IRE1α-XBP1 Activation Elicited by Viral Singled Stranded RNA via TLR8 May Modulate Lung Cytokine Induction in SARS-CoV-2 Pneumonia

Initial symptoms of COVID-19 infection depend on viral replication, while hyperinflammation is a hallmark of critical illness and may drive severe pneumonia and death. Among the mechanisms potentially involved in the hyperinflammatory state, we focused on the unfolded protein response, because the IRE1α-XBP1 branch can be activated as result of the endoplasmic reticulum stress produced by the overwhelming synthesis of viral components and synergizes with Toll-like receptor signaling to induce cytokine expression. Viral RNA may trigger the IRE1α-XBP1 branch via TLR7/8 activation and like TLR2 and TLR4 may underpin cytokine expression trough XBP1 splicing (sXBP1). The expression of IL1B, IL6, and TNF mRNA in bronchoalveolar aspirates (BAAs) were higher in COVID-19 patients under mechanical ventilation and intubation who showed sXBP1. The scrutiny of monocytic/macrophagic markers during active infection showed a reduction of those involved in antigen presentation and survival, as well as the IFN stimulated gene MX1. These changes reverted after infection tests turned negative. In contrast, the expression of the mRNA of the serine protease TMPRSS2 involved in S protein priming showed a high expression during active infection. TLR8 mRNA showed an overwhelming expression as compared to TLR7 mRNA, which suggests the presence of monocyte-derived dendritic cells (MDDCs). In vitro experiments in MDDCs activated with ssRNA40, a positive-sense, single-stranded RNA (+ssRNA) like SARS-CoV-2 RNA, induced sXBP1 and the expression of IL-1β, IL-6, and TNFα at mRNA and protein levels. These responses were blunted by the IRE1α ribonuclease inhibitor MKC8866. Given the analogies between the results observed in BAAs and the effects induced by +ssRNA in MDDCs, IRE1α ribonuclease inhibition might be a druggable target in severe COVID-19 disease.This study was funded by Fondo COVID-19 del Instituto de Salud Carlos III/Junta de Castilla y Leon (N.F.). European Commission-NextGenerationEU, through CSIC's Global Health Platform (PTI Salud Global) (project SGL2103016) (M.S.C.). Plan Nacional de Salud y Farmacia Grant SAF2017-83079-R and Grant PID2020-113751RB-I00 funded by MCIN/AEI/ 10.13039/501100011033 (M.S.C.). Junta de Castilla y Leon/Fondo Social Europeo Grants CSI035P17 (M.S.C.) and VA175P20 (N.F.). Proyecto SEAHORSE INFRARED: IR2020-1-UVA05 (JCyL).N

COVID-19 vaccine failure

COVID-19 affects the population unequally with a higher impact on aged and immunosuppressed people. Hence, we assessed the effect of SARS-CoV-2 vaccination in immune compromised patients (older adults and oncohematologic patients), compared with healthy counterparts. While the acquired humoral and cellular memory did not predict subsequent infection 18 months after full immunization, spectral and computational cytometry revealed several subsets within the CD8+ T-cells, B-cells, NK cells, monocytes and CD45RA+ CCR7- Tγδ cells differentially expressed in further infected and non-infected individuals not just following immunization, but also prior to that. Of note, up to 7 subsets were found within the CD45RA+ CCR7- Tγδ population with some of them being expanded and other decreased in subsequently infected individuals. Moreover, some of these subsets also predicted COVID-induced hospitalization in oncohematologic patients. Therefore, we hereby have identified several cellular subsets that, even before vaccination, strongly related to COVID-19 vulnerability as opposed to the acquisition of cellular and/or humoral memory following vaccination with SARS-CoV2 mRNA vaccines.This study has been funded through Programa Estratégico Instituto de Biología y Genética Molecular (IBGM Junta de Castilla y León. Ref. CCVC8485), Junta de Castilla y León (Proyectos COVID 07.04.467B04.74011.0) and the European Commission – NextGenerationEU (Regulation EU 2020/2094), through CSIC's Global Health Platform (PTI Salud Global; SGL21-03-026 and SGL2021-03-038)N