Impact of SARS-CoV-2 infection on the recovery of peripheral blood mononuclear cells by density gradient

Maria Manunta, Giuseppe Lamorte, Francesca Ferrari, Elena Trombetta, Mario Tirone, Cristiana Bianco, Alessandra Cattaneo, Luigi Santoro, Guido Baselli, Manuela Brasca, Mahnoosh Ostadreza, Elisa Erba, Andrea Gori, Alessandra Bandera, Laura Porretti, Luca Valenti, Daniele Prati

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Received date: 15th September 2020

SARS-CoV-2 virus infection is responsible for coronavirus disease (COVID-19), which is characterised by a hyperinflammatory response that plays a major role in determining the respiratory and immune-mediated complications of this condition.
While isolating peripheral blood mononuclear cells (PBMCs) from whole blood of COVID-19 patients by density gradient centrifugation, we noticed some changes in the floating properties and in the sedimentation of the cells on density medium. Investigating this further, we found that in early phase COVID-19 patients, characterised by reduced circulating lymphocytes and monocytes, the PBMC fraction contained surprisingly high levels of neutrophils. Furthermore, the neutrophil population exhibited alterations in the cell size and in the internal complexity, consistent with the presence of low density neutrophils (LDNs) and immature forms which may explain the shift seen in the floating abilities and that may be predictive of the severity of the disease. The percentage of this subset of neutrophils found in the PBMC band was rather spread (35.4±27.2%, with a median 28.8% and IQR 11.6-56.1, Welch’s t-test early phase COVID-19 versus blood donor healthy controls P<0.0001).
Results confirm the presence of an increased number of LDNs in patients with early stage COVID-19, which correlates with disease severity and may be recovered by centrifugation on a density gradient together with PBMCs.

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This is an abstract of a preprint hosted on a preprint server, which is currently undergoing peer review at Scientific Reports. The findings have yet to be thoroughly evaluated, nor has a decision on ultimate publication been made. Therefore, the results reported should not be considered conclusive, and these findings should not be used to inform clinical practice, or public health policy, or be promoted as verified information.

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