Inclusion Criteria:  Are willing and able to provide informed consent Received AAV2hAQP1 administered via Stensen's duct to a single parotid gland in the prior open-label, Phase 1, dose-escalation study (Study MGT016) Are willing and able to adhere to the protocol and long-term follow-up  Exclusion Criteria:  1. Subjects unwilling or unable to meet with the requirements of the study will be excluded