Oral USC-093, a novel homoserinamide analogue of the tyrosinamide (S)-HPMPA prodrug USC-087 has decreased nephrotoxicity while maintaining antiviral efficacy against human adenovirus infection of Syrian hamsters.

Adenovirus infections of immunocompromised humans are a significant source of morbidity and mortality. Presently, there is no drug specifically approved for the treatment of adenovirus infections by the FDA. The state-of-the-art treatment of such infections is the off-label use of cidofovir, an acyclic nucleotide phosphonate. While cidofovir inhibits adenovirus replication, it has dose-limiting kidney toxicity. There is an apparent need for a better compound to treat adenovirus infections. To this end, we have been developing acyclic nucleotide phosphonate prodrugs that utilize an amino acid scaffold equipped with a lipophilic modifier. Here, we compare the antiviral potential of two prodrugs of HPMPA that differ only in the amino acid-based promoiety: USC-087, based on an N-hexadecyl tyrosinamide, and USC-093, based on an N-hexadecyl serinamide. Oral administration of both compounds was very efficacious against disseminated HAdV-C6 infection in immunosuppressed Syrian hamsters, suppressing virus replication and mitigating pathology even when treatment was withheld until 4 days after challenge. We saw only marginal efficacy after respiratory infection of hamsters, which may reflect suboptimal distribution to the lung. Importantly, neither compound induced intestinal toxicity, which was observed as the major adverse effect in clinical trials of brincidofovir, a prodrug of cidofovir which also contains a C-16 modifier. Notably, we found that there was a significant difference in the nephrotoxicity of the two compounds: USC-087 caused significant kidney toxicity while USC-093 did not, at effective doses. These findings will be valuable guidepoints in the future evolution of this new class of potential prodrugs to treat adenovirus infections.

Generation of Human Embryonic Stem Cell-Derived Lung Organoids for Modeling Infection and Replication Differences between Human Adenovirus Types 3 and 55 and Evaluating Potential Antiviral Drugs.

Human adenoviruses type 3 (HAdV-3) and type 55 (HAdV-55) are frequently encountered, highly contagious respiratory pathogens with high morbidity rate. In contrast to HAdV-3, one of the most predominant types in children, HAdV-55 is a reemergent pathogen associated with more severe community-acquired pneumonia (CAP) in adults, especially in military camps. However, the infectivity and pathogenicity differences between these viruses remain unknown as in vivo models are not available. Here, we report a novel system utilizing human embryonic stem cells-derived 3-dimensional airway organoids (hAWOs) and alveolar organoids (hALOs) to investigate these two viruses. Firstly, HAdV-55 replicated more robustly than HAdV-3. Secondly, cell tropism analysis in hAWOs and hALOs by immunofluorescence staining revealed that HAdV-55 infected more airway and alveolar stem cells (basal and AT2 cells) than HAdV-3, which may lead to impairment of self-renewal functions post-injury and the loss of cell differentiation in lungs. Additionally, the viral life cycles of HAdV-3 and -55 in organoids were also observed using Transmission Electron Microscopy. This study presents a useful pair of lung organoids for modeling infection and replication differences between respiratory pathogens, illustrating that HAdV-55 has relatively higher replication efficiency and more specific cell tropism in human lung organoids than HAdV-3, which may result in relatively higher pathogenicity and virulence of HAdV-55 in human lungs. The model system is also suitable for evaluating potential antiviral drugs, as demonstrated with cidofovir. IMPORTANCE Human adenovirus (HAdV) infections are a major threat worldwide. HAdV-3 is one of the most predominant respiratory pathogen types found in children. Many clinical studies have reported that HAdV-3 causes less severe disease. In contrast, HAdV-55, a reemergent acute respiratory disease pathogen, is associated with severe community-acquired pneumonia in adults. Currently, no ideal in vivo models are available for studying HAdVs. Therefore, the mechanism of infectivity and pathogenicity differences between human adenoviruses remain unknown. In this study, a useful pair of 3-dimensional (3D) airway organoids (hAWOs) and alveolar organoids (hALOs) were developed to serve as a model. The life cycles of HAdV-3 and HAdV-55 in these human lung organoids were documented for the first time. These 3D organoids harbor different cell types, which are similar to the ones found in humans. This allows for the study of the natural target cells for infection. The finding of differences in replication efficiency and cell tropism between HAdV-55 and -3 may provide insights into the mechanism of clinical pathogenicity differences between these two important HAdV types. Additionally, this study provides a viable and effective in vitro tool for evaluating potential anti-adenoviral treatments.

