Transient transfection of mouse fibroblasts with type I interferon transgenes provides various degrees of protection against herpes simplex virus infection

Complement Suppresses the Initial Type 1 Interferon Response to Ocular Herpes Simplex Virus Type 1 Infection in Mice

The complement system (CS) contributes to the initial containment of viral and bacterial pathogens and clearance of dying cells in circulation. We previously reported mice deficient in complement component 3 (C3KO mice) were more sensitive than wild-type (WT) mice to ocular HSV-1 infection, as measured by a reduction in cumulative survival and elevated viral titers in the nervous system but not the cornea between days three and seven post infection (pi). The present study was undertaken to determine if complement deficiency impacted virus replication and associated changes in inflammation at earlier time points in the cornea. C3KO mice were found to possess significantly (p < 0.05) less infectious virus in the cornea at 24 h pi that corresponded with a decrease in HSV-1 lytic gene expression at 12 and 24 h pi compared to WT animals. Flow cytometry acquisition found no differences in the myeloid cell populations residing in the cornea including total macrophage and neutrophil populations at 24 h pi with minimal infiltrating cell populations detected at the 12 h pi time point. Analysis of cytokine and chemokine content in the cornea measured at 12 and 24 h pi revealed that only CCL3 (MIP-1α) was found to be different between WT and C3KO mice with >2-fold increased levels (p < 0.05, ANOVA and Tukey's post hoc t-test) in the cornea of WT mice at 12 h pi. C3KO mouse resistance to HSV-1 infection at the early time points correlated with a significant increase in type I interferon (IFN) gene expression including IFN-α1 and IFN-β and downstream effector genes including tetherin and RNase L (p < 0.05, Mann-Whitney rank order test). These results suggest early activation of the CS interferes with the induction of the type I IFN response and leads to a transient increase in virus replication following corneal HSV-1 infection.

Superior antiviral activity of IFNβ in genital HSV-1 infection

Type I interferons (IFNs) present the first line of defense against viral infections, providing antiviral, immunomodulatory and antiproliferative effects. The type I IFN family contains 12 IFNα subtypes and IFNβ, and although they share the same receptor, they are classified as non-redundant, capable to induce a variety of different IFN-stimulated genes. However, the biological impact of individual subtypes remains controversial. Recent data propose a subtype-specificity of type I IFNs revealing unique effector functions for different viruses and thus expanding the implications for IFNα-based antiviral immunotherapies. Despite extensive research, drug-resistant infections with herpes simplex virus type 1 (HSV-1), which is the common agent of recurrent orogenital lesions, are still lacking a protective or curing therapeutic. However, due to the risk of generalized infections in immunocompromised hosts as well as the increasing incidence of resistance to conventional antiherpetic agents, HSV infections raise major health concerns. Based on their pleiotropic effector functions, the application of type I IFNs represents a promising approach to inhibit HSV-1 replication, to improve host immunity and to further elucidate their qualitative differences. Here, selective IFNα subtypes and IFNβ were evaluated for their therapeutic potential in genital HSV-1 infections. Respective in vivo studies in mice revealed subtype-specific differences in the reduction of local viral loads. IFNβ had the strongest antiviral efficacy against genital HSV-1 infection in mice, whereas IFNα1, IFNα4, and IFNα11 had no impact on viral loads. Based on flow cytometric analyses of underlying immune responses at local and peripheral sites, these differences could be further assigned to specific modulations of the antiviral immunity early during HSV-1 infection. IFNβ led to enhanced systemic cytokine secretion and elevated cytotoxic responses, which negatively correlated with viral loads in the vaginal tract. These data provide further insights into the diversity of type I IFN effector functions and their impact on the immunological control of HSV-1 infections.

