The immunopathological pathways involved in the development of post-COVID-19 syndrome (PCS) are not entirely known. We performed a longitudinal analysis with COVID-19 patients who developed PCS to assess the immunological status associated with this disease. Therefore, several immunological markers were determined in the sera and after stimulation of whole blood cells with SARS-CoV-2 peptides. The participants will be examined a total of 3 times within one year. The results of the first examination time point are presented.
Whole blood and serum were collected from 72 PCS patients (81% female, median age 53 years), of whom 44% were hospitalized for COVID-19. The infection was detected 33 to 750 days before blood collection. All PCS patients were vaccinated against COVID-19. Patients reported two to 35 different symptoms using a questionnaire with fatigue syndrome being the most common.
Serum concentration of 13 neuroinflammatory mediators were assessed using multiplex assays in both the PCS patients and in 35 matched sera obtained from subjects before SARS-CoV-2 pandemic (controls). Serum Amyloid A (SAA) was determined only in the PCS sera (range 1.88 to 773.3 µg/ml). The initial results show that the BDNF concentrations were significantly higher and IL6, sRAGE and sTREM1 concentrations lower in the PCS group compared to the controls.
Flow cytometric analysis demonstrated increased CD25 expression on CD4+T cells after stimulation of whole blood with SARS-Cov2 peptides. Classification of the PCS group based on the median SAA concentration (29.3 µg/ml) into a low SAA (< median) and a high SAA group (>median) revealed that the high SAA group had a higher proportion of CD4+ effector memory cells (CD3+CD4+ CD45RO+CD197-).
Further relations between the immunological parameters and the health data of the PCS are being investigated and will be completed by results obtained six and twelve months after entry into this longitudinal study.