Development of a sensitive assay for detection of replication-competent recombinant lentivirus in large-scale HIV-based vector preparations.

Lentiviral vectors have demonstrated great potential as gene therapy vectors mediating efficient ex vivo and in vivo gene delivery and long-term transgene expression in both dividing and nondividing cells. However, for clinical studies it must be demonstrated that lentiviral vector preparations are safe and not contaminated by replication-competent recombinants related to the parental pathogenic virus. Here we describe a sensitive assay for the detection of replication-competent lentiviruses (RCL) in large-scale preparations of HIV-based lentiviral vectors. This RCL assay for lentiviral vectors is based on the principles used for retroviral vectors, using a highly permissive cell line, C8166-45, for RCL amplification and an appropriate positive control virus to establish the assay sensitivity. The assay is capable of detecting 1 RCL infectious unit in a background of 2.5 x 10(8) transducing units of vector in a single test culture. Statistically representative samples from large-scale lentiviral vector productions were assayed using multiple test cultures for each lot. Overall, a total of 1.4 x 10(10) transducing units of vector from 10 independent 14-liter production lots were screened and no RCL was detected. We propose to implement this assay as a release testing for clinical-grade lentiviral vector preparations intended for gene therapy clinical trials.

Progress toward a human CD4/CCR5 transgenic rat model for de novo infection by human immunodeficiency virus type 1.

The development of a permissive small animal model for the study of human immunodeficiency virus type (HIV)-1 pathogenesis and the testing of antiviral strategies has been hampered by the inability of HIV-1 to infect primary rodent cells productively. In this study, we explored transgenic rats expressing the HIV-1 receptor complex as a susceptible host. Rats transgenic for human CD4 (hCD4) and the human chemokine receptor CCR5 (hCCR5) were generated that express the transgenes in CD4(+) T lymphocytes, macrophages, and microglia. In ex vivo cultures, CD4(+) T lymphocytes, macrophages, and microglia from hCD4/hCCR5 transgenic rats were highly susceptible to infection by HIV-1 R5 viruses leading to expression of abundant levels of early HIV-1 gene products comparable to those found in human reference cultures. Primary rat macrophages and microglia, but not lymphocytes, from double-transgenic rats could be productively infected by various recombinant and primary R5 strains of HIV-1. Moreover, after systemic challenge with HIV-1, lymphatic organs from hCD4/hCCR5 transgenic rats contained episomal 2-long terminal repeat (LTR) circles, integrated provirus, and early viral gene products, demonstrating susceptibility to HIV-1 in vivo. Transgenic rats also displayed a low-level plasma viremia early in infection. Thus, transgenic rats expressing the appropriate human receptor complex are promising candidates for a small animal model of HIV-1 infection.