A new vaccine adjuvant developed by Vical promises to improve the immunogenicity of gene-based immunisation. The company has just been granted a US patent on the adjuvant.

Specific claims in the patent (No 6,586,409) include compositions and methods for gene-based vaccination using immunogen-encoding polynucleotides plus the Vaxfectin cationic lipid/co-lipid formulation.

Vijay Samant, Vical's chief executive, noted that Vaxfectin adds to the firm's position in adjuvants, which are considered essential to the development of naked DNA vaccines. The company is also evaluating cationic lipids such as DMRIE/DOPE and poloxamers as well as alum, which is the most commonly-used adjuvant in conventional vaccines.

"It is important to note that the only adjuvant approved in the USA for use in human vaccines is alum, which has been in use for more than 50 years", said Samant. The major obstacle for approval of additional adjuvants has been safety and the immune reactions they cause at the injection site, and Vaxfectin seems to fulfil these requirements, according to animal studies.