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.

A Phase I Study of OncoVEXGM-CSF, a Second-Generation Oncolytic Herpes Simplex Virus Expressing Granulocyte Macrophage Colony-Stimulating Factor

Abstract: PURPOSE: To conduct a phase I clinical trial with a second-generation oncolytic herpes simplex virus (HSV) expressing granulocyte macrophage colony-stimulating factor (Onco VEXGM-CSF) to determine the safety profile of the virus, look for evidence of biological activity, and identify a dosing schedule for later studies. EXPERIMENTAL DESIGN: The virus was administered by intratumoral injection in patients with cutaneous or s.c. deposits of breast, head and neck and gastrointestinal cancers, and malignant melanoma who had failed prior therapy. Thirteen patients were in a single-dose group, where doses of 10(6), 10(7), and 10(8) plaque-forming units (pfu)/mL were tested, and 17 patients were in a multidose group testing a number of dose regimens. RESULTS: The virus was generally well tolerated with local inflammation, erythema, and febrile responses being the main side effects. The local reaction to injection was dose limiting in HSV-seronegative patients at 10(7) pfu/mL. The multidosing phase thus tested seroconverting HSV-seronegative patients with 10(6) pfu/mL followed by multiple higher doses (up to 10(8) pfu/mL), which was well tolerated by all patients. Biological activity (virus replication, local reactions, granulocyte macrophage colony-stimulating factor expression, and HSV antigen-associated tumor necrosis), was observed. The duration of local reactions and virus replication suggested that dosing every 2 to 3 weeks was appropriate. Nineteen of 26 patient posttreatment biopsies contained residual tumor of which 14 showed tumor necrosis, which in some cases was extensive, or apoptosis. In all cases, areas of necrosis also strongly stained for HSV. The overall responses to treatment were that three patients had stable disease, six patients had tumors flattened (injected and/or uninjected lesions), and four patients showed inflammation of uninjected as well as the injected tumor, which, in nearly all cases, became inflamed. CONCLUSIONS: Onco VEXGM-CSF is well tolerated and can be safely administered using the multidosing protocol described. Evidence of an antitumor effect was seen.

Production of infectious RNA transcripts from Sindbis virus cDNA clones: mapping of lethal mutations, rescue of a temperature-sensitive marker, and in vitro mutagenesis to generate defined mutants.

Abstract: We constructed full-length cDNA clones of Sindbis virus that can be transcribed in vitro by SP6 RNA polymerase to produce infectious genome-length transcripts. Viruses produced from in vitro transcripts are identical to Sindbis virus and show strain-specific phenotypes reflecting the source of RNA used for cDNA synthesis. The cDNA clones were used to confirm the mapping of the causal mutation of ts2 to the capsid protein. A general strategy for mapping Sindbis virus mutations is described and was used to identify two lethal mutations in an original full-length construct which did not produce infectious transcripts. An XbaI linker was inserted in the cDNA clone near the transcriptional start of the subgenomic mRNA; the resulting virus retains the XbaI recognition sequence, thus providing formal evidence that viruses are derived from in vitro transcripts of cDNA clones. The potential applications of the cDNA clones are discussed.

Pathogenesis of Human Immunodeficiency Virus Infection

Abstract: The lentivirus human immunodeficiency virus (HIV) causes AIDS by interacting with a large number of different cells in the body and escaping the host immune response against it. HIV is transmitted primarily through blood and genital fluids and to newborn infants from infected mothers. The steps occurring in infection involve an interaction of HIV not only with the CD4 molecule on cells but also with other cellular receptors recently identified. Virus-cell fusion and HIV entry subsequently take place. Following virus infection, a variety of intracellular mechanisms determine the relative expression of viral regulatory and accessory genes leading to productive or latent infection. With CD4+ lymphocytes, HIV replication can cause syncytium formation and cell death; with other cells, such as macrophages, persistent infection can occur, creating reservoirs for the virus in many cells and tissues. HIV strains are highly heterogeneous, and certain biologic and serologic properties determined by specific genetic sequences can be linked to pathogenic pathways and resistance to the immune response. The host reaction against HIV, through neutralizing antibodies and particularly through strong cellular immune responses, can keep the virus suppressed for many years. Long-term survival appears to involve infection with a relatively low-virulence strain that remains sensitive to the immune response, particularly to control by CD8+ cell antiviral activity. Several therapeutic approaches have been attempted, and others are under investigation. Vaccine development has provided some encouraging results, but the observations indicate the major challenge of preventing infection by HIV. Ongoing research is necessary to find a solution to this devastating worldwide epidemic.

Inhibition of Alpha/Beta Interferon Signaling by the NS4B Protein of Flaviviruses

Abstract: Flaviviruses are insect-borne, positive-strand RNA viruses that have been disseminated worldwide. Their genome is translated into a polyprotein, which is subsequently cleaved by a combination of viral and host proteases to produce three structural proteins and seven nonstructural proteins. The nonstructural protein NS4B of dengue 2 virus partially blocks activation of STAT1 and interferon-stimulated response element (ISRE) promoters in cells stimulated with interferon (IFN). We have found that this function of NS4B is conserved in West Nile and yellow fever viruses. Deletion analysis shows that that the first 125 amino acids of dengue virus NS4B are sufficient for inhibition of alpha/beta IFN (IFN-α/β) signaling. The cleavable signal peptide at the N terminus of NS4B, a peptide with a molecular weight of 2,000, is required for IFN antagonism but can be replaced by an unrelated signal peptide. Coexpression of dengue virus NS4A and NS4B together results in enhanced inhibition of ISRE promoter activation in response to IFN-α/β. In contrast, expression of the precursor NS4A/B fusion protein does not cause an inhibition of IFN signaling unless this product is cleaved by the viral peptidase NS2B/NS3, indicating that proper viral polyprotein processing is required for anti-interferon function.

Inhibition of entry of HIV-1 in neural cell lines by antibodies against galactosyl ceramide.

Abstract: Although the CD4 molecule is the principal cellular receptor for the human immunodeficiency virus (HIV), several CD4-negative cell lines are susceptible to infection with one or more HIV strains. These findings indicate that there are alternate modes of viral entry, perhaps involving one or more receptor molecules. Antibodies against galactosyl ceramide (galactocerebroside, or GalC) inhibited viral internalization and infection in two CD4-negative cell lines derived from the nervous system: U373-MG and SK-N-MC. Furthermore, recombinant HIV surface glycoprotein gp120 bound to GalC but not to other glycolipids. These results suggest a role for GalC or a highly related molecule in HIV entry into neural cells.