[Diagnosis and treatment of adenoviral keratoconjunctivitis]. / Diagnostika i lechenie adenovirusnogo keratokon"yunktivita.

PURPOSE: To improve the treatment of adenoviral lesions of the eye based on express diagnostics by the fluorescent antibody technique (FAT) and the use of modern drugs. MATERIAL AND METHODS: The study included 184 patients (333 eyes) with various manifestations of adenoviral lesions of the ocular surface, who were divided into two groups: group 1 (149 patients, 196 eyes) - acute form, and group 2 (76 patients, 137 eyes) - long lasting form. Effectiveness of the proposed treatment was evaluated against separate group 3 (controls) consisting of 28 people (46 eyes) with completed acute adenovirus infection, who had previously received antibiotic and corticosteroid therapy in other clinics. Conjunctival scrapings of study patients were examined with FAT in our proposed modification. Study patients received local therapy with modern drugs (Okomistin, Aktipol). RESULTS: FAT detected the adenovirus antigen in 169 cases in group 1 (86%) and in 99 cases in group 2 (72%). Treatment duration amounted to 12±6 days in group 1, 18±8 days in group 2, and 29±7 days in controls. In both study groups, the duration of treatment was significantly reduced in comparison with the controls (p<0.01). Stable clinical effect and complete restoration of visual acuity have been achieved in most cases. There were no allergic and side effects from the therapy. CONCLUSION: Fluorescent antibody technique is a fast and effective way to diagnose adenovirus infection in ophthalmology. In terms of therapy, the use of an antiseptic, an antiviral drug and diluted corticosteroids is the most rational approach.

Fulminant Adenoviral-Induced Hepatitis in Immunosuppressed Patients.

Human adenovirus (HAdV) can often lead to fulminant hepatitis in immunocompromised patients, mostly after reactivation of HAdV. Different risk factors, e.g., transplantation and chemotherapy, increase the risk of developing a HAdV hepatitis. We retrospectively analyzed three patients who showed the characteristics of a HAdV hepatitis observed in disseminated disease. In addition to PCR, diagnosis could be proven by pathology, CT scan, and markedly elevated transaminases. All patients had a hemato-oncologic underlying disease. Two had received a stem-cell transplant, and one was under chemotherapy including rituximab. Despite therapy with cidofovir, all patients died. As the incidence of HAdV hepatitis is low, diagnosis may be easily overlooked. No treatment approaches have yet been established. HAdV hepatitis should be considered as a differential diagnosis, especially when risk factors are present. To avoid dissemination, treatment should be initiated as soon as possible.

Human Adenovirus Associated Hepatic Injury.

Human adenovirus (HAdV) is a common virus, but the infections it causes are relatively uncommon. At the same time, the methods for the detection of HAdV are varied, among which viral culture is still the gold standard. HAdV infection is usually self-limited but can also cause clinically symptomatic in lots of organs and tissues, of which human adenovirus pneumonia is the most common. In contrast, human adenovirus hepatitis is rarely reported. However, HAdV hepatitis has a high fatality rate once it occurs, especially in immunocompromised patients. Although human adenovirus hepatitis has some pathological and imaging features, its clinical symptoms are not typical. Therefore, HAdV hepatitis is not easy to be found in the clinic. There are kinds of treatments to treat this disease, but few are absolutely effective. In view of the above reasons, HAdV hepatitis is a disease that is difficult to be found in time. We reviewed and summarized the previously reported cases, hoping to bring some relatively common characteristics to clinicians, so as to facilitate early detection, early diagnosis, and early treatment of patients.

Identification of Inhibitors and Drug Targets for Human Adenovirus Infections.

