This study evaluates whether a 7-day course of Raltegravir 400mg bd or Raltegravir 400mg/lamivudine 150mg bd can prevent HIV from infecting genital tissue and will relate the level of drug in the blood to the level of drug in genital tissue and to the ability to of HIV to infect genital tissue. As well as determining whether these regimes can provide ex vivo protection against HIV, this study will also determine speed to provision of protection and a 48 hour PK/PD decay profile of Raltegravir following drug cessation after attaining steady state concentrations. The results will also inform all future HIV pre-exposure prophylaxis studies of Raltegravir and form the basis for large scale clinical trials without the need for tissue sampling. To date, efficacy studies assessing PrEP regimens have utilized HIV-acquisition endpoints with the consequence being such studies are required to be large in subject number in order to power observations. In addition the study will provide for the first time data on HIV protection rather than just Raltegravir drug levels in tissue, and allow assessment of the possibility of Raltegravir being used as an intermittent dosing regimen in PrEP.