Thomas C. Reynolds

T-cell mediated rejection of gene-modified HIV-specific cytotoxic T lymphocytes in HIV-infected patients

The introduction and expression of genes in somatic cells is an innovative therapy for correcting genetic deficiency diseases and augmenting immune function. A potential obstacle to gene therapy is the elimination of such gene–modified cells by an immune response to novel protein products of the introduced genes. We are conducting an immunotherapy trial in which individuals seropositive for human immunodeficiency virus (HIV) receive CD8+ HIV–specific cytotoxic T cells modified by retroviral transduction to express a gene permitting positive and negative selection. However, five of six subjects developed cytotoxic T–lymphocyte responses specific for the novel protein and eliminated the transduced cytotoxic T cells. The rejection of genetically modified cells by these immunocompromised hosts suggests that strategies to render gene–modified cells less susceptible to host immune surveillance will be required for successful gene therapy of immunocompetent hosts.

Endocytosis and Nuclear Trafficking of Adeno-Associated Virus Type 2 Are Controlled by Rac1 and Phosphatidylinositol-3 Kinase Activation

ABSTRACT Adeno-associated virus (AAV) is a single-stranded DNA parvovirus that causes no currently known pathology in humans. Despite the fact that this virus is of increasing interest to molecular medicine as a vector for gene delivery, relatively little is known about the cellular mechanisms controlling infection. In this study, we have examined endocytic and intracellular trafficking of AAV-2 using fluorescent (Cy3)-conjugated viral particles and molecular techniques. Our results demonstrate that internalization of heparan sulfate proteoglycan-bound AAV-2 requires αVβ5 integrin and activation of the small GTP-binding protein Rac1. Following endocytosis, activation of a phosphatidylinositol-3 (PI3) kinase pathway was necessary to initiate intracellular movement of AAV-2 to the nucleus via both microfilaments and microtubules. Inhibition of Rac1 using a dominant N17Rac1 mutant led to a decrease in AAV-2-mediated PI3 kinase activation, indicating that Rac1 may act proximal to PI3 kinase during AAV-2 infection. In summary, our results indicate that αVβ5 integrin-mediated endocytosis of AAV-2 occurs through a Rac1 and PI3 kinase activation cascade, which directs viral movement along the cytoskeletal network to the nucleus.

A Phase II, double-blind, randomized, placebo-controlled clinical trial of tgAAVCF using maxillary sinus delivery in patients with cystic fibrosis with antrostomies

tgAAVCF, an adeno-associated cystic fibrosis transmembrane conductance regulator (CFTR) viral vector/gene construct, was administered to 23 patients in a Phase II, double-blind, randomized, placebo-controlled clinical trial. For each patient, a dose of 100,000 replication units of tgAAVCF was administered to one maxillary sinus, while the contralateral maxillary sinus received a placebo treatment, thereby establishing an inpatient control. Neither the primary efficacy endpoint, defined as the rate of relapse of clinically defined, endoscopically diagnosed recurrent sinusitis, nor several secondary endpoints (sinus transepithelial potential difference [TEPD], histopathology, sinus fluid interleukin [IL]-8 measurements) achieved statistical significance when comparing treated to control sinuses within patients. One secondary endpoint, measurements of the anti-inflammatory cytokine IL-10 in sinus fluid, was significantly (p < 0.03) increased in the tgAAVCF-treated sinus relative to the placebo-treated sinus at day 90 after vector instillation. The tgAAVCF administration was well tolerated, without adverse respiratory events, and there was no evidence of enhanced inflammation in sinus histopathology or alterations in serum-neutralizing antibody titer to adeno-associated virus (AAV) capsid protein after vector administration. In summary, this Phase II trial confirms the safety of tgAAVCF but provides little support of its efficacy in the within-patient controlled sinus study. Various potentially confounding factors are discussed.

A Phase I Study of Aerosolized Administration of tgAAVCF to Cystic Fibrosis Subjects with Mild Lung Disease

Cystic fibrosis (CF) is one of the most common autosomal recessive disorders in North America, leading to significant morbidity and early mortality. The defect in the cystic fibrosis transmembrane conductance regulator protein (CFTR) function can be corrected in vitro by gene replacement with a wild-type gene. A Phase I, single administration, dose escalation trial was designed and executed to assess safety and delivery of tgAAVCF, an adeno-associated virus (AAV) vector encoding the human CFTR cDNA, by nebulization to the lungs of CF subjects. Four cohorts of three subjects each were administered increasing doses of the study agent, beginning with 10(10) DNase-resistant particles (DRP) and escalating in log increments up to 10(13) DRP. Sequential bronchoscopies were performed to gather analytical samples throughout the study. All 12 subjects completed the study. There were a total of 242 adverse events (AEs), six of which were defined as serious and three of which were defined as possibly being related to the study drug. A clear dose-response relationship was observed in vector gene transfer. A maximum of 0.6 and 0.1 vector copies per brushed cell were observed 14 days and 30 days, respectively, following nebulization of 10(13) DRP tgAAVCF, and this declined to nearly undetectable levels by day 90. Vector gene transfer was evenly distributed throughout the fourth airway generation following single-dose administration. RNA-specific PCR did not detect vector-derived mRNA. This Phase I trial shows that aerosolized tgAAVCF is safe and widely delivered to the proximal airways of CF subjects by nebulization.