Adenoviruses can cause infections in people of all ages at all seasons of the year. Adenovirus infections cause mild to severe illnesses. Children, immunocompromised patients, or those with existing respiratory or cardiac disease are at higher risk. Unfortunately, there are no commercial drugs or vaccines available on the market for adenovirus infections. Therefore, there is an urgent need to discover new antiviral drugs or drug targets for adenovirus infections. To identify potential antiviral agents for adenovirus infections, we screened a drug library containing 2138 compounds, most of which are drugs with known targets and past phase I clinical trials. On a cell-based assay, we identified 131 hits that inhibit adenoviruses type 3 and 5. A secondary screen confirmed the antiviral effects of 59 inhibitors that inhibit the replication of adenoviruses type 3 or 5. Most of the inhibitors target heat shock protein, protein tyrosine kinase, the mTOR signaling pathway, and other host factors, suggesting that these host factors may be essential for replicating adenoviruses. Through this study, the newly identified adenovirus inhibitors may provide a start point for developing new antiviral drugs to treat adenovirus infections. Further validation of the identified drug targets can help the development of new therapeutics against adenovirus infections.

Diagnostic accuracy of clinical signs, symptoms and point-of-care testing for early adenoviral conjunctivitis.

CLINICAL RELEVANCE: This study identifies key signs and symptoms of acute conjunctivitis, that when combined with a point-of-care test, can improve clinician accuracy of diagnosing adenoviral conjunctivitis. BACKGROUND: Adenoviral conjunctivitis is a common ocular infection with the potential for high economic impact due to widespread outbreaks and subsequent furloughs from work and school. In this report, we describe clinical signs and participant-reported symptoms that most accurately identify polymerase chain reaction (PCR)-confirmed adenoviral conjunctivitis. METHODS: Adults with 'red eye' symptoms of four days or less were enrolled. Participants rated 10 ocular symptoms from 0 (not bothersome) to 10 (very bothersome), and indicated the presence or absence of systemic flu-like symptoms. Clinicians determined the presence or absence of swollen lymph nodes and rated the severity of eight ocular signs using a 5-point scale. An immunoassay targeting adenovirus antigen was utilised for the point-of-care test, and conjunctival swab samples were obtained for subsequent adenovirus detection by PCR analyses. Univariate and multivariate logistic regression models were used to identify symptoms and signs associated with PCR-confirmed adenoviral conjunctivitis. The diagnostic accuracy of these clinical findings, and the potential benefit of incorporating point-of-care test results, was assessed by calculating areas under the receiver operating characteristic curves (AUC). RESULTS: Clinician-rated bulbar conjunctival redness, participant-rated eyelid swelling and overall ocular discomfort had the best predictive value in the multivariate logistic regression model with an AUC of 0.83. The addition of the point-of-care test results to these three clinical sign/symptom scores improved diagnostic accuracy, increasing the AUC to 0.94. CONCLUSIONS: Conjunctival redness severity and participant-reported eyelid swelling and overall discomfort, along with adenoviral point-of-care test results, were highly predictive in identifying individuals with PCR-confirmed adenoviral conjunctivitis. Improved diagnostic accuracy by clinicians at the initial presenting visit could prevent unnecessary work furloughs and facilitate earlier treatment decisions.

Success of Masking 5% Povidone-Iodine Treatment: The Reducing Adenoviral Patient Infected Days Study.

