Activation of Coagulation and Proinflammatory Pathways in Thrombosis with Thrombocytopenia Syndrome and Following COVID-19 Vaccination

Thrombosis with thrombocytopenia syndrome (TTS) is an extremely rare but potentially serious adverse event following immunization with the adenovirus vector-based COVID-19 vaccines Ad26.COV2.S (Janssen / Johnson & Johnson) or ChAdOx1 (AstraZeneca). However, no cases of TTS have been reported in over 1.5 million individuals who received a second immunization with Ad26.COV2.S in the United States, suggesting that anti-vector immunity may reduce TTS risk. Here we show robust stimulation of platelet activation and coagulation pathways and innate immune pathways in patients with TTS but only transient activation of these pathways following vaccination. We evaluated proteomic profiles in 2 patients with TTS and transcriptomic and proteomic profiles in 20 people following an initial dose and a booster dose of Ad26.COV2.S and in 14 people who received the mRNA vaccines BNT162b2 or mRNA-1273. Initial Ad26.COV2.S vaccination induced transient activation of platelet activation and coagulation pathways and innate proinflammatory pathways that resolved by day 7. TTS patients showed enhanced and sustained upregulation of these pathways, whereas a second immunization with Ad26.COV2.S or a reduced initial dose of Ad26.COV2.S resulted in lower activation of these pathways. These data provide insight into TTS pathogenesis and suggest a potential strategy for reducing TTS risk by lowering the dose of Ad26.COV2.S. Overall design: 30 outbred Indian-origin adult male (10) and female (20) rhesus macaques (Macaca mulatta) were randomly allocated to groups21. Animals were 5-8 kg. All animals were housed at Bioqual, Inc. (Rockville, MD). Animals received a single immunization of 1x1011, 5x1010, 1.125x1010, or 2x109 viral particles (vp) Ad26.COV2.S (Janssen; n = 5/group) or sham (n = 10) by the intramuscular route without adjuvant at week 0. Animal studies were conducted in compliance with all relevant local, state, and federal regulations and were approved by the Bioqual Institutional Animal Care and Use Committee (IACUC). Blood, PBMC, and serum samples were collected at baseline (D1) and on days 1 (D2), 7 (D8), and 14 (D14) following vaccination.