Reported adverse events related to use of hepatitis C virus direct-acting antivirals with opioids: 2017-2021.

INTRODUCTION: Due to concerns over potential interactions between some hepatitis C direct-acting antivirals (DAAs) and opioids, we describe adverse event (AE) reports of concomitant use of opioids and DAAs. METHODS: AEs reported (July 28, 2017-December 31, 2021) with the administration of the DAAs glecaprevir/pibrentasvir, sofosbuvir/velpatasvir, ledipasvir/sofosbuvir, sofosbuvir/velpatasvir/voxilaprevir, and elbasvir/grazoprevir as suspect products were downloaded from the US Food and Drug Administration AE Reporting System Public Dashboard. The number of AE reports containing opioids (fentanyl, hydrocodone, oxycodone) as co-suspect products/concomitant products were counted and summarized by severity, reporting country and whether an outcome of death was reported. Overdose AEs were counted irrespective of opioid use, and changes over time were assessed. RESULTS: In total, 40 AEs were reported for DAAs and concomitant fentanyl use, 25 (62.5%) were in the USA, 35 (87.5%) were considered serious, and 14 (35.0%) resulted in death; and 626 were reported with concomitant oxycodone/hydrocodone use, 596 (95.2%) were in the USA, 296 (47.3%) were considered serious, and 28 (4.5%) resulted in death. There were 196 overdose AEs (32 [16%] deaths) declining from 2018 (N = 56) to 2021 (N = 29). CONCLUSIONS: Treating people with hepatitis C virus (HCV) infection who use drugs is key to achieving HCV elimination. Low numbers of DAA AE reports with opioids may provide reassurance to prioritize HCV treatment in this population. These data contribute to evidence supporting the continued scale-up of DAA treatment among people who use drugs to achieve HCV elimination goals.

Safety analysis of glecaprevir/pibrentasvir in patients with markers of advanced liver disease in clinical and real-world cohorts.

Chronic hepatitis C virus (HCV) infection has the greatest health impact in patients with advanced liver disease. The direct-acting antiviral (DAA) regimen glecaprevir/pibrentasvir (G/P) is approved for treatment of HCV-infected patients without cirrhosis and with compensated cirrhosis. However, events of liver decompensation/failure have been reported in patients treated with protease-inhibitor-containing DAA regimens, often in patients with advanced liver disease. This study examines the safety of on-label G/P treatment in patients with compensated cirrhosis (F4 at baseline) with markers of advanced liver disease. Patients with cirrhosis were categorized into 4 subgroups, based on different noninvasive markers of advanced liver disease identified using laboratory measures: platelet count < or ≥ 100 × 109 /L, and Child-Pugh score 5 or 6. Separate analyses were performed using pooled data from clinical trials and from real-world post-marketing observational studies. G/P was well tolerated in patients with platelet count ≥100 × 109 /L (n = 800), platelet count <100 × 109 /L (n = 215), a Child-Pugh score of 5 (n = 915) and a Child-Pugh score of 6 (n = 95). In the clinical trial and real-world cohorts two patients and no patients experienced a serious adverse event (AE) possibly related to study drug, respectively; three patients and no patients experienced an AE of special interest for hepatic decompensation and hepatic failure. This analysis reaffirms G/P's safety profile in indicated patients with compensated cirrhosis, including those with markers of more advanced liver disease. Increasing the number of patients treated with short-duration G/P therapy may contribute to meeting HCV elimination targets.

High Sustained Virologic Response Rates of Glecaprevir/Pibrentasvir in Patients With Dosing Interruption or Suboptimal Adherence.

