Impaired antiviral response and alpha/beta interferon induction in mice lacking beta interferon

We have generated mice lacking the gene for beta interferon and report that they are highly susceptible to vaccinia virus infection. Furthermore, in cultured embryo fibroblasts, viral induction of alpha interferon and of 2-5A synthetase genes is impaired. We also show that beta interferon does not prime its own expression.     

Interleukin-2 and alpha/beta interferon down-regulate hepatitis B virus gene expression in vivo by tumor necrosis factor-dependent and -independent pathways.

We have recently reported that administration of recombinant tumor necrosis factor alpha (TNF-alpha) to hepatitis B virus (HBV) transgenic mice reduces the hepatic steady-state content of HBV-specific mRNA by up to 80% in the absence of liver cell injury. In the current study, we analyzed the regulatory effects of several other inflammatory cytokines in the same transgenic model system. Hepatic HBV mRNA content was reduced by up to 90% following administration of a single noncytopathic dose (100,000 U) of interleukin 2 (IL-2). Comparable effects were produced by administration of alpha and beta interferons (IFN-alpha and IFN-beta), but only after multiple injections of at least 500,000 U per mouse. Importantly, the regulatory effect of IL-2 was completely blocked by the prior administration of antibodies to tumor necrosis factor alpha (TNF-alpha), which did not block the effect of IFN-alpha or IFN-beta. In contrast to these observations, recombinant IFN-gamma, IL-1, IL-3, IL-6, TNF-beta, transforming growth factor beta, and granulocyte-monocyte colony-stimulating factor were inactive in this system. These results suggest that selected inflammatory cytokines can down-regulate HBV gene expression in vivo by at least two pathways, one that is dependent on TNF-alpha and another that is not. These results imply that antigen-nonspecific products of the intrahepatic HBV-specific inflammatory response may contribute to viral clearance or persistence during HBV infection.     

Critical roles for both STAT1-dependent and STAT1-independent pathways in the control of primary dengue virus infection in mice

Dengue virus (DEN), a flavivirus, causes dengue fever and dengue hemorrhagic fever/dengue shock syndrome, the most common mosquito-borne viral illnesses in humans worldwide. In this study, using STAT1(-/-) mice bearing two different mutant stat1 alleles in the 129/Sv/Ev background, we demonstrate that IFNR-dependent control of primary DEN infection involves both STAT1-dependent and STAT1-independent mechanisms. The STAT1 pathway is necessary for clearing the initial viral load, whereas the STAT1-independent pathway controls later viral burden and prevents DEN disease in mice. The STAT1-independent responses in mice with primary DEN infection included the early activation of B and NK cells as well as the up-regulation of MHC class I molecules on macrophages and dendritic cells. Infection of bone marrow-derived dendritic cell cultures with either DEN or Sindbis virus, another positive-strand RNA virus, confirmed the early vs late natures of the STAT1-dependent and STAT1-independent pathways. Collectively, these data begin to define the nature of the STAT1-dependent vs the STAT1-independent pathway in vivo.     

Herpes simplex virus type 2 virion host shutoff protein regulates alpha/beta interferon but not adaptive immune responses during primary infection in vivo

The herpes simplex virus (HSV) virion host shutoff (vhs) protein, the product of the UL41 (vhs) gene, is an important determinant of HSV virulence. vhs has been implicated in HSV interference with host antiviral immune responses, down-regulating expression of major histocompatibility complex molecules to help HSV evade host adaptive immunity. The severe attenuation of vhs-deficient viruses in vivo could reflect their inability to escape immune detection. To test this hypothesis, BALB/c or congenic SCID mice were infected intravaginally (i.vag.) with the HSV type 2 (HSV-2) vhs null mutant 333d41 or the vhs rescue virus 333d41(R). vhs-deficient virus remained severely attenuated in SCID mice compared with rescue virus, indicating that vhs regulation of adaptive immune responses does not influence HSV pathogenesis during acute infection. Innate antiviral effectors remain intact in SCID mice; prominent among these is alpha/beta interferon (IFN-alpha/beta). The attenuation of HSV-2 vhs mutants could reflect their failure to suppress IFN-alpha/beta-mediated antiviral activity. To test this hypothesis, 129 and congenic IFN-alpha/beta receptor-deficient (IFN-alpha/betaR(-/-)) mice were infected i.vag. with wild-type virus, vhs null mutants 333-vhsB or 333d41, or the vhs rescue virus 333d41(R). Whereas vhs-deficient viruses showed greatly reduced replication in the genital mucosa of 129 mice compared with wild-type or vhs rescue viruses, they were restored to nearly wild-type levels of replication in IFN-alpha/betaR(-/-) mice over the first 2 days postinfection. Only wild-type and vhs rescue viruses caused severe genital disease and hind limb paralysis in 129 mice, but infection of IFN-alpha/betaR(-/-) mice restored the virulence of vhs-deficient viruses. vhs-deficient viruses replicated as vigorously as wild-type and rescue viruses in the nervous systems of IFN-alpha/betaR(-/-) mice. Restoration was specific for the vhs mutation, because thymidine kinase-deficient HSV-2 did not regain virulence or the capacity to replicate in the nervous systems of IFN-alpha/betaR(-/-) mice. Furthermore, the defect in the IFN-alpha/beta response was required for restoration of vhs-deficient virus replication and virulence, but the IFN-alpha/beta-stimulated protein kinase R pathway was not involved. Finally, vhs of HSV-2 has a unique capacity to interfere with the IFN-alpha/beta response in vivo, because an HSV-1 vhs null mutant did not recover replication and virulence after i.vag. inoculation into IFN-alpha/betaR(-/-) mice. These results indicate that vhs plays an important role early in HSV-2 pathogenesis in vivo by interfering with the IFN-alpha/beta-mediated antiviral response.     

