Quantitative IgG response to SARS-CoV-2 membrane protein in infected individuals strongly correlates with lung injury

Abstract

The clinical manifestations of SARS-CoV-2 infection may range from asymptomatic or minor conditions to severe and life-threatening outcomes. The respiratory system is a principal target of the virus and in the majority of cases of severe disease, an acute form of pneumonia develops. Despite concerted global efforts to elucidate the pathogenic mechanisms of COVID-19, the progression of the infection leading to pulmonary damage remains poorly understood. The present study aimed to analyse the immunological profile of subjects with a previous SARS-CoV-2 infection and predisposition to lung injury. The results showed a strong correlation between IgG anti-membrane antibodies and lung injury.

Keywords: COVID-19; Lung injury; SARS-CoV-2 membrane protein.

Fig. 1

Graphical representation of the three logit functions. The panels illustrate the functions resulting from the estimation of the likelihood of lung injury (ordinate) plotted against the optical density (OD) resulting from the ELISA. As shown in panel A, only the membrane protein resembles a similar “S” shape and achieves the maximum probability (p = 1), while the other two proteins (spike, panel B; nucleocapsid, panel C) display a linear-like behavior and do not reach the maximum probability.

Fig. 2

Assessment of the optimal ELISA cutoff in lung injury detection. The figure depicts the graphical representation of the logit function obtained for the M, S, and N proteins, with samples labeled according to the presence or absence of lung injury (blue = absence; yellow = presence). The OD value (cutoff) for the ELISA to differentiate individuals at high risk of lung injury (OD = 1.5), as determined by Youden’s index, is shown.

Fig. 3

Relationship between disease likelihood and oxygen therapy. The figure shows the logit function obtained for M protein, with samples labelled according to the degree of lung injury as revealed by image analysis. The grading system employed was as follows: G0 (red) = absence of injury; G1 (blue) = low-grade injury; G2 (green) = medium-grade injury; G3 (violet) = high-grade injury. The asterisk indicates subjects who required oxygen therapy.