INTRODUCTION: Pangenotypic, all-oral direct-acting antivirals, such as glecaprevir/pibrentasvir (G/P), are recommended for treatment of hepatitis C virus (HCV) infection. Concerns exist about the impact on efficacy in patients with suboptimal adherence, particularly with shorter treatment durations. These post hoc analyses evaluated adherence (based on pill count) in patients prescribed 8- or 12-week G/P, the impact of nonadherence on sustained virologic response at post-treatment week 12 (SVR12), factors associated with nonadherence, and efficacy in patients interrupting G/P treatment. METHODS: Data were pooled from 10 phase 3 clinical trials of treatment-naive patients with HCV genotype 1-6 without cirrhosis/with compensated cirrhosis (treatment adherence analysis) and 13 phase 3 clinical trials of all patients with HCV (interruption analysis). RESULTS: Among 2,149 patients included, overall mean adherence was 99.4%. Over the treatment duration, adherence decreased (weeks 0-4: 100%; weeks 5-8: 98.3%; and weeks 9-12: 97.1%) and the percentage of patients with ≥80% or ≥90% adherence declined. SVR12 rate in the intention-to-treat (ITT) population was 97.7% (modified ITT SVR12 99.3%) and remained high in nonadherent patients in the modified ITT population (<90%: 94.4%-100%; <80%: 83.3%-100%). Psychiatric disorders were associated with <80% adherence, and shorter treatment duration was associated with ≥80% adherence. Among 2,902 patients in the interruption analysis, 33 (1.1%) had a G/P treatment interruption of ≥1 day, with an SVR12 rate of 93.9% (31/33). No virologic failures occurred. DISCUSSION: These findings support the impact of treatment duration on adherence rates and further reinforce the concept of "treatment forgiveness" with direct-acting antivirals.

Positive predictive value of sustained virologic response 4 weeks posttreatment for achieving sustained virologic response 12 weeks posttreatment in patients receiving glecaprevir/pibrentasvir in Phase 2 and 3 clinical trials.

Sustained virologic response at posttreatment Week 12 (SVR12) is the widely accepted efficacy endpoint for direct-acting antiviral agents. Those with hepatitis C virus (HCV) are presenting younger with milder liver disease, potentially reducing need for long-term liver posttreatment monitoring. This analysis aimed to determine the positive predictive value (PPV) of SVR at posttreatment Week 4 (SVR4) for achieving SVR12 in patients with HCV, without cirrhosis or with compensated cirrhosis, receiving glecaprevir/pibrentasvir (G/P) in clinical trials. An integrated dataset from 20 Phase 2 and 3 clinical trials of G/P was evaluated in patients with 8-, 12- or 16-week treatment duration consistent with the current label (label-consistent group), and in all patients regardless of treatment duration consistency with the current label (overall group). Sensitivity analyses handled missing data either by backward imputation or were excluded. SVR4 PPV, negative predictive value (NPV), sensitivity and specificity were calculated for achieving SVR12 in both groups, and by treatment duration in the label-consistent group. SVR was defined as HCV ribonucleic acid 99% in both groups regardless of treatment duration. Not achieving SVR4 had 100% NPV and sensitivity for all groups. SVR4 measure had 79.5% specificity for identifying patients who did not achieve SVR12. Across 20 Phase 2/3 clinical trials of G/P, SVR4 was highly predictive of SVR12. Long-term follow-up to confirm SVR may not be necessary for certain populations of patients with HCV.

Eight Weeks of Treatment With Glecaprevir/Pibrentasvir Is Safe and Efficacious in an Integrated Analysis of Treatment-Naïve Patients With Hepatitis C Virus Infection.