Organoid modeling of Zika and herpes simplex virus 1 infections reveals virus-specific responses leading to microcephaly

Viral infection in early pregnancy is a major cause of microcephaly. However, how distinct viruses impair human brain development remains poorly understood. Here we use human brain organoids to study the mechanisms underlying microcephaly caused by Zika virus (ZIKV) and herpes simplex virus (HSV-1). We find that both viruses efficiently replicate in brain organoids and attenuate their growth by causing cell death. However, transcriptional profiling reveals that ZIKV and HSV-1 elicit distinct cellular responses and that HSV-1 uniquely impairs neuroepithelial identity. Furthermore, we demonstrate that, although both viruses fail to potently induce the type I interferon system, the organoid defects caused by their infection can be rescued by distinct type I interferons. These phenotypes are not seen in 2D cultures, highlighting the superiority of brain organoids in modeling viral infections. These results uncover virus-specific mechanisms and complex cellular immune defenses associated with virus-induced microcephaly.

Understanding Interferon Subtype Therapy for Viral Infections: Harnessing the Power of the Innate Immune System

Type I and III interferons (IFNs) of the innate immune system belong to a polygenic family, however the individual subtype mediators of the antiviral response in viral infections have been hindered by a lack of reagents. Evaluation studies using different IFN subtypes have distinguished distinct protein properties with different efficacies towards different viruses, opening promising avenues for immunotherapy. This review largely focuses on the application of IFN-α/β and IFN-λ therapies for viral infections, influenza, herpes, HIV and hepatitis. Such IFN subtype therapies may help to cure patients with virus infections where no vaccine exists. The ability of cell types to secrete a number of IFN subtypes from a multi-gene family may be an intuitive counterattack on viruses that evade IFN subtype responses. Hence, clinical use of virus-targeted IFN subtypes may restore antiviral immunity in viral infections. Accumulating evidence suggests that individual IFN subtypes have differential efficacies in selectively activating immune cell subsets to enhance antiviral immune responses leading to production of sustained B and T cell memory. Cytokine therapy can augment innate immunity leading to clearance of acute virus infections but such treatments may have limited effects on chronic virus infections that establish lifelong latency. Therefore, exploiting individual IFN subtypes to select those with the ability to sculpt protective responses as well as reinstating those targeted by viral evasion mechanisms may inform development of improved antiviral therapy.

The type I interferons: Basic concepts and clinical relevance in immune-mediated inflammatory diseases

There is increasing scientific and clinical interest in elucidating the biology of type I Interferons, which began approximately 60 years ago with the concept of "viral interference", a property that reduces the ability of a virus to infect cells. Although our understanding of the multiple cellular and molecular functions of interferons has advanced significantly, much remains to be learned and type I Interferons remain an active and fascinating area of inquiry. In this review, we cover some general aspects of type I interferon genes, with emphasis on interferon-alpha, and various aspects of molecular mechanisms triggered by type I interferons and toll-like receptor signaling by the Janus activated kinase/signal transducer activation of transcription (JAK-STAT) pathway and interferon regulatory factor pathway. We will also describe the role of type I interferons in autoimmune and inflammatory diseases, and its potential use as therapeutic agent.

Interferon Beta and Interferon Alpha 2a Differentially Protect Head and Neck Cancer Cells from Vesicular Stomatitis Virus-Induced Oncolysis

