Biology subjects

Kang, H.-J.

Publications and source records attributed to Kang, H.-J..

5 recordsLinked to original sources

bioRxiv2024

Efficacy of late-onset antiviral treatment in immune-compromised hosts with persistent SARS-CoV-2 infection

The immunocompromised are at high risk of prolonged SARS-CoV-2 infection and progression to severe COVID-19. However, efficacy of late-onset direct-acting antiviral (DAA) therapy with therapeutics in clinical use and experimental drugs to mitigate persistent viral replication is unclear. In this study, we employed an immunocompromised mouse model, which supports prolonged replication of SARS-CoV-2 to explore late-onset treatment options. Tandem immuno-depletion of CD4+ and CD8+ T cells in C57BL/6 mice followed by infection with SARS-CoV-2 variant of concern (VOC) beta B.1.351 resulted in prolonged infection with virus replication for five weeks after inoculation. Early-onset treatment with nirmatrelvir/ritonavir (paxlovid) or molnupiravir was only moderately efficacious, whereas the experimental therapeutic 4-fluorourdine (4-FlU, EIDD-2749) significantly reduced virus load in upper and lower respiratory compartments four days post infection (dpi). All antivirals significantly lowered virus burden in a 7-day treatment regimen initiated 14 dpi, but paxlovid-treated animals experienced rebound virus replication in the upper respiratory tract seven days after treatment end. Viral RNA was detectable 28 dpi in paxlovid-treated animals, albeit not in the molnupiravir or 4-FlU groups, when treatment was initiated 14 dpi and continued for 14 days. Low-level virus replication continued 35 dpi in animals receiving vehicle but had ceased in all treatment groups. These data indicate that late-onset DAA therapy significantly shortens the duration of persistent virus replication in an immunocompromised host, which may have implications for clinical use of antiviral therapeutics to alleviate the risk of progression to severe disease in highly vulnerable patients. ImportanceFour years after the onset of the global COVID-19 pandemic, the immunocompromised are at greatest risk of developing life-threatening severe disease. However, specific treatment plans for this most vulnerable patient group have not yet been developed. Employing a CD4+ and CD8+ T cell-depleted immunocompromised mouse model of SARS-CoV-2 infection, we explored therapeutic options of persistent infections with standard-of-care paxlovid, molnupiravir, and the experimental therapeutic 4-FlU. Late-onset treatment initiated 14 days after infection was efficacious, but only 4-FlU was rapidly sterilizing. No treatment-experienced viral variants with reduced susceptibility to the drugs emerged, albeit virus replication rebounded in animals of the paxlovid group after treatment end. This study supports the use of direct-acting antivirals for late-onset management of persistent SARS-CoV-2 infection in immunocompromised hosts. However, treatment courses likely require to be extended for maximal therapeutic benefit, calling for appropriately powered clinical trials to meet the specific needs of this patient group.

microbiology↗

bioRxiv2023

Influenza A virus resistance to 4-fluorouridine coincides with viral attenuation in vitro and in vivo

