Pulmonary mesenchymal stem cells are engaged in distinct steps of host response to respiratory syncytial virus infection

CD34+CD45+ cells promote alveolar macrophage efferocytosis to alleviate phosgene-induced acute lung injury in rats

Phosgene is still widely used in industrial production nowadays. However, as a toxic gas, accidental exposure to phosgene can lead to acute lung injury (ALI). Our team previously identified a cell subpopulation as CD34+CD45+ cells in the bronchoalveolar lavage fluid (BALF) of rats. CD34+CD45+ cells were demonstrated to possess stem cell properties and alleviate pulmonary inflammation during phosgene-induced acute lung injury (P-ALI). However, how CD34+CD45+ cells contribute to the anti-inflammatory process remains unexplored. Rats with P-ALI were intratracheally administered with CD34+CD45+ cells, and it was found that both the infiltration of macrophages and apoptotic cells were reduced in the lung tissues. The macrophages were polarized to an anti-inflammatory CD45+CD3-CD163+MHC-IIlo phenotype and restored efferocytosis efficiency, with a decreased level of inflammatory cytokines in the BALF. Moreover, it was observed that CD34+CD45+ cells promoted macrophage efferocytosis ex vivo and in vitro. Exosomes derived from CD34+CD45+ cells were further demonstrated to mediate the enhancement of macrophage efferocytosis. The small RNA sequencing analysis suggested that exosomal rno-miR-149-5p contributed to the effect. The transfection of rno-miR-149-5p mimic induced the enhancement of efferocytosis in macrophages as the exosomes did, while rno-miR-149-5p inhibitor attenuated the effect by exosomes. Our findings provide convincing evidence that CD34+CD45+ cells can alleviate ALI by enhancing macrophage efferocytosis, offering valuable insights into their therapeutic potential in managing chemical-induced acute lung injuries.

Aging shapes infection profiles of influenza A virus and SARS-CoV-2 in human precision-cut lung slices

BACKGROUND

The coronavirus disease 2019 (COVID-19) outbreak revealed the susceptibility of elderly patients to respiratory virus infections, showing cell senescence or subclinical persistent inflammatory profiles and favoring the development of severe pneumonia.

METHODS

In our study, we evaluated the potential influence of lung aging on the efficiency of replication of influenza A virus (IAV) and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), as well as determining the pro-inflammatory and antiviral responses of the distal lung tissue.

RESULTS

Using precision-cut lung slices (PCLS) from donors of different ages, we found that pandemic H1N1 and avian H5N1 IAV replicated in the lung parenchyma with high efficacy. In contrast to these IAV strains, SARS-CoV-2 Early isolate and Delta variant of concern (VOC) replicated less efficiently in PCLS. Interestingly, both viruses showed reduced replication in PCLS from older compared to younger donors, suggesting that aged lung tissue represents a suboptimal environment for viral replication. Regardless of the age-dependent viral loads, PCLS responded to H5N1 IAV infection by an induction of IL-6 and IP10/CXCL10, both at the mRNA and protein levels, and to H1N1 IAV infection by induction of IP10/CXCL10 mRNA. Finally, while SARS-CoV-2 and H1N1 IAV infection were not causing detectable cell death, H5N1 IAV infection led to more cytotoxicity and induced significant early interferon responses.

CONCLUSIONS

In summary, our findings suggest that aged lung tissue might not favor viral dissemination, pointing to a determinant role of dysregulated immune mechanisms in the development of severe disease.

Highly Potent Host-Specific Small-Molecule Inhibitor of Paramyxovirus and Pneumovirus Replication with High Resistance Barrier

Multiple enveloped RNA viruses of the family Paramyxoviridae and Pneumoviridae, like measles virus (MeV), Nipah virus (NiV), canine distemper virus (CDV), or respiratory syncytial virus (RSV), are of high clinical relevance. Each year a huge number of lives are lost as a result of these viral infections. Worldwide, MeV infection alone is responsible for over a hundred thousand deaths each year despite available vaccine. Therefore, there is an urgent need for treatment options to counteract these viral infections. The development of antiviral drugs in general stands as a huge challenge due to the rapid emergence of viral escape mutants. Here, we disclose the discovery of a small-molecule antiviral, compound 1 (ZHAWOC9045), active against several pneumo-/paramyxoviruses, including MeV, NiV, CDV, RSV, and parainfluenza virus type 5 (PIV-5). A series of mechanistic characterizations revealed that compound 1 targets a host factor which is indispensable for viral genome replication. Drug resistance profiling against a paramyxovirus model (CDV) demonstrated no detectable adaptation despite prolonged time of investigation, thereby mitigating the rapid emergence of escape variants. Furthermore, a thorough structure-activity relationship analysis of compound 1 led to the invention of 100-times-more potent-derivatives, e.g., compound 2 (ZHAWOC21026). Collectively, we present in this study an attractive host-directed pneumoviral/paramyxoviral replication inhibitor with potential therapeutic application.