Influenza A and B virus-like particles produced in mammalian cells are highly immunogenic and induce functional antibodies.

Influenza virus-like particles (VLPs) represent an attractive alternative to traditional influenza vaccine formulations. Influenza VLPs mimic the natural virus while lacking the genetic material, are easily recognized by the immune system, and are considered safe. The use of a mammalian cell platform offers many advantages for VLP production, such as flexibility and the same glycosylation patterns as a human virus. In this study, the influenza VLPs containing hemagglutinin (HA), neuraminidase (NA) and matrix M1 proteins were expressed in CHO-K1, Vero or 293 T cell lines using transient transfection. After production in 3L bioreactor and purification, extensive characterization was performed on two batches of VLPs produced in 293 T, the best cell line for VLP expression; one batch expressed the HA and NA genes from A/Hong Kong/4801/2014 (H3N2) strain and the other, HA and NA genes from B/Phuket/3073/2013. Characterizations provided evidence that mammalian VLPs closely emulate the exterior of authentic virus particles in terms of both antigen presentation and biological properties. The two VLPs produced contained more NA proteins on their surface with a HA:NA ratio around 1:1 than influenza viruses which present a HA:NA ratio of around 4:1. Immunogenicity studies in BALB/c mice demonstrated that the VLPs, administered intra-muscularly, were highly immunogenic at low doses, with the induction of functional antibodies against HA and NA. Immunogenicity was also shown in a human in vitro model (MIMIC® system). In conclusion, we believe that influenza vaccines made of VLPs produced in mammalian cell lines, constitute a potential alternative to the classical influenza vaccines.

G-protein based ELISA as a potency test for rabies vaccines.

The NIH test is currently used to assess the potency of rabies vaccine, a key criterion for vaccine release. This test is based on mice immunization followed by intracerebral viral challenge. As part of global efforts to reduce animal experimentation and in the framework of the development of Sanofi Pasteur next generation, highly-purified vaccine, produced without any material of human or animal origin, we developed an ELISA as an alternative to the NIH test. This ELISA is based on monoclonal antibodies recognizing specifically the native form of the viral G-protein, the major antigen that induces neutralizing antibody response to rabies virus. We show here that our ELISA is able to distinguish between potent and different types of sub-potent vaccine lots. Satisfactory agreement was observed between the ELISA and the NIH test in the determination of the vaccine titer and their capacity to discern conform from non-conform batches. Our ELISA meets the criteria for a stability-indicating assay and has been successfully used to develop the new generation of rabies vaccine candidates. After an EPAA international pre-collaborative study, this ELISA was selected as the assay of choice for the EDQM collaborative study aimed at replacing the rabies vaccine NIH in vivo potency test.