MOG and myeloid sarcoma: A positive correlation was also observed between serum and CSF antibody concentration for MOG (r = 0.47 p = 0.01), HERV‐W (r = 0.72 p < 0.01), and three HERV‐K peptides (r = 0.49, 0.57, 0.61 and p = 0.0126, p < 0.01, and p < 0.01, respectively) among MS patients.