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TLR2 and TLR7 mediate distinct immunopathological and antiviral plasmacytoid dendritic cell responses to SARS-CoV-2 infection

ABSTRACT: Understanding the molecular pathways driving the acute antiviral and inflammatory response to SARS-CoV-2 infection is critical for developing treatments for severe COVID-19. Here, we find decreasing number of circulating plasmacytoid dendritic cells (pDCs) in COVID-19 patients early after symptom onset, correlating with disease severity. pDC depletion is transient and coincides with decreased expression of antiviral type I IFNα and of systemic inflammatory cytokines CXCL10 and IL-6. Using an in vitro stem cell-based human pDC model, we further demonstrate that pDCs, while not supporting SARS-CoV-2 replication, directly sense the virus and in response produce multiple antiviral (interferons: IFNα and IFNλ1) and inflammatory (IL-6, IL-8, CXCL10) cytokines that protect epithelial cells from de novo SARS-CoV-2 infection. Via targeted deletion of virus-recognition innate immune pathways, we identify TLR7-MyD88 signaling as crucial for production of antiviral interferons, whereas TLR2 is responsible for the inflammatory IL-6 response. We further show that SARS-CoV-2 engages the receptor neuropilin-1 on pDCs to selectively mitigate the antiviral interferon response, but not the IL-6 response, suggesting neuropilin-1 as potential therapeutic target for stimulation of TLR7-mediated antiviral protection.

SUBMITTER: Dr. renee, van der Sluis

PROVIDER: S-SCDT-EMBOJ-2021-109622 | biostudies-other |

REPOSITORIES: biostudies-other

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Project description:BACKGROUND:Atopy and viral respiratory tract infections synergistically promote asthma exacerbations. IgE cross-linking inhibits critical virus-induced IFN-? responses of plasmacytoid dendritic cells (pDCs), which can be deficient in patients with allergic asthma. OBJECTIVE:We sought to determine whether reducing IgE levels in vivo with omalizumab treatment increases pDC antiviral IFN-? responses in inner-city children with asthma. METHODS:PBMCs and pDCs isolated from children with exacerbation-prone asthma before and during omalizumab treatment were stimulated ex vivo with rhinovirus and influenza in the presence or absence of IgE cross-linking. IFN-? levels were measured in supernatants, and mRNA expression of IFN-? pathway genes was determined by using quantitative RT-PCR (qRT-PCR) in cell pellets. Fc?RI? protein levels and mRNA expression were measured in unstimulated cells by using flow cytometry and qRT-PCR, respectively. Changes in these outcomes and associations with clinical outcomes were analyzed, and statistical modeling was used to identify risk factors for asthma exacerbations. RESULTS:Omalizumab treatment increased rhinovirus- and influenza-induced PBMC and rhinovirus-induced pDC IFN-? responses in the presence of IgE cross-linking and reduced pDC surface Fc?RI? expression. Omalizumab-induced reductions in pDC Fc?RI? levels were significantly associated with a lower asthma exacerbation rate during the outcome period and correlated with increases in PBMC IFN-? responses. PBMC Fc?RI? mRNA expression measured on study entry significantly improved an existing model of exacerbation prediction. CONCLUSIONS:These findings indicate that omalizumab treatment augments pDC IFN-? responses and attenuates pDC Fc?RI? protein expression and provide evidence that these effects are related. These results support a potential mechanism underlying clinical observations that allergic sensitization is associated with increased susceptibility to virus-induced asthma exacerbations.

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TLR2 and TLR7 mediate distinct immunopathological and antiviral plasmacytoid dendritic cell responses to SARS-CoV-2 infection

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