Oncolytic viruses (OV) preferentially kill cancer cells due in part to defects in their antiviral responses upon exposure to type I interferons (IFNs). However, IFN responsiveness of some tumor cells confers resistance to OV treatment. The human type I IFNs include one IFN-β and multiple IFN-α subtypes that share the same receptor but are capable of differentially inducing biological responses. The role of individual IFN subtypes in promoting tumor cell resistance to OV is addressed here. Two human IFNs which have been produced for clinical use, IFN-α2a and IFN-β, were compared for activity in protecting human head and neck squamous cell carcinoma (HNSCC) lines from oncolysis by vesicular stomatitis virus (VSV). Susceptibility of HNSCC lines to killing by VSV varied. VSV infection induced increased production of IFN-β in resistant HNSCC cells. When added exogenously, IFN-β was significantly more effective at protecting HNSCC cells from VSV oncolysis than was IFN-α2a. In contrast, normal keratinocytes and endothelial cells were protected equivalently by both IFN subtypes. Differential responsiveness of tumor cells to IFN-α and -β was further supported by the finding that autocrine IFN-β but not IFN-α promoted survival of HNSCC cells during persistent VSV infection. Therefore, IFN-α and -β differentially affect VSV oncolysis, justifying the evaluation and comparison of IFN subtypes for use in combination with VSV therapy. Pairing VSV with IFN-α2a may enhance selectivity of oncolytic VSV therapy for HNSCC by inhibiting VSV replication in normal cells without a corresponding inhibition in cancer cells.

IMPORTANCE

There has been a great deal of progress in the development of oncolytic viruses. However, a major problem is that individual cancers vary in their sensitivity to oncolytic viruses. In many cases this is due to differences in their production and response to interferons (IFNs). The experiments described here compared the responses of head and neck squamous cell carcinoma cell lines to two IFN subtypes, IFN-α2a and IFN-β, in protection from oncolytic vesicular stomatitis virus. We found that IFN-α2a was significantly less protective for cancer cells than was IFN-β, whereas normal cells were equivalently protected by both IFNs. These results suggest that from a therapeutic standpoint, selectivity for cancer versus normal cells may be enhanced by pairing VSV with IFN-α2a.

Interferons as biomarkers and effectors: lessons learned from animal models

Interferons (IFNs) comprise type I, II and III families with multiple subtypes. Via transcription of IFN-stimulated genes (ISGs), IFNs can exert multiple biological effects on the cell. In infectious and chronic inflammatory diseases, the IFNs and their ISG sets can be potentially utilized as biomarkers of disease outcome. Animal models allow investigations into disease pathogenesis and gene knockout models have proved cause and effect relationships of molecules related to the IFN response. Sets of IFN subtypes and their ISG products provide immunological signature patterns for different viral and other diseases. In this article, we give an overview of IFNs in several virus infection models and autoimmune diseases of medical relevance. Lessons learned from animal models inform us of IFN system parameters as indicators of disease outcome and whether clinical research is warranted. Moreover, validated IFN biomarkers for prognosis enhance our understanding of therapeutic and vaccine development.

NK cells require type I IFN receptor for antiviral responses during genital HSV-2 infection

Type I interferon (IFN) signalling, NK cells and NK cell-derived IFN-γ are critical in the early control of genital HSV-2 infection. We have recently reported that NK cells are the source of early IFN-γ in the genital tract in response to HSV-2. However, the response of NK cells to genital HSV-2 infection is not well defined in the context of type I IFN signalling. Here we show that HSV-2 replication was significantly higher in mice deficient in the type I IFN receptor or NK cells compared to wild type controls. There was no detectable IFN-γ production in the genital washes from IFN-α/βR(-/-) mice or NK cell depleted mice in response to HSV-2 infection compared to control mice. Absence of the type I IFN receptor does not alter homing of NK cells to the genital mucosa. Moreover, the absence of IL-12 had no significant effect on NK cell-derived IFN-γ. Surprisingly, IFN-α/βR(-/-) mice had more IL-15 positive cells in the genital mucosa in response to HSV-2 infection compared to control mice. We then examined the expression of IL-15 receptors on NK cells. There was no significant differences in the levels of IL-15 receptor expression on NK cells from IFN-α/βR(-/-) or control mice. Our data clearly suggest that type I IFN receptor signalling is essential for NK cell activation in response to genital HSV-2 infection, and propose that NK cell activation by IL-15 may involve type I IFNs.