SIGNIFICANCE: The effectiveness of masking is rarely evaluated or reported in single- or double-masked clinical trials. Knowledge of treatment assignment by participants and clinicians can bias the assessment of treatment efficacy. PURPOSE: This study aimed to evaluate the effectiveness of masking in a double-masked trial of 5% povidone-iodine for the treatment of adenoviral conjunctivitis. METHODS: The Reducing Adenoviral Patient Infected Days study is a double-masked, randomized trial comparing a one-time, in-office administration of 5% povidone-iodine with artificial tears for the treatment of adenoviral conjunctivitis. Masking was assessed by asking participants and masked clinicians at designated time points if they believed the treatment administered was povidone-iodine or artificial tears, or if they were unsure. Adequacy of masking was quantified using a modified Bang Blinding Index. RESULTS: Immediately after treatment, 34% of participants who received povidone-iodine and 69% of those who received artificial tears guessed incorrectly or were unsure of their treatment (modified Bang Indices of 0.31 and -0.38, respectively). On day 4, 38% of the povidone-iodine participants and 52% of the artificial tear participants guessed incorrectly or were unsure of their treatment (modified Bang Indices of 0.24 and -0.05, respectively), indicating adequate and ideal masking. On days 1, 4, 7, 14, and 21, masked clinicians guessed incorrectly or were unsure of treatment in 53%, 50%, 40%, 39%, and 42% among povidone-iodine participants compared with 44%, 35%, 38%, 35%, and 39% among artificial tears participants, respectively. The modified Bang Indices for clinician masking in the povidone-iodine group ranged from -0.05 to 0.25 and from 0.13 to 0.29 in the artificial tears group. CONCLUSIONS: Masking of participants and clinicians was adequate. Successful masking increases confidence that subjective measurements are not biased. We recommend quantitative assessment and reporting the effectiveness of masking in ophthalmic clinical trials.

Quantitative Investigation of Viral Load in Acute to Subacute Human Adenovirus Type 54 Conjunctivitis.

To understand the clinical course of human adenoviral (HAdV) conjunctivitis and establish a better treatment regimen, 38 eyes of 19 patients with HAdV-54 conjunctivitis for less than one week from onset were evaluated for clinical signs and symptoms and DNA copy numbers. A viral load of 104-105 is required to develop symptoms of HAdV conjunctivitis, as symptoms were present in eyes with viral loads of ≥104 at least once during the course. Next, it was observed that asymptomatic infections in the contralateral eyes are common, as the virus was detected in most eyes that did not develop conjunctivitis. Furthermore, there was no rapid decrease in the viral load in healed eyes; on the contrary, the viral load in the healed eyes on day 15 was significantly higher than that in the unhealed eyes. This was likely due to corticosteroid instillation, which rapidly alleviated symptoms but prolonged the duration of viral shedding. Recently, combination treatment with iodine and corticosteroids has been recommended for HAdV conjunctivitis. Assessing changes in the viral load and clinical symptoms would be helpful to better understand the clinical course of this disease.

[Which drugs to treat Adenovirus infections?] / Quelles molécules pour traiter des infections à Adénovirus ?

Human adenoviruses (HAdV) infections are generally mild and resolve spontaneously in immunocompetent individuals. However, HAdV infections can have a major clinical impact in immunocompromised patients. HAdV infections are associated with high morbidity and mortality in recipients of allogeneic stem cell transplants, particularly children. There are currently no drug approved for the treatment of HAdV infections. Nevertheless, some nucleotide analogues are used under temporary authorization for use, such as cidofovir or brincidofovir. Cidofovir inhibits the replication of HAdV but its nephrotoxicity and its low tissue concentrations severely limit its use. Brincidofovir, a cidofovir prodrug, with a better bioavailability and no nephrotoxicity was evaluated in the treatment of HAdV infections, but its development was recently stopped and it is currently no longer available in ATU. Other molecules with anti-HAdV activity are still in early stages of development. Adoptive immunotherapy by adenovirus-specific T-cell transfer is an interesting option but should be anticipated in patients with high risks of disseminated infections. Given the small therapeutic panel available, it is critical to continue the search for new anti-HAdV molecules, which remains mainly conducted by academic laboratories.

Emerging antiviral therapeutics for human adenovirus infection: Recent developments and novel strategies.

Human adenoviruses (HAdV) are ubiquitous human pathogens that cause a significant burden of respiratory, ocular, and gastrointestinal illnesses. Although HAdV infections are generally self-limiting, pediatric and immunocompromised individuals are at particular risk for developing severe disease. Currently, no approved antiviral therapies specific to HAdV exist. Recent outbreaks underscore the need for effective antiviral agents to treat life-threatening infections. In this review we will focus on recent developments in search of potential therapeutic agents for controlling HAdV infections, with a focus on those targeting post-entry stages of the virus replicative cycle.

