3058 – SARS-COV-2 BINDING IN HEMATOPOIETIC STEM AND PROGENITOR CELLS UNDER LOW OXYGEN CONDITIONS

The SARS-CoV-2 pandemic highlighted a need for in-depth understanding of interaction/identification of receptors and mechanisms/functional consequences of viral binding/entry. SARS-CoV-2 spike protein (SBP) facilitates viral entry via ACE2 and/or NRP1 binding, with DPP4 as a potential co-receptor. These binding partners are expressed on various cell types including hematopoietic stem and progenitor (HSC/HSPC) cells [1-3]. HSC/HSPCs generate blood cells and reside in the low oxygen (lowO2, 1-4%) bone marrow niches that provide critical signals for maintenance, self-renewal, and differentiation. To investigate aspects of SARS-CoV-2 interactions with HSC/HSPC such as endogenous receptor expression, SPB binding and subsequent functional alterations in native low O2, we performed transcriptional and phenotypic/functional analysis. In lowO2, we identified increased surface expression of ACE2, DPP4 and NRP1, and enhanced binding of SBP to HSC/HSPC populations which amplified proliferation of SBP bound in lowO2. ACE2 and DPP4 surface expression were ∼2-fold higher in HSPCs (p=0.017, p=0.001) and HSCs (p=0.010, p=0.03), and NRP1 was ∼1.5-fold (p=0.002) higher in HSPCs in lowO2 compared to air. Interestingly, in lowO2, overall SBP binding was enhanced in HSPC (2.2-fold, p<.001) and HSC (2.6-fold, p=.018). Although not all cells expressing ACE2/DPP4/NRP1 bind SBP (∼50%), all cells exhibiting SBP binding in HSC/HSPC populations are triple positive for ACE2, NRP1, and DPP4. Additionally, we observed greater than a 2-fold increase in proliferation of SBP bound vs unbound cells in replating assays in lowO2 (p<.001). These data impart compelling evidence that SBP binding/functional outcomes are unique in low O2, providing a foundation that may have potential clinical implications for COVID19 treatment and expanding our baseline understanding of SARS-CoV-2 viral binding implications.