GAD1 and viral encephalitis: According to different antigens targeted by immune responses, autoimmune encephalitis can be divided into the following types: intraneuronal antibody-associated AE (paraneoplastic limbic encephalitis), neuronal surface antibody (NSAb)-associated AE, intracellular synaptic protein antibody-associated encephalitis, which is between the two types mentioned above such as glutamate decarboxylase (GAD) antibody-associated encephalitis, and other autoimmune encephalitis without definite antigens such as acute disseminated encephalomyelitis (ADEM) (2, 3).