The synthetic anionic polymer Carbopol has been shown to be an effective adjuvant, able to improve immune responses to HIV and influenza antigens.
Carbopol is a synthetic anionic polymer which is used in man for a variety of topical and drug delivery purposes. Now researchers at Oxford University have discovered carbopol also has potent adjuvant properties when administered systemically in mice, with high titre antigen-specific antibody responses, strong helper T-cell responses, and high levels of Th1 cytokines.
Carbopol was shown to be of equivalent potency to Freund’s Complete adjuvant and more potent than alum in stimulating both B and T cell responses against recombinant soluble HIV-1 envelope glycoprotein. In a lethal influenza challenge model, carbopol mixed with a low dose of influenza HA antigen completely protected mice from disease. Carbopol formulated with killed melanoma cells also delayed tumour growth in mice.
Other advantages of carbopol include the fact that there is no evidence of local or systemic toxicity, that the antigen can be mixed with the carbopol gel simply by shaking, and that there is no direct interaction with the antigen, so its conformation is maintained.
Subunit vaccines, containing recombinant or purified antigens, have generally sub-optimal immunogenicity in the absence of adjuvant. Antigens which contain neutralising epitopes that are highly conformational will require adjuvants which maintain these crucial antigenic structures. The researchers say carbopol could provide an effective way to do this.
This work is the subject of patent application covering the use of Carbapol as an adjuvant, and Isis, the technology transfer arm of Oxford University, would like to talk to companies interested in developing the commercial opportunity that this represents.