Fish Immunology & Vaccionology

ABOUT

The group is devoted to the study of host-pathogen interactions, i.e., studying the mechanisms of action of virulence factors at molecular, cellular and organism level, as well as the host defence mechanisms dealing with those virulence factors. We expect not only to generate knowledge for developing preventive and therapeutic measures to fight the diseases under study but also contributing to the understanding of the physiological events targeted by the virulence factors and using the virulence factors as novel therapeutics.

We are studying an AB toxin, named Apoptosis Inducing Protein of 56 kDa (AIP56), which acts by cleaving NF-kB. AIP56 is the founding member of a growing family of bacterial proteins identified in different organisms. Thus, expanding the knowledge on AIP56 will not only add to the understanding of its mechanism of action but also to the pathogenesis of other bacteria producing AIP56-like toxins. Despite some advances disclosing aspects of AIP56 and its interaction with cells, we aim to tackle many still open questions to help unveiling its structure-function relationship, detailed mechanisms of interaction with cells and translocation across the endosomal membrane, as well as understanding the molecular mechanisms behind its routing to the recycling pathway and how does this impacts on the bacterial pathogenesis. Finally, as AIP56 targets NF-kB, we also intend to use it as biotechnological tool, so it can be applied to studying and treating situations associated to the uncontrolled activation of KF-kB such as inflammatory diseases and cancer.

 

RESEARCH

We have been studying host-pathogen interactions using sea bass (Dicentrarchus labrax), an important Mediterranean cultured fish species, and Photobacterium damselae piscicida (Phdp), one of the biggest bacterial threats to marine aquaculture. From this study, we were able to correlate the Phdp-associated pathogenicity with AIP56 and show that neutralizing antibodies to AIP56 protect fish against Phdp, resulting in the development of an AIP56-based vaccine. We have also shown that AIP56 is an AB toxin acting on NF-kB p65, resulting in the apoptotic killing of fish phagocytes. Moreover, after endocytosis, a significant pool of AIP56 that does not translocate to the cytosol from the endosomal compartment, follows the recycling pathway back to the extracellular medium, adding a novel route to the ones so far described for AB toxins. Notably, we found that, although mammals are not susceptible to Phdp, the toxin is able to cleave NF-kB p65 and induce apoptotic killing of mammalian macrophages. Since uncontrolled activation of NF-κB is associated with several human pathologies the observation that AIP56 acts on mammalian cells confers great biotechnological potential to the toxin. 

After endocytosis, a significant pool of AIP56 that does not translocate to the cytosol from the endosomal compartment, follows the recycling pathway back to the extracellular medium. Mouse bone marrow derived macrophages with endocytosed AIP56 (green) co-localizing with the endocytic recycling-path