Pre-existing or rapidly emerging resistance of influenza viruses to approved antivirals makes the development of novel therapeutics to mitigate seasonal influenza and improve preparedness against future influenza pandemics an urgent priority. We have recently identified the chain-terminating broad-spectrum nucleoside analog clinical candidate 4-fluorouridine (4-FlU) and demonstrated oral efficacy against seasonal, pandemic, and highly pathogenic avian influenza viruses in the mouse and ferret model. Here, we have resistance-profiled 4-FlU against a pandemic A/CA/07/2009 (H1N1) (CA09). In vitro viral adaptation yielded six independently generated escape lineages with distinct mutations that mediated moderate resistance to 4-FlU in the genetically controlled background of recombinant CA09 (recCA09). Mutations adhered to three distinct structural clusters that are all predicted to affect the geometry of the active site of the viral RNA-dependent RNA polymerase (RdRP) complex for phosphodiester bond formation. Escape could be achieved through an individual causal mutation, a combination of mutations acting additively, or mutations functioning synergistically. Fitness of all resistant variants was impaired in cell culture, and all were attenuated in the mouse model. Oral 4-FlU administered at lowest-efficacious (2 mg/kg) or elevated (10 mg/kg) dose overcame moderate resistance when mice were inoculated with 10 LD50 units of parental or resistant recCA09, demonstrated by significantly reduced virus load and complete survival. In the ferret model, invasion of the lower respiratory tract by variants representing four adaptation lineages was impaired. Resistant variants were either transmission-incompetent, or spread to untreated sentinels was fully blocked by therapeutic treatment of source animals with 4-FlU. Author SummaryReduced sensitivity to FDA-approved influenza drugs is a major obstacle to effective antiviral therapy. We have previously demonstrated oral efficacy of a novel clinical candidate drug, 4-FlU, against seasonal, pandemic, and highly pathogenic avian influenza viruses. In this study, we have determined possible routes of influenza virus escape from 4-FlU and addressed whether resistance imposes a viral fitness penalty, affecting pathogenicity or ability to transmit. We identified three distinct clusters of mutations that lead to moderately reduced viral sensitivity to the drug. Testing of resistant variants against two chemically unrelated nucleoside analog inhibitors of influenza virus, conditionally approved favipiravir and the broad-spectrum SARS-CoV-2 drug molnupiravir, revealed cross-resistance of one cluster with favipiravir, whereas no viral escape from molnupiravir was noted. We found that the resistant variants are severely attenuated in mice, impaired in their ability to invade the lower respiratory tract and cause viral pneumonia in ferrets, and transmission-defective or compromised. We could fully mitigate lethal infection of mice with the resistant variants with standard or 5-fold elevated oral dose of 4-FlU. These results demonstrate that partial viral escape from 4-FlU is feasible in principle, but escape mutation clusters are unlikely to reach clinical significance or persist in circulating influenza virus strains.

microbiology↗

bioRxiv2023

Therapeutic mitigation of measles-like immune amnesia and exacerbated disease after prior respiratory virus infections in ferrets

After years of the COVID-19 pandemic, over 40 million children worldwide are at risk of measles due to delayed vaccination1 and temporary SARS-CoV-2 viral dominance2. Acute measles has a case-fatality rate of [~]1%, but most morbidity and mortality arise post-measles due to destruction of pre-existing immune memory by lymphotropic measles virus (MeV)3,4, a paramyxovirus of the Morbillivirus genus. MeV-induced immune amnesia is not mitigated by post-exposure vaccination and the impact of unrelated respiratory virus disease history on measles severity has not been defined. We used a lethal canine distemper virus (CDV)-ferret model as surrogate for human morbillivirus disease5 and employed the orally efficacious broad-spectrum paramyxovirus polymerase inhibitor GHP-883096 to establish measles treatment paradigms. Applying a receptor tropism-intact recombinant CDV with low lethality, we provide in vivo confirmation of the morbillivirus immune amnesia hypothesis and reveal an 8-day advantage of antiviral treatment versus therapeutic vaccination in preserving immune memory. Infection of ferrets with non-lethal influenza A virus (IAV) A/CA/07/2009 (H1N1) or respiratory syncytial virus (RSV) four weeks prior to CDV caused exacerbated CDV disease that rapidly advanced to fatal hemorrhagic pneumonia associated with lung onslaught by commensal bacteria. RNAseq of BAL samples and lung tissue identified CDV-induced expression of trefoil factor (TFF) peptides, which was absent in animals pre-infected with IAV, thus highlighting that immune priming by unrelated respiratory viruses influences morbillivirus infection outcome. Non-invasive pulmonary ferret MRI revealed that severe outcomes of consecutive IAV/CDV infections were prevented by oral GHP-88309 treatment even when initiated after peak clinical signs of CDV. These findings validate the morbillivirus immune amnesia hypothesis, define treatment paradigms for measles, identify prior disease history as risk factor for exacerbated morbillivirus disease, and demonstrate that treating morbillivirus infection with direct-acting oral antivirals provides therapeutic benefit regardless of whether the time window to mitigate primary clinical signs of infection has closed.

microbiology↗

bioRxiv2022

4-Fluorouridine mitigates lethal infection with pandemic human and highly pathogenic avian influenza viruses

