Strategies for the development of photonic sensors for COVID-19

Beyond the optical and analytical performance of the sensor itself, the development of an optical detection tool in response to a pressing research or diagnostic need requires consideration of a host of additional factors. This talk will provide an overview of two photonic sensor systems developed for profiling the human immune response to COVID-19 infection and/or vaccination. One, focused on the design goal of high multiplexing (many targets per sensor), was built on the Arrayed Imaging Reflectometry (AIR) platform. AIR is a free-space optics technique that relies on the creation and target molecule binding-induced disruption of an antireflective coating on the surface of a silicon chip. The second method, focused on low cost and high speed, uses a small (1 x 4 mm) ring resonator photonic chip embedded in a plastic card able to provide passive transport of human samples. This “disposable photonics” platform is able to detect and quantify anti-COVID antibodies in a human sample in a minute, making it attractive for high-throughput testing applications. © 2022 SPIE

Early and strong antibody responses to SARS-CoV-2 predict disease severity in COVID-19 patients.

BACKGROUND: Antibody response to SARS-CoV-2 is a valuable biomarker for the assessment of the spread of the virus in a population and evaluation of the vaccine candidates. Recent data suggest that antibody levels also may have a prognostic significance in COVID-19. Most of the serological studies so far rely on testing antibodies against spike (S) or nucleocapsid (N) protein, however antibodies can be directed against other structural and nonstructural proteins of the virus, whereas their frequency, biological and clinical significance is unknown. METHODS: A novel antigen array comprising 30 SARS-CoV-2 antigens or their fragments was developed and used to examine IgG, IgA, IgE and IgM responses to SARS-CoV-2 in sera from 103 patients with COVID-19 including 34 patients for whom sequential samples were available, and 20 pre-pandemic healthy controls. RESULTS: Antibody responses to various antigens are highly correlated and the frequencies and peak levels of antibodies are higher in patients with severe/moderate disease than in those with mild disease. This finding supports the idea that antibodies against SARS-CoV-2 may exacerbate the severity of the disease via antibody-dependent enhancement. Moreover, early IgG and IgA responses to full length S protein may be used as an additional biomarker for the identification of patients who are at risk of developing severe disease. Importantly, this is the first study reporting that SARS-CoV-2 elicits IgE responses and their serum levels positively correlate with the severity of the disease thus suggesting a link between high levels of antibodies and mast cell activation. CONCLUSIONS: This is the first study assessing the prevalence and dynamics IgG, IgA, IgE and IgM responses to multiple SARS-CoV-2 antigens simultaneously. Results provide important insights into the pathogenesis of COVID-19 and have implications in planning and interpreting antibody-based epidemiological studies.

Array-based analysis of SARS-CoV-2, other coronaviruses, and influenza antibodies in convalescent COVID-19 patients.

Detection of antibodies to upper respiratory pathogens is critical to surveillance, assessment of the immune status of individuals, vaccine development, and basic biology. The urgent need for antibody detection tools has proven particularly acute in the COVID-19 era. We report a multiplex label-free antigen microarray on the Arrayed Imaging Reflectometry (AIR) platform for detection of antibodies to SARS-CoV-2, SARS-CoV-1, MERS, three circulating coronavirus strains (HKU1, 229E, OC43) and three strains of influenza. We find that the array is readily able to distinguish uninfected from convalescent COVID-19 subjects, and provides quantitative information about total Ig, as well as IgG- and IgM-specific responses.