• Mycobacterium tuberculosis
• ATG4B
• ATG9B
• Autophagy
• Immune evasion
• miR-30c-1-3p

• MicroRNAs/genetics
• MicroRNAs/metabolism
• Autophagy-Related Proteins/genetics
• Autophagy-Related Proteins/metabolism
• Autophagy/genetics
• Mycobacterium tuberculosis/physiology
• Humans
• Macrophages/microbiology
• Macrophages/metabolism
• Cysteine Endopeptidases/genetics
• Cysteine Endopeptidases/metabolism
• Tuberculosis/microbiology
• Tuberculosis/genetics
• Membrane Proteins/genetics
• Membrane Proteins/metabolism
• Cell Line
• THP-1 Cells
• Host-Pathogen Interactions

• WX21M02 The Medical Research Project of Wuhan Municipal Health Commission

• microRNA recognition elements
• Influenza
• cross-species transmission
• host barrier
• microRNA
• sialic acid

• M. tuberculosis
• host-directed therapy
• inflammation
• long noncoding RNAs
• macrophages

Bacterial infections in the respiratory tract are considered as one of the major challenges to the public health worldwide. Pulmonary delivery is an attractive approach in the management of bacterial respiratory infections with a few inhaled antibiotics approved. However, with the rapid emergence of antibiotic-resistant bacteria, it is necessary to develop new/alternative inhaled antibacterial agents in the post-antibiotic era. A pipeline of novel biological antibacterial agents, including antimicrobial peptides, RNAi therapeutics, and bacteriophages, has emerged to combat bacterial infections with excellent performance. In this review, the causal effects of bacterial infections on the related pulmonary infectious diseases will be firstly introduced. This is followed by an overview on the development of emerging antibacterial therapeutics for managing lung bacterial infections through nebulization/inhalation of dried powders. The obstacles and underlying proposals regarding their clinical transformation are also discussed to seek insights for further development. Research on inhaled therapy of these emerging antibacterials are still in the infancy, but the promising progress warrants further attention.

• RNAi
• antimicrobial peptides
• bacteriophages
• emerging antibacterials
• pulmonary delivery
• respiratory bacterial infections

• clinical application
• delivery systems
• drug delivery barriers
• inhaled siRNA formulations
• respiratory diseases
• structural modification

• ITS/348/18FX Innovation and Technology Commission of Hong Kong [grant number

• antimicrobial
• bacteria
• infection
• miRNAs
• pathogen

• LE044P20 Junta de Castilla y León
• BEAGAL18/00068 Ministerio de Economía y Competitividad
• Margarita Salas Ministerio de Universidades

Porcine deltacoronavirus (PDCoV) is a recently identified coronavirus that causes intestinal diseases in neonatal piglets with diarrhea, vomiting, dehydration, and post-infection mortality of 50–100%. Currently, there are no effective treatments or vaccines available to control PDCoV. To study the potential of RNA interference (RNAi) as a strategy against PDCoV infection, two short hairpin RNA (shRNA)-expressing plasmids (pGenesil-M and pGenesil-N) that targeted the M and N genes of PDCoV were constructed and transfected separately into swine testicular (ST) cells, which were then infected with PDCoV strain HB-BD. The potential of the plasmids to inhibit PDCoV replication was evaluated by cytopathic effect, virus titers, and real-time quantitative RT-PCR assay. The cytopathogenicity assays demonstrated that pGenesil-M and pGenesil-N protected ST cells against pathological changes with high specificity and efficacy. The 50% tissue culture infective dose showed that the PDCoV titers in ST cells treated with pGenesil-M and pGenesil-N were reduced 13.2- and 32.4-fold, respectively. Real-time quantitative RT-PCR also confirmed that the amount of viral RNA in cell cultures pre-transfected with pGenesil-M and pGenesil-N was reduced by 45.8 and 56.1%, respectively. This is believed to be the first report to show that shRNAs targeting the M and N genes of PDCoV exert antiviral effects in vitro, which suggests that RNAi is a promising new strategy against PDCoV infection.

