Active immunoprophylaxis with a synthetic DNA-encoded monoclonal anti-respiratory syncytial virus scFv-Fc fusion protein confers protection against infection and durable activity.

Respiratory Syncytial virus (RSV) is a major threat to many vulnerable populations. There are currently no approved vaccines, and RSV remains a high unmet global medical need. Here we describe the employment of a novel synthetic DNA-encoded antibody technology platform to develop and deliver an engineered human DNA-encoded monoclonal antibody (dMAbTM) targeting the fusion protein (F) of RSV as a new approach to prevention or therapy of at risk populations. In in vivo models, a single administration of synthetic DNA-encoding the single-chain fragment variable-constant fragment (scFv-Fc) RSV-F dMAb resulted in robust and durable circulating levels of a functional antibody systemically and in mucosal tissue. In cotton rats, which are the gold-standard animals to model RSV infection, we observed sustained scFv-Fc RSV-F dMAb in the sera and lung-lavage samples, demonstrating the potential for both long-lasting immunity to RSV and effective biodistribution. The scFv-Fc RSV-F dMAb harbored in the sera exhibited RSV antigen-specific binding and potent viral neutralizing activity. Importantly, in vivo delivery of synthetic DNA-encoding, the scFv-Fc RSV-F dMAb protected animals against viral challenge. Our findings support the significance of dMAbs as a potential platform technology for durable protection against RSV disease.

Immunogenicity of a protective intradermal DNA vaccine against lassa virus in cynomolgus macaques.

Lassa virus (LASV) is a hemorrhagic fever virus of the Arenaviridae family with high rates of mortality and co-morbidities, including chronic seizures and permanent bilateral or unilateral deafness. LASV is endemic in West Africa and Lassa fever accounts for 10-16% of hospitalizations annually in parts of Sierra Leone and Liberia according to the CDC. An ongoing outbreak in Nigeria has resulted in 144 deaths in 568 cases confirmed as LASV as of November 2018, with many more suspected, highlighting the urgent need for a vaccine to prevent this severe disease. We previously reported on a DNA vaccine encoding a codon-optimized LASV glycoprotein precursor gene, pLASV-GPC, which completely protects Guinea pigs and nonhuman primates (NHPs) against viremia, clinical disease, and death following lethal LASV challenge. Herein we report on the immunogenicity profile of the LASV DNA vaccine in protected NHPs. Antigen-specific binding antibodies were generated in 100% (6/6) NHPs after two immunizations with pLASV-GPC. These antibodies bound predominantly to the assembled LASV glycoprotein complex and had robust neutralizing activity in a pseudovirus assay. pLASV-GPC DNA-immunized NHPs (5/6) also developed T cell responses as measured by IFNγ ELISpot assay. These results revealed that the pLASV-GPC DNA vaccine is capable of generating functional, LASV-specific T cell and antibody responses, and the assays developed in this study will provide a framework to identify correlates of protection and characterize immune responses in future clinical trials.

Patient monitoring and follow-up in lentiviral clinical trials.

BACKGROUND: Lentiviral vectors are being used with increasing frequency in human clinical trials. We were the first to use lentiviral vectors in clinical trials in 2003. Our lentiviral vector encoded a long RNA antisense sequence to the HIV-1 envelope and was used in an ex vivo autologous setting to provide viral load control in HIV-1 positive subjects failing anti-HIV therapy. A total of 65 subjects have been treated in Phase 1 and Phase 2 trials in six institutions. METHODS: Good manufacturing practices (GMP) lots of the lentiviral vector used in our clinical trials were assayed for the presence of replication competent lentivirus (RCL). RCL assays were conducted at two stages. The first testing was performed on samples collected immediately following bulk harvest of the GMP product lot and consisted of 1 × 10(8) cells used in production. RCL assays were also performed on aliquots of the final fill of the vector by the inoculation of at least 5% of the GMP final fill volume into C8166 cells, passaged for at least ten passages and tested for RCL by p24 enzyme-linked immunosorbent assay and vesicular stomatitis virus-G envelope DNA. RESULTS: Following 263 infusions of autologous, transduced cells, no adverse events have been detected in these subjects, with some followed for more than 8 years following infusions. More than 4.3 × 10(12) VRX496 proviral copies were administered to these 65 subjects. CONCLUSIONS: Data from this small population suggest that there is no apparent risk for serious adverse events with the use of lentiviral vectors.

