A recombinant rabies vaccine expressing the trimeric form of the glycoprotein confers enhanced immunogenicity and protection in outbred mice.

Rabies is a disease characterized by an invariably lethal encephalitis of viral origin that can be controlled by preventive vaccination programs of wildlife, domestic animals and humans in areas with a high risk of exposure. Currently available vaccines are expensive, cumbersome to produce and require intensive immunization and booster schemes to induce and maintain protective immunity. In the present study, we describe the development of candidate recombinant subunit rabies vaccines based on the glycoprotein G of the prototype rabies virus (RABV-G) expressed either as a monomer (RABV-mG) or in its native trimeric configuration (RABV-tG), with or without Matrix-M™ adjuvant. Immunogenicity and protective efficacy of the respective candidate vaccines were tested in outbred NIH Swiss albino mice. The RABV-tG candidate vaccine proved to be superior to the RABV-mG vaccine candidate both in terms of immunogenicity and efficacy. The relatively poor immunogenicity of the RABV-mG vaccine candidate was greatly improved by the addition of the adjuvant. A single, low dose of RABV-tG in combination with Matrix-M™ induced high levels of high avidity neutralizing antibodies and protected all mice against challenge with a lethal dose of RABV. Consequently RABV-tG used in combination with Matrix-M™ is a promising vaccine candidate that overcomes the limitations of currently used vaccines.

Development of a simple and high-yielding fed-batch process for the production of influenza vaccines.

A robust and reliable GMP-compatible fed-batch process was successfully developed for the production of recombinant hemagglutinin (rHA) proteins by expresSF cells. The feeding solution, feeding strategy as well as the cell density at infection were optimized to maximize the final rHA production yields without affecting the existing rHA recovery protocol and downstream process. A simple and stable feeding solution was formulated and a rational feeding regimen designed to yield, depending on the rHA baculovirus used, between 2- and 3-fold enhancements in volumetric rHA production with increased specific productivity compared to the batch culture. Recombinant HA from fed-batch cultures could be simply recovered following cell lysis and purified through chromatographic steps. Overall, the increased rHA yield was maintained throughout the whole process. The performance, reproducibility and scalability of the fed-batch process was successfully demonstrated in 12 bioreactor runs of 2- and 10-L working volume using five different rHA encoding baculoviruses.

A recombinant baculovirus-expressed S glycoprotein vaccine elicits high titers of SARS-associated coronavirus (SARS-CoV) neutralizing antibodies in mice.

A recombinant SARS-CoV spike (S) glycoprotein vaccine produced in insect cells in a pre-clinical development stage is described. A truncated version of S glycoprotein, containing only the ecto-domain, as well as a His-tagged full-length version were cloned and expressed in a serum-free insect cell line, ExpresSF+. The proteins, purified to apparent homogeneity by liquid column chromatography, were formulated without adjuvant at 3, 9, 27, and 50 microg per dose in phosphate saline and used to immunize mice. Both antigens in each formulation elicited a strong immune response after two or three vaccinations with the antigen. Neutralizing antibody titers correlated closely with standard ELISA reactivity against the S glycoprotein. The truncated S protein was also formulated with an adjuvant, aluminum hydroxide, at 1 microg per dose (+/-adjuvant), and 5 microg per dose (+/-adjuvant). Significantly enhanced immune responses, manifested by higher titers of serum ELISA and viral neutralizing antibodies, were achieved in adjuvanted groups with fewer doses and lower concentration of S glycoprotein. These findings indicate that the ecto-domain of SARS-CoV S glycoprotein vaccine, with or without adjuvant, is immunogenic and induces high titers of virus neutralizing antibodies to levels similar to those achieved with the full S glycoprotein vaccine.