Caterpillars may edge out chicken eggs for vaccine production

Caterpillars may be more effective than chicken eggs as a vehicle for flu vaccines, according to a new study that evaluated the efficacy of a newer, DNA-based flu vaccine.

The study, “Efficacy of Recombinant Influenza Vaccine in Adults 50 Years of Age or Older,” was published in the New England Journal of Medicine and revealed that a vaccine grown in caterpillar cells was 30% more effective at preventing influenza infection than standard vaccines grown in chicken eggs.

The study investigated more than 9,000 patients who were given either the caterpillar-grown vaccine (FluBlok) or a standard flu vaccine. Lisa M. Dunkle, MD, chief medical officer at vaccine developer Protein Sciences Corp., and one of the report authors, told Medical Economics the vaccine is likely more effective because while chickens and their eggs are a good host to vaccine growth due to their susceptibility to the viruses, the viruses also tend to mutate while growing in the eggs. FluBlok is made through genetic engineering, with a piece of human flu virus grafted onto an insect virus and grown in a type of caterpillar called the fall army worm, or Spodoptera frugiperd. Researchers believe this host may result in fewer mutations of the antigen in the vaccine and a higher dosage of those antigens.

Dunkle said Flublok is made in a way that produces a pure influenza hemagglutinin protein that is an exact genetic match to the vaccine strain selected each season by WHO and FDA.

“Each Flublok dose contains three times the quantity of active ingredient (hemagglutinin) as standard dose inactivated vaccines and is the only higher-dose flu vaccine that is a quadrivalent product,” Dunkle said.

Next: A more rapid response to outbreaks

More rapid response

The efficacy of the vaccine in clinical trials was largely tested against influenza A sub-type H3N2 because that was the predominant circulating strain in 2014-15 when the trial was conducted. Flubok has been very potent against this strain in testing, Dunkle said, and has also offered a broader immune response against strains of H3N2 that drifted from the strain the original vaccine for that season targeted.

The process used for the caterpillar-grown vaccine can also be completed more quickly than standard vaccines, Dunkle said. She said the process used to create FluBlok can produce a vaccine in 6 weeks to 8 weeks in comparison to the 6 months needed to produce an inactivated vaccine.

“This will mean a more rapid response to pandemic when that occurs, and a possibility of reacting with a new vaccine if the circulating flu virus differs from the one chosen for the annual seasonal vaccine,” Dunkle said.

Additionally, the cell line used in the new vaccine are known to produce large quantities of protein due to a very effective promoter gene, Dunkle said. The cells are grown in bioreactors ranging in size from 460 to 2,000 liters and can produce enough influenza protein to create up to 5 million doses of vaccine, she said.

Researchers are now investigating whether the process used to create the flu vaccine can be replicated for other viruses.

“Our baculovirus expression system technology (BEST) process can produce any vaccine that is a protein,” Dunkle said. “Some examples of vaccines that we have produced using our BEST technology include rabies, SARS, MERS, West Nile virus and Zika.”

Dunkle said she hopes this modern recombinant technology could be used to replace all processes that produce an antigenic protein from infectious viruses, as these processes require inactivation and purification that could result in residual components including formaldehyde, egg proteins and antibiotics.