Borna disease virus (BDV) causes a central nervous system disease in several vertebrate species which is characterized by behavioral disturbances. Seroepidemiological data indicate an association of BDV infection with certain human mental disorders. Sclerosis of the hippocampus and astrocytosis constitute histopathological hallmarks of BDV infection in animals. Therefore, we searched for human brain autopsy cases with such histopathological features. Five of 600 cases examined were identified as having hippocampus sclerosis and astrocytosis. Using immunocytochemistry, RT-PCR, and in situ hybridization, we detected both BDV antigen and RNA in autopsy brain samples from 4 of these 5 patients, who presented with a clinical history of mental disorders involving memory loss and depression. This is the first demonstration that BDV can infect human brain tissue, possibly contributing to the pathophysiology of specific human neuropsychiatric disorders.

The haploid human genome contains at least one human endogenous retrovirus K (HERV-K) env gene displaying an open reading frame, as evidenced by the high antibody titers against HERV-K Env in germ cell tumor patients at the time of tumor detection. However, the chromosomal assignment of an intact HERV-K env sequence is complicated by the existence of 25–30 HERV-K copies per haploid human genome. Recently, we reported the application of the protein truncation test (PTT) to chromosomally assign HERV-K gag open reading frames. Here, we set out to determine the chromosomal distribution of full-length HERV-K env genes. As demonstrated by somatic hybrid mapping and the PTT, HERV-K env open reading frames were found on human chromosomes 7, 19, and Y. By sequencing chromosome-specific HERV-K env subregions, we assigned two recently reported intact HERV-K sequences on human chromosomes 7 and 19, respectively. Chromosomes 7 and 19 and the Y are furthermore candidates for harboring a putative completely intact HERV-K locus.

Human endogenous retrovirus HERV-K is present in 25–30 copies per haploid human genome. At least one of these loci is capable of producing full-length Gag protein, high amounts of which have been detected in germ cell tumors and derived cell lines. The latter display HERV-K Gag-encoded retroviral particles. Here, we employed the protein truncation test (PTT) in combination with a monochromosomal hybrid mapping panel to identify the human chromosomes harboring HERV-K gag genes with an open reading frame for Gag protein. Eight human chromosomes were found to contain intact HERV-K gag genes. PTT results were corroborated by partial sequencing of subregions from different HERV-K gag genes. The high number of HERV-K Gag open reading frames supports the idea of retroviral sequences retaining a biological benefit in the human genome.

Cell lines were established by co-transfection of cloned M-ABA Epstein-Barr virus (EBV) DNA fragments with plasmids conferring resistance to dominant selective markers. A baby hamster kidney cel line carrying the HindIlI-I1 fragment exhibits a nuclear antigen of 82 000 daltons, serologicaily defined as EBV-determined nuclear antigen (EBNA) 1. Furthermore, a Rat-i cell line transfected with DNA of the clone pM 780-28 containing three large internal repeats (Bgl-U) and the adjacent BgMl-C fragment expresses a nuclear antigen of 82 000 daltons which can be visualized only by a subset of anti EBNA-positive human sera. Sera recognizing the 82 000-dalton protein of the transfected cell line reacted with a protein of the same size in the non-producer line Raji, designated as EBNA 2. Conversely, sera without reactivity to the 82 000-dalton protein failed to react with EBNA 2 of Raji cells. P3HR-1 and Daudi cells with large deletions in BgM-U and -C are devoid of EBNA 2. The data presented provide evidence that a second EBNA protein is encoded by the region of the EBV genome which is deleted in the non-transforming P3HR-1 strain.

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