Gene transfer of human TCR in primary murine T cells is improved by pseudo-typing with amphotropic and ecotropic envelopes

BACKGROUND

T cell receptor (TCR) gene therapy represents an attractive anti-cancer treatment but requires further optimization of its efficacy and safety in clinically relevant models, such as those using a tumor antigen and TCR of human origin. Currently, however, there is no consensus as to what protocol is most optimal for retroviral human TCR gene transfer into primary murine T cells, most notably with respect to virus pseudo-type.

METHODS

Primary murine T cells were transduced, expanded and subsequently tested for transgene expression, proliferation and antigen-specific function. To this end, murine leukemia virus (MLV) retroviruses were produced upon transfection of various packaging cells with genes encoding either green fluorescent protein (GFP) or TCRalphabeta specific for human melanoma antigen gp100(280-288) and the helper elements GAG/POL and ENV. Next to viral pseudotyping, the following parameters were studied: T cell densities; T cell activation; the amounts of IL-2 and the source of serum used to supplement medium.

RESULTS

The pseudo-type of virus produced by packaging cells critically determines T cell transduction efficiencies. In fact, MLV-A and MLV-E pseudo-typed viruses derived from a co-culture of Phoenix-A and 293T cells resulted in T cell transduction efficiencies that were two-fold higher than those based on retroviruses expressing either VSV-G, GALV, MLV-A or MLV-E envelopes. In addition, T cell densities during transduction were inversely related to transduction efficiencies. Further optimization resulted in transduction efficiencies of over 90% for GFP, and 68% for both a murine and a human (i.e. murinized) TCR. Importantly, TCR-transduced T cells proliferate (i.e. showing a log increase in cell number in a few days) and show antigen-specific function.

CONCLUSIONS

We set up a quick and versatile method to genetically modify primary murine T cells based on transient production of TCR-positive retroviruses, and show that retroviral gene transfer of a human TCR into primary murine T cells is critically improved by viral pseudo-typing with both MLV-A and MLV-E envelopes.

Identification by phage display of single-domain antibody fragments specific for the ODD domain in hypoxia-inducible factor 1alpha

Hypoxia triggers the transcription of genes responsible for cell survival via the key player transcription factor hypoxia-inducible factor 1alpha (HIF-1alpha). Overexpression of this protein has been implicated in cardiovascular disorders, carcinogenesis and cancer progression. For functional and diagnostic studies on the HIF-1alpha protein, we have identified single-domain antibody fragments directed against this protein by using a llama-derived nonimmune phage display library. This library displays the variable domains of the heavy-chain antibody subclass, found in these animals. Phage display selection with six recombinant HIF-1alpha proteins yielded five different antibody fragments. By epitope-mapping, we show that all five antibody fragments bind within the functionally important oxygen-dependent degradation domain of the HIF-1alpha protein. Two of these antibody fragments were engineered into bivalent antibodies that were able to detect human HIF-1alpha by immunohistochemistry, Western blotting and immunoprecipitation, and mouse HIF-1alpha by immunofluorescence and immunoprecipitation. These are the first single-domain antibody fragments that may be used in exploration of HIF-1alpha as a possible therapeutic target through molecular applications.