This is a prospective, single-arm, open-label dose-escalation and dose-expansion study, designed to evaluate the safety, tolerability, pharmacokinetics, and preliminary efficacy of the LVIVO-TaVec400, an in vivo chimeric antigen receptor (CAR) -T cell therapy in subjects with relapsed/refractory autoimmune diseases. The subject who meets the defined eligibility criteria will follow the sequential stages: screening, treatment (LVIVO-TaVec400 infusion) and follow-up (Up to 15 years).