Search results for "VIROLOGY"

Hepatosplenic cat-scratch fever with seropositivity for Bartonella quintana?

2008

Repression of Human Papillomavirus Oncogene Expression under Hypoxia Is Mediated by PI3K/mTORC2/AKT Signaling

2019

Oncogenic HPV types are major human carcinogens. Under hypoxia, HPV-positive cancer cells can repress the viral E6/E7 oncogenes and induce a reversible growth arrest. This response could contribute to therapy resistance, immune evasion, and tumor recurrence upon reoxygenation. Here, we uncover evidence that HPV oncogene repression is mediated by hypoxia-induced activation of canonical PI3K/mTORC2/AKT signaling. AKT-dependent downregulation of E6/E7 is only observed under hypoxia and occurs, at least in part, at the transcriptional level. Quantitative proteome analyses identify additional factors as candidates to be involved in AKT-dependent E6/E7 repression and/or hypoxic PI3K/mTORC2/AKT ac…

Inhibition of the herpes simplex virus-coded thymidine kinase-complex by 9-?-D-arabinofuranosyladenine 5?-monophosphate (ara-AMP) and 9-(2-hydroxyeth…

1984

The thymidine kinase-complex isolated from herpes simplex virus type 1 and type 2 (HSV-1 and HSV-2) is associated with the following enzyme activities: ATP:dThd (dCyd) deoxypyrimidine kinase, ATP:dTMP thymidylate kinase, ADP:dThd- and AMP:dThd5′-phosphotransferase. In kinetic experiments it is shown that ara-AMP inhibits AMP:dThd- and ADP:dThd phosphotransferase activity, while acyclo-GMP impairs ADP:dThd phosphotransferase reaction only; the inhibition was found to be non-compertitive. The functional subunit ATP:dThd kinase was not affected by either compound.

Characterization of the DNA-binding activity of the E1 and E2 proteins and the E1/E2 complex of human papillomavirus type 33.

1997

The E1 and E2 proteins of papillomaviruses are essential for the initiation of viral DNA replication. We have purified the E2 protein of human papillomavirus type 33 (HPV-33) by immunoaffinity chromatography. The purified E2 protein bound with high affinity to all four consensus binding sites of HPV-33 (Kd approximately equal to 2 x 10(-10)M). A putative E2 binding site differing at one position in the second stem of the palindrome was not bound by E2. The E1 protein of HPV-33 purified by affinity chromatography using glutathione S-transferase as tag displayed specific DNA-binding activity in footprint analyses protecting HPV-33 nucleotides 7896 to 7909/1 to 18 from DNasel digestion. Hypers…

Possible transmission flow of SARS-CoV-2 based on ACE2 features

2020

AbstractAngiotensin-converting enzyme 2 (ACE2) is the cellular receptor for the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) that is engendering the severe coronavirus disease 2019 (COVID-19) pandemic. The spike (S) protein receptor-binding domain (RBD) of SARS-CoV-2 binds to the three sub-domains viz. amino acids (aa) 22-42, aa 79-84, and aa 330-393 of ACE2 on human cells to initiate entry. It was reported earlier that the receptor utilization capacity of ACE2 proteins from different species, such as cats, chimpanzees, dogs, and cattle, are different. A comprehensive analysis of ACE2 receptors of nineteen species was carried out in this study, and the findings propose a pos…

Improved detection of melanoma antigen-specific T cells expressing low or high levels of CD8 by HLA-A2 tetramers presenting a Melan-A/Mart-1 peptide …

2001

MHC class I tetramers containing peptide epitopes are sensitive tools for detecting antigen-specific CD8(+) T-cell responses. We demonstrate here that binding of HLA-A2 tetramers to CD8(+) T cells specific for the melanoma-associated antigen Melan-A/MART-1 can be fine-tuned by altering either the bound peptide epitope or residues in the alpha 3 domain of HLA-A2, which is important for CD8 binding. Antigen-specific T cells expressing high levels of CD8 could be detected using HLA-A2 tetramers containing the peptide AAGIGILTV, an epitope which is naturally processed and presented from Melan-A/MART-1. In contrast, low CD8-expressing, antigen-specific T cells could be detected efficiently only …

Deoxyribonucleases in Herpes simplex Virus Type 1 and 2 Infected Primary Rabbit Kidney Cells

1980

Abstract In primary rabbit kidney cells infected with herpes simplex virus four different neutral deoxyribonuclease activities can be detected by means of the deoxyribonuclease assay in DNA-containing polyacrylamide gels following their separation by discelectrophoresis. The method is suitable to follow independently the change in each activity of the different enzymes using only about 5 × 105 cells for each assay during the time-course of infection. Under these conditions one enzyme activity is constant, two disappear while the activity of a fourth one present only in infected cells, increases.

Deletion and insertion mutants of HBsAg particles

1992

We have found previously that hybrid 22-nm HBsAg particles can be created by insertion of short antigenic sequences into the HBV major envelope protein [1]. We have now performed a detailed deletion mutagenesis of the S gene of HBV encoding HBsAg. Deletion of the 51 C-terminal amino acids including most of the third and all of the fourth hydrophobic domain of the S protein did not affect particle assembly and secretion. However, secretion of 22-nm particles was abolished by minor deletions in the N-terminal region. Insertion and deletion/substitution mutants carrying a poliovirus epitope at the N-terminus and the preSl region at the C-terminus have been characterized.

Biochemical and Kinetic Analyses of NS5B RNA-Dependent RNA Polymerase of the Hepatitis C Virus

1998

The biochemical properties of the RNA-dependent RNA polymerase (RdRp) of the hepatitis C virus were analyzed. A hexahistidine affinity-tagged NS5B fusion protein was expressed with recombinant baculoviruses in insect cells and purified to near homogeneity. Enzymatic activity of the purified protein was inhibited by KCl or high concentrations of NaCl and was absolutely dependent on Mg2+, which could be replaced by Mn2+. NS5B was found to be processive and able to copy long heteropolymeric templates with an elongation rate of 150-200 nucleotides/min at 22 degreesC. Kinetic constants were determined for all four nucleoside triphosphates and different templates. In case of a heteropolymeric RNA…

Proteins of Human Cytomegalovirus that Elicit Humoral Immunity

1993

Several of the cytomegalovirus (CMV) genes encoding glycoproteins, structural proteins, and infected-cell proteins that elicit an immune response in human infection have been mapped. Human sera and monoclonal antibodies react with these viral polypeptides made as native molecules in CMV-infected cells, as genetically engineered proteins, as truncated derivatives expressed in eukaryotic cells, and as bacterial fusion proteins from portions of the reading frames cloned into prokaryotic expression vectors. Synthetic oligopeptides from immunodominant regions of these molecules have also been used as antibody targets. Studies on proteins encoded by reading frames UL55, UL32, and UL44, on glycopr…