Specific integrin alpha and beta chain phosphorylations regulate LFA-1 activation through affinity-dependent and -independent mechanisms

Integrins are adhesion receptors that are crucial to the functions of multicellular organisms. Integrin-mediated adhesion is a complex process that involves both affinity regulation and cytoskeletal coupling, but the molecular mechanisms behind this process have remained incompletely understood. In this study, we report that the phosphorylation of each cytoplasmic domain of the leukocyte function-associated antigen-1 integrin mediates different modes of integrin activation. alpha Chain phosphorylation on Ser1140 is needed for conformational changes in the integrin after chemokine- or integrin ligand-induced activation or after activation induced by active Rap1 (Rap1V12). In contrast, the beta chain Thr758 phosphorylation mediates selective binding to 14-3-3 proteins in response to inside-out activation through the T cell receptor, resulting in cytoskeletal rearrangements. Thus, site-specific phosphorylation of the integrin cytoplasmic domains is important for the dynamic regulation of these complex receptors in cells.     

Early B-cell activation after West Nile virus infection requires alpha/beta interferon but not antigen receptor signaling

The B-cell response against West Nile virus (WNV), an encephalitic Flavivirus of global concern, is critical to controlling central nervous system dissemination and neurological sequelae, including death. Here, using a well-characterized mouse model of WNV infection, we examine the factors that govern early B-cell activation. Subcutaneous inoculation with a low dose of replicating WNV results in extensive B-cell activation in the draining lymph node (LN) within days of infection as judged by upregulation of the surface markers CD69, class II major histocompatibility complex, and CD86 on CD19(+) cells. B-cell activation in the LN but not the spleen was dependent on signals through the type I alpha/beta interferon (IFN-alpha/beta) receptor. Despite significant activation in the draining LN at day 3 after infection, WNV-specific B cells were not detected by immunoglobulin M enzyme-linked immunospot analysis until day 7. Liposome depletion experiments demonstrate that B-cell activation after WNV infection was not affected by the loss of F4/80(+) or CD169(+) subcapsular macrophages. Nonetheless, LN myeloid cells were essential for control of viral replication and survival from infection. Overall, our data suggest that the massive, early polyclonal B-cell activation occurring in the draining LN after WNV infection is immunoglobulin receptor and macrophage independent but requires sustained signals through the type I IFN-alpha/beta receptor.     

Quantitative multiplex real-time PCR for the sensitive detection of interferon beta gene induction and viral suppression of interferon beta expression

Interferon-beta (IFN-beta) protein and activity can be detected by enzyme immunoassays and biological assays. However, precise quantification of low IFN-beta mRNA concentrations, which is advantageous for investigating IFN-beta gene expression in small tissue samples or during the early stage of a virus infection, remains a challenge. Therefore, we established a quantitative real-time PCR (qPCR) for IFN-beta and the housekeeping gene porphobilinogen deanimase (PBGD) in separated assays as well as in a multiplex procedure. Sensitivity for both the templates was less than 20 copies with an intra- and interassay variability of less than 5%. IFN-beta qPCR was utilized to optimize IFN-beta induction with dsRNA polyinosic-polycytidylic acid (poly I:C), delivered by a liposomal transfection agent for reproducible but low, non-cell-toxic IFN-beta concentrations. For studying coxsackievirus B3 (CVB3) interference with IFN-beta expression, CVB3 infected fibroblasts were induced with poly I:C. A significant reduction of IFN-beta mRNA but not PBGD mRNA was demonstrated 5 h after CVB3 infection, indicating a specific inhibition of IFN-beta expression by CVB3 on the mRNA level, in addition to previously reported effects on the translation/post-translation level. In conclusion, sensitive IFN-beta/PBGD multiplex qPCR proved to be a useful tool to study viral interaction with IFN-beta expression.     

