Abstract
It has been reported that patients diagnosed with COVID-19 become critically ill primarily around the time of activation of the adaptive immune response. However the role of antibodies in the worsening of disease is not obvious. Higher titers of anti-spike immunoglobulin IgG1 associated with low fucosylation of the antibody Fc tail have been associated to excessive inflammatory response. In contrast it has been also reported that NP-, S-, RBD- specific IgA, IgG, and IgM are not associated with SARS-CoV-2 viral load, indicating that there is no obvious correlation between antibody response and viral antigen detection. In the present work the micro-Fourier-transform infrared reflectance spectroscopy (micro-FTIR) was employed to investigate blood serum samples of healthy and COVID-19-ill (mild or oligosymptomatic) individuals (82 healthcare workers volunteers in “Instituto de Infectologia Emilio Ribas”, São Paulo, Brazil). The molecular-level-sensitive, multiplexing quantitative and qualitative FTIR data probed on 1 µL of dried biofluid was compared to signal-to-cutoff index of chemiluminescent immunoassays CLIA and ELISA (IgG antibodies against SARS-CoV-2). Our main result indicated that 1702–1785 hbox {cm}^{-1} spectral window (carbonyl C=O vibration) is a spectral marker of the degree of IgG glycosylation, allowing to probe distinctive sub-populations of COVID-19 patients, depending on their degree of severity. The specificity was 87.5 % while the detection rate of true positive was 100%. The computed area under the receiver operating curve was equivalent to CLIA, ELISA and other ATR-FTIR methods (>0.85). In summary, overall discrimination of healthy and COVID-19 individuals and severity prediction as well could be potentially implemented using micro-FTIR reflectance spectroscopy on blood serum samples. Considering the minimal and reagent-free sample preparation procedures combined to fast (few minutes) outcome of FTIR we can state that this technology is suitable for fast screening of immune response of individuals with COVID-19. It would be an important tool in prospective studies, helping investigate the physiology of the asymptomatic, oligosymptomatic, or severe individuals and measure the extension of infection dissemination in patients.
Highlights
It has been reported that patients diagnosed with COVID-19 become critically ill primarily around the time of activation of the adaptive immune response
Luo et al.[4] showed that NP, S, RBD- specific IgA, IgG, and IgM were not associated with SARS-CoV-2 viral load, suggesting that there is no obvious correlation between antibody response and viral antigen detected in nasopharyngeal swabs
The correlation between comorbidities and prevalence of COVID-19 is well reported in literature and our findings give one more piece of evidence concerning this important aspect of etiology of COVID-1930
Summary
It has been reported that patients diagnosed with COVID-19 become critically ill primarily around the time of activation of the adaptive immune response. Luo et al.[4] showed that NP -, S-, RBD- specific IgA, IgG, and IgM were not associated with SARS-CoV-2 viral load, suggesting that there is no obvious correlation between antibody response and viral antigen detected in nasopharyngeal swabs They analyzed antibody and cytokine responses in COVID-19 from asymptomatic to severe patients (123 serum samples from 63 COVID -19 patients) and evaluated the impact of various risk factors, including comorbidities, male sex, and advancing age on the host immune response COVID-19 patients. These antagonistic data highlight the relevance of investigating structural aspects of serum IgG from COVID-19 patients to establish its rule as a severity marker Vibrational spectroscopic techniques such as Fourier-transform infrared absorption (FTIR) have been successfully used to study biological samples. It is a suitable technology to study structural changes in IgG induced by COVID-19
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