Biomedical subjects

E R Quinn

Publications and source records attributed to E R Quinn.

4 recordsLinked to original sources

PubMed2001

The B-cell receptor of a hepatitis C virus (HCV)-associated non-Hodgkin lymphoma binds the viral E2 envelope protein, implicating HCV in lymphomagenesis.

Hepatitis C virus (HCV) infection is associated with extrahepatic B-cell lymphoproliferative disorders. To determine whether a viral antigen drives this B-cell expansion, the B-cell receptors were cloned from HCV-associated lymphomas and were expressed as soluble immunoglobulins. The rescued immunoglobulins were then tested for their ability to bind the HCV-E2 envelope glycoprotein, an antigen that was previously implicated in the pathogenesis of HCV-associated B-cell diseases. One of 2 lymphoma immunoglobulin test cases bound the E2 protein in a manner identical to a bona fide human anti-E2 antibody. Moreover, it bound E2 from multiple viral genotypes, suggesting reactivity with a conserved E2 epitope. These findings support the hypothesis that some HCV-associated lymphomas originate from B cells that were initially activated by the HCV-E2 protein and might explain the association between HCV infection and some B-cell lymphoproliferative disorders.

Amino Acid Sequence↗

PubMed2001

In search of hepatitis C virus receptor(s).

Since the genomic sequence of HCV was determined, significant progress has been made towards understanding the functions of the HCV-encoded proteins, despite the lack of an efficient in-vitro replication system or convenient small-animal model. The identity of the receptor for HCV remains elusive, however. Low-density lipoprotein receptor, CD81, and GAGs may all act as receptors for HCV, either sequentially or by different viral quasispecies. Recent work using pseudotypic VSV bearing E1 or E2 chimeric molecules showed that entry of the E1 pseudotype can be inhibited by recombinant LDLr, whereas the E2 pseudotype is more sensitive to inhibition by recombinant CD81 or heparin. These results suggest that E1 and E2 may be responsible for interactions with different cellular molecules. It is also conceivable that additional, yet unidentified, cellular proteins are involved in viral binding and entry. Intriguingly, the reports of HCV-RNA associated with PBMC suggest that HCV infection may not be restricted to hepatocytes. Thus, separate reservoirs of virus may exist, and HCV may use different receptors to access these different cell types.

Animals↗

PubMed2000

Identification of amino acid residues in CD81 critical for interaction with hepatitis C virus envelope glycoprotein E2.

Human CD81 has been previously identified as the putative receptor for the hepatitis C virus envelope glycoprotein E2. The large extracellular loop (LEL) of human CD81 differs in four amino acid residues from that of the African green monkey (AGM), which does not bind E2. We mutated each of the four positions in human CD81 to the corresponding AGM residues and expressed them as soluble fusion LEL proteins in bacteria or as complete membrane proteins in mammalian cells. We found human amino acid 186 to be critical for the interaction with the viral envelope glycoprotein. This residue was also important for binding of certain anti-CD81 monoclonal antibodies. Mutating residues 188 and 196 did not affect E2 or antibody binding. Interestingly, mutation of residue 163 increased both E2 and antibody binding, suggesting that this amino acid contributes to the tertiary structure of CD81 and its ligand-binding ability. These observations have implications for the design of soluble high-affinity molecules that could target the CD81-E2 interaction site(s).

Amino Acid Sequence↗

PubMed1998

T cell activation modulates retrovirus-mediated gene expression.

Important considerations for T lymphocyte-based gene therapy include efficient gene delivery and expression in primary, human T cells. In this study, retrovirus-mediated gene transfer and the fate of proviral gene expression were evaluated in human T cells activated using (1) immobilized anti-CD3 monoclonal antibody (MAb) plus interleukin 2, or (2) cis costimulation using beads carrying coimmobilized anti-CD3 and anti-CD28 MAbs. By cross-linking the CD3 and CD28 receptors, these MAbs mimic in vivo signaling events, leading to cytokine production and proliferation. A modified human interleukin 1beta (IL-1beta) cDNA inserted into the MFG retroviral vector served as an indicator gene. Retroviral transduction frequencies were similar for T lymphocytes activated by the respective methods. However, early after MAb stimulation and virus exposure, proviral gene expression was greater at the RNA and protein levels in optimized anti-CD3/anti-CD28 bead-activated T cells, corresponding with augmented endogenous cytokine responses and mitogenesis. Proviral gene expression was not regulated by extrinsic cell factors present in activated T cell supernatants. Regardless of the MAb stimulation method, proviral IL-1beta expression declined in later T cell cultures concomitant with a decrease in cellular cytokines. Restimulation by either method reinduced both T cell activity and vector expression. Our finding that proviral gene regulation is downmodulated in the absence of T cell signaling events has implications for clinical strategies using retrovirus-modified T cells.

CD4-Positive T-Lymphocytes↗