High-Throughput Screening and Identification of Human Adenovirus Type 5 Inhibitors.

Human adenovirus infections can develop into diffuse multi-organ diseases in young children and immunocompromised patients, and severe cases can lead to death. However, there are no approved antiviral drugs available to treat adenovirus diseases. In this study, a chemiluminescence-based, high-throughput screening (HTS) assay was developed and applied to screen human adenovirus 5(HAdV5)inhibitors from 1,813 approved drug library and 556 traditional Chinese medicine-sourced small-molecule compounds. We identified three compounds with in vitro anti-HAdV5 activities in the low-micromolar range (EC50 values 0.3-4.5 µM, selectivity index values 20-300) that also showed inhibitory effects on HAdV3. Cardamomin (CDM) had good anti-HAdV5 activity in vitro. Furthermore, three dilutions of CDM (150, 75, and 37.5 mg/kg/d) administered to BALB/c mouse models inhibited HAdV5-fluc infection at 1 day post-infection by 80% (p < 0.05), 76% (p < 0.05), and 58% (p < 0.05), respectively. HE-staining of pathological tissue sections of mice infected with a wildtype adenoviral strain showed that CDM had a protective effect on tissues, especially in the liver, and greatly inhibited virus-induced necrosis of liver tissue. Thus, CDM inhibits adenovirus replication in vivo and in vitro. This study established a high-throughput screening method for anti-HAdV5 drugs and demonstrated CDM to be a candidate for HAdV5 therapy, potentially providing a new treatment for patients infected with adenoviruses.

Identification of human adenovirus replication inhibitors from a library of small molecules targeting cellular epigenetic regulators.

Human adenovirus (HAdV) can cause severe disease in certain at-risk populations such as newborns, young children, the elderly and individuals with a compromised immune system. Unfortunately, no FDA-approved antiviraldrug is currently available for the treatment of HAdV infections. Within the nucleus of infected cells, the HAdV genome associates with histones and forms a chromatin-like structure during early infection, and viral gene expression appears to be regulated by cellular epigenetic processes. Thus, one potential therapeutic strategy to combat HAdV disease may be to target the cellular proteins involved in modifying the viral nucleoprotein structure and facilitating HAdV gene expression and replication. We have screened a panel of small molecules that modulate the activity of epigenetic regulatory proteins for compounds affecting HAdV gene expression. Several of the compounds, specifically chaetocin, gemcitabine and lestaurtinib, reduced HAdV recovery by 100- to 1000-fold, while showing limited effects on cell health, suggesting that these compounds may indeed be promising as anti-HAdV therapeutics.

The Treatment Models for Adenoviral Keratoconjunctivitis in the Childhood Population.

Purpose: To examine the effects of treatments performed on children with adenoviral conjunctivitis.Methods: 50 children with Adenoviral keratoconjunctivitis (AK) were evaluated. Patients were divided into four groups according to the medical treatment agents that were used previously. AK symptoms were clinically scored and analyzed. The diagnosis of all children was confirmed by an in-office lateral flow immunoassay.Results: Fifty patients with AK were included in the study. 24 (48%) were female and 26 (52%) were male. The mean age was 12.88 ± 2.66 (8-17). In PVP-I groups clinical findings shows faster improvement than other groups (p < .05).Conclusions: Conjunctival irrigation with 2.5% PVP-I is very effective for the treatment of adenoviral conjunctivitis in childhood. Ganciclovir ophthalmic gel 0.15% increases the effect of 2.5% PVP-I on AK, but this was not statistically significant.

Comparative study of topical regimen for adenoviral kearoconjunctivitis by 0.1% fluorometholone with and without polyvinyl alcohol iodine.

