Virus

About: Virus is a research topic. Over the lifetime, 136914 publications have been published within this topic receiving 5209107 citations. The topic is also known as: infectious agent & viruses.

Zn2+ inhibits coronavirus and arterivirus RNA polymerase activity in vitro and zinc ionophores block the replication of these viruses in cell culture

Abstract: Increasing the intracellular Zn2+ concentration with zinc-ionophores like pyrithione (PT) can efficiently impair the replication of a variety of RNA viruses, including poliovirus and influenza virus. For some viruses this effect has been attributed to interference with viral polyprotein processing. In this study we demonstrate that the combination of Zn2+ and PT at low concentrations (2 µM Zn2+ and 2 µM PT) inhibits the replication of SARS-coronavirus (SARS-CoV) and equine arteritis virus (EAV) in cell culture. The RNA synthesis of these two distantly related nidoviruses is catalyzed by an RNA-dependent RNA polymerase (RdRp), which is the core enzyme of their multiprotein replication and transcription complex (RTC). Using an activity assay for RTCs isolated from cells infected with SARS-CoV or EAV—thus eliminating the need for PT to transport Zn2+ across the plasma membrane—we show that Zn2+ efficiently inhibits the RNA-synthesizing activity of the RTCs of both viruses. Enzymatic studies using recombinant RdRps (SARS-CoV nsp12 and EAV nsp9) purified from E. coli subsequently revealed that Zn2+ directly inhibited the in vitro activity of both nidovirus polymerases. More specifically, Zn2+ was found to block the initiation step of EAV RNA synthesis, whereas in the case of the SARS-CoV RdRp elongation was inhibited and template binding reduced. By chelating Zn2+ with MgEDTA, the inhibitory effect of the divalent cation could be reversed, which provides a novel experimental tool for in vitro studies of the molecular details of nidovirus replication and transcription.

High titers of cytopathic virus in plasma of patients with symptomatic primary HIV-1 infection.

Abstract: Background. Primary infection with the human immunodeficiency virus (HIV-1) frequently causes an acute, self-limited viral syndrome. To examine the relations among viral replication, the immune response of the host, and clinical illness during this initial phase of infection, we undertook a quantitative, molecular, and biologic analysis of infectious HIV-1 in the blood and plasma of three patients with symptomatic primary infection and of a sexual partner of one of them. Methods. During an eight-week period of primary infection, HIV-1 was cultured frequently in dilutions of plasma and peripheral-blood mononuclear cells (PBMC), and levels of HIV-1 antigen and antibody were determined sequentially by enzyme-linked immunosorbent assay and immunoblotting. Replication-competent HIV-1 proviruses were cloned and characterized biologically. Results. Six to 15 days after the onset of symptoms, high titers of infectious HIV-1 (from 10 to 103 tissue-culture—infective doses per milliliter of plasma) and vira...

Cellular targets of infection and route of viral dissemination after an intravaginal inoculation of simian immunodeficiency virus into rhesus macaques.

Abstract: We used the simian immunodeficiency virus (SIV)/rhesus macaque model to study events that underlie sexual transmission of human immunodeficiency virus type 1 (HIV-1). Four female rhesus macaques were inoculated intravaginally with SIVmac251, and then killed 2, 5, 7, and 9 d later. A technique that detected polymerase chain reaction-amplified SIV in situ showed that the first cellular targets for SIV were in the lamina propria of the cervicovaginal mucosa, immediately subjacent to the epithelium. Phenotypic and localization studies demonstrated that many of the infected cells were likely to be dendritic cells. Within 2 d of inoculation, infected cells were identified in the paracortex and subcapsular sinus of the draining internal iliac lymph nodes. Subsequently, systemic dissemination of SIV was rapid, since culturable virus was detectable in the blood by day 5. From these results, we present a model for mucosal transmission of SIV and HIV-1.

Expression cloning of new receptors used by simian and human immunodeficiency viruses

Abstract: Several members of the chemokine-receptor family serve, in conjunction with CD4, as receptors for the entry of human immunodeficiency virus type I (HIV-1) into cells1,2,3,4,5,6 The principal receptor for entry of macrophage-tropic (M-tropic) HIV-1 strains is CCR5, whereas that for T-cell-line-tropic (T-tropic) strains is CXCR4 Unlike HIV-1, infection with either M-tropic or T-tropic strains of simian immunodeficiency virus (SIV) can be mediated by CCR5, but not CXCR4 (refs 7, 8, 9, 10) SIV strains will also infect CD4+ cells that lack CCR5, which suggests that these strains use as yet unidentified receptors7,9,10 Here we use an expression-cloning strategy to identify SIV receptors and have isolated genes encoding two members of the seven-transmembrane G-protein-coupled receptor family that are used not only by SIVs, but also by strains of HIV-2 and M-tropic HIV-1 Both receptors are closely related to the chemokine-receptor family and are expressed in lymphoid tissues One of the receptors is also expressed in colon and may therefore be important in viral transmission Usage of these new receptors following experimental infection of non-human primates with SIV strains may provide important insight into viral transmission and the mechanisms of SIV- and HIV-induced acquired immune-deficiency syndrome

General method for production and selection of infectious vaccinia virus recombinants expressing foreign genes.

Abstract: The production and selection of infectious vaccinia virus recombinants expressing foreign genes was facilitated by the construction of plasmid vectors These vectors contain all or part of the vaccinia virus thymidine kinase (TK) gene interrupted by multiple unique restriction endonuclease sites placed adjacent to the TK promoter or another promoter translocated within the TK gene The insertion of a continuous coding sequence for a foreign protein at one of the unique restriction endonuclease sites juxtaposes the transcriptional start site of a vaccinia promoter and the translational start site of a foreign gene After transfection of vaccinia virus-infected cells with such plasmids, homologous recombination occurs between the vaccinia virus sequences flanking the chimeric gene and the same sequences within the virus genome Recombinants formed in this manner have the chimeric gene inserted within the body of the vaccinia virus TK gene under control of a vaccinia virus promoter Since recombinants have an interrupted TK gene, they are selected on the basis of their TK- phenotype and then checked for the presence and expression of the foreign gene Infectious recombinant viruses expressing the procaryotic enzyme chloramphenicol acetyltransferase were constructed to optimize the system The absence of chloramphenicol acetyltransferase activity in uninfected cells or in cells infected with wild-type vaccinia virus and the availability of a sensitive and quantitative enzyme assay allowed an estimation of the relative strengths of various promoter constructs The expression of chloramphenicol acetyltransferase was detected within 1 h after infection of cells with recombinant virus, reflecting the early nature of the promoters used