 Before administration, CN54gp140 or placebo will be mixed into an aqueous gel vehicle. The treatments will be administered intravaginally in a regimen of 9 immunisations over 3 weeks. Each immunisation of CN54gp140 vaccine will contain 100 μg of CN54gp140 protein, meaning that a total dose of 900 μg will be given to subjects in the active treatment group. 