BACKGROUND & AIMS: The direct-acting antiviral combination glecaprevir/pibrentasvir has been approved by the Food and Drug Administration for 8 weeks of treatment in treatment-naïve patients with hepatitis C virus (HCV) infection without cirrhosis or with compensated cirrhosis. We performed an integrated analysis of data from trials to evaluate the overall efficacy and safety of 8 weeks of glecaprevir/pibrentasvir in treatment-naïve patients without cirrhosis or with compensated cirrhosis. METHODS: We pooled data from 8 phase 2 or phase 3 trials of treatment-naïve patients with HCV genotype 1 to 6 infections, without cirrhosis or with compensated cirrhosis, who received 8 weeks of glecaprevir/pibrentasvir. RESULTS: Of 1248 patients, 343 (27%) had cirrhosis. Most patients were white (80%) and had HCV genotype 1 infection (47%) or genotype 3 infection (22%); the median age was 54 years. Overall rates of sustained virologic response at post-treatment week 12 were 97.6% (1218 of 1248) in the intention to treat (ITT) and 99.3% (1218 of 1226) in the modified ITT populations. When we excluded patients with genotype 3 infections with compensated cirrhosis (consistent with the European label), rates of sustained virologic response at post-treatment week 12 were 97.6% in the ITT and 99.4% in the modified ITT populations. Eight virologic failures (7 in patients without cirrhosis and 1 in a patient with cirrhosis) occurred in the ITT population. Virologic failure was not associated with markers of advanced liver disease or populations of interest (current alcohol use, opioid substitution therapy, history of injection-drug use, and severe renal impairment). Treatment-emergent adverse events (AEs) occurred in 58% of patients. The most frequent AEs (>10%) were headache (12%) and fatigue (12%). Serious AEs and AEs that led to glecaprevir/pibrentasvir discontinuation were reported in 2% and less than 1% of patients, respectively. CONCLUSIONS: In a pooled analysis of data from 8 trials, we found that 8 weeks of treatment with glecaprevir/pibrentasvir is efficacious and well tolerated in treatment-naïve patients with HCV genotype 1 to 6 infections, with or without cirrhosis.

Assessment of Drug-Drug Interaction Risk Between Intravenous Fentanyl and the Glecaprevir/Pibrentasvir Combination Regimen in Hepatitis C Patients Using Physiologically Based Pharmacokinetic Modeling and Simulations.

INTRODUCTION: An unsafe injection practice is one of the major contributors to new hepatitis C virus (HCV) infections; thus, people who inject drugs are a key population to prioritize to achieve HCV elimination. The introduction of highly effective and well-tolerated pangenotypic direct-acting antivirals, including glecaprevir/pibrentasvir (GLE/PIB), has revolutionized the HCV treatment landscape. Glecaprevir is a weak cytochrome P450 3A4 (CYP3A4) inhibitor, so there is the potential for drug-drug interactions (DDIs) with some opioids metabolized by CYP3A4, such as fentanyl. This study estimated the impact of GLE/PIB on the pharmacokinetics of intravenous fentanyl by building a physiologically based pharmacokinetic (PBPK) model. METHODS: A PBPK model was developed for intravenous fentanyl by incorporating published information on fentanyl metabolism, distribution, and elimination in healthy individuals. Three clinical DDI studies were used to verify DDIs within the fentanyl PBPK model. This model was integrated with a previously developed GLE/PIB PBPK model. After model validation, DDI simulations were conducted by coadministering GLE 300 mg + PIB 120 mg with a single dose of intravenous fentanyl (0.5 µg/kg). RESULTS: The predicted maximum plasma concentration ratio between GLE/PIB + fentanyl and fentanyl alone was 1.00, and the predicted area under the curve ratio was 1.04, suggesting an increase of only 4% in fentanyl exposure. CONCLUSION: The administration of a therapeutic dose of GLE/PIB has very little effect on the pharmacokinetics of intravenous fentanyl. This negligible increase would not be expected to increase the risk of fentanyl overdose beyond the inherent risks related to the amount and purity of the fentanyl received during recreational use.

Shorter Duration Hepatitis C Virus Treatment is Associated with Better Persistence to Prescription Refills in People Who Inject Drugs: A Real-World Study.

