We report the generation, characterization and epitope mapping of a panel of 26 monoclonal antibodies (MAbs) against the VP1 capsid protein of feline calicivirus (FCV). Two close but distinct linear epitopes were identified at the capsid outermost surface (P2 subdomain) of VP1, within the E5′HVR antigenic hypervariable region: one spanning amino acids 431-435 (PAGDY), highly conserved and recognized by non-neutralizing MAbs; and a second epitope spanning amino acids 445-451 (ITTANQY), highly variable and recognized by neutralizing MAbs. These antibodies might be valuable for diagnostic applications, as well as for further research in different aspects of the biology of FCV.

Although the European rabbit is an “endangered” species and a notorious biological model, the analysis and comparative characterization of new tissue sources of rabbit mesenchymal stem cells (rMSCs) have not been well addressed. Here, we report for the first time the isolation and characterization of rMSCs derived from an animal belonging to a natural rabbit population within the native region of the species. New rMSC lines were isolated from different tissues: oral mucosa (rOM-MSC), dermal skin (rDS-MSC), subcutaneous adipose tissue (rSCA-MSC), ovarian adipose tissue (rOA-MSC), oviduct (rO-MSC), and mammary gland (rMG-MSC). The six rMSC lines showed plastic adhesion with fibroblast-like morphology and were all shown to be positive for CD44 and CD29 expression (characteristic markers of MSCs), and negative for CD34 or CD45 expression. In terms of pluripotency features, all rMSC lines expressed NANOG, OCT4, and SOX2. Furthermore, all rMSC lines cultured under osteogenic, chondrogenic, and adipogenic conditions showed differentiation capacity. In conclusion, this study describes the isolation and characterization of new rabbit cell lines from different tissue origins, with a clear mesenchymal pattern. We show that rMSC do not exhibit differences in terms of morphological features, expression of the cell surface, and intracellular markers of pluripotency and in vitro differentiation capacities, attributable to their tissue of origin.

The rabbit hemorrhagic disease virus (RHDV) vaccine platform is a nanoparticle composed of 180 copies of the viral capsid protein, VP60, self-assembled into virus-like particles (VLPs). RHDV VLPs are able to accept the simultaneous incorporation of target epitopes at different insertion sites. The resulting chimeric RHDV VLPs displaying immunogenic foreign antigens have been shown to induce specific protective immune responses against inserted heterologous T-cytotoxic and B-cell epitopes in the mouse and pig models. In this study, we explored whether RHDV-based engineered VLPs can be developed as efficient multivalent vaccines co-delivering different foreign B-cell antigens. We generated bivalent chimeric RHDV VLPs displaying two model B-cell epitopes at different surface-exposed insertion sites, as well as the corresponding monovalent chimeric VLPs. The immunogenic potential of the bivalent chimeric VLPs versus the monovalent constructs was assessed in the mouse model. We found that the bivalent chimeric VLPs elicited a strong and balanced antibody response towards the two target epitopes tested, although slight reductions were observed in the levels of specific serum antibody titers induced by bivalent chimeric VLPs as compared with the corresponding monovalent constructs. These results suggest that RHDV VLPs could represent a promising platform for the development of efficient multivalent vaccines.

The diversity of goat scrapie strains in Europe has recently been studied using bioassays in a wide collection of rodent models, resulting in the classification of classical scrapie into four different categories. However, the sole use of the first passage does not lead to isolate adaptation and identification of the strains involved and might therefore lead to misclassification of some scrapie isolates. Therefore, this work reports the complete transmission study of a wide collection of goat transmissible spongiform encephalopathy (TSE) isolates by intracranial inoculation in two transgenic mouse lines overexpressing either small ruminant (TgGoat-ARQ) or bovine (TgBov) PrPC. To compare scrapie strains in sheep and goats, sheep scrapie isolates from different European countries were also included in the study. Once the species barrier phenomenon was overcome, an accurate classification of the isolates was attained. Thus, the use of just two rodent models allowed us to fully differentiate at least four different classical scrapie strains in small ruminants and to identify isolates containing mixtures of strains. This work reinforces the idea that classical scrapie in small ruminants is a prion disease caused by multiple different prion strains and not by a single strain, as is the case for epidemic classical bovine spongiform encephalopathy (BSE-C). In addition, the clear dissimilarity between the different scrapie strains and BSE-C does not support the idea that classical scrapie is the origin of epidemic BSE-C.

Although the European rabbit is an "endangered" species and a notorious biological model, the analysis and comparative characterization of new tissue sources of rabbit mesenchymal stem cells (rMSCs) has not been well studied. Here we report for the first time the isolation and characterization of rMSCs derived from an animal belonging to a natural rabbit population within the species native region. New rMSC lines were isolated from different tissues: oral mucosa (rOM-MSC), dermal skin (rDS-MSC), subcutaneous adipose tissue (rSCA-MSC), ovarian adipose tissue (rOA-MSC), oviduct (rO-MSC), and mammary gland (rMG­MSC). The six rMSC lines showed plastic adhesion with fibroblast-like morphology and were all shown to be positive for CD44 and CD29 expression (characteristic markers of MSCs), and negative for CD34 or CD45 expression. In terms of pluripotency features, all rMSC lines expressed NANOG, OCT4, and SOX2. Furthermore, all rMSC lines cultured under osteogenic, chondrogenic, and adipogenic conditions showed differentiation capacity. In conclusion, this study describes the isolation and characterization of new rabbit cell lines from different tissue origins, with a clear mesenchymal pattern. We show that rMSC do not exhibit differences in terms of morphological features, expression of the cell surface, and intracellular markers of pluripotency and in vitro differentiation capacities, attributable to their tissue of origin.