Development of a low bias method for characterizing viral populations using next generation sequencing technology.

BACKGROUND: With an estimated 38 million people worldwide currently infected with human immunodeficiency virus (HIV), and an additional 4.1 million people becoming infected each year, it is important to understand how this virus mutates and develops resistance in order to design successful therapies. METHODOLOGY/PRINCIPAL FINDINGS: We report a novel experimental method for amplifying full-length HIV genomes without the use of sequence-specific primers for high throughput DNA sequencing, followed by assembly of full length viral genome sequences from the resulting large dataset. Illumina was chosen for sequencing due to its ability to provide greater coverage of the HIV genome compared to prior methods, allowing for more comprehensive characterization of the heterogeneity present in the HIV samples analyzed. Our novel amplification method in combination with Illumina sequencing was used to analyze two HIV populations: a homogenous HIV population based on the canonical NL4-3 strain and a heterogeneous viral population obtained from a HIV patient's infected T cells. In addition, the resulting sequence was analyzed using a new computational approach to obtain a consensus sequence and several metrics of diversity. SIGNIFICANCE: This study demonstrates how a lower bias amplification method in combination with next generation DNA sequencing provides in-depth, complete coverage of the HIV genome, enabling a stronger characterization of the quasispecies present in a clinically relevant HIV population as well as future study of how HIV mutates in response to a selective pressure.

Lentiviral vectors in clinical trials: Current status.

Lentiviral vectors (LVs) are the most recently developed viral-derived vectors for gene therapy applications, and have demonstrated much promise. The ability to transduce dividing and non-dividing cells, and sustain long-term transgene expression makes LVs uniquely desirable as gene therapy vectors. With advances in vector design and large-scale production, LVs have become safer and more effective gene delivery systems. Since the first clinical trial was approved in 2002, several trials to treat patients with both infectious and genetic diseases have been approved. This review focuses on ongoing and planned trials of LV-based gene therapy.

The CXCR4-tropic human immunodeficiency virus envelope promotes more-efficient gene delivery to resting CD4+ T cells than the vesicular stomatitis virus glycoprotein G envelope.

Current gene transfer protocols for resting CD4(+) T cells include an activation step to enhance transduction efficiency. This step is performed because it is thought that resting cells are resistant to transduction by lentiviral-based gene therapy vectors. However, activating resting cells prior to transduction alters their physiology, with foreseeable and unforeseeable negative consequences. Thus, it would be desirable to transduce resting CD4(+) T cells without activation. We recently demonstrated, contrary to the prevailing belief, that wild-type human immunodeficiency virus (HIV) integrates into resting CD4(+) T cells. Based on that finding, we investigated whether a commonly used, vesicular stomatitis virus glycoprotein G (VSV-G)-pseudotyped lentiviral gene therapy vector could also integrate into resting CD4(+) T cells. To investigate this, we inoculated resting CD4(+) T cells with lentiviral particles that were pseudotyped with VSV-G or CXCR4-tropic HIV Env and assayed binding, fusion, reverse transcription, and integration. We found that the VSV-G-pseudotyped lentiviral vector failed to fuse to resting CD4(+) T cells while HIV Env-pseudotyped lentiviral vectors fused, reverse transcribed, and integrated in resting cells. Our findings suggest that HIV Env could be used effectively for the delivery of therapeutic genes to resting CD4(+) T cells and suggest that fusion may be the critical step restricting transduction of resting CD4(+) T cells by lentiviral gene therapy vectors.