INTRODUCTION: Direct-acting antiviral (DAA) therapy is highly effective in curing hepatitis C virus (HCV) infection in people who inject drugs (PWID). Previous studies showed declining persistence to DAA therapy over the course of treatment. This study compares real-world medication persistence to prescription refills for 8- versus 12-week DAA in treatment-naïve PWID with chronic HCV with compensated cirrhosis or without cirrhosis. METHODS: Symphony Health's claims database was used to collect data from patients with chronic HCV aged ≥ 12 years who were prescribed 8- or 12-week DAA therapy between August 2017 and November 2020 and had a diagnosis of addicted drug use within 6 months prior to index date. Eligible patients had medical/pharmacy claims in the 6 months before and 3 months after the first index medication fill date (i.e., index date). Patients completing all refills (8-week = 1 refill, 12-week = 2 refills) were deemed persistent. The percentage of persistent patients in each group, and at each refill step, was determined; outcomes were also assessed in a subgroup of Medicaid-insured patients. RESULTS: This study assessed 7203 PWID with chronic HCV (8-week, 4002; 12-week, 3201). Patients prescribed 8-week DAA treatment were younger (42.9 ± 12.4 vs 47.5 ± 13.2, P < 0.001) and had fewer comorbidities (P < 0.001). Patients receiving 8- versus 12-week DAA had greater refill persistence (87.9% vs 64.4%, P < 0.001). Similar percentages of patients missed their first refill (8-week, 12.1% vs 12-week, 10.8%); nearly 25% of patients receiving 12-week DAA missed their second refill. After baseline characteristics were controlled, patients prescribed 8- versus 12-week DAA were more likely to be persistent (odds ratio [95% confidence interval] 4.3 [3.8, 5.0]). Findings in the Medicaid-insured subgroup were consistent. CONCLUSION: Patients prescribed 8- vs 12-week DAA therapy had significantly greater prescription refill persistence. Most nonpersistence was due to missed second refills, highlighting the potential benefit of shorter treatment durations in this population.

Awareness and Epidemiology of Chronic Hepatitis C Virus Infections in Florida.

INTRODUCTION: Progress towards achieving hepatitis C virus (HCV) elimination in Florida has been hampered by barriers to screening, linkage to care, and treatment. This study aims to describe the HCV care cascade and patient characteristics in Florida. METHODS: This analysis combined HCV-related laboratory data and patient characteristics from two, large US laboratory datasets that included individuals tested for HCV antibody (Ab) and HCV ribonucleic acid (RNA) viral load between January 2015 and December 2019. A decline in sequential HCV RNA viral loads was used to impute HCV treatment. Machine-learning algorithms were used to identify cured patients. The actual number of individuals with HCV Ab screening, and the number and percentage of persons who were HCV RNA-positive and treated, were calculated. RESULTS: The number of persons in Florida diagnosed as HCV RNA-positive was 31,659 in 2019. The number of individuals HCV Ab screened in 2019 was 1,024,379, an increase of 82.5% from 2015. The percentage of HCV Ab-positive individuals was 4.1%, demonstrating a 16.2% decrease from 2015. The percentage of HCV RNA-positive patients who were treated was 27.0%, a 10.5% decrease from 2015 to 2019. CONCLUSION: An Ab positivity rate > 4-times higher than national estimates with increased screening among baby boomers, but decreased screening among younger individuals, suggests risk-based screening is still common practice in Florida, despite universal screening recommendations. Public health efforts to decrease barriers to screening, linkage to care, and treatment are needed to reduce the burden of HCV in Florida and to ensure progress toward virus elimination.

Altering α-dystroglycan receptor affinity of LCMV pseudotyped lentivirus yields unique cell and tissue tropism.

