Characterisation of T-cell Response to Keyhole Limpet Hemocyanin (KLH) and Tuberculin Purified Protein Derivative (PPD)

This is an exploratory study to develop methodologies for the assessment of T-cell mediated therapies via skin immune challenges studies in healthy volunteers. The study will investigate what is the most appropriate; skin challenge agent, time and methodology to sample and characterise T-cells in the delayed type hypersensitivity (DTH) skin reaction. The skin challenge agents to be used in this study will be the neoantigen Keyhole Limpet Hemocyanin (KLH) and recall antigen Tuberculin Purified Protein Derivative (PPD). Part A of the study will assess an intradermal (ID) KLH challenge in three subjects to assess if the immune response to KLH is initiated by the innate or adaptive immune system. Each subject will receive one ID dose of 0.1 milligram (mg) KLH and will be assessed for a skin inflammatory response. Part B of the study will assess repeat ID challenges 28 days apart; the objective will be to characterise the T-cell response to each challenge and the kinetics of that response. For Cohorts 1A and 1B, 16 subjects will receive an initial subcutaneous (SC) 5 mg dose of KLH. Fifteen days later the subjects will receive 0.1 mg ID KLH dose and the response will then be assessed 48 and 120 hours after the initial challenge. The ID KLH challenge will then be repeated 28 days later and the response will be assessed at 48 hours (Cohort 1A, 8 subjects) and at 120 hours (Cohort 1B, 8 subjects) post challenge. For Cohort 2, a repeat challenge of either 2 tuberculin Unit (TU) or 10 TU ID PPD will be administered 28 days apart, to 8 subjects. The first challenge response will be assessed 48 and 120 hours post challenge. The second challenge will be administered 28 days after the first and will be assessed at the same timepoints. The repeat challenge 28 days later will allow an intra-subject analysis and will determine if a subject can be used as their own control. Part C of the study will assess repeat ID challenges of PPD and PBS; the objective will be to characterise the