"Introduction
Umbilical cord blood (UCB) is the blood originating from the neonate. UCB differs from that of adult peripheral blood, in which UCB contains higher numbers of monocytes and nucleated red blood cells (RBCs), and lower numbers of matured RBCs and T cells, especially CD8+T cells. Lymphocytes in UCB produce fewer absolute levels of cytokines and have higher abundance of anti-inflammatory cytokines than adult peripheral blood sources. More importantly, UCB is highly enriched with multipotent hematopoietic stem progenitor cells (HSPCs) as identified by the surface expression of CD34 molecules, which are essential for the maintenance of the bone marrow and blood systems...
Little is known about the impacts of previous SARS-CoV-2 infection, including asymptomatic infection, and/or COVID-19 vaccination on the functionality of CD34+ HSPCs. In general, HSPCs are considered as one of the first responders to infection as well as vaccination which include releasing pro-inflammatory cytokines, such as type I and II interferons (IFNs), tumor necrosis factor (TNF), interleukin (IL)-1, 6, and 8; all of which are crucially important for functional regulation of HSPCs...
Here, the impact of previous SARS-CoV-2 infection, specifically asymptomatic or undocumented infection, and COVID-19 vaccination on CD34+ HSPCs in UCB was investigated. A total of 111 UCB donor samples from Alabama were eligible and/or tested for the assays as shown in Table S1. Striking changes were observed in the CD34+ cell fraction: the total numbers of CD34+ cells drastically reduced 4-fold in the vaccinated donor group, in which this change was correlated with the induction of apoptosis in CD34+ cells, likely mediated by IFN-g-related pathways as determined by a total transcriptome assay. In addition, the hematopoietic abilities of these CD34+ cells showed skewing in two different hematopoiesis assays – an in vitro colony-formation unit (CFU) and a mouse humanization assay – as represented by high T cell/B cell ratios and higher erythrocyte and lower granulocyte-macrophage colony formations. These data indicate that both previous SARS-CoV-2 infection and/or vaccination impair CD34+ HSPCs quantitatively and qualitatively by stress-induced hematopoiesis, which is a great concern in the collection as well as the utilization of UCB as a source of CD34+ HSPCs used in/for future therapies, treatments, and research...
Discussion
... [T]hese reductions in CD34+ cell numbers and frequencies correlated with the timing of the second-vaccination in donors the numbers and frequencies inversely correlated with the period after the vaccination until delivery, indicating that factors causing these damages are maintained over the gestation period."
© 2022 The Author(s).
This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).