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Paracatenula galateia sp. nov. is a mouthless marine catenulid platyhelminth with bacterial intracellular endosymbionts. The worms live in shallow back-reef sands in the Belize Barrier Reef system and are distinguished from the four previously described members of the genus by their large size combined with a ribbon-shaped body and characteristic bipartite inclusions in cells, which are interpreted as sperm. The bacteria are presumed to be sulphur-oxidizing chemoautotrophs. They are found in bacteriocytes which fill the body region (‘trophosome region’) posterior to the brain, whereas the anterior part of the worm (rostrum) is bacteria-free. Phalloidin staining reveals a delicate system of subepitheliar circular and longitudinal muscles and dorsoventral fibres. The serotonergic nervous system consists of a brain at the base of the rostrum and longitudinal fibres extending both anteriorly and posteriorly, the latter being concentrated in a structure called the ‘dorsal cord’.

Jacqueline Montanaro,1 Aleksandra Inic-Kanada,1 Angela Ladurner,1 Elisabeth Stein,1 SandraBelij,1 Nora Bintner,1 Simone Schlacher,1 Nadine Schuerer,1 Ulrike Beate Mayr,2 WernerLubitz,2 Nikolaus Leisch,3 Talin Barisani-Asenbauer11Laura Bassi Centres of Expertise, OCUVAC – Centre of Ocular Inflammation and Infection, Centre for Pathophysiology, Infectiology, and Immunology, Medical University of Vienna, Vienna, Austria; 2BIRD-C GmbH & Co KG, Kritzendorf, Austria; 3Department of Ecogenomics and Systems Biology, University of Vienna, Vienna, AustriaAbstract: To target chronic inflammatory ocular surface diseases, a drug delivery platform is needed that is safe, possesses immunomodulatory properties, and can be used either for drug delivery, or as a foreign antigen carrier. A new therapeutic approach that we have previously proposed uses nonliving bacterial ghosts (BGs) as a carrier-delivery system which can be engineered to carry foreign antigens and/or be loaded with therapeutic drugs. The parent strain chosen for development of our BG delivery system is the probiotic Escherichia coli strain Nissle 1917 (EcN), whose intrinsic properties trigger the innate immune system with the flagella and fimbriae used to attach and stimulate epithelial cells. In previous studies, we have shown that EcN BGs are safe for the ocular surface route, but evidence that EcN BGs retain flagella and fimbriae after transformation, has never been visually confirmed. In this study, we used different visualization techniques to determine whether flagella and fimbriae are retained on EcN BGs engineered either for drug delivery or as a foreign antigen carrier. We have also shown by immunoelectron microscopy that EcN retains two foreign antigens after processing to become EcN BGs. Furthermore, we demonstrated that BGs derived from EcN and expressing a foreign antigen attachment to conjunctival epithelial cells in vitro without causing reduced cell viability. These results are an important step in constructing a delivery system based on a nonliving probiotic that is suitable for use in ocular surface diseases pairing immunomodulation and targeted delivery.Keywords: delivery system, flagella, fimbriae, foreign antigen, electron microscopy, epithelial cells