Chiron Corporation

About: Chiron Corporation is a based out in . It is known for research contribution in the topics: Antigen & Hepatitis C virus. The organization has 1973 authors who have published 1969 publications receiving 172330 citations.

Hepatitis C virus-specific CTL responses in the liver of chimpanzees with acute and chronic hepatitis C.

Abstract: Hepatitis C virus (HCV)-specific CTL responses were evaluated in two chimpanzees (Pan troglodytes) during the acute and chronic phases of HCV infection. CD8+ T lymphocytes were isolated from liver tissue homogenates using anti-CD8 antibody-coated magnetic beads and then stimulated with anti-CD3 antibodies, IL-2, and irradiated human PBMC using limiting dilution culture conditions. HCV-specific cytotoxic activity of expanding CD8+ cell lines was assessed against autologous lymphoblastoid cell lines infected with recombinant vaccinia virus vectors encoding HCV Ag. CD8+ T cell lines specific for structural and nonstructural proteins of HCV were established from both animals. Cytolytic activity was blocked with anti-CD8 or anti-class I MHC antibodies, indicating that class I MHC molecules were involved in presentation of viral Ag to the CTL. Overlapping synthetic peptides were used to define a 12 amino acid segment of the nonstructural 3 (NS3) protein recognized by CTL lines from both chimpanzees. Studies with truncated peptides revealed that these CD8+ cell lines were directed against overlapping epitopes presented by distinct class I restriction elements of the chimpanzee MHC complex. CD8+ cell lines with identical specificities for an NS3 epitope were generated from one chronically infected animal at 16 and 28 wk postinfection. These results indicate that virus-specific CTL populations persist in the liver for months, but are unable to resolve chronic HCV infection.

Transient immunosuppression allows transgene expression following readministration of adeno-associated viral vectors.

Abstract: Adeno-associated viral (AAV) vectors have much promise in gene therapy. Among the many properties that make AAV an ideal vector for gene therapy are its ability to infect both dividing and nondividing cells and the longevity of expression in tissues such as brain, skeletal muscle, and liver. However, like other viral vectors, readministration of vector is limited because of the host's immune response to viral components of the vector. Using class I, class II, and CD40 ligand (CD40L)-deficient mice, we demonstrate that neutralizing antibodies to the viral capsid proteins prevent transgene expression following readministration of rAAV vectors. Transient immunosuppression of mice by treatment with antibody to CD4 at the time of primary infection allowed transgene expression after readministration of rAAV vectors to animals. Transient immunosuppression with antibody to CD40L had only a modest effect on the efficacy of readministration. The ability to readminister virus was inversely correlated with both AAV capsid enzyme-linked immunosorbent assay titers and AAV neutralizing antibody titers. These studies demonstrate that readministration of rAAV can be accomplished by down regulating the anti-AAV immune response and suggest the use of repeated administration of rAAV as a viable form of therapy for the treatment of chronic diseases.

Human Cu/Zn superoxide dismutase cDNA: isolation of clones synthesising high levels of active or inactive enzyme from an expression library

Abstract: The molecular cloning and nucleotide sequence of the cDNA for human Cu/Zn superoxide dismutase (SOD) is reported. The tacI promoter has been used to direct the synthesis in E. coli of this SOD which is soluble, stable, and of normal specific activity. The N-terminal methionine is removed from this protein. A construction with a ribosome binding site identical to that of the lacz gene 5' of the initiator methionine codon, resulted in low levels of SOD. An in vitro mutagenesis procedure was used to randomize the four nucleotides preceding the initiator methionine codon and the silent third positions of the codons specifying the second and third amino acids. Analysis of a sample of 500 clones showed that ca. 25 clones synthesised 5% or more of soluble cell protein as SOD. The nucleotide sequences of high level expressors showed a predominance of A and T residues in the variable positions 5' of the initiator methionine codon. An SOD mutant (ala4----gln) was discovered during the sequencing and shown to lack dismutation activity. Secondary structure predictions for the 5' regions of the mRNAs from high and low level expressors support the hypothesis that initiation of translation is much reduced if part of the region complementary to 16s rRNA is base paired in a stem structure.