BACKGROUND: The envelope glycoprotein of lymphocytic choriomeningitis virus (LCMV) can efficiently pseudotype lentiviral vectors. Some strains of LCMV exploit high affinity interactions with α-dystroglycan (α-DG) to bind to cell surfaces and subsequently fuse in low pH endosomes. LCMV strains with low α-DG affinity utilize an unknown receptor and display unique tissue tropisms. We pseudotyped non-primate feline immunodeficiency virus (FIV) vectors using LCMV derived glycoproteins with high or low affinity to α-DG and evaluated their properties in vitro and in vivo. METHODS: We pseudotyped FIV with the LCMV WE54 strain envelope glycoprotein and also engineered a point mutation in the WE54 envelope glycoprotein (L260F) to diminish α-DG affinity and direct binding to alternate receptors. We hypothesized that this change would alter in vivo tissue tropism and enhance gene transfer to neonatal animals. RESULTS: In mice, hepatic α- and ß-DG expression was greatest at the late gestational and neonatal time points. When displayed on the surface of the FIV lentivirus the WE54 L260F mutant glycoprotein bound weakly to immobilized α-DG. Additionally, LCMV WE54 pseudotyped FIV vector transduction was neutralized by pre-incubation with soluble α-DG, while the mutant glycoprotein pseudotyped vector was not. In vivo gene transfer in adult mice with either envelope yielded low transduction efficiencies in hepatocytes following intravenous delivery. In marked contrast, neonatal gene transfer with the LCMV envelopes, and notably with the FIV-L260F vector, conferred abundant liver and lower level cardiomyocyte transduction as detected by luciferase assays, bioluminescent imaging, and ß-galactosidase staining. CONCLUSIONS: These results suggest that a developmentally regulated receptor for LCMV is expressed abundantly in neonatal mice. LCMV pseudotyped vectors may have applications for neonatal gene transfer. ABBREVIATIONS: Armstrong 53b (Arm53b); baculovirus Autographa californica GP64 (GP64); charge-coupled device (CCD); dystroglycan (DG); feline immunodeficiency virus (FIV); glycoprotein precursor (GP-C); firefly luciferase (Luc); lymphocytic choriomeningitis virus (LCMV); nuclear targeted ß-galactosidase (ntLacZ); optical density (OD); PBS/0.1% (w/v) Tween-20 (PBST); relative light units (RLU); Rous sarcoma virus (RSV); transducing units per milliliter (TU/ml); vesicular stomatitis virus (VSV-G); wheat germ agglutinin (WGA); 50% reduction in binding (C50).

Epidemiology and Clinical Characteristics of Individuals with Hepatitis C Virus Infection in the United States, 2017-2019.

INTRODUCTION: Hepatitis C virus (HCV) is the most common bloodborne chronic infection in the US. Following approval of highly effective, direct-acting antivirals in 2014, the diagnostic and treatment rates for HCV infection in the US have evolved. This study assessed the number of individuals with HCV screening or diagnostic testing and the clinical characteristics and treatment of HCV-infected individuals between 2017 and 2019. METHODS: Individuals screened for HCV antibody and/or tested for HCV ribonucleic acid (RNA) from 2017 to 2019 by two large US laboratory companies were included in this analysis. Clinical characteristics, such as HCV genotype, fibrosis stage, HIV coinfection and demographics, were assessed in HCV RNA-positive individuals. HCV treatment and subsequent achievement of sustained virologic response were imputed using data-driven algorithms based on successive viral load decline and negativity. RESULTS: From 2017 to 2019, the number of individuals tested for HCV antibody increased by 5.7%, from 7,580,303 in 2017 to 8,009,081 in 2019. The percentage of individuals tested who were HCV antibody positive was stable, ranging from 5.0% in 2017 to 4.9% in 2018 and 2019. The number of HCV RNA-positive individuals decreased by 5.0% from 382,500 in 2017 to 363,532 in 2019. Of HCV RNA-positive individuals, the proportions with genotype (GT) 3 and minimal fibrosis increased over time; proportions of individuals aged < 40 years increased, while the proportion aged 50 to 59 years decreased. Treatment rates increased from 23.4% in 2017 to 26.8% in 2019. CONCLUSIONS: The percentage of HCV antibody-positive individuals remained stable from 2017 to 2019. The number of individuals tested HCV RNA positive decreased over the years. Demographics shifted toward a younger population with less fibrosis and higher rates of GT3. More than 70% of diagnosed individuals were not treated during this interval, highlighting a need for unfettered access to treatment.

