Retroviral targeted delivery.

The systemic delivery of genes will open new applications for gene therapy. The deployment of retroviral vectors for this purpose is being considered and requires the development of retroviral vectors with a defined target cell specificity of infection. Several reports have recently described attempts to engineer the envelope protein of murine retroviruses in order to expand the host range and enable them to infect specific human cells. The strategies are based on the introduction of binding sites specific for receptors on the surface of target cells. Although the attempts to manipulate the specificity of viral target cell recognition are ambitious and promising, they are not without pitfalls. We summarize the results obtained and the difficulties encountered.