Seasonal influenza A virus (IAV) infections still pose a major burden for public health worldwide. Severe disease progression or even death is often related to superinfections of the virus and a secondary bacterial pathogen. However, fungi, especially Aspergillus fumigatus, are also frequently diagnosed during IAV infection. Although, clinical studies have reported the severity of influenza-associated pulmonary aspergillosis, the molecular mechanisms underlying this type of disease are poorly understood. Here, a new in vitro model is introduced that allows the investigation of complex pathogen-host and pathogen-pathogen interactions during coinfection of lung epithelial cells with IAV and A. fumigatus. Our data reveal a reduced IAV load and IAV-induced cytokine and chemokine expression in the presence of A. fumigatus. At the same time, IAV infection promotes the growth of A. fumigatus. Even in the absence of the human host cell, purified IAV particles are able to induce hyphal growth, due to a direct interaction of the virus particles with the fungal surface. Thus, our study gives first insights into the complex interplay between IAV, A. fumigatus and the host cell as well as the two pathogens alone.

As vaccination efforts against SARS-CoV-2 progress in many countries, there is still an urgent need for efficient antiviral treatment strategies for those with severer disease courses, and lately, considerable efforts have been undertaken to repurpose existing drugs as antivirals. The local anaesthetic procaine has been investigated for antiviral properties against several viruses over the past decades. Here, we present data on the inhibitory effect of the procaine prodrugs ProcCluster^® and procaine hydrochloride on SARS-CoV-2 infection in vitro. Both procaine prodrugs limit SARS-CoV-2 progeny virus titres as well as reduce interferon and cytokine responses in a proportional manner to the virus load. The addition of procaine during the early stages of the SARS-CoV-2 replication cycle in a cell culture first limits the production of subgenomic RNA transcripts, and later affects the replication of the viral genomic RNA. Interestingly, procaine additionally exerts a prominent effect on SARS-CoV-2 progeny virus release when added late during the replication cycle, when viral RNA production and protein production are already largely completed.

Influenza A virus (IAV) infections continue to threaten public health. Current strategies, such as vaccines and antiviral drugs, are limited due to their time-consuming development and drug-resistant strains. Therefore, new effective treatments are needed. Here, virus-supportive cellular factors are promising drug targets, and the encapsulation of candidate substances in poly(D,L-lactic-co-glycolic acid) (PLGA) nanoparticles (NPs) is intended to improve their bioavailability. This study investigates the potential of the indirubin derivative 6-bromoindirubin-3′-glycerol-oxime ether (6BIGOE), a glycogen synthase kinase 3 (GSK-3)β inhibitor, for its potential to regulate IAV replication in vitro. The effects of 6BIGOE-loaded PLGA NPs on cell metabolism were assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and lactate dehydrogenase (LDH) assays in A549 and Calu-3 cells. Viral replication and spread were monitored in various IAV-infected cell lines in the absence and presence of free and 6BIGOE-loaded PLGA NPs via plaque assays and Western blot analysis. The encapsulation of 6BIGOE in PLGA NPs resulted in reduced negative side effects on cell viability while maintaining antiviral efficacy. Both encapsulated and free 6BIGOE exhibited antiviral activity, potentially through GSK-3β inhibition and the disruption of key signaling pathways required for viral replication. The data indicate 6BIGOE, particularly after encapsulation in NPs, as a potential candidate for further investigation and development as an antiviral agent to treat IAV infections.