Loss of the type I interferon pathway increases vulnerability of mice to genital herpes simplex virus 2 infection

The mouse model of genital herpes relies on medoxyprogesterone treatment of female mice to render the vaginal lumen susceptible to inoculation with herpes simplex virus 2 (HSV-2). In the present study, we report that mice deficient in the A1 chain of the type I interferon receptor (CD118(-/-)) are susceptible to HSV-2 in the absence of medroxyprogesterone preconditioning. In the absence of hormone pretreatment, 2,000 PFU of a clinical isolate of HSV-2 was sufficient to establish a productive infection in the vagina of 75% ± 17% and in the spinal cord of 71% ± 14% of CD118(-/-) mice, whereas the same dose of HSV-2 replicated to detectable levels in only 13% ± 13% of vaginal samples and 0% of spinal cord samples from wild-type mice, as determined at day 5 postinfection. The susceptibility to HSV-2 infection in the CD118(-/-) mice was associated with a significant reduction in the infiltration of HSV-specific cytotoxic T lymphocytes into the vaginal tissue, the local production of gamma interferon (IFN-γ), and the expression of T cell-recruiting chemokines CCL5, CXCL9, and CXCL10. Collectively, the results underscore the significant contribution of type I IFNs in resistance to genital HSV-2 infection.

Overexpression of interleukin-15 compromises CD4-dependent adaptive immune responses against herpes simplex virus 2

Interleukin-15 (IL-15) is necessary for the development and function of NK/NKT cells and the maintenance of naive and memory CD8(+) T cells. In the absence of IL-15, protective innate immunity is not available; however, a functional adaptive immune response against vaginal herpes simplex virus 2 (HSV-2) is generated. Mice overexpressing IL-15 (IL-15tg mice) have higher numbers of NK cells, greater NK-derived gamma interferon, and more CD8(+) T cells. Here we examined the consequences of IL-15 overexpression for innate and adaptive immunity against genital HSV-2. Surprisingly, IL-15tg mice immunized against HSV-2 were not protected against genital HSV-2 challenge compared to control immunized mice. IL-15tg mice had a higher frequency of NK cells in the genital mucosa than control mice. However, immunized IL-15tg mice had significantly lower numbers of HSV-2-specific CD4(+) T cells than B6 mice. We then confirmed that CD4(+) T cells, but not CD8(+) T cells, are essential for protection against intravaginal HSV-2 challenge. Since we observed less protection in immunized IL-15tg mice, we then examined if the adaptive immune responses generated in an environment with overexpression of IL-15 could provide protection against HSV-2 in an environment with normal levels of IL-15 expression. We adoptively transferred immunized cells from IL-15tg and B6 mice into naive RAG-1(-/-) mice and found that the cells from immunized IL-15tg mice were able to provide protection in this IL-15-normal environment. Our data suggest that overexpression of IL-15 results in a reduced CD4(+) T cell-mediated adaptive immune response against genital HSV-2.

Herpes simplex virus type 2-mediated disease is reduced in mice lacking RNase L

RNase L helps mediate the antiviral state induced by type I interferons (IFNalphabeta). Although herpes simplex virus (HSV) encodes inhibitors of the IFNalphabeta-induced antiviral response, the IFNalphabeta system serves the body as a first line of defense against HSV. We investigated whether RNase L limits HSV-2 replication and virulence. RNaseL(-/-) and wild-type C57BL/6 mice were infected intravaginally with HSV-2 strain 333. Although initial replication in the genital epithelium was similar, mice lacking RNase L developed less severe genital and neurologic disease than wild-type mice, survived longer, and contained lower viral titers in the nervous system. CD4(+) T cell infiltration into the genital tract and spinal cord of RNase L(-/-) mice was reduced, suggesting that a restricted inflammatory response may account for reduction in disease. Thus, RNase L does not play a significant role in control of HSV-2 infection in vivo; instead, RNase L may regulate aspects of the inflammatory response that contribute to disease.