Safety of Patients with Hepatitis C Virus Treated with Glecaprevir/Pibrentasvir from Clinical Trials and Real-World Cohorts.

INTRODUCTION: More than 70 million people are estimated to be infected with hepatitis C virus (HCV) globally. If left untreated, HCV infection can lead to complications such as extensive liver fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). Evolution of treatments has resulted in highly effective and well-tolerated all-oral direct-acting antivirals. The pangenotypic regimen of glecaprevir/pibrentasvir is approved for treating HCV for patients without cirrhosis or with compensated cirrhosis (CC). Guidelines have evolved to simplify treatment to enable non-specialists to manage and treat HCV-infected patients. Simultaneously, such treatment algorithms provide guidance on the pretreatment identification of small subsets of patients who may require specialist treatment and long-term follow-up for advanced liver disease, including those at risk of developing HCC. This study describes the safety profile of glecaprevir/pibrentasvir in patients identified using previously described noninvasive laboratory measures who may be eligible for treatment by non-liver specialists. METHODS: This post hoc analysis of glecaprevir/pibrentasvir in patients, identified by noninvasive laboratory measures, intended to exclude patients with advanced liver disease and severe renal impairment, who can be managed within non-liver specialist settings. Patients were included from clinical trials and real-world studies of glecaprevir/pibrentasvir for HCV treatment. Baseline demographics, clinical characteristics, and safety assessments, including adverse events and laboratory abnormalities, were summarized. RESULTS: Data across these large-scale studies confirm that glecaprevir/pibrentasvir is well tolerated across different patient populations, with fewer than 0.1% of patients experiencing a serious adverse event related to treatment drugs, and few patients developing HCC during or after treatment. CONCLUSION: The safety profile of glecaprevir/pibrentasvir enhances the confidence of non-liver specialists to treat the majority of HCV-infected patients, and provides an opportunity to expand the treater pool, potentially increasing diagnosis and treatment rates for HCV, contributing to elimination of HCV.

Effectiveness of 8-Week Glecaprevir/Pibrentasvir for Treatment-Naïve, Compensated Cirrhotic Patients with Chronic Hepatitis C Infection.

INTRODUCTION: Glecaprevir/pibrentasvir (G/P) was approved on 26 September 2019 by the US Food and Drug Administration for 8-week duration in treatment-naïve (TN) hepatitis C virus (HCV)-infected patients with compensated cirrhosis (CC). Evidence from the EXPEDITION-8 study demonstrated that 8 weeks of G/P achieved a 98% intent-to-treat (ITT) sustained virologic response rate 12 weeks post treatment (SVR12) in 343 TN/CC patients. The aim of this study is to demonstrate the first US real-world effectiveness of G/P 8-week treatment in genotype 1-6 TN/CC HCV patients. METHODS: Data from 73 TN/CC patients who initiated 8 weeks of G/P treatment between August 2017 and November 2018 were collected electronically from providers and specialty pharmacies of the Trio Health network and analyzed. Cirrhosis was determined by FIB-4 > 5.2 or was physician reported. The primary outcome was Per Protocol (PP) SVR12. RESULTS: The majority (60%) of patients were male, with (mean values): age 59 years, body mass index (BMI) of 30, aspartate aminotransferase (AST) 105, and alanine aminotransferase (ALT) 101 IU/ml. HCV genotypes (GT) were: GT1 81% (59/73), GT2 10% (7/73), GT3 5% (4/73), GT4 3% (2/73), and GT6 1% (1/73). Eight percent (6/73) of patients had concurrent proton pump inhibitor (PPI) use, and 15% (11/72) had a baseline viral load > 6 MM IU/ml. Zero patients discontinued, two patients were reported as lost to follow-up, and there was one virologic failure. PP sustained virologic response at 12 weeks (SVR12) rate was 99% (70/71), and the intent-to-treat (ITT) SVR12 rate was 96% (70/73). CONCLUSIONS: Early real-world experience indicates high effectiveness of the 8-week G/P regimen in a diverse treatment-naïve, compensated cirrhotic US population.

