| Summary: | Smoking is now recognized as the single largest avoidable cause of premature death and disability in Britain and probably the greatest avoidable threat to public health worldwide. There are several therapies available to combat nicotine addiction ranging from psychological therapy to pharmacological interventions such as Nicotine Replacement Therapy. However, success rates for these therapies individually and mixture of therapies together, are still low and can be improved. A new strategy in helping quit rates is immunotherapy. This research project has focused on targeting cotinine, the major metabolite of nicotine, to produce a vaccine as a cessation method. The effect of cotinine on nicotine-evoked dopamine release was first examined using 96-well plate assay in chapter 2. Cotinine was shown to decrease nicotine - evoked dopamine release, probably by desensitising the nAChRs. a6p2*, a4p2 receptor subtypes were implicated, using competitive antagonists. Trans-4-thiol cotinine was produced as a viable derivative and conjugated to ovalbumin in the appendix and chapter 3. Vaccination of rats generated anti-cotinine antibodies, although mid-point titres were low. Improvements were made in chapter 4 which increased the mid-point antibody titres. The improvements included change of carrier molecule to Tenatus Toxoid, allowing for 15 derivative attachments per carrier molecule, and change of adjuvant. The best concentration of conjugate to be used in vaccination was determined to be 5 pg which produced specific antibodies towards cotinine. Blood nicotine and cotinine concentrations after chronic nicotine treatment showed vaccination resulted in the retention of cotinine in the blood, presumably reducing the concentration reaching the brain, in chapters 4 and 5. Similar results were also obtained after acute nicotine treatment in chapter 5. The effect of vaccination on nicotine - evoked dopamine release was studied in chapters 4 and 5; an increase in nicotine-evoked dopamine release was observed in vaccinated animals. This suggests the retention of cotinine in the blood and the consequent reduction of antagonism of the actions of nicotine by cotinine, allowed nicotine to have a larger effect. Nicotineinduced locomotor activity was not affected by vaccination, however future work is needed to give conclusive results. These results have provided preliminary proof of concept for this immunotherapy approach. Future in vivo experiments will elucidate the actions of this vaccine on addiction mechanisms and facilitate the development of this approach as a therapy to help people overcome nicotine addiction.
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