Differential activities of alpha/beta IFN subtypes against influenza virus in vivo and enhancement of specific immune responses in DNA vaccinated mice expressing haemagglutinin and nucleoprotein

Vaccines are urgently needed to elicit immunity to different influenza virus strains. DNA vaccines can elicit partial protective immunity, however their efficacy requires improvement. We assessed the capacity of individual type I IFN multigene family members as subtype transgenes to abrogate influenza virus replication in a vaccination/challenge mouse model. Differences in antiviral efficacy were found among the subtypes with IFNA5 and IFNA6 being most effective, while IFNA1 was the least effective in reducing lung virus replication. Mice vaccinated with combinatorial HA/IFNA6 or NP/IFNA6 showed reduced lung viral titres, clinical score, body weight loss, and pulmonary tissue damage compared to IFNA6, HA, or NP viral vaccination alone. In addition, IFNA6 increased IgG2a titres with upregulation of IFN-gamma response in the respiratory tract. We conclude that IFN-alpha 6 has antiviral and immunomodulatory effects, which improve efficacy of DNA vaccines for enhanced control of influenza.

The lack of RNA-dependent protein kinase enhances susceptibility of mice to genital herpes simplex virus type 2 infection

Mice deficient in RNA-dependent protein kinase (PKR-/-) or deficient in PKR and a functional 2',5'-oligoadenylate synthetase (OAS) pathway (PKR/RL-/-) are more susceptible to genital herpes simplex virus type 2 (HSV-2) infection than wild-type mice or mice that are deficient only in a functional OAS pathway (RL-/-) as measured by survival over 30 days. The increase in susceptibility correlated with an increase in virus titre recovered from vaginal tissue or brainstem of infected mice during acute infection. There was also an increase in CD45+ cells and CD8+ T cells residing in the central nervous system of HSV-2-infected PKR/RL-/- mice in comparison with RL-/- or wild-type control animals. In contrast, there was a reduction in the HSV-specific CD8+ T cells within the draining lymph node of the PKR/RL-/- mice. Collectively, activation of PKR, but not of OAS, contributes significantly to the local control and spread of HSV-2 following genital infection.

Direct application of plasmid DNA containing type I interferon transgenes to vaginal mucosa inhibits HSV-2 mediated mortality

The application of naked DNA containing type I interferon (IFN) transgenes is a promising potential therapeutic approach for controlling chronic viral infections. Herein, we detail the application of this approach that has been extensively used to restrain ocular HSV-1 infection, for antagonizing vaginal HSV-2 infection. We show that application of IFN-alpha1, -alpha5, and -beta transgenes to vaginal mouse lumen 24 hours prior to HSV-2 infection reduces HSV-2 mediated mortality by 2.5 to 3-fold. However, other type I IFN transgenes (IFN- alpha4, -alpha5, -alpha6, and -alpha9) are non effectual against HSV-2. We further show that the efficacy of IFN-alpha1 transgene treatment is independent of CD4+ T lymphocytes. However, in mice depleted of CD8+ T lymphocytes, the ability of IFN-alpha1 transgene treatment to antagonize HSV-2 was lost.

Critical role for the oligoadenylate synthetase/RNase L pathway in response to IFN-beta during acute ocular herpes simplex virus type 1 infection

