Oncoretroviral vector-mediated gene therapy for murine WAS fails to correct most of the deficient biological responses to S. pneumonia or M. bovis
Authors: Ted S. Strom, Jon McCullers, Robert Rutschman, Peter Murray, Marguerite Evans-Galea, John M. Cunningham, Arthur W. Nienhuis
Journal: Molecular Therapy (2004)

The Wiskott-Aldrich syndrome is an X-linked congenital condition manifesting as variable degrees of immunodeficiency and thrombocytopenia. Bone marrow transplantation is apparently curative, but frequent lack of donor availability, and variable outcomes after transplantation with matched unrelated donors, indicate a need for alternative therapies. A murine model of WAS demonstrates features similar to the clinical condition, including lymphocytopenia, thrombocytopenia, and increased susceptibility to certain infectious agents. WAS- mice show improvement in several cellular and physiological parameters after transplantation with WT bone marrow cells. Gene corrected animals, generated by retroviral-vector mediated transduction of murine bone marrow cells followed by transplantation into lethally irradiated recipients, show improvement in the colitis seen in a subset of these animals, and also demonstrate improvement in their deficient secondary T-cell response to influenza inoculation. Here we demonstrate that WAS- mice show increased susceptibility to, and mortality from, pneumonia following intranasal inoculation with S. pneumonia. Specifically, after intranasal inoculation with 105 cfu of luciferase-labeled S. pneumonia, 0 of 10 WT WAS (C57Bl/6, 5th generation backcross from 129SvEv) mice developed pneumonia or died, while 6 of 10 WAS- mice developed pneumonia and died. However, gene-corrected animals did not show a significant improvement in these outcomes. After inoculation with a lower dose (0.5 × 105 cfu) of S. pneumonia, 4 of 7 gene corrected mice, 5 of 6 negative control mice (WAS- mice transplanted with WAS-, GFP-vector transduced bone marrow cells), and 4 of 8 positive controls (WAS- mice transplanted with WT, GFP-vector transduced bone marrow cells) developed pneumonia and died. Susceptibility did not correlate with the extent of engraftment of gene corrected cells in any hematologic lineage. We conclude that diminished resistance of positive control mice was at least partially responsible for the lack of observable phenotypic correction. We have also observed reduced clearance of M. bovis (bcg) from the organs of intravenously inoculated WAS- animals. Here too, however, gene-corrected animals showed only inconsistent indications of improvement in M. bovis clearance. Specifically, gene corrected WAS- mice showed improved clearance from liver, but no overall improvement in clearance from spleen or lung. Clearance correlated with the extent of engraftment of gene corrected lymphocytes and monocytes in liver and spleen, but not in lung. Our results suggest that technical improvements will be required in order to evaluate the biological efficacy of gene therapy for murine WAS. Specifically, we are investigating whether lethal irradiation alone, lack of a perfect genetic match among donors and recipients, or GFP expression diminishes resistance to these agents in recipients of control vector transduced, WT bone marrow cells, as well as whether improved vector design could enhance efficacy.