Mice lacking alpha/beta and gamma interferon receptors are susceptible to junin virus infection

Junin virus (JUNV) causes a highly lethal human disease, Argentine hemorrhagic fever. Previous work has demonstrated the requirement for human transferrin receptor 1 for virus entry, and the absence of the receptor was proposed to be a major cause for the resistance of laboratory mice to JUNV infection. In this study, we present for the first time in vivo evidence that the disruption of interferon signaling is sufficient to generate a disease-susceptible mouse model for JUNV infection. After peripheral inoculation with virulent JUNV, adult mice lacking alpha/beta and gamma interferon receptors developed disseminated infection and severe disease.     

Establishment of a poliovirus oral infection system in human poliovirus receptor-expressing transgenic mice that are deficient in alpha/beta interferon receptor

Poliovirus (PV) is easily transferred to humans orally; however, no rodent model for oral infections has been developed because of the alimentary tract's low sensitivity to the virus. Here we showed that PV is inactivated by the low pH of the gastric contents in mice. The addition of 3% NaHCO3 to the viral inoculum increased the titer of virus reaching the small intestine through the stomach after intragastric inoculation of PV. Transgenic mice (Tg) carrying the human PV receptor (hPVR/CD155) gene and lacking the alpha/beta interferon receptor (IFNAR) gene (hPVR-Tg/IfnarKO) were sensitive to the oral administration of PV with 3% NaHCO3, whereas hPVR-Tg expressing IFNAR were much less sensitive. The virus was detected in the epithelia of the small intestine and proliferated in the alimentary tract of hPVR-Tg/IfnarKO. By the ninth day after the administration of a virulent PV, the mice had died. These results suggest that IFNAR plays an important role in determining permissivity in the alimentary tract as well as the generation of virus-specific immune responses to PV via the oral route. Thus, hPVR-Tg/IfnarKO are considered to be the first oral infection model for PV, although levels of anti-PV antibodies were not elevated dramatically in serum and intestinal secretions of surviving mice when hPVR-Tg/IfnarKO were administered an attenuated PV.     

Changes in the conformation of the interferon beta gene during differentiation and induction

DNase I sensitivity was used to investigate the chromatin conformation of the interferon beta gene during differentiation of the mouse teratocarcinoma cell line PC13 . These cells do not produce interferon upon viral induction in their undifferentiated state, but do so on differentiation from stem cells to endoderm. Only in induced differentiated cells were the interferon beta genes digested by DNase I. A similar effect was seen in a line of human cells ( MG63 ) upon induction. We conclude that it is induction of interferon production that brings about the change in the DNase I sensitivity of these genes, rather than differentiation.     

Integrin alpha5/beta1 mediates fibronectin-dependent epithelial cell proliferation through epidermal growth factor receptor activation

Human integrin alpha5 was transfected into the integrin alpha5/beta1-negative intestinal epithelial cell line Caco-2 to study EGF receptor (EGFR) and integrin alpha5/beta1 signaling interactions involved in epithelial cell proliferation. On uncoated or fibronectin-coated plastic, the integrin alpha5 and control (vector only) transfectants grew at similar rates. In the presence of the EGFR antagonistic mAb 225, the integrin alpha5 transfectants and controls were significantly growth inhibited on plastic. However, when cultured on fibronectin, the integrin alpha5 transfectants were not growth inhibited by mAb 225. The reversal of mAb 225-mediated growth inhibition on fibronectin for the integrin alpha5 transfectants correlated with activation of the EGFR, activation of MAPK, and expression of proliferating cell nuclear antigen. EGFR kinase activity was necessary for both MAPK activation and integrin alpha5/beta1-mediated cell proliferation. Although EGFR activation occurred when either the integrin alpha5-transfected or control cells were cultured on fibronectin, coprecipitation of the EGFR with SHC could be demonstrated only in the integrin alpha5-transfected cells. These results suggest that integrin alpha5/beta1 mediates fibronectin-induced epithelial cell proliferation through activation of the EGFR.