JC virus (JCV) belongs to the polyomavirus family of double-stranded DNA viruses and in humans causes a demyelinating disease of the central nervous system, progressive multifocal leukoencephalopathy. Its hemagglutination activity and entry into host cells have been reported to depend on an N-linked glycoprotein containing sialic acid. In order to identify the receptors of JCV, we generated virus-like particles (VLP) consisting of major viral capsid protein VP1. We then developed an indirect VLP overlay assay to detect VLP binding to glycoproteins and a panel of glycolipids. We found that VLP bound to sialoglycoproteins, including ␣1-acid glycoprotein, fetuin, and transferrin receptor, and that this binding depended on ␣2-3-linked sialic acids and N-linked sugar chains. Neoglycoproteins were synthesized by using ovalbumin and conjugation with oligosaccharides containing the terminal ␣2-3-or ␣2-6-linked sialic acid or the branched ␣2-6-linked sialic acid. We show that the neoglycoprotein containing the terminal ␣2-6-linked sialic acid had the highest affinity for VLP, inhibited the hemagglutination activity of VLP and JCV, and inhibited the attachment of VLP to cells. We also demonstrate that VLP bound to specific glycolipids, such as lactosylceramide, and gangliosides, including GM3, GD2, GD3, GD1b, GT1b, and GQ1b, and that VLP bound weakly to GD1a but did not bind to GM1a, GM2, or galactocerebroside. Furthermore, the neoglycoprotein containing the terminal ␣2-6-linked sialic acid and the ganglioside GT1b inhibited JCV infection in the susceptible cell line IMR-32. These results suggest that the oligosaccharides of glycoproteins and glycolipids work as JCV receptors and may be feasible as anti-JCV agents.The human neurotopic polyomavirus JC virus (JCV) is the causative agent of a fatal demyelinating disease known as progressive multifocal leukoencephalopathy (PML). To date, the mortality rate from PML is high, and there is no appropriate therapy for treating PML. The viral route of infection and the mechanisms of viral spread have not been conclusively identified; however, as JCV is frequently detected in untreated urban sewage and in sewage-exposed shellfish, a fecal-oral route of transmission has been suggested (4). Recently, JCV DNA was detected in several organs, including the tonsils and upper and lower gastrointestinal tracts (13,22). Given that JCV ingested by the oral route may enter the intestinal wall and Peyer's patches and thus peripheral blood lymphocytes and various organs (4), the cell surface receptor for JCV is one of the potential therapeutic targets for controlling JCV infection.The JCV receptor has been described as a glycoprotein containing terminal ␣2-6-linked sialic acid, on the basis of the finding that sialidase but not ␣2-3-specific sialidase inhibited infection of glial cells by JCV. In addition, the N glycosylation inhibitor tunicamycin inhibited JCV infection (12). Certain viruses utilize the sialooligosaccharides of glycoproteins and glycolipids for their attachment to host cells an...

To investigate the early events of JC virus (JCV) infection, including attachment, penetration, transport to the nuclei, and replication of the virus, we analyzed the susceptibility of 15 different cell lines to infection using a semiquantitative polymerase chain reaction (PCR) assay, in situ hybridization, laser scanning confocal microscopy, and a viral replication assay. The cell lines examined were human permissive and nonpermissive cells as well as cells of monkey and mouse origin. JCV entry into the nuclei of the all cell lines was observed within 10 min after inoculation, demonstrating that the virus receptor is widely distributed among mammalian cells. Inhibition of viral entry by an anti-JCV VP1 antibody and sialidase treatment to remove sialic acid residues, which are considered a candidate for the JCV receptor, suggested that VP1 may interact with the cellular surface sialic acid. In addition, chlorpromazine, a clathrin-dependent pathway inhibitor, significantly suppressed entry of JCV into nuclei. In spite of the broad spectrum of cells susceptible to JCV entry, replication of the virus occurred exclusively in human neuroblastoma cell lines. These results suggest that whereas JCV can enter a wide variety of cell types and localize to the nuclei, cell-specific intranuclear mechanisms are required for virus replication.

The increasing burden of tick-borne orthonairovirus infections, such as Crimean-Congo hemorrhagic fever, is becoming a global concern for public health. In the present study, we identify a novel orthonairovirus, designated Yezo virus (YEZV), from two patients showing acute febrile illness with thrombocytopenia and leukopenia after tick bite in Hokkaido, Japan, in 2019 and 2020, respectively. YEZV is phylogenetically grouped with Sulina virus detected in Ixodes ricinus ticks in Romania. YEZV infection has been confirmed in seven patients from 2014–2020, four of whom were co-infected with Borrelia spp. Antibodies to YEZV are found in wild deer and raccoons, and YEZV RNAs have been detected in ticks from Hokkaido. In this work, we demonstrate that YEZV is highly likely to be the causative pathogen of febrile illness, representing the first report of an endemic infection associated with an orthonairovirus potentially transmitted by ticks in Japan.

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ABSTRACT. Leptin is the ob gene product secreted from adipocytes in mammals, and thereby its plasma level reflects body fat content. To establish an assay method for leptin in the dog, rabbit anti-canine leptin antibody was obtained using canine recombinant leptin as an antigen. This antibody reacted to canine leptin much stronger than mouse, rat and human leptins. Sandwich enzyme-linked immunosorbent assay (ELISA) using this antibody was developed. The serum leptin levels of 13 healthy dogs were in a range from 1.4 to 5.6 ng/ml with the mean ± SEM of 3.0 ± 0.3 ng/ml.-KEY WORDS: canine, ELISA, leptin.

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