• Nucleocapsidgene
• Porcine deltacoronavirus
• RNA interference
• Short hairpin RNA
• Swine testicular cells

• Animals
• Coronavirus/genetics
• Coronavirus/pathogenicity
• Coronavirus Infections/genetics
• Coronavirus Infections/pathology
• Coronavirus Infections/virology
• Diarrhea/genetics
• Diarrhea/pathology
• Diarrhea/veterinary
• Diarrhea/virology
• Male
• Plasmids/genetics
• RNA Interference
• RNA, Small Interfering/genetics
• RNA, Viral/genetics
• Swine/virology
• Swine Diseases/genetics
• Swine Diseases/virology
• Testis/growth & development
• Testis/virology
• Viral Proteins/genetics
• Virus Replication/genetics

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) kills millions every year, and there is urgent need to develop novel anti-TB agents due to the fast-growing of drug-resistant TB. Although autophagy regulates the intracellular survival of Mtb, the role of calcium (Ca²⁺) signaling in modulating autophagy during Mtb infection remains largely unknown. Here, we show that microRNA miR-27a is abundantly expressed in active TB patients, Mtb-infected mice and macrophages. The target of miR-27a is the ER-located Ca²⁺ transporter CACNA2D3. Targeting of this transporter leads to the downregulation of Ca²⁺ signaling, thus inhibiting autophagosome formation and promoting the intracellular survival of Mtb. Mice lacking of miR-27a and mice treated with an antagomir to miR-27a are more resistant to Mtb infection. Our findings reveal a strategy for Mtb to increase intracellular survival by manipulating the Ca²⁺-associated autophagy, and may also support the development of host-directed anti-TB therapeutic approaches.

How Mycobacterium tuberculosis (Mtb) escapes autophagy-mediated clearance is poorly understood. Here, Liu et al. show that Mtb-induced MicroRNA-27a targets the ER-associated calcium transporter CACNA2D3, leading to suppression of antimicrobial autophagy and to enhanced intracellular survival of Mtb.

The therapeutic potential of small nucleic acids such as small interfering RNA (siRNA) to treat lung diseases has been successfully demonstrated in many in vivo studies. A major barrier to their clinical application is the lack of a safe and efficient inhaled formulation. In this study, spray freeze drying was employed to prepare dry powder of small nucleic acids. Mannitol and herring sperm DNA were used as bulking agent and model of small nucleic acid therapeutics, respectively. Formulations containing different solute concentration and DNA concentration were produced. The scanning electron microscope (SEM) images showed that the porosity of the particles increased as the solute concentration decreased. Powders prepared with solute concentration of 5% w/v were found to maintain a balance between porosity and robustness. Increasing concentration of DNA improved the aerosol performance of the formulation. The dry powder formulation containing 2% w/w DNA had a median diameter of 12.5 µm, and the aerosol performance study using next generation impactor (NGI) showed an emitted fraction (EF) and fine particle fraction (FPF) of 91% and 28% respectively. This formulation (5% w/v solute concentration and 2% w/w nucleic acid) was adopted subsequently to produce siRNA powder. The gel retardation and liquid chromatography assays showed that the siRNA remained intact after spray freeze drying even in the absence of delivery vector. The siRNA powder formulation exhibited a high EF of 92.4% and a modest FPF of around 20%. Further exploration of this technology to optimise inhaled siRNA powder formulation is warranted.

• Inhalation
• Pulmonary delivery
• Small interfering RNA
• Spray freeze drying

• Dendriplexes
• Dry powder inhalers (DPIs)
• Inhalation therapy
• PAMAM dendrimers
• Pressurized metered dose inhalers (pMDIs)
• Short interfering RNA (siRNA)
• Triphenylphosphonium (TPP) ion

• Biodegradable nanoparticles
• chitosan
• poly(glycerol methacrylate)
• polyethylenimine
• siRNA

• MicroRNA
• autophagy
• innate immunity
• macrophages
• mycobacteria
• tuberculosis

RNA interference (RNAi) is a potent and specific post-transcriptional gene silencing process. Since its discovery, tremendous efforts have been made to translate RNAi technology into therapeutic applications for the treatment of different human diseases including respiratory diseases, by manipulating the expression of disease-associated gene(s). Similar to other nucleic acid-based therapeutics, the major hurdle of RNAi therapy is delivery. Pulmonary delivery is a promising approach of delivering RNAi therapeutics directly to the airways for treating local conditions and minimizing systemic side effects. It is a non-invasive route of administration that is generally well accepted by patients. However, pulmonary drug delivery is a challenge as the lungs pose a series of anatomical, physiological and immunological barriers to drug delivery. Understanding these barriers is essential for the development an effective RNA delivery system. In this review, the different barriers to pulmonary drug delivery are introduced. The potential of RNAi molecules as new class of therapeutics, and the latest preclinical and clinical studies of using RNAi therapeutics in different respiratory conditions are discussed in details. We hope this review can provide some useful insights for moving inhaled RNAi therapeutics from bench to bedside.

• RNA interference
• inhalation
• microRNA (miRNA)
• pulmonary delivery
• respiratory diseases
• short hairpin RNA (shRNA)
• short interfering RNA (siRNA)