Immunopathogenesis of SARS-CoV-2 infection

National Institute Of Allergy And Infectious Diseases

Investigators

Linked publications, trials & patents

Abstract

The aim of this project is to test the hypothesis that specific chemokines and chemokine receptors drive either immunopathology or immune control of SARS-CoV-2 infection in a mouse model. The motivation for this aim is that chemokines regulate leukocyte trafficking and covid-19 disease pathogenesis involves severe immunopathology in the lung dependent on leukocyte influx. We are using huACE2 transgenic mice on a C57BL/6 background infected with the Wuhan strain of the virus as well as non-huACE2 mice infected with the MA-10 mouse adapted strain of the virus. Our goal is to test a WT LD50 dose first, screening for receptor knockouts that increase survival, since any positive results will have translational potential. Receptors that screen negative will be rescreened at an LDzero looking for protective chemokine receptors in the model. Both females and males will be tested and are expected to have differences in clinical progression of coronaviral disease and histopathology, based on other infectious disease models in mice, and differences between the sexes observed in humans infected with SARS-CoV and SARS-CoV-2. In all subsequent experiments, clinical disease progression will be assessed by virus recovery from throat swabs, blood and stool; serum antibody titers, hemograms, blood chemistries and serum cytokines before and at multiple intervals after infection; as well as physical appearance, weight loss, and progression to moribundity and survival for a month after infection. Animals will be euthanized by CO2 and cervical dislocation at the latest one-month post-infection. In our experience, to observe significant differences in survival we will need 20 mice/cohort in each experiment and repeat the experiment 3 times due to the variance in survival between experiments. These numbers should be sufficient to observe significant differences in the other clinical data as well. Fewer non-infected mice will be needed since there is expected to be less variance among these controls. In this reporting period, the results of our ko screen has revealed harmful effects of Cxcl10 deficiency. In FY25, we extended our analysis of chemokine regulation of mouse-adapted SARS-CoV-2 pathogenesis. In FY23 we had reported in BioRxiv that atypical chemokine receptor 1 (Ackr1, also known as Duffy antigen receptor for chemokines/DARC) was the most highly upregulated chemokine receptor in infected lung, where it localized to endothelial cells of veins and arterioles, and facilitated mortality in the model. We have now completed screening all chemokine receptors encoded by genes located in the GWAS hospot for severe COVID-19 at human 3p21, as well as several other chemokine receptors and chemokines. In FY25, we reported that Cxcl10 regulates lymphocyte infiltration in lung of mice infected with the mouse adapted strain of SARS-CoV-2 and confers protection against mortality. Infected male, but not female, Cxcl10-/- mice displayed increased mortality compared to wild type controls. Histopathological damage, inflammatory gene induction, and virus load in the lungs of male mice were not broadly influenced by Cxcl10 deficiency. However, accumulation of B and T lymphocytes in the lung parenchyma of infected mice was reduced in the absence of Cxcl10. Contrary to circulating levels of CXCL10 being strongly positively associated with poor outcome in COVID-19 patients, our preclinical mechanistic results do not support targeting CXCL10 therapeutically in severe COVID-19 in mice.