US firm Vical has announced study results revealing a flu vaccine reinforced with the firm's Vaxfectin adjuvant results in an antibody response 60 times higher than the vaccine alone, and allowed a 10-fold reduction in vaccine dose.
The news suggests that the adjuvant has significant potential in contributing to dose-sparing tactics in the fight against seasonal and pandemic flu.
Vaxfectin was incorporated in Sanofi Pasteur's seasonal influenza vaccine, Fluzone, and in a study in mice showed considerable efficacy, with equivalent or better antibody responses compared with vaccine alone, even at the lowest doses tested.
This is Vical's latest trial of its Vaxfectin product, and has confirmed the dose-sparing potential of the adjuvant, and its further refinement and optimisation since earlier trials, says the company.
Vical is also developing its own Vaxfectin-formulated DNA vaccine to protect against emerging strains of influenza that have the potential to cause a pandemic. The company's DNA vaccine relies on its 'DNA delivery technology', which is based on the discovery that muscle tissues are able to take up polynucleotide genetic material (such as DNA or RNA) directly, without the use of viral components or other delivery vehicles.
Using the company's platform technology, a segment of DNA that encodes certain proteins associated with a target pathogen is inserted into a plasmid (a loop of DNA). These plasmids are injected into the body, where the encoded proteins are then produced within cells and presented to the cells of the immune system causing antibody and T-cell immune responses and helping confer protection against the target pathogen.
Vical has tested its Vaxfectin-formulated DNA vaccine against a highly pathogenic strain of the avian flu virus H5N1, and found that it provided 100 per cent protection against the virus in mice and ferrets. Human trials are due to begin in the second half of this year.
Other studies illustrate the impact this dose-sparing adjuvant could have on vaccine stocks; for example, the company cites a previous study of Sanofi Pasteur's stockpiled H5N1 pandemic influenza vaccine with no adjuvant that revealed that target levels of antibodies were achieved in less than half the subjects even after two 90mcg doses - six times the normal 15mcg dose that provides 75 - 90 per cent protection against seasonal influenza.
This clearly demonstrates the wall manufacturers are up against when faced with the threat of an avian or seasonal flu pandemic. Current global capacity is simply not enough to be able to effectively protect the population should a pandemic strike any time soon.
With World Health Organization (WHO) estimates putting global flu vaccine capacity at under 400 million doses a year, and current demand hitting 300 million doses a year, the industry is woefully under-prepared for a pandemic that could shoot demand up by 20 times, as well as requiring stronger doses.
Vical believes its Vaxfectin product could be put to good use helping ease the burden of limited vaccines stocks, both in the case of a pandemic and the shortage often associated with seasonal flu.
"The Fluzone data suggest Vaxfectin could provide a dose-sparing effect with the government-stockpiled H5N1 pandemic influenza produced by Sanofi Pasteur," said the company in a statement.
"Since neither Fluzone nor the Sanofi Pasteur H5N1 pandemic influenza vaccine are formulated with an adjuvant, Vaxfectin could, if approved, simply be added to either vaccine prior to administration."
The company also believes the adjuvant may have applications for use with other protein-based vaccines.