Altered leukocyte pattern and inflammatory markers in unvaccinated long covid patients: a cross-sectional study

Abstract Long Covid results from the damage caused by SARS-CoV-2, involving the release of cytokines and the continuous activation of immune cells. This cross-sectional study investigates leukocyte and cytokine profiles in Long Covid patients in the Amazon, a region where such studies are limited. Blood samples were analysed for differential leukocyte counts and cytokine levels. We suggest elevated lymphocyte counts in hospitalised patients and those with severe COVID-19. Higher eosinophil counts were observed in patients with up to three months of Long Covid, and increased monocyte counts in those with up to six months. IL-2 levels were higher in patients with fewer symptoms and Long Covid duration of more than three months, whereas IL-10 may remain elevated for up to 12 months. We suggest positive correlations between neutrophils, monocytes, eosinophils, and lymphocytes with different cytokines (IFN-γ, IL-6, IL-4, IL-17a, IL-2). Women were associated with lower hospitalisation rates and longer durations of Long Covid; increased lymphocyte counts were linked to hospitalisation due to COVID-19, while higher monocyte counts were associated with Long Covid durations of up to six months. We suggest that Long Covid patients may exhibit alterations in inflammatory markers, indicating a persistently pro-inflammatory microenvironment that tends to diminish after 12 months of Long Covid.