As a response to viral infection, cells express the early inflammatory genes that encode small proteins generally called cytokines or chemokines. These protein can activate immune responses to viral infection as well as to modulate directly the outcome of viral infection. The group of proteins with the direct antiviral effects have been called interferons. The stimulation of interferon synthesis in infected cells is regulated on a transcriptional level and two families of cellular transcriptional factors seem to play a critical role in the transcriptional activation of interferon genes. The first one are the proteins of NF-kappaB family and the second is the family of the interferon responsive factors. While both of the types of the transcriptional factors are important for the induction of interferon beta gene, the NF-kappaB factor do not seems to participate in the induction of interferon alpha genes. The present review is focused on the recently identified new members of cellular IRF family and their role in virus mediated response, responses and cell growth. In addition the HHV-8 encoded vIRFs are described.

Cell Division↗

PubMedDate not supplied

Herpes simplex virus type-1 can reactivate transcription of latent human immunodeficiency virus.

The human immunodeficiency virus, HIV (formerly T-cell lymphotropic virus type III, HTLV-III or lymphadenopathy-associated virus, LAV) is the primary cause of AIDS (acquired immune deficiency syndrome). Patients with AIDS have profound immunosuppression as a result of almost complete absence of the OKT4+ cell population and are predisposed to a number of opportunistic infections as well as to certain malignant diseases such as Kaposi's sarcoma and B-cell tumours. The majority of the opportunistic infections observed in AIDS patients are from the herpesvirus group and these are frequently the cause of death in AIDS patients. We have therefore investigated the effect of herpes virus infection on the expression of HIV and we provide evidence that herpes simplex virus type I (HSV-I) can reactivate transcription of latent HIV. In OKT4+ human T-cells HIV replicates to high virus titres, resulting in high level expression of viral RNA. This high level of expression has been attributed to virus-associated trans-acting factors that increase gene expression, directed by the HIV long terminal repeats (LTR), post-transcriptionally. In our studies we have tested whether transcription directed by the LTR of HIV is stimulated by HSV-I.

Antibodies, Monoclonal↗

PubMedDate not supplied

Interferon downregulates CXCR4 (fusin) gene expression in peripheral blood mononuclear cells.

OBJECTIVE: Cytokines modulate human immunodeficiency virus type 1 (HIV-1) replication at multiple stages of its life cycle. We examined the effects of several HIV-1-stimulatory and HIV-1-inhibitory cytokines on CXCR4 (fusin) gene expression in lymphoid cells. STUDY DESIGN/METHODS: Peripheral blood mononuclear cells (PBMCs) were treated with various cytokines, and CXCR4 gene expression was assessed by Northern blot analysis. Cell-cell fusion was assessed using HeLa-MAGI cells expressing T-cell-tropic HIV-1 (i.e., LAV strain) envelope glycoproteins and U937 cells expressing HIV-1 tat. RESULTS: Although treatment of PBMCs with interferon-alpha (IFN-alpha) and IFN-gamma led to a significant repression of CXCR4 gene expression, interleukin-1 beta (IL-1 beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha) had no significant effect on CXCR4 gene expression in PBMCs. IFN-alpha and IFN-gamma also inhibited CXCR4 gene expression in the promyelocytic cell line U937, and this inhibition led to a decrease in cell-cell fusion between U937 cells and HeLa-MAGI cells. In U937 cells, TNF-alpha and phorbol myristate acetate (PMA) stimulated CXCR4 gene transcription; this effect was reversed with prior treatment of cells with IFN-gamma. CONCLUSIONS: IFN-alpha and IFN-gamma effectively downmodulate fusin gene expression in lymphoid cells, indicating that IFNs modulate HIV-1 replication at postentry levels as well as at the level of HIV-1 entry.

Blotting, Northern↗

PubMedDate not supplied

Unique properties of a second human herpesvirus 8-encoded interferon regulatory factor (vIRF-2).

OBJECTIVE: Human herpesvirus 8/Kaposi's sarcoma herpesvirus (HHV-8/KSHV) contains, in addition to genes required for viral replication, an unique set of nonstructural genes which may be part of viral mimicry and contribute to viral replication and pathogenesis in vivo. Among these, HHV-8 encodes four open reading frames (ORFs) that show homology to the transcription factors of the interferon regulatory factor (IRF) family. In this study we demonstrate that one of these ORFs (vIRF-2) encodes a protein with mobility of 18 kd which has distinct pattern of expression and properties from the cellular IRFs and the previously characterized vIRF-1. METHODS: We cloned vIRF-2 by polymerase chain reaction (PCR) and studied its expression by Northern blot and reverse transcription-polymerase chain reaction (RT-PCR). Biologic activities were tested by chloramphenicol acetyltransferase (CAT) assay in transiently transfected mammalian cells. We characterized its DNA binding specificity by electrophoretic mobility shift analysis (EMSA) and its protein-protein interactions by in vitro pull-down assay. RESULTS: Although low levels of vIRF-2 mRNAs can be detected in the HHV-8-positive BCBL-1 tumor cell line, 12-0-tetradecanoylphorbol-13-acetate (TPA) treatment does not stimulate expression of vIRF-2 gene together with primary lytic cycle genes. Recombinant vIRF-2, which can form homodimers, does not bind specifically to the oligodeoxynucleotide repeats corresponding to the interferon-stimulated response element (ISRE), but it does bind to the NF-kappa B binding site. The fusion protein generated from vIRF-2 and the RelA (p65) activation domain stimulates transcriptional activity of HIV LTR, which contains two NF-kappa B sites, but does not stimulate the interferon-beta (IFNB) promoter, which contains only one NF-kappa B site. Interaction between recombinant vIRF-2 and cellular IRFs such as IRF-1, IRF-2, and ICSBP was detected by in vitro binding assay, but no interaction between IRF-3 and vIRF-2 was found. Interaction of vIRF-2 with RelA (p65) and the carboxy-terminal part of p300 was also observed. In a transient transfection assay, vIRF-2 inhibits the IRF-1- or IRF-3-mediated transcriptional activation of interferon-alpha (IFNA) gene promoter in infected cells and downmodulates RelA (p65)-stimulated activity of HIV LTR. CONCLUSIONS: These results suggest that, by interacting with cellular transcription factors and cofactors, vIRF-2 may modulate the expression of the early inflammatory genes and potentially deregulate the immune system.

3T3 Cells↗

PubMedDate not supplied

Effect of interferon on retrovirus replication.

Interferon block of retrovirus replication can be explained as a consequence of interferon induced changes in physiology (e.g. fluidity) of cellular plasma membranes. Thus, both the membrane associated virus uptake and assembly of progency virus are altered in interferon treated cells (Fig. 1). The relative unsensitivity of retroviral mRNA to the enzymatic systems alternating efficiency of viral mRNA translation in interferon treated cells may be only a relative phenomenon, since the inhibition of viral protein synthesis is observed under conditions of limited viral expression.

Animals↗