Persistence of High Levels of Serum Complement C5a in Severe COVID-19 Cases After Hospital Discharge

Evidence supports a role of complement anaphylatoxin C5a in the pathophysiology of COVID-19. However, information about the evolution and impact of C5a levels after hospital discharge is lacking. We analyzed the association between circulating C5a levels and the clinical evolution of hospitalized patients infected with SARS-CoV-2. Serum C5a levels were determined in 32 hospitalized and 17 non-hospitalized patients from Clinica Universidad de Navarra. One hundred and eighty eight serial samples were collected during the hospitalization stay and up to three months during the follow-up. Median C5a levels were 27.71 ng/ml (25th to 75th percentile: 19.35-34.96) for samples collected during hospitalization, versus 16.76 ng/ml (12.90-25.08) for samples collected during the follow-up (p<0.001). There was a negative correlation between serum C5a levels and the number of days from symptom onset (p<0.001). C5a levels also correlated with a previously validated clinical risk score (p<0.001), and was associated with the severity of the disease (p<0.001). An overall reduction of C5a levels was observed after hospital discharge. However, elevated C5a levels persisted in those patients with high COVID-19 severity (i.e. those with a longest stay in the hospital), even after months from hospital discharge (p=0.020). Moreover, high C5a levels appeared to be associated with the presence of long-term respiratory symptoms (p=0.004). In conclusion, serum C5a levels remain high in severe cases of COVID-19, and are associated with the presence of respiratory symptoms after hospital discharge. These results may suggest a role for C5a in the long-term effects of COVID-19 infection.

The Role of Ferritin in Assessing COVID-19 Severity

Ferritin is one of the biomarkers requiring special attention; its blood level increases significantly especially in the severe course of COVID-19. Information on the effect of hyperferritinemia on the disease outcome is very contradictory as are the ideas about the causes of its development.The objective: to study the effect of hyperferritinemia on the disease outcome and analyse the possible causes of its development in severe COVID-19.Subjects and Methods. Data on 479 patients with severe course of coronavirus infection treated in intensive care units (ICU) were retrospectively analyzed. Of them, the proportion of patients with a favorable outcome (Group 1) was 51.0% (n = 241), and with an unfavorable outcome (Group 2) - 49.0% (n = 235). The following parameters were assessed: the levels of ferritin, C-reactive protein, fibrinogen, IL-6, IL-10, IL-18, procalcitonin, complement C5a, total, direct and indirect bilirubin, ALT, AST, and the blood level of lactate dehydrogenase (LDH). The changes of erythrocyte count and hemoglobin blood level were also monitored. In order to form a clear view of iron metabolism, free iron, transferrin, and myoglobin levels were assessed in several patients with high ferritin values (more than 1,500 pg/L).Results. In the unfavorable outcome, ferritin levels increase very significantly, reaching maximum by day 6 of patients' stay in ICU. The difference in the level of ferritin between the groups of survivors and deceased during this period is clear and significant (p = 0.0013). The association of ferritin values with the outcome is detected as early as day 1, but by day 4 it becomes highly significant (the cut-off point is 1,080 pg/l). No data have been obtained that would indicate the association of hyperferritinemia with impaired iron metabolism, the development of hepatic dysfunction, or cellular destruction. In contrast to survivors, those who died on day 6 had elevated IL-6 while C5a level remained unchanged. Conclusions. The rapid increase in ferritin blood levels to 1,000 pg/L or higher is an unfavorable prognostic sign indicating a high probability of a lethal outcome. When assessing genesis of hyperferritinemia in COVID-19, the crucial significance should be attributed to the cytokine storm rather than disorders of iron metabolism or hemotoxic effects of the virus. The persistent increase of ferritin level in blood during 4-6 days of stay in ICU should be considered as a reason to intensify anticytokine therapy.