CD93 is a cell surface lectin receptor involved in the control of the inflammatory response stimulated by exogenous DNA.

Bacterial DNA contains CpG oligonucleotide (ODN) motifs to trigger innate immune responses through the endosomal receptor Toll-like receptor 9 (TLR9). One of the cell surface receptors to capture and deliver microbial DNA to intracellular TLR9 is the C-type lectin molecule DEC-205 through its N-terminal C-type lectin-like domain (CTLD). CD93 is a cell surface protein and member of the lectin group XIV with a CTLD. We hypothesized that CD93 could interact with CpG motifs, and possibly serve as a novel receptor to deliver bacterial DNA to endosomal TLR9. Using ELISA and tryptophan fluorescence binding studies we observed that the soluble histidine-tagged CD93-CTLD was specifically binding to CpG ODN and bacterial DNA. Moreover, we found that CpG ODN could bind to CD93-expressing IMR32 neuroblastoma cells and induced more robust interleukin-6 secretion when compared with mock-transfected IMR32 control cells. Our data argue for a possible contribution of CD93 to control cell responsiveness to bacterial DNA in a manner reminiscent of DEC-205. We postulate that CD93 may act as a receptor at plasma membrane for DNA or CpG ODN and to grant delivery to endosomal TLR9.

The SARS-CoV-2 spike residues 616/644 and 1138/1169 delineate two antibody epitopes in COVID-19 mRNA COMINARTY vaccine (Pfizer/BioNTech).

The newly identified coronavirus SARS-CoV-2 is responsible for the worldwide pandemic COVID-19. Considerable efforts have been devoted for the development of effective vaccine strategies against COVID-19. The SARS-CoV-2 spike protein has been identified as the major antigen candidate for the development of COVID-19 vaccines. The Pfizer-BioNTech COVID-19 vaccine COMIRNATY is a lipid nanoparticle-encapsulated mRNA encoding a full-length and prefusion-stabilized SARS-CoV-2 spike protein. In the present study, synthetic peptide-based ELISA assays were performed to identify linear B-cell epitopes into the spike protein that contribute to elicitation of antibody response in COMIRNATY-vaccinated individuals. The synthetic S2P6 peptide containing the spike residues 1138/1169 and to a lesser extent, the synthetic S1P4 peptide containing the spike residues 616/644 were recognized by the immune sera from COMIRNATY vaccine recipients but not COVID-19 recovered patients. We assume that the synthetic S2P6 peptide and to a lesser extent the synthetic S1P4 peptide, could be of interest to measure the dynamic of antibody response to COVID-19 mRNA vaccines. The S2P6 peptide has been identified as immunogenic in adult BALB/c mice that received protein-peptide conjugates in a prime-boost schedule. This raises the question on the role of the B-cell epitope peptide containing the SARS-CoV-2 spike residues 1138/1169 in protective efficacy of the Pfizer-BioNTech COVID-19 vaccine COMIRNATY.

Piezoelectric core-shell PHBV/PDX blend scaffolds for reduced superficial wound contraction and scarless tissue regeneration.

The use of non-invasive scaffold materials which can mimic the innate piezoelectric properties of biological tissues is a promising strategy to promote native tissue regeneration. Piezoelectric and cell instructive electrospun core-shell PDX/PHBV mats have been engineered to promote native tissue and skin regeneration. In depth physicochemical characterisation, in vitro and in vivo studies of a rat model showed that the 20/80 PDX/PHBV composition possessed the right balance of physicochemical and piezoelectric properties leading to enhanced fibroblast stimulation, proliferation and migration, reduced fibroblast-mediated contraction and macrophage-induced inflammation, improved keratinocyte proliferation, proper balance between endothelial cell phenotypes, decreased in vivo fibrosis and accelerated in vivo scarless wound regeneration. Overall, this study highlights the importance of exploiting cell-material interactions to match tissue biological needs to sustain the wound healing cascade.

Sugar-cane bagasse cellulose-based scaffolds promote multi-cellular interactions, angiogenesis and reduce inflammation for skin tissue regeneration.

