Structural characterization of the feline-immunodeficiency-virus envelope glycoprotein 36 ectodomain for the development of new antivirals.

In the fight against the human HIV, new targets are being explored, such as the proteins involved in the process of fusion of the virus with the host cell. Recently, the first generation of fusion inhibitors (enfuvirtide), targeting gp41 (virus envelope glycoprotein 41), has become commercially available. However, this promising class of drugs has to be improved in respect of their efficacy and bioavailability. Considering the strong homologies between HIV and FIV (feline immunodeficiency virus), as well as the highly conserved structure of the transmembrane envelope protein among species, FIV represents a relevant model of pre-screening studies for HIV. Taking into account (i) sequence homologies between the ectodomain of HIV gp41 and FIV gp36 (envelope glycoprotein 36), (ii) structural data available for gp41 and (iii) the fact that synthetic peptides derived from gp36 are effective inhibitors of FIV infection, we designed several peptides derived from gp36 sequence. We checked that these peptides had the same structural features as the corresponding peptides from gp41 HIV by CD, analytical ultracentrifugation and 1H-2H (hydrogen-deuterium) exchange combined with MS. By combining this latter technique with surface-plasmon-resonance assays, we identified the amino acid residues of the C-terminal region of the ectodomain of gp36 that are critical for interaction with the N-terminal region. This gave clues for therapy and vaccines against FIV, thus providing helpful data for treatments against HIV.

The EB66® cell line as a valuable cell substrate for MVA-based vaccines production.

The selection of a cell substrate is a critical step for the development and manufacturing of a viral vaccine candidate. Several parameters such as cell susceptibility and permissiveness to the viral pathogens but also performance in terms of viral antigens quality and production yields are important considerations when identifying the ideal match between a viral vaccine and cell substrate. The modified vaccinia virus Ankara (MVA) is a replication-deficient viral vector that holds great promise as a vaccine platform, however only limited cell substrates have been tested or are available for industrialization. Here we evaluate the duck embryo-derived EB66® cell line as potential cell substrate for MVA production. To this end, we used two recombinant MVA constructs and demonstrated that EB66® cells are propagating the tested MVA viruses very efficiently, while preserving viral attenuation and transgene expression for up to 20 serial passages. Furthermore we developed upstream and downstream processes that enable industrialization of the virus production. In conclusion, we showed that EB66® cells can be used as potent cell substrate for MVA-based vaccines and represent therefore an attractive alternative for vaccine production.

Undiagnosed leptospirosis cases in naïve and vaccinated dogs: properties of a serological test based on a synthetic peptide derived from Hap1/LipL32 (residues 154-178).

Leptospirosis is a common disease in dogs, despite having current vaccinations. However, leptospirosis diagnosis based on the routine Microscopic Agglutination Test (MAT) leads to confusing conclusions, especially for infected vaccinated dogs. Indeed, both bacterin and natural infection stimulate the production of agglutinating antibodies. In experimentally infected dogs, antibodies against the peptide PP derived from Hap1/Lipl32 were raised earlier than agglutinating antibodies. The background level of these antibodies was determined in a group of 109 healthy dogs, either vaccinated or not against leptospirosis, with a specificity for IgM of 96.4% and for IgG of 95.5%. PP ELISA was subsequently performed with 118 sera from dogs with suspected leptospirosis that was not confirmed by MAT. New leptospirosis cases based on the PP ELISA results were suspected in 14 out of 102 vaccinated dogs and in two out of 16 non-vaccinated dogs. These results highlight the importance of serological diagnosis corresponding to an interesting window when it is too late for PCR detection and too early to be confirmed by MAT.