in the world. Because of that, mussels farming has a strong economic impact. Due to their status as sessile and filter-feeding animals, bivalves accumulate in their tissues environmental pollutants and a larger amount of microorganisms and between these, a multitude of infective bacteria for higher vertebrates and humans, such as Vibrio species. Several immunological responses of M. galloprovincialis were investigated and described after Vibrio infection both, in vitro and in vivo conditions, such as hemocytes count and different cellular subpopulations. Particularly, intracellular signaling pathways are activated to trigger the synthesis of antimicrobial effectors Here, were investigated the modulation of immunological cellular markers of the Mediterranean bivalve M. galloprovincialis in response to in vivo exposure with Vibrio splendidus. The activation of inflammatory cascade was examined through immunolabeling with antibodies involved in the pathway: Toll-like receptors 4 (TLR4), myeloid differentiation factor 88 (MYD88), Allograft inflammatory factor-1 (AIF1) and ribonucleases RNASET2 (T2 family), that trigger the recruitment and activation of macrophages in vertebrates. Results confirmed the activation of TRL4 during bacterial infection and MYD88 adapter suggesting a role in recognition and intracellular signaling. Moreover, Gram-negative bacteria determine the recruitment by the ribonuclease RNASET2 of haemocytes and a huge migration of AIF-1+ cells. This approach is suitable to understand the molecular defense mechanisms in invertebrates during the exposure to possible pathogens, also in order to develop new technics and tools to evaluate mussel immunity response used in aquaculture to prevent mass mortality of these mollusks, economic loss and potential risks for consumers of seafood.