PURPOSE: The aim of this study was to compare the efficacy of the topical regimens of iodine/steroids vs. antibiotics/steroids in acute to subacute adenoviral keratoconjunctivitis. STUDY DESIGN: A prospective open-label study. PATIENTS AND METHODS: Nineteen patients diagnosed with unilateral or bilateral adenoviral conjunctivitis at less than 1 week from onset were enrolled in this study. Patients were divided randomly into two groups; group 1 was treated with 1.5% levofloxacin with 0.1% fluorometholone administered four times a day and group 2 was treated with a sixfold dilution of polyvinyl alcohol iodine (PAI) solution with 0.1% fluorometholone four times a day. Conjunctival samples from all affected eyes were obtained for real-time PCR. The total scores of acute signs (i.e., eyelid edema, conjunctival injecton, conjunctival discharge, follicules, pseudomembranes, subconjunctival hemorrhage) and symptoms, HAdV DNA copy number, and the presence of multiple subepithelial corneal infiltrates (MSI) were evaluated every 5 visits up to Day 30 after diagnosis. RESULTS: Comparing the total scores of acute signs and symptoms and viral load, we observed no significant differences between the two groups. At day 15 after diagnosis the proportion of patients with MSI in group 2 (35.7%) was significantly lower than in group 1 (0%). CONCLUSIONS: The impact of topical iodine/steroid therapy on acute signs and symptoms associated with adenoviral conjunctivitis is limited and not substantially different in the responses to antibiotics/steroids. However, this regimen results in a significant decrease in the incidence of MSI during the subacute phase of infection.

Corticosteroids Versus Cyclosporine for Subepithelial Infiltrates Secondary to Epidemic Keratoconjunctivitis: A Prospective Randomized Double-Blind Study.

PURPOSE: To compare efficiency and tolerance between topical 0.5% cyclosporine A (CSA) and fluorometholone (FML) for subepithelial infiltrates (SEI) complicating epidemic keratoconjunctivitis. METHODS: We conducted a prospective double-blind randomized study involving 72 eyes with SEI. Thirty-eight eyes were treated with topical FML (FML group) and 34 eyes with CSA 0.5% eye drops (CSA group). Treatment was considered successful in case of SEI reduction and visual acuity improvement. Tolerance was evaluated by Schirmer test value, burning on eye drops instillation, and conjunctival injection. RESULTS: Baseline characteristics of both groups were similar (P > 0.05). After 3 months of the regimen, resolution of SEI was 3 times more observed in the FML group than that in the CSA group (P = 0.026). After 6 months, resolution of SEI was observed in 70% of the FML group and in 47% of the CSA group (P = 0.068). The recurrence of SEI was almost twice higher in the FML group than that in the CSA group (16% vs. 9%). FML was better tolerated during the first 3 months: a higher Schirmer test value (P = 0.0003), less burning on instillation (P = 0.242), and less conjunctival injection (P = 0.003). For the rest of the follow-up period, the 2 groups were comparable in tolerance. No ocular hypertension was noted. CONCLUSIONS: Epidemic keratoconjunctivitis can evolve favorably under both FML and CSA. The effect of FML is faster and CSA is more durable with fewer recurrences. Both are safe therapeutic options for long-term control of SEI.

Respiratory Virus Infections in Asthma: Research Developments and Therapeutic Advances.

In this review, we discuss the latest developments in research pertaining to virus-induced asthma exacerbations and consider recent advances in treatment options. Asthma is a chronic disease of the airways that continues to impose a substantial clinical burden worldwide. Asthma exacerbations, characterised by an acute deterioration in respiratory symptoms and airflow obstruction, are associated with significant morbidity and mortality. These episodes are most commonly triggered by respiratory virus infections. The mechanisms underlying the pathogenesis of virus-induced exacerbations have been the focus of extensive biomedical research. Developing a robust understanding of the interplay between respiratory viruses and the host immune response will be critical for developing more efficacious, targeted therapies for exacerbations. CONCLUSION: There has been significant recent progress in our understanding of the mechanisms underlying virus-induced airway inflammation in asthma and these advances will underpin the development of future clinical therapies.

A synthetic stigmastane displays antiadenoviral activity and reduces the inflammatory response to viral infection.