In a previous article, we reported on the physico-chemical properties of cellulose-based scaffolds derived from sugar-cane bagasse and their preliminary in vitro assessment. In view of skin tissue regeneration, we here present our findings of an extensive in vitro testing of these scaffolds using key cells involved in the wound healing cascade namely fibroblasts, keratinocytes, endothelial cells and macrophages either singly or in various combinations to mimic in vivo conditions. Inflammation was quantified using TNF-α. In vivo biocompatibility as well as wound healing potential of the scaffolds was demonstrated using Wistar rats. Finally, we discuss the effect of curcumin-loaded scaffolds on inflammation and angiogenesis in vitro and in vivo. Nanosilica extracted from sugar-cane bagasse ash was also loaded in the scaffolds and its effect on biological response was assessed.

Immune Reactivity of a 20-mer Peptide Representing the Zika E Glycan Loop Involves the Antigenic Determinants E-152/156/158.

Mosquito-borne Zika virus (ZIKV) causes a severe congenital syndrome and neurological disorders in humans. With the aim to develop a live-attenuated ZIKV strain, we generated a chimeric viral clone ZIKALIVax with African MR766-NIID strain as backbone and the envelope E protein of epidemic Brazilian BeH810915 strain. The MR766-NIID residues E-T152/I156/Y158 were introduced into BeH810915 E protein leading to a nonglycosylated ZIKALIVax. Recently, we reported that the residues E-152/156/158 that are part of ZIKV glycan loop (GL) region might have an impact on the availability of neutralizing antibody epitopes on ZIKV surface. In the present study, we evaluated the antigenic reactivity of a synthetic 20-mer peptide representing the ZIKALIVax GL region. The GL-related peptide was effective for the detection of GL-reactive antibody in mouse anti-ZIKALIVax immune serum. We showed that the residue E-158 influences the antigenic reactivity of GL-related peptide. The ZIKALIVax peptide was effective in generating mouse antibodies with reactivity against a recombinant E domain I that encompasses the GL region. The GL peptide-reactive antibodies revealed that antigenic reactivity of E-domain I may be impacted by both residues E-152 and E-156. In conclusion, we proposed a role for the residues E-152/156/158 as key antigenic determinants of ZIKV glycan loop region.

Soluble expression of disulfide-bonded C-type lectin like domain of human CD93 in the cytoplasm of Escherichia coli.

CD93 belongs to the group XIV C-type lectin like domain (CTLD) and is closely related to thrombomodulin (CD141). Although CD93 is known to be involved in the regulation of cell adhesion and phagocytosis, its role in innate immunity remains to be fully investigated. Critically, published data about CD141 suggest that CD93 CTLD could be involved in the control of inflammation. In order to address further functional and structural analyses, we expressed human CD93 CTLD with several disulfide bonds in an E. coli expression system. As the E. coli cytoplasm is a reducing compartment, production of disulfide-bond proteins remains a challenge. Hence, we decided to over express CD93 CTLD in commercially available strains of E. coli and co-expressed a sulfhydryl oxidase (Erv1p) and a disulfide isomerase (DsbC). This strategy led to high yield expression of a native form of CD93 CTLD. NMR studies revealed that Ca2+ was not able to bind to CD93 CTLD. We also showed that the recombinant protein could alter LPS pro-inflammatory activity on THP1. This work provides new tool for further functional and structural studies to decipher the functions associated to the CTLD of CD93. This approach may also be used for others members of the group XIV C-type lectin like domain (CD141, CD248 and CLec14A).

Soluble HMGB1 is a novel adipokine stimulating IL-6 secretion through RAGE receptor in SW872 preadipocyte cell line: contribution to chronic inflammation in fat tissue.

Low-grade inflammation (LGI) is a central phenomenon in the genesis of obesity and insulin-resistance characterized by IL-6 in human serum. Whereas this LGI was initially thought to be mainly attributed to macrophage activation, it is now known that pre-adipocytes and adipocytes secrete several adipokines including IL-6 and participate to LGI and associated pathologies. In macrophages, HMGB1 is a nuclear yet secreted protein and acts as a cytokine to drive the production of inflammatory molecules through RAGE and TLR2/4. In this paper we tested the secretion of HMGB1 and the auto- and paracrine contribution to fat inflammation using the human preadipocyte cell line SW872 as a model. We showed that 1) human SW872 secreted actively HMGB1, 2) IL-6 production was positively linked to high levels of secreted HMGB1, 3) recombinant HMGB1 boosted IL-6 expression and this effect was mediated by the receptor RAGE and did not involve TLR2 or TLR4. These results suggest that HMGB1 is a major adipokine contributing to LGI implementation and maintenance, and can be considered as a target to develop news therapeutics in LGI associated pathologies such as obesity and type II diabetes.