Borna disease virus-specific circulating immune complexes, antigenemia, and free antibodies--the key marker triplet determining infection and prevailing in severe mood disorders.

Borna disease virus (BDV), a unique genetically highly conserved RNA virus (Bornaviridae; Mononegavirales), preferentially targets neurons of limbic structures causing behavioral abnormalities in animals. Markers and virus in patients with affective disorders and schizophrenia have raised worldwide interest. A persistent infection was suggestive from follow-up studies, but inconstant detectability weakened a possible linkage.This study for the first time discloses that detection gaps are caused by BDV-specific circulating immune complexes (CIC), and their interplay with free antibodies and plasma antigens (p40/p24). Screening 3000 sera each from human and equine patients over the past 4 years by new enzyme immunoassays (EIAs) revealed that BDV-CICs indicate 10 times higher infection rates (up to 30% in controls, up to 100% in patients) than did previous serology. Persistence of high amounts of CICs and plasma antigens correlates with severity of depression. Even BDV RNA could be detected in plasma samples with strong antigenemia. Our discovery not only explains the course of persistent infection, but offers novel easy-to-use diagnostic tools by which new insights into BDV-related etiopathogenesis of disease and epidemiology are possible.

Neutralization of borna disease virus depends upon terminal carbohydrate residues (alpha-D-man, beta-D-GlcNAc) of glycoproteins gp17 and gp94.

Borna disease virus (BDV) is an enveloped, nonsegmented, negative-stranded RNA virus that causes infections of the brain in a wide range of animal species and man. The third open reading frame codes for a protein of 17 kD (gp17) that is N-glycosylated and contains terminal alpha-D-mannose and N-acetyl-beta-D-glucosamine residues. Rat sera raised against these carbohydrates (anti-sugar antisera) show high in vitro neutralization activity and were capable of precipitating BDV. The neutralizing capacity of sera derived from experimentally BDV-infected rabbits, in turn, decreased after adsorption with those carbohydrates. They partially inhibited infection of primary young rabbit brain cells in a dose-dependent manner. Furthermore, the anti-sugar antisera recognized a second virus-specific glycoprotein with an apparent molecular mass of 94 kD (gp94), providing indirect evidence that gp94 is involved in virus adsorption and/or entry into cells. Neutralization of BDV comprises a complex event and, as shown for the first time, involves the carbohydrate residues of both glycoproteins of BDV.

The glycosylated matrix protein of Borna disease virus is a tetrameric membrane-bound viral component essential for infection.

Borna disease virus (BDV) is representative of the family of Bornaviridae in the order Mononegavirales (negative-stranded, non-segmented, enveloped RNA viruses). It is the causal agent for Borna disease, characterized as an encephalomyelitis (typical form) in a wide variety of domestic animals (from rodents to birds). Recent information shows the involvement of BDV in the pathogenesis of some human psychiatric disorders. The 8.9-kb viral antigenome codes for five major ORF. The third ORF codes for a 16-kDa protein (matrix protein) that is posttranslationally modified, yielding an N-linked glycoprotein. Our data show that the glycosylated matrix protein exists as a stable tetrameric structure detectable either by electrospray ionization or matrix-assisted laser-desorption ionization mass spectrometry. Under native conditions, the tetramer, with a relative molecular mass of 68 kDa, was isolated from a sediment-free brain suspension of a BDV-infected horse. The 68-kDa entity is stable in the presence of ionic and nonionic detergents but dissociates into subunits when heated. We found that the tetrameric matrix protein inhibits in vitro BDV infection in a dose-dependent manner. In contrast to inhibition of BDV infection with hydrophobic carbohydrate derivatives and protein-bound glycoconjugates, the glycosylated matrix protein is a very potent inhibitor of BDV infection, indicating that this protein represents an essential virus-specific membrane component for viral attachment.

N-glycosylated protein(s) are important for the infectivity of Borna disease virus (BDV).

Tunicamycin inhibited the production of infectious Borna disease virus (BDV) and glycosidase treatment eliminated the infectivity of cell-free virus. A glycoprotein of approximately 17 kDa, found in association with infectious virus, was identified by Concanavalin A binding.