A genetically engineered spleen necrosis virus-derived retroviral vector that displays the HIV type 1 glycoprotein 120 envelope peptide

Targeting retroviral vector infection to cells that express heregulin receptors using a TVA-heregulin bridge protein

Previously we have shown that it is possible to target retroviral vectors to cells using avian sarcoma and leukosis virus (ASLV) receptor-ligand and receptor-single-chain antibody bridge proteins (now designated as GATEs for guided adaptors for targeted entry). In this report we were interested in determining whether this approach can be used to deliver retroviral vectors specifically to cells that express heregulin receptors. Heregulin receptors are attractive targets for retroviral vector-based gene delivery protocols since they are often overexpressed on the surfaces of cancer cells. To explore this possibility, the TVA-herbeta1 protein was generated, consisting of the extracellular domain of the TVA receptor for ASLV-A fused to the EGF-like region of heregulin beta1. TVA-herbeta1 bound specifically to cells that express heregulin receptors, rendering them susceptible to efficient and specific infection by subgroup A ASLV vectors. In addition, these activities of TVA-herbeta1 were abrogated specifically in the presence of another bridge protein that contained the same ligand domain. These data confirm that the GATE protein TVA-herbeta1 mediates targeted retroviral infection via cell surface heregulin receptors.

A TVA-single-chain antibody fusion protein mediates specific targeting of a subgroup A avian leukosis virus vector to cells expressing a tumor-specific form of epidermal growth factor receptor

We have previously described an approach that employs retroviral receptor-ligand bridge proteins to target retroviral vectors to specific cell types. To determine whether targeted retroviral entry can also be achieved using a retroviral receptor-single-chain antibody bridge protein, the TVA-MR1 fusion protein was generated. TVA-MR1 is comprised of the extracellular domain of the TVA receptor for subgroup A avian leukosis viruses (ALV-A), fused to the MR1 single-chain antibody that binds specifically to EGFRvIII, a tumor-specific form of the epidermal growth factor receptor. We show that TVA-MR1 binds specifically to a murine version of EGFRvIII and promotes ALV-A entry selectively into cells that express this cell surface marker. These studies demonstrate that it is possible to target retroviral vectors to specific cell types through the use of a retroviral receptor-single-chain antibody fusion protein.

Anti-human immunodeficiency virus type 1 gene therapy in human central nervous system-based cells: an initial approach against a potential viral reservoir

Studies have demonstrated that human immunodeficiency virus type 1 (HIV-1) infection of central nervous system (CNS)-based cells in vivo results in a series of devastating clinical conditions collectively termed acquired immune deficiency syndrome (AIDS) dementia complex (ADC). Gene therapy for these neurovirological disorders necessitates utilization of a vector system that can mediate in vivo delivery and long-term expression of an antiretroviral transgene in nondividing/postmitotic CNS cellular elements. The present studies focus on the transfer of an anti-HIV-1 gene to primary isolated CNS microvascular endothelial cells (MVECs) and neuronal-based cells, for its effects in protecting these cells from HIV-1 infection. By using an HIV-1-based vector system, it was possible to efficiently transduce and maintain expression of a marker transgene, beta-galactosidase (beta-Gal), in human CNS MVECs, human fetal astrocytes, plus immature and mature (differentiated) NT2 cells. Significant transduction of the marker gene, beta-Gal, in CNS-based cells prompted the utilization of this system with an anti-HIV-1 gene therapeutic construct, RevM10, a trans-dominant negative mutant Rev protein. Initially, it was not possible to generate any HIV-1 vector particles with the RevM10 gene in the transducing construct, because of inhibitory effects on the HIV-1 vector by this gene product. However, the vector could be partially rescued by adding an additional construct that supplied wild-type rev, in trans, during a multiple construct transfection in the packaging 293T cells. Thus, it was possible to significantly improve the titer of RevM10-expressing viral particles generated from these cells. Moreover, this RevM10 vector transduced the neuronal precursor cell line NT2, retinoic acid-differentiated human neurons (hNT) from the precursor cells, and primary isolated human brain MVECs with high efficiency. RevM10 generated from the HIV-1-based vector system potently inhibited replication of diverse HIV-1 strains in human CNS MVECs and neuronal cells. The data generated from these studies represent an initial approach for future development of anti-HIV-1 gene therapy in the CNS.