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24 p.-10 fig.-3 tab., D-amino acid oxidase (DAAO) is an enzyme that catalyzes the oxidation of D-amino acids generating H2O2. The enzymatic chimera formed by DAAO bound to the choline-binding domain of N-acetylmuramoyl-L-alanine amidase (CLytA) induces cytotoxicity in several pancreatic and colorectal carcinoma and glioblastoma cell models. In the current work, we determined whether the effect of CLytA-DAAO immobilized in magnetic nanoparticles, gold nanoparticles, and alginate capsules offered some advantages as compared to the free CLytA-DAAO. Results indicate that the immobilization of CLytA-DAAO in magnetic nanoparticles increases the stability of the enzyme, extending its time of action. Besides, we compared the effect induced by CLytA-DAAO with the direct addition of hydrogen peroxide, demonstrating that the progressive generation of reactive oxygen species by CLytA-DAAO is more effective in inducing cytotoxicity than the direct addition of H2O2. Furthermore, a pilot study has been initiated in biopsies obtained from pancreatic and colorectal carcinoma and glioblastoma patients to evaluate the expression of the main genes involved in resistance to CLytA-DAAO cytotoxicity. Based on our findings, we propose that CLytA-DAAO immobilized in magnetic nanoparticles could be effective in a high percentage of patients and, therefore, be used as an anti-cancer therapy for pancreatic and colorectal carcinoma and glioblastoma., This research was funded by Foundation for the Promotion of Health and Biomedical Research of Valencia Region (FISABIO), grant number UGP-19-063, and co-supported by PRECIPITA crowdfunding platform from Spanish Foundation for Science and Technology (FECYT) and donations from Association of women affected by breast cancer in Elche and the region (AMACMEC) to M.S., Miguel Servet Program from Instituto de Salud Carlos III (CP19/00095) to C.d.J.R. and grants from the Spanish Ministry of Economy, Industry and Competitiveness, grant numbers BIO2013-47684-R and BIO2016-79323-R, and the RETICS-FEDER RICET, RD16/0027/0010, to J.M.S. The CIBER of Enfermedades Respiratorias (CIBERES) is an initiative of the Spanish Instituto de Salud Carlos III and Spanish National Research Council (CSIC Grant 201820I132).

BACKGROUND The α1,3-galactosyltransferase gene-knockout (GalT KO) mice are able to produce natural anti-αGal antibodies apparently without any specific immunization. GalT KO mice are commonly used as a model immunological system for studying anti-αGal responses to Gal-positive xenografts in human. In this study, we compared the specificity of mouse and human αGal antibodies to realize the adequacy of the murine model. METHODS Using hapten-specific affinity chromatography antibodies against Galα1-3Galβ1-4GlcNAcβ epitope were isolated from both human and GalT KO mice blood sera. Specificity of isolated antibodies was determined using a printed glycan array (PGA) containing 400 mammalian glycans and 200 bacterial polysaccharides. RESULTS The quantity of isolated specific anti-Galα antibodies corresponds to a content of

19 p.-8 fig.-1 tab., D-amino acid oxidase (DAAO) catalyzes the oxidation of D-amino acids generating hydrogen peroxide, a potential producer of reactive oxygen species. In this study, we used a CLytA-DAAO chimera, both free and bound to magnetic nanoparticles, against colon carcinoma, pancreatic adenocarcinoma, and glioblastoma cell lines. We found that the enzyme induces cell death in most of the cell lines tested and its efficiency increases significantly when it is immobilized in nanoparticles. We also tested this enzyme therapy in non-tumor cells, and we found that there is not cell death induction, or it is significantly lower than in tumor cells. The mechanism triggering cell death is apparently a classical apoptosis pathway in the glioblastoma cell lines, while in colon and pancreatic carcinoma cell lines, CLytA-DAAO-induced cell death is a necrosis. Our results constitute a proof of concept that an enzymatic therapy, based on magnetic nanoparticles-delivering CLytA-DAAO, could constitute a useful therapy against cancer and besides it could be used as an enhancer of other treatments such as epigenetic therapy, radiotherapy, and treatments based on DNA repair., This research was funded by Spanish Instituto de Salud Carlos III, grant number PI01202025, and donations from Association of women affected by breast cancer in Elche and the region (AMACMEC) to MS and grants from the Spanish Ministry of Economy, Industry and Competitiveness, grant numbers BIO2013-47684-R and BIO2016-79323-R, and the RETICS-FEDER RICET, RD16/0027/0010, to JMS. The CIBER of Enfermedades Respiratorias (CIBERES) is an initiative of the Spanish Instituto de Salud Carlos III and Spanish National Research Council (CSIC Grant 201820I132).