Potent inhibition of simian immunodeficiency virus (SIV) replication by an SIV-based lentiviral vector expressing antisense Env.

In light of findings demonstrating that the macaque TRIM5alpha protein inhibits infection of cells by human immunodeficiency virus (HIV)-1, simian immunodeficiency virus (SIV)-based lentiviral vectors may have distinct advantages over HIV-1 vectors for the transduction of macaque hematopoietic stem cells. We evaluated the ability of an SIV vector (VRX859) encoding an antisense SIV envelope sequence and enhanced green fluorescent protein (GFP) to inhibit viral replication and to transduce rhesus CD34(+) lymphoid progenitor cells. After infection with homologous SIV strains, CD4(+) cell lines transduced with VRX859 exhibited more than 600-fold inhibition of viral replication compared with control cells. Less inhibition was observed with the divergent SIV strain SIVsmE660. Partial inhibition of a chimeric simian-human immunodeficiency virus, which contains an HIV-1 envelope in an SIV backbone, was observed, suggesting that the SIV vector also contributes to viral inhibition independent of the antisense envelope inhibitor. Transduction of rhesus CD34(+) cells with VRX859 at various multiplicities of infection resulted in transduction efficiencies comparable to those obtained with the HIV vector VRX494. However, when we evaluated transduction of rhesus T lymphocyte progenitors by examining GFP expression in CD4(+) T cells derived from transduced CD34(+) cells, we observed more efficient transduction with the SIV-based vector. GFP(+)CD4(+) T cells derived from VRX859-transduced CD34(+) cells strongly inhibited SIVmac239 replication as compared with control CD4(+) T cells. The ability of this SIV-based vector to mediate potent inhibition of SIV replication, coupled with its efficient transduction of rhesus hematopoietic progenitor cells, make it an important candidate for proof-of-principle experiments of stem cell gene therapy in the SIV-macaque model.

Gene transfer in humans using a conditionally replicating lentiviral vector.

We report findings from a clinical evaluation of lentiviral vectors in a phase I open-label nonrandomized clinical trial for HIV. This trial evaluated the safety of a conditionally replicating HIV-1-derived vector expressing an antisense gene against the HIV envelope. Five subjects with chronic HIV infection who had failed to respond to at least two antiviral regimens were enrolled. A single i.v. infusion of gene-modified autologous CD4 T cells was well tolerated in all patients. Viral loads were stable, and one subject exhibited a sustained decrease in viral load. CD4 counts remained steady or increased in four subjects, and sustained gene transfer was observed. Self-limiting mobilization of the vector was observed in four of five patients. There is no evidence for insertional mutagenesis after 21-36 months of observation. Immune function improved in four subjects. Lentiviral vectors appear promising for gene transfer to humans.

Regulatory considerations for novel gene therapy products: a review of the process leading to the first clinical lentiviral vector.

This review is intended to exemplify the roles and responsibilities of the two agencies under the Department of Health and Human Services, the National Institutes of Health and the Food and Drug Administration, that have oversight for human gene transfer clinical protocols, as seen through our experience of bringing a first-in-its-class lentiviral vector to clinical trials. In response to the changing circumstances in gene therapy research between 1999 and 2002, the concerns of these agencies regarding gene therapy have been evolving. This review provides an overview of the major safety concerns regarding insertional oncogenesis, the generation of a replication- competent lentivirus (RCL), and vector mobilization thought to be related to lentiviral vectors, which had to be addressed during the regulatory review process before initiating the clinical trial. Specific monitoring assays to address these concerns were established to test for RCL generation, vector mobilization, persistence of vector-modified cells, and abnormal clonal expansion of modified cells. We hope to provide a basic understanding and appreciation of the regulatory process and major safety concerns, toward providing useful insight to those presently embarking on the development of clinical application of lentiviral vectors.