A borna virus cDNA encoding a protein recognized by antibodies in humans with behavioral diseases.
 Borna disease virus (BDV) causes a rare neurological disease in horses and sheep.
 The virus has not been classified because neither an infectious particle nor a specific nucleic acid had been identified.
 To identify the genome of BDV, a subtractive complementary DNA expression library was constructed with polyadenylate-selected RNA from a BDV-infected MDCK cell line.
 A clone (B8) was isolated that specifically hybridized to RNA isolated from BDV-infected brain tissue and BDV-infected cell lines.
 This clone hybridized to four BDV-specific positive strand RNAs (10.5, 3.6, 2.1, and 0.85 kilobases) and one negative strand RNA (10.5 kilobases) in BDV-infected rat brain.
 Nucleotide sequence analysis of the clone suggested that it represented a full-length messenger RNA which contained several open reading frames.
 In vitro transcription and translation of the clone resulted in the synthesis of the 14- and 24-kilodalton BDV-specific proteins.
 The 24-kilodalton protein, when translated in vitro from the clone, was recognized by antibodies in the sera of patients (three of seven) with behavioral disorders.
 This BDV-specific clone will provide the means to isolate the other BDV-specific nucleic acids and to identify the virus responsible for Borna disease.
 In addition, the significance of BDV or a BDV-related virus as a human pathogen can now be more directly examined.