We previously demonstrated that IFN-beta transgene treatment protects mouse trigeminal ganglia (TG) cells from acute HSV-1 infection in vitro. However, IFN-alpha6 transgene treatment does not provide protection against acute HSV-1 infection in vitro, even though equivalent levels of IFN are expressed with both transgene treatments. In the present study we show that IFN-beta transgene treatment before acute ocular HSV-1 infection protects mice from HSV-1-mediated mortality, whereas IFN-alpha6 transgene treatment does not reduce mortality. Treatment with the IFN-beta and IFN-alpha6 transgenes was associated with increased expression of oligoadenylate synthetase (OAS)1a mRNA in the eye. However, protein kinase R mRNA was not up-regulated in the eye. In TG, only IFN-beta transgene treatment reduced infectious virus levels. Furthermore, in the absence of a functional OAS pathway, corneal HSV-1 Ag expression was more widespread, and the ability of IFN-beta transgene treatment to reduce infectious HSV-1 in eyes and TG was lost. Along with selective up-regulation of OAS1a mRNA expression in TG from IFN-beta transgene-treated mice, we found increased levels of phospho-STAT1. Likewise, p38 MAPK phosphorylation was increased in TG from IFN-beta transgene-treated mice, compared with both IFN-alpha6 and vector-treated mice. We also observed a time-dependent increase in JNK phosphorylation in TG from IFN-beta transgene-treated vs IFN-alpha6 and vector-treated mice. Our results demonstrate that IFN-beta is a potent antiviral cytokine that exerts protection against ocular HSV-1 infection via selective up-regulation of OAS1a mRNA in TG and by altering the phosphorylation of proteins in antiviral signaling cascades.

Biocatalysed synthesis of beta-O-glucosides from 9-fluorenon-2-carbohydroxyesters. Part 3: IFN-inducing and anti-HSV-2 properties

In pursuing research on the antiviral, interferon (IFN)-inducing tilorone congeners, a new series of fluoren-carboxyhydroxyesters has been prepared and biologically explored. These esters have subsequently been used as sugar acceptors in the enzymatic transglycosylation reaction using the 'retaining' beta-glycosidase from the archaeon Sulfolobus solfataricus (Ssbeta-Gly). Both aglycones (1-6) and corresponding beta-glucosides (beta-glu 1-beta-glu 6) have been screened for cytotoxicity, interferon-stimulating and antiviral properties against HSV-2. It was found that the addition of compounds beta-glu 5, beta-glu 6 and beta-glu 4 to HSV-2 infected U937 cells downregulates viral replication and triggers cells to release IFN-alpha/beta. Taken together, the results showed improved pharmacological profiles as a consequence of glycosylation. A molecular modelling study carried out on this series of compounds completed the structural characterisation of the novel compounds.

IFN-alpha5 mediates stronger Tyk2-stat-dependent activation and higher expression of 2',5'-oligoadenylate synthetase than IFN-alpha2 in liver cells

Interferon-alpha5 (IFN-alpha5) is the main IFN-alpha subtype expressed in the liver. Hepatitis C virus (HCV) infection is associated with low IFN-alpha5 mRNA levels, possibly reflecting an escape mechanism of the virus. In this work, we sought to compare IFN-alpha2 and IFN-alpha5 with respect to activation of early cell signaling cascades and induction of antiviral genes in the human hepatoma HepG2 and Huh7 cell lines. We found that the Tyr701 phosphorylation kinetics of Stat1 mediated by IFN stimulation was higher when cells were incubated with IFN-alpha5 than when using IFN-alpha2. Similarly, Tyr(1054/1055) phosphorylation kinetics of Tyk2 were more intense after exposure to IFN-alpha5 than when using IFN-alpha2. Concomitantly, Tyr705 phosphorylation of Stat3 was higher after stimulation with IFN-alpha5 than with IFN-alpha2. In parallel to these findings, the mRNA levels of the antiviral IFN-inducible gene 2',5'-oligoadenylate synthetase were higher in cell samples treated with IFN-alpha5 than with IFN-alpha2. These findings suggest that interaction of IFN-alpha5 and IFN-alpha2 subtypes with IFN type I receptor occurs differently, and this affects the intensity of expression of antiviral genes. In conclusion, our data show that in hepatocytic cells, IFN-alpha5 induces stronger signaling and higher expression of antiviral genes than IFN-alpha2. These data warrant clinical trials to evaluate the efficacy of IFN-alpha5 in chronic viral hepatitis.