Influenza A virus (IAV) infections remain a major global health threat, as current vaccines and antivirals often lose efficacy due to frequent viral mutation and resistance development. This underscores the urgent need for novel therapeutic strategies, such as targeting host factors, which may reduce the likelihood of resistance. Here, we evaluated inhibitors of G protein‐coupled receptor kinases (GRKs; paroxetine, CMPD101) and protein kinase C (PKC; Gö6983, bisindolylmaleimide‐I (BIM‐I)) for anti‐IAV activity. GRK inhibition showed no significant effect, whereas PKC inhibition, particularly with BIM‐I, significantly reduced infection. To overcome BIM‐I's poor solubility and concentration‐dependent cytotoxicity, it is encapsulated into poly(lactic‐ co ‐glycolic acid) (PLGA)‐based nanoparticles. To enhance nanoparticle performance, stealth polymers like polyethylene glycol (PEG) are commonly incorporated. However, concerns about PEG immunogenicity have increased interest in alternatives like poly(2‐ethyl‐2‐oxazoline) (PEtOx). We formulated BIM‐I‐loaded nanoparticles containing either PEG or PEtOx and characterized them for their physicochemical properties, cytotoxicity, antiviral efficacy, and cellular uptake. Encapsulation improved the cellular tolerability of BIM‐I while preserving its antiviral activity. Confocal microscopy confirmed efficient uptake of all formulations, particularly PEGylated and PEtOxylated nanoparticles. These findings highlight nanoparticle‐mediated delivery of BIM‐I as a promising host‐directed antiviral strategy against IAV and support PEtOx as a viable PEG alternative in nanomedicine.

Influenza A viruses (IAVs) remain a significant global health concern, causing seasonal outbreaks and pandemics with substantial morbidity and mortality, particularly among vulnerable groups. Annual vaccination serves as the primary preventative measure, but its limited effectiveness against emerging subtypes and insufficient coverage underscore the urgent need for novel antiviral strategies. Resistance to Food and Drug Administration (FDA)- and European Medicines Agency (EMA)-approved direct antivirals further emphasizes this necessity. Host-directed therapeutic strategies, such as those targeting phosphatidylinositol 3-kinases (PI3Ks), which are utilized by IAVs during replication, offer promising alternatives to reduce infection severity. In parallel, advances in nanotechnology have facilitated the use of lipid nanoparticles (LNPs) as efficient drug delivery systems, enhancing bioavailability, optimizing therapeutic stability, and enabling precise site-specific delivery to infected cells. This study investigates the combined use of pictilisib, a PI3K inhibitor, and LNPs, as a novel approach to combat IAV infections. Polyethylene glycol (PEG)- and poly(2-oxazoline) (POx)-Lipids were incorporated into the drug delivery carriers, with POx-Lipids emerging as promising alternatives due to allergenic concerns associated with PEG. Pictilisib was successfully encapsulated in LNPs and demonstrated comparable antiviral and anti-inflammatory properties to the free drug in vitro. Notably, ex vivo experiments revealed that POx-Lipid LNPs encapsulating pictilisib had a more potent effect on infection compared to free pictilisib, suggesting improved pharmacokinetics, drug stability, and targeted delivery. This integrated approach combining targeted PI3K inhibition and advanced nanocarrier technology represents a significant advance in addressing the challenges associated with IAV treatment, paving the way for further exploration of these strategies to combat infectious diseases.

Influenza A virus (IAV) infections continue to threaten public health. Current strategies, such as vaccines and antiviral drugs, are limited due to time-consuming development and drug-resistant strains. Therefore, new effective treatments are needed. Here, virus-supportive cellular factors are promising drug targets, and encapsulation of candidate substances in PLGA nanoparticles (NPs) is intended to improve their bioavailability. This study investigates the potential of the indirubin derivative 6BIGOE, a GSK-3β inhibitor, for its potential to regulate IAV replication in vitro. The effects of 6BIGOE-loaded PLGA NPs on cell metabolism were assessed by MTT and LDH assays in A549 and Calu-3 cells. Viral replication and spread were monitored in various IAV-infected cell lines in absence and presence of free and 6BIGOE-loaded PLGA NPs via plaque assays and Western blot analysis. Encapsulation of 6BIGOE in PLGA NPs resulted in reduced negative side effects on cell viability while maintaining antiviral efficacy. Both encapsulated and free 6BIGOE exhibited antiviral activity, potentially through GSK-3β inhibition and disruption of key signaling pathways required for viral replication. The data indicate 6BIGOE, particularly after encapsulation in NPs, as a potential candidate for further investigation and development as an antiviral agent to treat IAV infections.