SARS-CoV-2 Spike Protein Expression In Vitro and Hematologic Effects in Mice Vaccinated With AZD1222 (ChAdOx1 nCoV-19)

Abstract

Severe COVID-19 can be associated with a prothrombotic state, increasing risk of morbidity and mortality. The SARS-CoV-2 spike glycoprotein is purported to directly promote platelet activation via the S1 subunit and is cleaved from host cells during infection. High plasma concentrations of S1 subunit are associated with disease progression and respiratory failure during severe COVID-19. There is limited evidence on whether COVID-19 vaccine-induced spike protein is similarly cleaved and on the immediate effects of vaccination on host immune responses or hematology parameters. We investigated vaccine-induced S1 subunit cleavage and effects on hematology parameters using AZD1222 (ChAdOx1 nCoV-19), a simian, replication-deficient adenovirus-vectored COVID-19 vaccine. We observed S1 subunit cleavage in vitro following AZD1222 transduction of HEK293x cells. S1 subunit cleavage also occurred in vivo and was detectable in sera 12 hours post intramuscular immunization (1x1010 viral particles) in CD-1 mice. Soluble S1 protein levels decreased within 3 days and were no longer detectable 7–14 days post immunization. Intravenous immunization (1x109 viral particles) produced higher soluble S1 protein levels with similar expression kinetics. Spike protein was undetectable by immunohistochemistry 14 days post intramuscular immunization. Intramuscular immunization resulted in transiently lower platelet (12 hours) and white blood cell (12–24 hours) counts relative to vehicle. Similarly, intravenous immunization resulted in lower platelet (24–72 hours) and white blood cell (12–24 hours) counts, and increased neutrophil (2 hours) counts. The responses observed with either route of immunization represent transient hematologic changes and correspond to expected innate immune responses to adenoviral infection.

Thymidine Phosphorylase Mediates SARS-CoV-2 Spike Protein Enhanced Thrombosis in K18-hACE2TGMice

“…S1 was detectable via western blot in our severe COVID-19 patient plasma samples only after immunoprecipitation. Similarly, S1 was detectable in the plasma of mice injected with the SP-containing lysate, but not full-length SP (data not shown), consistent with previous findings in mice vaccinated against full-length SP 57 . A serial dilution of recombinant S1 showed that S1 could not be detected at or below 100 ng/ml via our western blot protocol (Fig.…”

The role of lymphocyte transformation tests (LTT) in suspected severe delayed hypersensitivity reactions following COVID-19 vaccination

“…Interestingly, her repeat LTT following natural SARS-CoV-2 infection showed reactivity to both ChAdOx1 and NVX-CoV2373 COVID-19 vaccines, the agents which she has never encountered. One hypothesis is that the ChAdOx1 vaccine produced spike protein in vitro as other groups have demonstrated 8 and induced a T-cell-mediated response to the spike protein generated in vitro rather than an allergic response. Similarly, the positive reaction NVX-CoV2373 was suspected to be a T-cell response to the recombinant spike protein in the vaccine after vaccination and previous infection.…”

Vaccine-Induced Immune Thrombotic Thrombocytopenia Two Years Later: Should It Still Be on the Scientific Agenda?

“…Here too however it should be considered that the expression of ACE2 on platelets is still controversial, and ACE2-independent binding of SARS-CoV-2 to platelets has been proposed (55). Moreover, against this hypothesis are the findings that sSP was detected in vaccinated healthy subjects both after ChAdOx1 nCoV-19 and mRNA-1273 vaccines (54,56), and in sera of CD-1 mice injected intramuscularly with ChAdOx1 nCoV-19 without being associated with any catastrophic effects (57). Finally, several VITT patients subsequently developed COVID-19 (58).…”

“…55 Moreover, against this hypothesis are the findings that sSP was detected in vaccinated healthy subjects both after ChAdOx1 nCoV-19 and mRNA-1273 vaccines, 54 56 and in sera of CD-1 mice injected intramuscularly with ChAdOx1 nCoV-19 without being associated with any catastrophic effects. 57 Finally, several VITT patients subsequently developed COVID-19 58 and given that in COVID-19 patients circulating sSP protein is found, 59 the lack of VITT recurrence as an anamnestic response in these patients does not support the hypothetical role of vaccine-induced circulating spike for VITT.…”