Although human adenovirus (ADV) infections are mild and self-limited in immunocompetent individuals, they can be severe and life-threatening in immunocompromised patients. Despite their significant clinical impact, there are not currently approved antiviral therapies for ADV infections. On the other hand, in some cases, the immune response induced by ADV infection can cause tissue damage. Even more, in the case of adenovirus vectors used in gene therapy, host immunity generally antagonize viral efficacy. Therefore, the need for searching an effective and safe therapy is increasing. In this work, we describe the antiadenoviral activity of the synthetic stigmastane (22S, 23S)-22,23-dihydroxystigmast-4-en-3-one (Compound 1) with already reported antiviral and antiinflammatory activities against other viruses of clinical importance. Compound 1 displayed no virucidal activity and did not affect ADV entry to the cells. The compound inhibited viral replication and it also reduced cytokine secretion in epithelial and inflammatory infected cells. Thus, Compound 1 would be a promissory drug potentially useful against adenoviral infections as well as an adjuvant of adenoviral vectors in gene therapy.

Filociclovir Is a Potent In Vitro and In Vivo Inhibitor of Human Adenoviruses.

Human adenovirus (HAdV) infection is common in the general population and can cause a range of clinical manifestations, among which pneumonia and keratoconjunctivitis are the most common. Although HAdV infections are mostly self-limiting, infections in immunocompromised individuals can be severe. No antiviral drug has been approved for treating adenoviruses. Filociclovir (FCV) is a nucleoside analogue which has successfully completed phase I human clinical safety studies and is now being developed for treatment of human cytomegalovirus (HCMV)-related disease in immunocompromised patients. In this report, we show that FCV is a potent broad-spectrum inhibitor of HAdV types 4 to 8, with 50% effective concentrations (EC50s) ranging between 1.24 and 3.6 µM and a 50% cytotoxic concentration (CC50) of 100 to 150 µM in human foreskin fibroblasts (HFFs). We also show that the prophylactic oral administration of FCV (10 mg/kg of body weight) 1 day prior to virus challenge and then daily for 14 days to immunosuppressed Syrian hamsters infected intravenously with HAdV6 was sufficient to prevent morbidity and mortality. FCV also mitigated tissue damage and inhibited virus replication in the liver. The 10-mg/kg dose had similar effects even when the treatment was started on day 4 after virus challenge. Furthermore, FCV administered at the same dose after intranasal challenge with HAdV6 partially mitigated body weight loss but significantly reduced pathology and virus replication in the lung. These findings suggest that FCV could potentially be developed as a pan-adenoviral inhibitor.

The FDA-Approved Drug Nelfinavir Inhibits Lytic Cell-Free but Not Cell-Associated Nonlytic Transmission of Human Adenovirus.

Adenoviruses (AdVs) are prevalent and give rise to chronic and recurrent disease. Human AdV (HAdV) species B and C, such as HAdV-C2, -C5, and -B14, cause respiratory disease and constitute a health threat for immunocompromised individuals. HAdV-Cs are well known for lysing cells owing to the E3 CR1-ß-encoded adenovirus death protein (ADP). We previously reported a high-throughput image-based screening framework and identified an inhibitor of HAdV-C2 multiround infection, nelfinavir mesylate. Nelfinavir is the active ingredient of Viracept, an FDA-approved inhibitor of human immunodeficiency virus (HIV) aspartyl protease that is used to treat AIDS. It is not effective against single-round HAdV infections. Here, we show that nelfinavir inhibits lytic cell-free transmission of HAdV, indicated by the suppression of comet-shaped infection foci in cell culture. Comet-shaped foci occur upon convection-based transmission of cell-free viral particles from an infected cell to neighboring uninfected cells. HAdV lacking ADP was insensitive to nelfinavir but gave rise to comet-shaped foci, indicating that ADP enhances but is not required for cell lysis. This was supported by the notion that HAdV-B14 and -B14p1 lacking ADP were highly sensitive to nelfinavir, although HAdV-A31, -B3, -B7, -B11, -B16, -B21, -D8, -D30, and -D37 were less sensitive. Conspicuously, nelfinavir uncovered slow-growing round HAdV-C2 foci, independent of neutralizing antibodies in the medium, indicative of nonlytic cell-to-cell transmission. Our study demonstrates the repurposing potential of nelfinavir with postexposure efficacy against different HAdVs and describes an alternative nonlytic cell-to-cell transmission mode of HAdV.