HIV-specific Immunity Derived From Chimeric Antigen Receptor-engineered Stem Cells.

The human immunodeficiency virus (HIV)-specific cytotoxic T lymphocyte (CTL) response is critical in controlling HIV infection. Since the immune response does not eliminate HIV, it would be beneficial to develop ways to enhance the HIV-specific CTL response to allow long-term viral suppression or clearance. Here, we report the use of a protective chimeric antigen receptor (CAR) in a hematopoietic stem/progenitor cell (HSPC)-based approach to engineer HIV immunity. We determined that CAR-modified HSPCs differentiate into functional T cells as well as natural killer (NK) cells in vivo in humanized mice and these cells are resistant to HIV infection and suppress HIV replication. These results strongly suggest that stem cell-based gene therapy with a CAR may be feasible and effective in treating chronic HIV infection and other morbidities.

Methodology and software to detect viral integration site hot-spots.

BACKGROUND: Modern gene therapy methods have limited control over where a therapeutic viral vector inserts into the host genome. Vector integration can activate local gene expression, which can cause cancer if the vector inserts near an oncogene. Viral integration hot-spots or 'common insertion sites' (CIS) are scrutinized to evaluate and predict patient safety. CIS are typically defined by a minimum density of insertions (such as 2-4 within a 30-100 kb region), which unfortunately depends on the total number of observed VIS. This is problematic for comparing hot-spot distributions across data sets and patients, where the VIS numbers may vary. RESULTS: We develop two new methods for defining hot-spots that are relatively independent of data set size. Both methods operate on distributions of VIS across consecutive 1 Mb 'bins' of the genome. The first method 'z-threshold' tallies the number of VIS per bin, converts these counts to z-scores, and applies a threshold to define high density bins. The second method 'BCP' applies a Bayesian change-point model to the z-scores to define hot-spots. The novel hot-spot methods are compared with a conventional CIS method using simulated data sets and data sets from five published human studies, including the X-linked ALD (adrenoleukodystrophy), CGD (chronic granulomatous disease) and SCID-X1 (X-linked severe combined immunodeficiency) trials. The BCP analysis of the human X-linked ALD data for two patients separately (774 and 1627 VIS) and combined (2401 VIS) resulted in 5-6 hot-spots covering 0.17-0.251% of the genome and containing 5.56-7.74% of the total VIS. In comparison, the CIS analysis resulted in 12-110 hot-spots covering 0.018-0.246% of the genome and containing 5.81-22.7% of the VIS, corresponding to a greater number of hot-spots as the data set size increased. Our hot-spot methods enable one to evaluate the extent of VIS clustering, and formally compare data sets in terms of hot-spot overlap. Finally, we show that the BCP hot-spots from the repopulating samples coincide with greater gene and CpG island density than the median genome density. CONCLUSIONS: The z-threshold and BCP methods are useful for comparing hot-spot patterns across data sets of disparate sizes. The methodology and software provided here should enable one to study hot-spot conservation across a variety of VIS data sets and evaluate vector safety for gene therapy trials.

Stem cell-derived CAR T cells traffic to HIV reservoirs in macaques.

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) with CCR5- donor cells is the only treatment known to cure HIV-1 in patients with underlying malignancy. This is likely due to a donor cell-mediated graft-versus-host effect targeting HIV reservoirs. Allo-HSCT would not be an acceptable therapy for most people living with HIV due to the transplant-related side effects. Chimeric antigen receptor (CAR) immunotherapies specifically traffic to malignant lymphoid tissues (lymphomas) and, in some settings, are able to replace allo-HSCT. Here, we quantified the engraftment of HSC-derived, virus-directed CAR T cells within HIV reservoirs in a macaque model of HIV infection, using potentially novel IHC assays. HSC-derived CAR cells trafficked to and displayed multilineage engraftment within tissue-associated viral reservoirs, persisting for nearly 2 years in lymphoid germinal centers, the brain, and the gastrointestinal tract. Our findings demonstrate that HSC-derived CAR+ cells reside long-term and proliferate in numerous tissues relevant for HIV infection and cancer.

Characterization of a potent non-cytotoxic shRNA directed to the HIV-1 co-receptor CCR5.

BACKGROUND: The use of shRNAs to downregulate the expression of specific genes is now relatively routine in experimentation but still hypothetical for clinical application. A potential therapeutic approach for HIV-1 disease is shRNA mediated downregulation of the HIV-1 co-receptor, CCR5. It is increasingly recognized that siRNAs and shRNAs can have unintended consequences such as cytotoxicities in cells, particularly when used for long term therapeutic purposes. For the clinical use of shRNAs, it is crucial to identify a shRNA that can potently inhibit CCR5 expression without inducing unintended cytotoxicities. RESULTS: Previous shRNAs to CCR5 identified using conventional commercial algorithms showed cytotoxicity when expressed using the highly active U6 pol III promoter in primary human peripheral blood derived mononuclear cells. Expression using the lower activity H1 promoter significantly reduced toxicity, but all shRNAs also reduced RNAi activity. In an effort to identify shRNAs that were both potent and non-cytotoxic, we created a shRNA library representing all potential CCR5 20 to 22-nucleotide shRNA sequences expressed using an H1 promoter and screened this library for downregulation of CCR5. We identified one potent CCR5 shRNA that was also non-cytotoxic when expressed at a low level with the H1 promoter. We characterized this shRNA in regards to its function and structure. This shRNA was unique that the use of commercial and published algorithms to predict effective siRNA sequences did not result in identification of the same shRNA. We found that this shRNA could induce sequence specific reduction of CCR5 at post transcriptional level, consistent with the RNA interference mechanism. Importantly, this shRNA showed no obvious cytotoxicity and was effective at downregulating CCR5 in primary human peripheral blood derived mononuclear cells. CONCLUSION: We report on the characterization of a rare shRNA with atypical structural features having potent RNAi activity specific to CCR5. These results have implications for the application of RNAi technology for therapeutic purposes.

Preclinical safety and efficacy of an anti-HIV-1 lentiviral vector containing a short hairpin RNA to CCR5 and the C46 fusion inhibitor.

Gene transfer has therapeutic potential for treating HIV-1 infection by generating cells that are resistant to the virus. We have engineered a novel self-inactivating lentiviral vector, LVsh5/C46, using two viral-entry inhibitors to block early steps of HIV-1 cycle. The LVsh5/C46 vector encodes a short hairpin RNA (shRNA) for downregulation of CCR5, in combination with the HIV-1 fusion inhibitor, C46. We demonstrate here the effective delivery of LVsh5/C46 to human T cell lines, peripheral blood mononuclear cells, primary CD4(+) T lymphocytes, and CD34(+) hematopoietic stem/progenitor cells (HSPC). CCR5-targeted shRNA (sh5) and C46 peptide were stably expressed in the target cells and were able to effectively protect gene-modified cells against infection with CCR5- and CXCR4-tropic strains of HIV-1. LVsh5/C46 treatment was nontoxic as assessed by cell growth and viability, was noninflammatory, and had no adverse effect on HSPC differentiation. LVsh5/C46 could be produced at a scale sufficient for clinical development and resulted in active viral particles with very low mutagenic potential and the absence of replication-competent lentivirus. Based on these in vitro results, plus additional in vivo safety and efficacy data, LVsh5/C46 is now being tested in a phase 1/2 clinical trial for the treatment of HIV-1 disease.