Critically Ill COVID-19 Patients Exhibit Anti-SARS-CoV-2 Serological Responses

Area of Science:

• Immunology
• Virology
• Critical Care Medicine

Background:

• Coronavirus disease 2019 (COVID-19), caused by SARS-CoV-2, presents a significant global health challenge.
• Understanding the humoral immune response in critically ill patients is crucial for disease management and therapeutic development.

Purpose of the Study:

• To perform anti-SARS-CoV-2 serological profiling in critically ill patients to determine their humoral immune response.
• To assess the correlation between immunoglobulin levels (IgM, IgA, IgG, Total Ig) and COVID-19 status and mortality.

Main Methods:

• Blood samples were collected from intensive care unit (ICU) patients, categorized as COVID-19 positive (+) or negative (-).
• Anti-SARS-CoV-2 IgM, IgA, IgG, and Total Ig levels were measured.
• Classification accuracies for determining COVID-19 status based on serological responses were calculated at various ICU days.

Main Results:

• COVID-19+ patients exhibited higher body mass indexes, increased rates of bilateral pneumonia, and greater hypoxia compared to COVID-19- patients.
• COVID-19 status was accurately determined by serological responses, with classification accuracies reaching 100% by ICU days 7-10.
• Total Ig, IgM, and IgA were the most important isotypes for determining COVID-19 status, while IgG played a minor role.
• Peak serological responses varied by isotype, with Total Ig peaking around ICU day 18.
• Patients who died had earlier or similar peaks in IgA and Total Ig compared to survivors, suggesting blunted responses did not cause mortality.

Conclusions:

• Critically ill COVID-19 patients mount significant anti-SARS-CoV-2 serological responses, irrespective of mortality.
• Blunted humoral immune responses do not appear to contribute to mortality in severe COVID-19.
• Serological profiling can aid in disease surveillance, patient cohorting, and guiding antibody-based therapies like convalescent plasma.