Basolateral entry and release of New and Old World arenaviruses from human airway epithelia.

Transmission of arenaviruses from rodent hosts to humans is generally thought to occur through inhalation or ingestion of dust or droplets containing viral particles. Here we demonstrate that two identified arenavirus receptors, alpha-dystroglycan (alpha-DG) and transferrin receptor 1 (TfR1), are expressed in polarized human airway epithelia. Lymphocytic choriomeningitis virus strains with high or low alpha-DG affinity and Junin virus, which binds TfR1, efficiently infected polarized epithelia only when applied to the basolateral surface or when injury compromised tight junction integrity. Viral egress from infected epithelia exhibited basolateral polarity. This study demonstrates that respiratory entry of arenaviruses occurs via basolateral receptors.

Lentiviral vector gene transfer to porcine airways.

In this study, we investigated lentiviral vector development and transduction efficiencies in well-differentiated primary cultures of pig airway epithelia (PAE) and wild-type pigs in vivo. We noted gene transfer efficiencies similar to that observed for human airway epithelia (HAE). Interestingly, feline immunodeficiency virus (FIV)-based vectors transduced immortalized pig cells as well as pig primary cells more efficiently than HIV-1-based vectors. PAE express TRIM5α, a well-characterized species-specific lentiviral restriction factor. We contrasted the restrictive properties of porcine TRIM5α against FIV- and HIV-based vectors using gain and loss of function approaches. We observed no effect on HIV-1 or FIV conferred transgene expression in response to porcine TRIM5α overexpression or knockdown. To evaluate the ability of GP64-FIV to transduce porcine airways in vivo, we delivered vector expressing mCherry to the tracheal lobe of the lung and the ethmoid sinus of 4-week-old pigs. One week later, epithelial cells expressing mCherry were readily detected. Our findings indicate that pseudotyped FIV vectors confer similar tropisms in porcine epithelia as observed in human HAE and provide further support for the selection of GP64 as an appropriate envelope pseudotype for future preclinical gene therapy studies in the porcine model of cystic fibrosis (CF).Molecular Therapy - Nucleic Acids (2012) 1, e56; doi:10.1038/mtna.2012.47; published online 27 November 2012.

Lentivirus vectors pseudotyped with filoviral envelope glycoproteins transduce airway epithelia from the apical surface independently of folate receptor alpha.

The practical application of gene therapy as a treatment for cystic fibrosis is limited by poor gene transfer efficiency with vectors applied to the apical surface of airway epithelia. Recently, folate receptor alpha (FR alpha), a glycosylphosphatidylinositol-linked surface protein, was reported to be a cellular receptor for the filoviruses. We found that polarized human airway epithelia expressed abundant FR alpha on their apical surface. In an attempt to target these apical receptors, we pseudotyped feline immunodeficiency virus (FIV)-based vectors by using envelope glycoproteins (GPs) from the filoviruses Marburg virus and Ebola virus. Importantly, primary cultures of well-differentiated human airway epithelia were transduced when filovirus GP-pseudotyped FIV was applied to the apical surface. Furthermore, by deleting a heavily O-glycosylated extracellular domain of the Ebola GP, we improved the titer of concentrated vector severalfold. To investigate the folate receptor dependence of gene transfer with the filovirus pseudotypes, we compared gene transfer efficiency in immortalized airway epithelium cell lines and primary cultures. By utilizing phosphatidylinositol-specific phospholipase C (PI-PLC) treatment and FR alpha-blocking antibodies, we demonstrated FR alpha-dependent and -independent entry by filovirus glycoprotein-pseudotyped FIV-based vectors in airway epithelia. Of particular interest, entry independent of FR alpha was observed in primary cultures of human airway epithelia. Understanding viral vector binding and entry pathways is fundamental for developing cystic fibrosis gene therapy applications.