Christian Becker

Mutations in RDH12 encoding a photoreceptor cell retinol dehydrogenase cause childhood-onset severe retinal dystrophy

We identified three consanguineous Austrian kindreds with 15 members affected by autosomal recessive childhood-onset severe retinal dystrophy, a genetically heterogeneous group of disorders characterized by degeneration of the photoreceptor cells. A whole-genome scan by microarray analysis of single-nucleotide polymorphisms (ref. 2) identified a founder haplotype and defined a critical interval of 1.53 cM on chromosome 14q23.3–q24.1 that contains the gene associated with this form of retinal dystrophy. RDH12 maps in this region and encodes a retinol dehydrogenase proposed to function in the visual cycle. A homozygous 677A→G transition (resulting in Y226C) in RDH12 was present in all affected family members studied, as well as in two Austrian individuals with sporadic retinal dystrophy. We identified additional mutations in RDH12 in 3 of 89 non-Austrian individuals with retinal dystrophy: a 5-nucleotide deletion (806delCCCTG) and the transition 565C→T (resulting in Q189X), each in the homozygous state, and 146C→T (resulting in T49M) and 184C→T (resulting in R62X) in compound heterozygosity. When expressed in COS-7 cells, Cys226 and Met49 variants had diminished and aberrant activity, respectively, in interconverting isomers of retinol and retinal. The severe visual impairment of individuals with mutations in RDH12 is in marked contrast to the mild visual deficiency in individuals with fundus albipunctatus caused by mutations in RDH5, encoding another retinal dehydrogenase. Our studies show that RDH12 is associated with retinal dystrophy and encodes an enzyme with a unique, nonredundant role in the photoreceptor cells.

Adoptive tumor therapy with T lymphocytes enriched through an IFN-gamma capture assay

Successful adoptive T-cell therapy has been demonstrated in viral disease and selected forms of cancer. However, it is limited by the difficulty to efficiently isolate and amplify autologous tumor-reactive T-cell clones. Tetramers of major histocompatibility complex (MHC) class I and peptide have facilitated the characterization of CD8+ T cells specific for tumor-associated antigens. However, for adoptive T-cell therapy, MHC-tetramers have limitations: they require knowledge of tumor antigens, which is often not available; they select T cells with a single specificity, thereby posing risk for selection of tumor escape variants; they do not select for function, so that T cells may be anergic when isolated from cancer patients; and they do not allow the isolation of CD4+ T cells that can be essential for tumor rejection. Because interferon (IFN)-γ is essential for tumor rejection, we isolated live T cells based on their IFN-γ production. IFN-γ secreted by previously activated T cells is retained on the cell surface, allowing their specific isolation and expansion. We show here that IFN-γ+ but not IFN-γ− T cells from tumor-immunized mice are cytolytic and mediate tumor rejection upon adoptive transfer. Importantly, tumor-specific T cells can be enriched from lymphocytes infiltrating human renal cell carcinoma by the IFN-γ capture assay.

Efficient gene transfer into primary human CD8+ T lymphocytes by MuLV-10A1 retrovirus pseudotype.

Efficient and stable gene transfer into primary human T lymphocytes would greatly improve their use for adoptive transfer to treat acquired disorders, viral diseases, and cancer. We have constructed retroviral vector pseudotypes of amphotropic murine leukemia viruses (A-MuLV, MuLV-10A1), gibbon ape leukemia virus (GaLV), and feline endogenous virus (RD114) containing the enhanced green fluorescent protein (GFP) as a marker gene. Transduction of primary human CD8+ T lymphocytes by the different GFP-retrovirus pseudotypes revealed the superiority of MuLV-10A1 in comparison with A-MuLV, GaLV, and RD114, respectively. The superior transduction efficacy of CD8+ T cells by MuLV-10A1 correlates with a longer half-life of this pseudotype in comparison with A-MuLV and, as shown by interference analysis with the human T cell line HUT78, by the utilization of both the A-MuLV receptor (Pit2) and the GaLV receptor (Pit1) for cell entry.

Direct and indirect T cell priming by dendritic cell vaccines

The mechanisms by which dendritic cell (DC) vaccines prime host Tu2009cells in vivo was analyzed. Mice were immunized with syngeneic bone marrow‐derived DC and as surrogate antigen β‐galactosidase (β‐gal) was used. DC either pulsed with peptide, loaded with β‐gal antigen or gene‐modified induced β‐gal‐specific cytotoxic T lymphocytes (CTL) and moderate rejection of an in vivo challenge with β‐gal expressing tumors. In addition, β‐gal‐specific CTL lysed the syngeneic DC that were used as vaccines. Using SCID mice reconstituted with F1 lymphocytes, direct priming by gene‐modified DC vaccines was demonstrated by the presence of β‐gal‐specific CTL of the haplotype exclusively expressed by DC while indirect priming by host antigen‐presenting cells (APC) was shown by the detection of CTL of the haplo type exclusively present on host APC and absent on DC vaccines. Since DC immunization in syngeneic mice was associated with an increase in NK1.1+/Ly49C− cells and detectable lysis of DC in vitro by lymphokine‐activated killer cells, DC vaccines appear to interact with host natural killer cells as well as with antigen‐specific Tu2009cells. These effector cells in turn may lyse DC vaccines thereby leading to the release of antigens that can be taken up by host APC.

MLV-10A1 retrovirus pseudotype efficiently transduces primary human CD4+ T lymphocytes

Previously, we showed that retroviral vectors pseudotyped with the envelope of the amphotropic murine leukemia virus 10A1 (MLV‐10A1) more efficiently transduce primary human CD8+ T lymphocytes when compared with other A‐MLV, gibbon ape leukemia virus (GaLV) and feline endogenous retrovirus (RD114) vector pseudotypes. For the success of several gene therapeutic approaches (ADA, HIV) it is important to effectively transduce primary human CD4+ T lymphocytes.