Bluetongue is a major infectious disease of ruminants that is caused by bluetongue virus (BTV). In this study, we analyzed virulence and genetic differences of (i) three BTV field strains from Italy maintained at either a low (L strains) or high (H strains) passage number in cell culture and (ii) three South African “reference” wild-type strains and their corresponding live attenuated vaccine strains. The Italian BTV L strains, in general, were lethal for both newborn NIH-Swiss mice inoculated intracerebrally and adult type I interferon receptor-deficient (IFNAR^−/−) mice, while the virulence of the H strains was attenuated significantly in both experimental models. Similarly, the South African vaccine strains were not pathogenic for IFNAR^−/−mice, while the corresponding wild-type strains were virulent. Thus, attenuation of the virulence of the BTV strains used in this study is not mediated by the presence of an intact interferon system. No clear distinction in virulence was observed for the South African BTV strains in newborn NIH-Swiss mice. Full genomic sequencing revealed relatively few amino acid substitutions, scattered in several different viral proteins, for the strains found to be attenuated in mice compared to the pathogenic related strains. However, only the genome segments encoding VP1, VP2, and NS2 consistently showed nonsynonymous changes between all virulent and attenuated strain pairs. This study established an experimental platform for investigating the determinants of BTV virulence. Future studies using reverse genetics will allow researchers to precisely map and “weight” the relative influences of the various genome segments and viral proteins on BTV virulence.

Monoclonal antibodies (MAbs) specific for the lipopolysaccharide (LPS) of Escherichia coli O104:H4 were produced by fusion of Sp2/O-Ag-14 mouse myeloma cells with spleen cells of Balb/c mice, immunized with heat-inactivated and sonicated E. coli O104:H4 bacterial cells. Four MAbs specific for the E. coli O104:H4 LPS (1E6G6, 1F4C9, 3G6G7 and 4G10D2) were characterized and evaluated for the use in a method for the detection of E. coli O104:H4 in milk samples that involves antibody conjugation to magnetic microbeads to reduce time and increase the efficiency of isolation. MAb 1E6G6 was selected and coupled to microbeads, then used for immuno-magnetic separation (IMS); the efficiency of the IMS method for E. coli O104:H4 isolation from milk was evaluated and compared to that of the EU RL VTEC conventional culture-based isolation procedure. Milk suspensions also containing other pathogenic bacteria that could potentially be found in milk (Campylobacter jejuni, Listeria monocytogenes and Staphylococcus aureus) were also tested to evaluate the specificity of MAb-coated beads. Beads coated with MAb 1E6G6 showed a good ability to capture the E. coli O104:H4, even in milk samples contaminated with other bacteria, with a higher number of E. coli O104:H4 CFU reisolated in comparison with the official method (121 and 41 CFU respectively at 103 E. coli O104:H4 initial load; 19 and 6 CFU respectively at 102 E. coli O104:H4 initial load; 1 and 0 CFU respectively at 101 E. coli O104:H4 initial load). The specificity was 100%.

Four hybridoma cell lines (C4B, 10C2G5, 6C5F4C7, 2D10G11) were adapted to grow in serum-free conditions. Cell proliferation, viability, and antibody production in Nutridoma SP and Ex-Cell HSF 610 media were evaluated and results compared with those obtained using DMEM containing 10% fetal bovine serum (control medium). Clone C4B showed the best IgG productivity in control medium, but viability and number of cells per milliliter were similar for the three media. For clone 10C2G5, the highest values of cell viability were obtained with both control medium and Nutridoma SP; no significant differences in IgG yields and number of cells/mL were observed among the three media. Clone 6C5F4C7 provided no significant differences when grown in the two serum-free media and in control medium. Clone 2D10G11 showed the best IgG productivity in control medium and in Ex-Cell HSF 610, even if Ex-Cell HSF 610 provided the lowest number of cells/mL; no significant differences among the three media were obtained for viability. Purified antibodies produced from each hybridoma cell line grown in serum-free media showed a higher degree of purity than those produced by the same cell lines grown in control medium. Purified MAbs were also titrated by ELISA to test MAb-antigen affinity.