A recent report posted to the Research Square* preprint server, whilst under consideration at the Clinical and Molecular Allergy journal, illustrated the association of immunoglobulins (Igs) with blood characteristics in severe coronavirus disease 2019 (COVID-19) patients.
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is commonly diagnosed based on clinical manifestations, laboratory examinations, and computed tomography (CT) imaging.
Presently, the laboratory diagnosis of COVID-19 is conducted via SARS-CoV-2 ribonucleic acid (RNA) detection in nasal or throat swabs by real-time reverse transcription-polymerase chain reaction (RT-PCR) tests. Nevertheless, several factors, such as the low accuracy of quantitative RT-PCR (RT-qPCR) kits and operation protocols, affect the accuracy and sensitivity of the RT-PCR assay in COVID-19 diagnosis. Thus, a combination of non-PCR-based and PCR strategies is required for rapid and accurate detection of SARS-CoV-2.
Since SARS-CoV-2 harbors epidemiological and genetic features similar to Middle East respiratory CoV (MERS-CoV) and SARS-CoV, a serologic analysis employed for the detection of IgG/IgM antibodies developed against these CoVs might be beneficial in shedding light on COVID-19 or the duration of disease in suspected patients. The humoral immunological response to SARS-CoV-2, on the other hand, has been largely unclear.
About the study
In the present retrospective cross-sectional research, the investigators determined the IgG and IgM antibody responses to SARS-CoV-2 and clinical features in 100 COVID-19 patients with varying disease severity. The 18 to 75 years old SARS-CoV-2-infected individuals admitted to the Shahid Beheshti Hospital of Kashan University of Medical Science between June 21 and September 20, 2020, were included in this study. Patients with immune disorders or cancer were excluded from the present research.
SARS-CoV-2 diagnosis of the enrolled volunteers was based on clinical symptoms and a positive RT-PCR test. Laboratory and clinical details of the study volunteers, including IgG/IgM levels, were procured and assessed upon SARS-CoV-2-linked hospitalization and two months after the hospital admission. The IgG and IgM antibody levels were estimated using the enzyme-linked immunosorbent assay (ELISA). The clinical data of the patients were gathered from their health records.
The study volunteers were stratified into three cohorts based on the following guidelines: 1) severe cases: COVID-19 patients with either hypoxia, acute respiratory distress syndrome (ARDS), shock, respiratory failure requiring mechanical ventilation, or other organ failures that need intensive care unit (ICU) care; 2) moderate cases: SARS-CoV-2-infected people with radiological evidence of pneumonia along with respiratory symptoms, fever, and other symptoms; 3) mild cases: COVID-19 patients without imaging evidence of pneumonia.
Results and discussions
The study results showed that there were 22, 38, and 40 SARS-CoV-2-infected patients in the mild, moderate, and severe COVID-19 groups, respectively. Among the 100 COVID-19 patients, 52 were males, and 48 were females. The average age of the study participants was 50 years, and the median age of the severe and moderate groups was marginally higher than the mild cohort. As a result, there was no discernible link between patient age and SARS-CoV-2 severity. Additionally, the proportion of males was slightly higher than females in the moderate and severe cohorts relative to the mild group.
In total, 78 COVID-19 patients had radiological manifestations of pneumonia during their initial clinical assessment. The most frequent underlying comorbidity in SARS-CoV-2-infected patients was cardiovascular disease, diabetes, asthma, and hypertension. The clinical symptoms of COVID-19 patients, which substantially correlated with SARS-CoV-2 infection severity, included obesity, fever, shortness of breath, taste disorder, muscle soreness, chill, loss of consciousness, anorexia, and odor disorder.
Nonetheless, the researchers found no drastic associations between COVID-19 severity and gender, blood group, age, and underlying comorbidities such as hypertension, diabetes, organ failure, cardiovascular disease, asthma, also other symptoms like sore throat, fatigue, headache, chest pain, vomiting, nausea, visual impairment, and diarrhea.
While various laboratory markers such as lactate dehydrogenase (LDH), D-dimer, and ferritin were elevated in the majority of SARS-CoV-2-infected patients, fibrinogen level was reduced at baseline upon COVID-19-related hospitalization relative to two months post-hospital admission.
Liver injury markers like alanine transaminase (ALT), alkaline phosphatase (ALP), and aspartate transaminase (AST) were also substantially elevated at baseline in SARS-CoV-2-infected patients. Furthermore, a correlation was observed between high neutrophil (NUT), white blood count (WBU), and low lymphocyte (LYM) counts with elevated IgG levels two months following SARS-CoV-2-linked hospitalization, leading to durable immune responses. As a result, severe COVID-19 patients exhibited longer and better immunity relative to mild groups.
The study findings indicated that the anti-SARS-CoV-2 IgG antibody titers were drastically higher in severe COVID-19 patients than in the mild and moderate cohorts two months following SARS-CoV-2-related hospitalization. Additionally, the IgG levels positively correlated with elevated NUT and WBC and decreased LYM counts in severe SARS-CoV-2 patients than in moderate or mild cohorts after two months of COVID-19-linked hospitalization.
Collectively, the authors state that serological markers, especially IgG levels, were the most significant anti-SARS-CoV-2 antibody responses in COVID-19 patients. The researchers further suggested that IgG levels could assist in the diagnosis of cured or active SARS-CoV-2 infection.
The current work indicated that COVID-19 patients with severe disease probably experience long SARS-CoV-2 exposure times and robust antibody response against the viral infection. Hence, severe COVID-19 patients demonstrate durable immunity versus other SARS-CoV-2 infection severity groups.
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