Sars-CoV2- infection as a trigger of humoral response against apolipoprotein A-1

Background

Unravelling autoimmune targets triggered by SARS-CoV-2 infection may provide crucial insights in the physiopathology of the disease and foster the development of potential therapeutic candidate targets and prognostic tools. SARS-CoV-2 autoimmune-mediated inflammation have been reported, but the existence of autoantibodies against apolipoprotein A-1 (anti-apoA-1 IgG) in COVID-19 remains unexplored. Anti-apoA-1 IgGs have emerged as an independent biomarker for cardiovascular disease and mortality in humans with proinflammatory and proatherogenic functions in vivo and in vitro.

Purpose

We want to determine i) the degree of homology between SARS-CoV-2, apoA-1, and Toll-like receptor-2 (TLR2) epitopes, ii) the association between anti-SARSCoV2 and anti-apoA-1 IgGs, and iii) their relationship to prognosis.

Methods

We performed bioinformatics modelling coupled with mimetic peptides engineering, as well as functional and competition assays with antibodies to identify molecular mimicry between SARS-CoV-2, apoA-1 and TLR2 epitopes. Anti-Spike domain 1 (SD1) IgGs, anti-apoA-1 IgGs and against mimic peptides, as well as cytokines were assessed by immunoassays on a case-control (n=101), an intensive care unit (ICU; n=126) with a 28-days follow-up for overall mortality, and a general population cohort (n=663) with available samples in the pre and post-pandemic period.

Results

Linear sequence homologies and antibodies cross-reactivity between apoA-1, TLR2, and Spike epitopes were identified. Overall, anti-apoA-1 IgG levels were higher in COVID-19 patients or anti-SARS-CoV-2 seropositive individuals than in healthy donors or anti-SARS-CoV-2 seronegative individuals (p<0.0001). Significant and similar associations were noted between anti-apoA-1, anti-SARS-CoV-2 IgG, cytokines, and lipid profile. In ICU patients, anti-SARS-CoV-2 and anti-apoA-1 seroconversion rates displayed similar 7-days kinetics, reaching 82% for anti-apoA-1 seropositivity. C-statistics (CS) indicated that baseline anti-Spike/TLR2 mimic-peptide IgGs displayed a significant prognostic accuracy for overall mortality at 28 days (CS: 0.64; p=0.02). In the general population, SARS-CoV-2 exposure increased baseline anti-apoA-1 IgG levels.

Conclusions

COVID-19 induces a marked humoral response against the major protein of high-density lipoproteins. As a correlate of poorer prognosis in other clinical settings, such autoimmunity signatures may relate to long-term COVID-19 prognosis assessment and warrant further scrutiny in the current COVID-19 pandemic.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): This study was funded by the Swiss Federal Office of Public Health, Swiss School of Public Health (Corona Immunitas research program), the Fondation de Bienfaisance du Groupe Pictet, the Fondation Ancrage, the Fondation Privée des HUG, and the Center for Emerging Viral Diseases. The De Reuter (grant Nr 657) and the Schmidheiny Foundation.

Multi-Stage Group Testing Improves Efficiency of Large-Scale COVID-19 Screening

Background

SARS-CoV-2 test kits are in critical shortage in many countries. This limits large-scale population testing and hinders the effort to identify and isolate infected individuals.

Objective

Herein, we developed and evaluated multi-stage group testing schemes that test samples in groups of various pool sizes in multiple stages. Through this approach, groups of negative samples can be eliminated with a single test, avoiding the need for individual testing and achieving considerable savings of resources.

Study design

We designed and parameterized various multi-stage testing schemes and compared their efficiency at different prevalence rates using computer simulations.

Results

We found that three-stage testing schemes with pool sizes of maximum 16 samples can test up to three and seven times as many individuals with the same number of test kits for prevalence rates of around 5% and 1%, respectively. We propose an adaptive approach, where the optimal testing scheme is selected based on the expected prevalence rate.

Conclusion

These group testing schemes could lead to a major reduction in the number of testing kits required and help improve large-scale population testing in general and in the context of the current COVID-19 pandemic.