Characterization of the murine alpha interferon gene family

Mouse and human genomes carry more than a dozen genes coding for closely related alpha interferon (IFN-alpha) subtypes. IFN-alpha, as well as IFN-beta, IFN-kappa, IFN-epsilon, and limitin, are thought to bind the same receptor, raising the question of whether different IFN subtypes possess specific functions. As some confusion existed in the identity and characteristics of mouse IFN-alpha subtypes, the availability of data from the mouse genome sequence prompted us to characterize the murine IFN-alpha family. A total of 14 IFN-alpha genes were detected in the mouse genome, in addition to three IFN-alpha pseudogenes. Four IFN-alpha genes (IFN-alpha1, IFN-alpha7/10, IFN-alpha8/6, and IFN-alpha11) exhibited surprising allelic divergence between 129/Sv and C57BL/6 mice. All IFN-alpha subtypes were found to be stable at pH 2 and to exhibit antiviral activity. Interestingly, some IFN subtypes (IFN-alpha4, IFN-alpha11, IFN-alpha12, IFN-beta, and limitin) showed higher biological activity levels than others, whereas IFN-alpha7/10 exhibited lower activity. Most murine IFN-alpha turned out to be N-glycosylated. However, no correlation was found between N-glycosylation and activity. The various IFN-alpha subtypes displayed a good correlation between their antiviral and antiproliferative potencies, suggesting that IFN-alpha subtypes did not diverge primarily to acquire specific biological activities but probably evolved to acquire specific expression patterns. In L929 cells, IFN genes activated in response to poly(I*C) transfection or to viral infection were, however, similar.

Herpes simplex virus 2 virion host shutoff protein interferes with type I interferon production and responsiveness

The herpes simplex virus 2 (HSV-2) virion host shutoff (vhs) protein is a ribonuclease contained in the virion tegument. vhs-deficient mutants of HSV-2 are profoundly attenuated in vivo, and we have previously shown that replication and virulence of vhs-deficient HSV-2 are largely restored to levels of wild-type virus in mice lacking the interferon alpha/beta receptor (IFNalphabetaR(-/-)). This result demonstrated that HSV-2 vhs interferes with the type I IFN response, but whether vhs inhibits production of type I IFN or synthesis or function of key mediators of the IFN-induced antiviral state was not clear. Here we address these questions using primary murine embryonic fibroblasts (MEFs), which produce and respond to IFNalphabeta. The vhs-deficient HSV-2 strain 333d41 replicated similarly to wild-type virus (333 clone SB5) and vhs rescue virus (333d41(R)) after infection of MEFs at high moi, but at low moi, 333d41 replication was severely attenuated, recapitulating the attenuated phenotype of vhs-deficient HSV-2 in vivo. Replication of 333d41 at low moi was restored to levels of wild-type virus in MEFs lacking the IFNalphabeta receptor or when IFNalphabeta was neutralized, thus establishing the IFNalphabeta response as the sole mechanism attenuating vhs-deficient HSV-2 replication in MEFs. MEFs infected with 333d41 produced >50-fold more IFNalphabeta than cells infected with 333 and 333d41(R). Pretreatment of MEFs with type I IFN inhibited replication of 333d41 more than 333 and 333d41(R), indicating that vhs also interferes with activation of the IFNalphabeta-induced antiviral response. We therefore examined vhs interference with PKR and RNase L, two key mediators of the IFNalphabeta response. 333d41 replication was restored to wild-type levels after low moi infection of PKR(-/-) and RNase L(-/-) MEFs, and was not inhibited in PKR(-/-) MEFs pretreated with IFNalpha. Together, these observations indicate that HSV-2 vhs is a broad and potent countermeasure to the IFN-mediated antiviral response in IFN-naïve and -sensitized MEFs.

