Cell-based vaccines are at the forefront of influenza vaccine development, according to findings presented March 10 at the 14th International Congress on Infectious Diseases in Miami and reported by Pediatric SuperSite.
Professor Robert L. Atmar described emerging trends in influenza vaccines. In addition to cell-based substrates, strategies for vaccine development include hemagglutinin synthesis using baculovirus expression, alternative routes of administration, increased dosages and use of adjuvants.
“Novel strategies can increase stability, simplify storage requirements and increase immunogenicity,” said Atmar, a professor in the department of medicine and molecular virology and microbiology at Baylor College of Medicine in Houston.
“However, each new strategy presents a new set of challenges.”
Cell-based vaccines may make isolation of strains easier, match circulating strains more effectively and allow faster production.
“Cell-based vaccines may overcome the need for the use of eggs to produce antigen,” he said. “However, the seeds that are being used are being adapted to eggs and then adapted back to cell cultures. Some of the advantage gets obscured by passage through eggs.”
FluBlok, a candidate from Protein Sciences, is a recombinant hemagglutinin expressed in the baculovirus expression system.
“This product has a high antigen content,” Atmar said. “Also, it is produced in insect cells and eliminates the need for adaptation to eggs. It is being considered by the FDA for licensure and could be available for clinicians soon.”
An intradermal vaccine is also an attractive vaccine option, according to Atmar, who noted that these vaccines offer better immune response and increased immunogenicity.
“Though we have seen difficulties with delivery systems for intradermal vaccines, data for geometric mean titers, seroprotection and seroconversion have been encouraging,” he said.
Atmar said vaccines with an increased antigen dose have also performed well in phase-3 trials and have received FDA approval. Adjuvanted vaccines, including the MF59 oil-in-water emulsion adjuvant, may provide increased protection against drifted strains.