Eicosanoid signalling blockade protects middle-aged mice from severe COVID-19.

Coronavirus disease 2019 (COVID-19) is especially severe in aged populations 1 . Vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are highly effective, but vaccine efficacy is partly compromised by the emergence of SARS-CoV-2 variants with enhanced transmissibility 2 . The emergence of these variants emphasizes the need for further development of anti-SARS-CoV-2 therapies, especially for aged populations. Here we describe the isolation of highly virulent mouse-adapted viruses and use them to test a new therapeutic drug in infected aged animals. Many of the alterations observed in SARS-CoV-2 during mouse adaptation (positions 417, 484, 493, 498 and 501 of the spike protein) also arise in humans in variants of concern 2 . Their appearance during mouse adaptation indicates that immune pressure is not required for selection. For murine SARS, for which severity is also age dependent, elevated levels of an eicosanoid (prostaglandin D 2 (PGD 2 )) and a phospholipase (phospholipase A2 group 2D (PLA 2 G2D)) contributed to poor outcomes in aged mice 3,4 . mRNA expression of PLA 2 G2D and prostaglandin D 2 receptor (PTGDR), and production of PGD 2 also increase with ageing and after SARS-CoV-2 infection in dendritic cells derived from human peripheral blood mononuclear cells. Using our mouse-adapted SARS-CoV-2, we show that middle-aged mice lacking expression of PTGDR or PLA 2 G2D are protected from severe disease. Furthermore, treatment with a PTGDR antagonist, asapiprant, protected aged mice from lethal infection. PTGDR antagonism is one of the first interventions in SARS-CoV-2-infected animals that specifically protects aged animals, suggesting that the PLA 2 G2D-PGD 2 /PTGDR pathway is a useful target for therapeutic interventions.