Synthesis and biological evaluation of cleistocaltone A, an inhibitor of respiratory syncytial virus (RSV).

The first chemical synthesis of the phloroglucinol meroterpenoid cleistocaltone A (1) is presented. This compound, previously isolated from Cleistocalyx operculatus was reported to show promising antiviral properties. Based on a modified biosynthesis proposal, a synthetic strategy was devised featuring an intramolecular Diels-Alder reaction and an epoxidation/elimination sequence to generate the allyl alcohol handle in the side chain. The strategy was successfully executed and synthetic cleistcaltone A was evaluated against a contemporary RSV-A strain.

Host Responses to Respiratory Syncytial Virus Infection.

Respiratory syncytial virus (RSV) infections are a constant public health problem, especially in infants and older adults. Virtually all children will have been infected with RSV by the age of two, and reinfections are common throughout life. Since antigenic variation, which is frequently observed among other respiratory viruses such as SARS-CoV-2 or influenza viruses, can only be observed for RSV to a limited extent, reinfections may result from short-term or incomplete immunity. After decades of research, two RSV vaccines were approved to prevent lower respiratory tract infections in older adults. Recently, the FDA approved a vaccine for active vaccination of pregnant women to prevent severe RSV disease in infants during their first RSV season. This review focuses on the host response to RSV infections mediated by epithelial cells as the first physical barrier, followed by responses of the innate and adaptive immune systems. We address possible RSV-mediated immunomodulatory and pathogenic mechanisms during infections and discuss the current vaccine candidates and alternative treatment options.

Toll-like receptor activation and hypoxia use distinct signaling pathways to stabilize hypoxia-inducible factor 1α (HIF1A) and result in differential HIF1A-dependent gene expression.

HIF1A is a transcription factor that plays a central role for the adaptation to tissue hypoxia and for the inflammatory response of myeloid cells, including DCs. HIF1A is stabilized by hypoxia but also by TLR ligands under normoxic conditions. The underlying signaling events leading to the accumulation of HIF1A in the presence of oxygen are still poorly understood. Here, we show that in contrast to hypoxic stabilization of HIF1A, normoxic, TLR-mediated HIF1A accumulation in DCs follows a different pathway that predominantly requires MYD88-dependent NF-κB activity. The TLR-induced HIF1A controls a subset of proinflammatory genes that are insufficiently induced following hypoxia-mediated HIF1A induction. Thus, TLR activation and hypoxia stabilize HIF1A via distinct signaling pathways, resulting in differential HIF1A-dependent gene expression.