. Hyper-inflammation and complement activation have been implicated in Coronavirus disease 2019 (COVID-19) pathogenesis and outcomes; however, the pathophysiological mechanisms underlying these phenomena remain unknown. SARS-CoV2 infects gut cells, and viral infections in the gut causes changes in gut structure and breakdown of the epithelial barrier, which can increase permeability to gut microbes and microbial products. This microbial translocation has a direct impact on systemic inflammation, but it may also indirectly impact it by modulating circulating glycomes. Recently, it has been shown that viral- infections-mediated alterations to glycans, in particular loss of sialic acid and loss of galactose, on circulating glycoproteins and antibodies (IgG and IgA) mediate and drive inflammation and complement activation. Gut microbial translocation is a potential source of glycomic alterations during viral infections. Translocation of glycan-degrading enzymes (such as sialidase and galactosidases) released by several members of the gut microbiome can efficiently alter circulating glycomes, leading to the exacerbation of inflammation. In our preliminary data, we found that levels of several gut bacteria genera correlate with plasma IgG glycosylation during viral infection. We also found that these pro-inflammatory glycans on IgG correlate with both markers of microbial translocation, as well as with markers of systemic inflammation. These data suggest a link between microbial dysbiosis, microbial translocation, circulating glycomes, and systemic inflammation during viral infections. However, the role of circulating glycomes in regulating inflammation during COVID-19 has never been investigated. To fill this knowledge gap, we propose to test the hypothesis that SARS-CoV2 impairs intestinal barrier integrity leading to translocation of microbial products that alter circulating glycomes, which impact COVID-19 pathogenesis and outcomes.
In Aim 1, we will test the hypothesis that severe COVID-19 is associated with disrupted intestinal barrier integrity and dysregulated circulating glycomes. 1.a) We will compare plasma markers of mucosal structural integrity, bacterial translocation, and microbial metabolites of 120 COVID- 19 patients (with varying disease outcomes); and 120 controls (matched for age, gender, and ethnicity). 1.b) We will compare the glycomic profiles of total plasma, plasma IgG, and plasma IgA of the 120 COVID-19 patients and controls. 1.c) We will test if levels of plasma markers of mucosal structural integrity and bacterial translocation associate with the glycosylation of plasma, plasma IgG, and plasma IgA.
In Aim 2, we will test the hypothesis that circulating hyposialylated and agalactosylated glycomic signatures are linked to higher inflammation, higher immune activation, and worse clinical outcomes during COVID-19. This supplement can advance our knowledge of the microbial and glycomic underpinnings of COVID-19, which can serve as 1) novel biomarkers for disease risk stratification, disease course, and therapeutic response (to be used immediately upon validation); and 2) a foundation to develop innovative therapeutics in the future.
SARS-CoV2 infects gut cells, and viral infections of the gut can cause translocation of bacteria and bacterial products from the gut to the blood; this translocation leads to systemic inflammation that could trigger a cytokine storm, leading to severe COVID19. This study seeks to understand the role of intestinal barrier integrity, microbial translocation, and inflammation in COVID-19 pathogenesis and disease outcomes, with the hypothesis that microbial translocation leads to a loss of certain anti-inflammatory circulating carbohydrate molecules (glycans) in the body, promoting the development of inflammation and worse disease outcomes. The idea is that, if these glycan structures are altered, then by understanding exactly how they are altered, we will lay the groundwork for developing both novel biomarkers for disease risk stratification and disease course as well as novel therapeutic interventions to reduce SARS-CoV2-induced cytokine storm to prevent severe COVID19 and its associated death.