Influenza outbreaks are associated with substantial morbidity, mortality and economic burden. Next generation antivirals are needed to treat seasonal infections and prepare against zoonotic spillover of avian influenza viruses with pandemic potential. Having previously identified oral efficacy of the nucleoside analog 4-Fluorouridine (4-FlU, EIDD-2749) against SARS-CoV-2 and respiratory syncytial virus, we explored activity of the compound against seasonal and highly pathogenic influenza (HPAI) viruses in cell culture, human airway epithelium organoids, and/or two animal models, ferrets and mice, that assess IAV transmission and lethal viral pneumonia, respectively. 4-FlU inhibited a panel of relevant influenza A and B viruses with nanomolar potency in organoids. In vitro polymerase assays revealed immediate chain termination of IAV polymerase after 4-FlU incorporation, in contrast to delayed chain termination of SARS-CoV-2 and RSV polymerase. Once-daily oral treatment of ferrets with 2 mg/kg 4-FlU initiated 12 hours after infection rapidly stopped virus shedding and prevented direct-contact transmission to untreated sentinels. Treatment of mice infected with a lethal inoculum of pandemic A/CA/07/2009 (H1N1)pdm09 (Ca09) with 2 mg/kg 4-FlU alleviated pneumonia. Three doses mediated complete survival when treatment was initiated up to 60 hours after infection, indicating an unusually broad window for effective intervention. Therapeutic oral 4-FlU ensured survival of animals infected with HPAI A/VN/12/2003 (H5N1) and of immunocompromised mice infected with pandemic Ca09. Recoverees were fully protected against homologous reinfection. This study defines the mechanistic foundation for high sensitivity of influenza viruses to 4-FlU and supports 4-FlU as developmental candidate for the treatment of seasonal and pandemic influenza. Author SummaryNext-generation antiviral therapeutics are needed to better mitigate seasonal influenza and prepare against zoonotic virus spillover from animal reservoirs. At greatest risk are the immunocompromised and patients infected with highly pathogenic influenza viruses. In this study, we have demonstrated efficacy of a broad-spectrum nucleoside analog, 4-fluorouridine, against a representative panel of influenza viruses in cell culture, human organoids, and two animal models, ferrets and mice. Acting as an immediate chain terminator of the influenza virus polymerase, once-daily oral treatment protected against lethal infection with seasonal and highly pathogenic avian influenza viruses, prevented direct-contact transmission to untreated sentinels, and mitigated lethal infection of immunocompromised hosts. These results support the developmental potential of 4-fluorouridine for treatment of vulnerable patient groups and mitigation of pandemic influenza, providing a much-needed additional therapeutic option for improved disease management.

microbiology↗

bioRxiv2017

Investigating on relationship between effective quantum efficiency and irradiance

AbstractModels describing the relationship between effective quantum efficiency of PS II ({Phi}PSII) and irradiance (I) are routinely used to determine how irradiance influences effective quantum efficiency and photosynthetic electron transport rate (ETR). However, with no single model one can accurately describe the relationship between{Phi} PSII and I, and explain the interdependence between{Phi} PSII and biophysical properties of photosynthetic pigments, especially in plants growing under low level irradiances. Basing on the mechanistic model of photosynthetic electron transport rate we have developed the model of the relationship between{Phi} PSII and I. The new model reveals that{Phi} PSII increases with photochemistry (kP) and heat dissipation (kD). Furthermore, the values of key parameters calculated using the new model were compared with the values calculated with two other empirical models. The new model was perfectly fitted to the light-response curves of{Phi} PSII. The key calculated photosynthetic parameters: maximum{Phi} PSII, maximum ETR and their corresponding saturation irradiance were close to the measured values. In addition, our model associates{Phi} PSII with intrinsic features of photosynthetic pigments. We concluded that{Phi} PSII decreased with increasing I due to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.\n\nHighlightA model of the relationship between effective quantum efficiency of PS II ({Phi}PSII) and irradiance (I) has been developed. Using this new model it was found that{Phi} PSII decreased with increasing I due to the decrease in the effective absorption cross-section of photosynthetic pigments molecules.\n\nAbbreviations

plant biology↗