The transporters SLC35A1 and SLC30A1 play opposite roles in cell survival upon VSV virus infection.

Host factor requirements for different classes of viruses have not been fully unraveled. Replication of the viral genome and synthesis of viral proteins within the human host cell are associated with an increased demand for nutrients and specific metabolites. With more than 400 acknowledged members to date in humans, solute carriers (SLCs) represent the largest family of transmembrane proteins dedicated to the transport of ions and small molecules such as amino acids, sugars and nucleotides. Consistent with their impact on cellular metabolism, several SLCs have been implicated as host factors affecting the viral life cycle and the cellular response to infection. In this study, we aimed at characterizing the role of host SLCs in cell survival upon viral infection by performing unbiased genetic screens using a focused CRISPR knockout library. Genetic screens with the cytolytic vesicular stomatitis virus (VSV) showed that the loss of two SLCs genes, encoding the sialic acid transporter SLC35A1/CST and the zinc transporter SLC30A1/ZnT1, affected cell survival upon infection. Further characterization of these genes suggests a role for both of these transporters in the apoptotic response induced by VSV, offering new insights into the cellular response to oncolytic virus infections.

Subcapsular sinus macrophages prevent CNS invasion on peripheral infection with a neurotropic virus.

Lymph nodes (LNs) capture microorganisms that breach the body's external barriers and enter draining lymphatics, limiting the systemic spread of pathogens. Recent work has shown that CD11b(+)CD169(+) macrophages, which populate the subcapsular sinus (SCS) of LNs, are critical for the clearance of viruses from the lymph and for initiating antiviral humoral immune responses. Here we show, using vesicular stomatitis virus (VSV), a relative of rabies virus transmitted by insect bites, that SCS macrophages perform a third vital function: they prevent lymph-borne neurotropic viruses from infecting the central nervous system (CNS). On local depletion of LN macrophages, about 60% of mice developed ascending paralysis and died 7-10 days after subcutaneous infection with a small dose of VSV, whereas macrophage-sufficient animals remained asymptomatic and cleared the virus. VSV gained access to the nervous system through peripheral nerves in macrophage-depleted LNs. In contrast, within macrophage-sufficient LNs VSV replicated preferentially in SCS macrophages but not in adjacent nerves. Removal of SCS macrophages did not compromise adaptive immune responses against VSV, but decreased type I interferon (IFN-I) production within infected LNs. VSV-infected macrophages recruited IFN-I-producing plasmacytoid dendritic cells to the SCS and in addition were a major source of IFN-I themselves. Experiments in bone marrow chimaeric mice revealed that IFN-I must act on both haematopoietic and stromal compartments, including the intranodal nerves, to prevent lethal infection with VSV. These results identify SCS macrophages as crucial gatekeepers to the CNS that prevent fatal viral invasion of the nervous system on peripheral infection.

Comparison of two birnavirus-rhabdovirus coinfections in fish cell lines.

Aquabirnaviruses, such as the infectious pancreatic necrosis virus (IPNV), Novirhabdoviruses, such as the infectious hematopoiteic necrosis virus (IHNV) and the viral hemorrhagic septicemia virus (VHSV), cause considerable losses to the salmonid industry worldwide. Coinfections of 2 viruses have been described, but the interactions between rhabdoviruses and birnaviruses have not been examined closely. Using virus titration, flow cytometry and RT-PCR assays, we compared the effect of IPNV on the replication of IHNV and VHSV in tissue culture cells. RT-PCR assays indicated that simultaneous infection of IPNV with VHSV does not affect the replication of the rhabdovirus either in the first or successive passages; the infective titers were similar in single and double infections. In contrast, coinfection of IPNV with IHNV induced a fall in infectivity, with reduced expression of IHNV viral antigens in BF-2 cells from Lepomis macrochirus and a loss of 4.5 log10 units of the infective titer after 3 successive passages. It was possible to stimulate BF-2 cells to produce significant interferon-like activity against IHNV but not against VHSV.

Lyssaviral infection and lead poisoning in black flying foxes from Queensland.

Pteropid lyssaviral infection, lead poisoning, and the difficulties in diagnosing pteropid lyssaviral infection using histopathological examination of tissues are described in wild black flying foxes (Pteropus alecto) from northern Queensland (Australia). An adult female P. alecto showed aggression before death in January 1995. Lead poisoning was diagnosed due to the presence of intranuclear lead inclusion bodies in renal proximal convoluted tubular epithelium and high concentrations of lead in renal and hepatic tissues, 370.03 +/- 7.35 ppm and 16.76 +/- 0.53 ppm, respectively. Renal inclusion bodies were composed of lead, calcium, phosphorus, and possibly sulphur; some inclusions had their granules arranged in concentric bands. This bat also had a moderate concentration (8.09 +/- 0.18 ppm) of cadmium in renal tissue. An adult male P. alecto presented with ascending paralysis before it died in May 1996. Pteropid lyssaviral infection was diagnosed subsequently in both bats in September 1996 by immunofluorescent and immunoperoxidase antibody tests for rabies on brains and viral culture from brains. Neither bat had gross or microscopic lesions of the brain that suggested a lyssaviral infection, apart from occasional, subtle, eosinophilic cytoplasmic inclusions in the neurones of the brain stem of the female. These cases illustrate the need for a specific test to detect pteropid lyssavirus such as an immunofluorescent antibody test for lyssavirus rather than histopathological examination of tissues.

Study of a viral-dual infection in rainbow trout (Oncorhynchus mykiss) by seroneutralization, western blot and polymerase chain reaction assays.

Viral-dual infections in fish are of interest to aquaculture practices but they are rarely described and studied. Several methods were applied in this work to demonstrate a case of coinfection in a reared rainbow trout (Oncorhynchus mykiss) population. Inoculation in cell cultures and cross-neutralization tests were the standard procedures that made it possible to isolate and identify a birnavirus, the infectious pancreatic necrosis virus (IPNV), and suspect of a second virus. Western blotting with both polyclonal and monoclonal antibodies, and reverse transcriptional-polymerase chain reaction (RT-PCR) demonstrate coexistence of both, IPNV and a rhabdovirus.