Phase I Trial of Intranasal and Endobronchial Administration of a Recombinant Adeno-Associated Virus Serotype 2 (rAAV2)-CFTR Vector in Adult Cystic Fibrosis Patients: A Two-Part Clinical Study

Recombinant adeno-associated serotype 2-based vectors (rAAV2) possess a number of theoretical advantages for cystic fibrosis (CF) gene therapy because they elicit little or no inflammatory response and generally result in stable expression. rAAV2 vectors expressing the cystic fibrosis transmembrane conductance regulator (CFTR) gene have previously been shown to mediate stable correction of the CF defect in CF bronchial epithelial cells and stable expression of CFTR in rabbit and nonhuman primate models. Here we report the results of the first trial initiated with rAAV in humans, a phase I study in 25 adult and adolescent CF patients with mild to moderate lung disease. Doses of the rAAV-CFTR vector (tgAAVCF) ranging from 3 x 10(1) to 1 x 10(9) replication units (RU), which is equivalent to approximately 6 x 10(4) to 2 x 10(12) DNase resistant particles (DRP), were administered to one side of the nose and to the superior segment of the lower lobe of the right lung. Several adverse events were noted prior to and/or after vector delivery, but most of them appeared to be related to the endogenous CF lung disease or a result of the bronchoscopic procedures. Only one of the serious events was judged to be possibly vector-related (based on temporal association), and this event was a pulmonary exacerbation very similar to several others experienced by the same subject in the three months preceding vector delivery. Vector shedding was minimal throughout the study, and serum-neutralizing antibodies were detected after vector delivery to subjects in the highest dosage cohorts. Gene transfer as measured by DNA polymerase chain reaction (PCR) was not observed until cohort 10 in nasal and bronchial epithelia. Sporadic low-level copy numbers suggested gene transfer of anywhere from 0.002 copies per cell up to 0.5 copies per cell was possible; however, DNA PCR was positive in lungs prior to direct dosing suggesting aspiration from the nasal dosing. These data indicate the need for continued evaluation of rAAV-CFTR vectors in additional clinical trials.

Safety and Biological Efficacy of an Adeno‐Associated Virus Vector–Cystic Fibrosis Transmembrane Regulator (AAV‐CFTR) in the Cystic Fibrosis Maxillary Sinus

Objective: The host immune response and low vector efficiency have been key impediments to effective cystic fibrosis transmembrane regulator (CFTR) gene transfer for cystic fibrosis (CF). An adeno‐associated virus vector (AAV‐CFTR) was used in a phase I dose‐escalation study to transfer CFTR cDNA into respiratory epithelial cells of the maxillary sinus of 10 CF patients. Study Design: A prospective, randomized, unblinded, dose‐escalation, within‐subjects, phase I clinical trial of AAV‐CFTR was conducted. Patients: Ten patients with previous bilateral maxillary antrostomies were treated. Main Outcome Measures: Safety, gene transfer as measured by semiquantitative polymerase chain reaction (PCR), and sinus transepithelial potential difference (TEPD) were measured. Results: The highest level of gene transfer was observed in the range of 0.1–1 AAV‐CFTR vector copy per cell in biopsy specimens obtained 2 weeks after treatment. When tested, persistence was observed in one patient for 41 days and in another for 10 weeks. Dose‐dependent changes in TEPD responses to pharmacologic intervention were observed following treatments. Little or no inflammatory or immune responses were observed. Conclusion: AAV‐CFTR administration to the maxillary sinus results in successful, dose‐dependent gene transfer to the maxillary sinus and alterations in sinus TEPD suggestive of a functional effect, with little or no cytopathic or host immune response. Further study is warranted for AAV vectors as they may prove useful for CFTR gene transfer and other in vivo gene transfer therapies. A prospective, randomized, double‐blind, placebo‐controlled, within‐subjects, phase II clinical trial of the effect AAV‐CFTR on clinical recurrence of sinusitis will determine the clinical efficacy of AAV gene therapy for CF.