Gut commensal bacteria are known to have a significant role in regulating the innate and adaptive immune homeostasis. Alterations in the intestinal microbial composition have been associated with several disease states, including autoimmune and inflammatory conditions. However, it is not entirely clear how commensal gut microbiota modulate and contribute to the systemic immunity, and whether circulating elements of the host immune system could regulate the microbiome. Thus, we have studied the diversity and abundance of specific taxons in the gut microbiota of inbred GalT-KO mice during 7 months of animal life by metagenetic high-throughput sequencing (16S rRNA gene, variable regions V3–V5). The repertoire of glycan-specific natural antibodies, obtained by printed glycan array technology, was then associated with the microbial diversity for each animal by metagenome-wide association studies (MWAS). Our data show that the orders clostridiales (most abundant), bacteriodales, lactobacillales, and deferribacterales may be associated with the development of the final repertoire of natural anti-glycan antibodies in GalT-KO mice. The main changes in microbiota diversity (month-2 and month-3) were related to important changes in levels and repertoire of natural anti-glycan antibodies in these mice. Additionally, significant positive and negative associations were found between the gut microbiota and the pattern of specific anti-glycan antibodies. Regarding individual features, the gut microbiota and the corresponding repertoire of natural anti-glycan antibodies showed differences among the examined animals. We also found redundancy in different taxa associated with the development of specific anti-glycan antibodies. Differences in microbial diversity did not, therefore, necessarily influence the overall functional output of the gut microbiome of GalT-KO mice. In summary, the repertoire of natural anti-carbohydrate antibodies may be partially determined by the continuous antigenic stimulation produced by the gut bacterial population of each GalT-KO mouse. Small differences in gut microbiota diversity could determine different repertoire and levels of natural anti-glycan antibodies and consequently might induce different immune responses to pathogens or other potential threats.

44 p.-6 fig.-2 tab.-5 fig.supl., Polyhydroxyalkanoates (PHAs) are biodegradable polyesters that accumulate in the cytoplasm of certain bacteria. One promising biotechnological application of these biopolymers contemplates its utilization as supports for protein immobilization. Here, the PHA-binding domain of the Pseudomonas putida KT2440 PhaF phasin (BioF polypeptide) was investigated as affinity tag for in vitro functionalization of poly-3-hydroxybutyrate (PHB) particles with recombinant proteins, namely full-length PhaF and two fusion proteins tagged to BioF (BioF-C-LytA and BioF- β-galactosidase, containing the choline-binding module C-LytA and the β-galactosidase enzyme, respectively). Protein-biopolyester interaction was strong and stable in a wide range of pH and temperature, and the bound protein was highly protected from self-degradation, while binding strength could be modulated upon particle coating with amphiphilic compounds. Finally, a mini-bioreactor with immobilized BioF- β-galactosidase displayed a very stable enzymatic activity after several continuous activity+washing cycles. Our results demonstrate the potentialities of PHA and the BioF tag for the construction of novel bioactive materials., Importance: Our results confirm the biotechnological potential of the BioF affinity tag as a versatile tool for functionalizing PHA supports with recombinant proteins, leading to novel bioactive materials. The BioF tag wide substrate range presumably allows protein immobilization in vitro to virtually all natural PHAs as well as blends, copolymers or artificial, chemically-modified derivatives with novel physical-chemical properties. Moreover, the strength of protein adsorption may be easily modulated by varying the coating of the support, providing new perspectives for the engineering of bioactive materials that require a tight control of protein loading., This work was supported by Spanish Ministry of Economy and Competitiveness (grants BFU2010-17824, BIO2013-44878-R, BIO2013-47684-R and BIO2016-79323-R) and Community of Madrid (Spain) (NanoBIOSOMA S20 1473 3/M lT-2807)

12 p.-6 fig.-2 tab., The presence of synthetic dyes in wastewaters generated by the textile industry constitutes a serious environmental and health problem that urges the scientific community on an appropriate action. As a proof-of-concept, we have developed a novel approach to design enzymatic bioreactors with the ability to decolorize dye solutions through the immobilization of the bacterial CueO laccase-like multicopper oxidase from Escherichia coli on polyhydroxybutyrate (PHB) beads by making use of the BioF affinity tag. The decolorization efficiency of the system was characterized by a series of parameters, namely maximum enzyme adsorption capacity, pH profile, kinetic constants, substrate range, temperature and bioreactor recycling. Depending on the tested dye, immobilization increased the catalytic activity of CueO by up to 40-fold with respect to the soluble enzyme, reaching decolorization efficiencies of 45-90%. Our results indicate that oxidase bioreactors based on polyhydroxyalkanoates are a promising alternative for the treatment of coloured industrial wastewaters., This work was supported by Spanish Ministry of Economy and Competitiveness (grants BIO2013-47684-R and BIO2016-79323-R),IVACE (Institut Valenciá de Competitivitat Empresarial, SPAIN) and FEDER (Fondo Europeo de Desarrollo Regional, Europe).

One of the most common genetic backgrounds for mice used as a model to investigate human diseases is the inbred BALB/c strain. This work is aimed to characterize the pattern of natural anti-carbohydrate antibodies present in the serum of 20 BALB/c mice by printed glycan array technology, and to compare their binding specificities with that of human natural anti-carbohydrate antibodies. Natural antibodies from the serum of BALB/c mice interacted with 71 glycans from a library of 419 different carbohydrate structures. However, only seven of these glycans were recognized by the serum of all the animals studied, and other five glycans by at least 80% of mice. The pattern of the 12 glycans mostly recognized by the circulating antibodies of BALB/c mice differed significantly from that observed with natural anti-carbohydrate antibodies in humans. This lack of identical repertoires of natural anti-carbohydrate antibodies between individual inbred mice, and between mice and humans, should be taken into consideration when mouse models are intended to be used for investigation of natural antibodies in biomedical research.