This is the second study of AMT-130 in patients with early manifest HD and is designed as part of an integrated two-study phase I/II program under a single data safety monitoring board (DSMB) with staggered enrollment based upon continued demonstration of safety of AMT-130 administration. Cohort 3 participants will receive either high or low dose (1:1 randomization). Participants enrolled in Cohort 3 will also receive an immunosuppression regimen consisting of dexamethasone, sirolimus, and rituximab.