Innate immunity to herpes simplex virus type 2

Herpes simplex virus type 2 (HSV-2) is responsible for most cases of genital herpes and also can cause fatal disseminated disease in perinatally infected newborns. Sexually transmitted infections initiate in the skin or mucosa and quickly spread into peripheral nerves to establish latency. Innate immunity, the first line of defense during both primary and recurrent infection, is essential during this period of acute infection to limit initial viral replication and to facilitate an appropriate adaptive immune response. The innate immune response consists of a complex multilayered system of mechanical and secreted defenses, immediate chemokine and IFN responses, and rapidly recruited cellular defenses. HSV has devised equally elaborate strategies to evade or interfere with innate immunity. This review summarizes our current understanding of the innate immune responses to HSV-2 and the mechanisms by which HSV-2 can overcome these barriers. Newly emerging links between products of innate responses and the development of adaptive immune responses are also discussed.

Cloning and characterization of an Mx gene and its corresponding promoter from the zebrafish, Danio rerio

Type I interferons (IFNs) represent a crucial component of the innate immune response to viruses. An important downstream effector of IFN is the Mx gene, which is activated solely through this pathway. Mx proteins are characterized by a tripartite GTP-binding domain, dynamin family signature, and leucine zipper motif. Mx genes are transcribed upon activation of an interferon-stimulated response element (ISRE) located in the Mx promoter region. In this article, we describe the cloning and analysis of an Mx gene and its corresponding promoter from the zebrafish (Danio rerio). The deduced amino acid sequence of zebrafish Mx contains the conserved GTP-binding domain, dynamin family signature, and leucine zipper motif common to Mx proteins, and shows a 50% identity to human MxA and 69% identity both to rainbow trout and to Atlantic salmon. Zebrafish liver cells produced high levels of Mx mRNA in response to induction by the known IFN-inducer polyinosinic-polycytidylic acid (Poly[I:C]). The zebrafish Mx promoter contains two ISREs homologous to those found in the promoter regions of many IFN-inducible genes, and was able to drive transcription of a luciferase reporter gene when induced by either purified zebrafish IFN or Poly[I:C].

Viral infections: their elusive role in regulating susceptibility to autoimmune disease

Viral infections may trigger autoimmune disease. Complicating our understanding of how viral infections promote disease is the realization that viral infections can sometimes prevent auto-aggressive reactions. Here, we will discuss recent findings that provide insights into how viral infections may alter susceptibility to autoimmunity.

Type I interferon differential therapy for erythroleukemia: specificity of STAT activation

Type I interferons (IFNs), pleiotropic cytokines with antiviral, antiproliferative, apoptotic, and immunoregulatory functions, are efficacious in the treatment of malignancies, viral infections, and autoimmune diseases. Binding of these cytokines to their cognate receptor leads to activation of the Jak-signal transducers and activators of transcription (STAT) signaling pathway and altered gene expression. This signal pathway has been intensely studied using human IFN-alpha 2 and IFN-beta. However, there are over 14 human IFN-alpha subtypes and over 10 murine IFN-alpha subtypes, with a single IFN-beta subtype in both species. J2E cells are immortalized at the proerythroblast stage of development and produce a rapid and fatal erythroleukemia in vivo. These cells retain the ability to respond to erythropoietin in vitro by proliferating, differentiating, and remaining viable in the absence of serum. Here, we show that J2E cells are also functionally regulated differentially by IFN subtype treatment in vitro. A novel finding was the selective activation of STAT and mitogen-activated protein kinase (MAPK) molecules by different subtypes binding the IFN receptor. These findings indicate distinct effects for individual type I IFN subtypes, which are able to differentially activate members of the STAT and MAPK family. Finally, we investigated the efficacy of IFN naked DNA therapy in treating J2E-induced erythroleukemia in athymic nude mice. IFN subtypes differentially regulated the onset of erythroleukemia with delayed onset and increased survival, possibly via a reduction in cell viability, and enhanced antiproliferative and apoptotic effects observed for IFNA6 and IFNA9 treatment, respectively. Moreover, these data highlight the necessity to choose the best IFN subtype in disease treatment.