Defective transport of hemagglutinin-neuraminidase glycoprotein of bovine parainfluenza-3 virus in interferon treated cell

Resistance of Paramyxoviridae to Type I Interferon-InducedBos taurusMx1 Dynamin

Typical targets of type I interferon (IFN)-induced antiviral Mx proteins known to date have been shown to share a common profile: single-stranded negative-sense RNA viruses. Among them, human MxA is known to interfere with the replication of measles, human, and bovine parainfluenza-3 viruses (BoPi3V), that is, three members of the Paramyxoviridae family. Recently, bovine Mx1 protein (BoMx1) was included in the group of Mx proteins with authenticated antiviral potential, as it dramatically represses the replication of vesicular stomatitis virus (VSV). As replication in bovine cells of Pi3, respiratory syncytial (RS), and Sendai (Se) viruses, all members of the same family, is known to be reduced on IFN-alpha incorporation into the culture medium, it was hypothesized that the BoMx1 pathway possibly was involved, its antiviral spectrum thus probably extending to Paramyxoviridae. In this study, probing of BoMx1-inhibiting effects was carried out by infecting a transgenic Vero cell line that allows tightly regulated conditional expression of BoMx1 after doxycycline treatment with a wide array of Paramyxoviridae. Expressing and nonexpressing cells displayed similar viability, cytopathic effects (CPEs), and amounts of infectious virus yields, whatever the infecting virus or the multiplicity of infection (moi) imposed. It is, therefore, concluded that BoMx1 does not interfere with Paramyxoviridae.

Mechanism of enhancement of the antiviral action of interferon against herpes simplex virus-1 by chloroquine

Using double immunofluorescence, we have shown previously that interferon (IFN) treatment inhibits the transport of herpes simplex virus-1 (HSV-1) gD from the Golgi complex to the plasma membrane in the virus infected and gD cDNA transfected LMtk-cells. In the present study, we quantitated the gD protein on the cell surface and localized the gD protein in the trans-Golgi network (TGN). The results showed 10-fold less fluorescence for the gD protein on the cell surface in IFN-treated LMtk-cells. Subcellular fractionation studies demonstrated that gD was associated with TGN-enriched membranes. Gold labeling for DAMP distribution using electron microscopy showed that IFN raised the pH of TGN. IFNs induced alkalinization of TGN may be related to the block in the transport of HSV-1 gD. Earlier we reported that a subeffective dose of chloroquine (CHL) or IFN does not change the pHi. However, both CHL and IFN together raise the pHi significantly. To study the biologic significance of the finding, the effect of these subeffective doses of IFN and CHL on the antiviral activity and the transport of the gD protein was studied. Results suggested that CHL enhance the antiviral activity of IFN against HSV-1 and concomitantly increase the inhibition of HSV-1 gD transport. This IFN-induced increase in pHi of the TGN may also explain the inhibitory effect of IFN reported on the terminal steps of some of the enveloped viruses.

Defective transport of herpes simplex virus glycoprotein in interferon-treated cells: role of intracellular pH

We have investigated the mechanism(s) of interferon (IFN)-induced inhibition of assembly steps of herpes simplex virus (HSV-1) in mouse LB cells. Data showed that physiological doses of mouse IFN-beta (10-100 IU/ml) significantly inhibited the infectivity (5- to 100-fold) of HSV-1; however, viral protein synthesis was marginally inhibited (2- to 5-fold). Immunofluorescence studies showed that most of the HSV-1gD glycoprotein accumulated intracellularly in IFN-treated LB and LMtk- cells transfected with gD cDNA, as compared to untreated controls, where most of the gD was localized on the plasma membrane. Double-immunofluorescence studies demonstrated that rhodamine-labeled wheat germ agglutinin (WGA) was co-localized with gD protein, suggesting the block was in the transport from the trans-Golgi to the plasma membrane. IFN treatment of LB and LMtk- cells raised the intracellular pH as measured by DAMP distribution and SNARF-1 using laser spectroscopy; this could play an important role in the inhibition of transport of HSV-1gD.

Monoclonal and polyclonal antibodies for immunohistochemical detection of bovine parainfluenza type 3 virus in frozen and formalin-fixed paraffin-embedded tissues

Accurate identification of bovine parainfluenza type 3 virus in bovine respiratory disease requires dependable, sensitive, and specific techniques for detection in affected animals. Immunohistochemical testing can be a rapid and reliable means of demonstration of virus in tissues from suspect cases; however, this procedure is dependent upon the quality of the antisera directed against the viral antigens. The production of rabbit polyclonal and murine monoclonal antibodies directed against bovine parainfluenza type 3 virus and techniques for their use in fresh-frozen and formalin-fixed paraffin-embedded tissues in immunofluorescence and immunoperoxidase-based immunohistochemical tests are described.

Use of Brefeldin A to localize block in intracellular transport of vesicular stomatitis virus G protein on interferon-treated cells

Brefeldin A (BFA) induced a rapid redistribution of vesicular stomatitis virus G protein (VSV-G) to the endoplasmatic reticulum (ER) in interferon (IFN)-pretreated cells. This result is consistent with accumulation of VSV-G in the trans-Golgi (GC) complex in cells pretreated with IFN and implies that IFN does not interfere with the ability of BFA to induce redistribution of proteins from GC to ER.

Development of an in vitro model for study of non-O1 Vibrio cholerae virulence using Caco-2 cells

Non-O1 Vibrio cholerae strains have been reported as a causative agent of diarrhea throughout the world. We recently reported that non-O1 V. cholerae strains cause diarrhea in human volunteers. In this study we evaluated the virulence of three strains of non-O1 V. cholerae in a Caco-2 cell adherence assay by light and electron microscopy. A-5 is an environmental isolate which failed to colonized volunteers and did not cause diarrhea. It exhibited low numbers of organisms adherent to Caco-2 cells, leaving the microvilli intact. Strain 2076-79, isolated from a patient with diarrhea, colonized human volunteers without producing disease. It adhered to Caco-2 cells in moderate numbers without producing any damage to the microvilli. Strain NRT36S, a clinical isolate, colonized human volunteers and produced significant diarrhea disease. This strain adhered in very large numbers to Caco-2 cells and caused damage to the brush borders. Membrane-bound bacteria were also seen within the cytoplasm of these cells. Scanning electron microscopy confirmed the generalized adherence of NRT36S to the microvilli of Caco-2 cells. The three strains did not appear to compete with each other for binding sites on Caco-2 cells and were not adherent when assays were conducted at 4 degrees C. Our results with strains A-5, 2076-79, and NRT36S correlate well with observations in human volunteer studies, suggesting that Caco-2 cells provide an appropriate in vitro system for further investigation of the pathogenesis of non-O1 V. cholerae gastroenteritis.