The invention relates to in vitro method for quantitating the antibodies specific for High mobility group box I (HMGB1) contained in a sample, in particular a serum sample or a cerebrospinal fluid sample obtained from a patient, and the use of this method in the prognostic and/or diagnosis of neurological disorders. These methods are in particular applicable to the monitoring of the human immunodeficiency virus (HIV) infection of a subject who is known to be infected with HIV and in the prognostic and/or diagnostic of the state of progression of Acquired immune deficiency syndrome (AIDS) or the state of progression toward AIDS, in particular the state of progression or the state of progression toward neurological disorders associated with AIDS. Finally, the invention is also about method to determine the immune deficiency or level of immune activation of a patient, in particular a HIV-infected patient.