Persistence of SARS CoV-2 S1 Protein in CD16+ Monocytes in Post-Acute Sequelae of COVID-19 (PASC) up to 15 Months Post-Infection

Abstract

The recent COVID-19 pandemic is a treatment challenge in the acute infection stage but the recognition of chronic COVID-19 symptoms termed post-acute sequelae SARS-CoV-2 infection (PASC) may affect up to 30% of all infected individuals. The underlying mechanism and source of this distinct immunologic condition three months or more after initial infection remains elusive. Here, we investigated the presence of SARS-CoV-2 S1 protein in 46 individuals. We analyzed T-cell, B-cell, and monocytic subsets in both severe COVID-19 patients and in patients with post-acute sequelae of COVID-19 (PASC). The levels of both intermediate (CD14+, CD16+) and non-classical monocyte (CD14Lo, CD16+) were significantly elevated in PASC patients up to 15 months post-acute infection compared to healthy controls (P=0.002 and P=0.01, respectively). A statistically significant number of non-classical monocytes contained SARS-CoV-2 S1 protein in both severe (P=0.004) and PASC patients (P=0.02) out to 15 months post-infection. Non-classical monocytes were sorted from PASC patients using flow cytometric sorting and the SARS-CoV-2 S1 protein was confirmed by mass spectrometry. Cells from 4 out of 11 severe COVID-19 patients and 1 out of 26 PASC patients contained ddPCR+ peripheral blood mononuclear cells, however, only fragmented SARS-CoV-2 RNA was found in PASC patients. No full length sequences were identified, and no sequences that could account for the observed S1 protein were identified in any patient. That non-classical monocytes may be a source of inflammation in PASC warrants further study.

HLA‐dependent variation in SARS‐CoV‐2 CD8 + T cell cross‐reactivity with human coronaviruses

“…Interestingly, CCR1 variants are linked to pulmonary macrophage infiltration in severe COVID‐19 [ 53 ] and inhibition of CCR5 in critical COVID‐19 patients has been associated with a decrease in plasma IL‐6 and SARS‐CoV‐2 RNA and an increase in CD8 + T cells [ 54 ]. Additionally, intermediate monocytes which constitutively express high levels of CCR5 have recently been suggested as playing a role in post‐acute sequelae of COVID‐19 [ 55 ] (often referred to as ‘long‐COVID’). Of further interest, we found SMPD4 and SLC1A4, which together with CCL3 and CCL3L1 are involved in the response to TNF, which is part of the cytokine storm following COVID‐19 disease.…”

A central role for amyloid fibrin microclots in long COVID/PASC: origins and therapeutic implications

“…Another is the continued release of sequestered microbially derived substances than can act as stimuli for continuing microclot formation. Here, the finding [ 202 ] that S1 spike protein can itself persist in CD16 + Monocytes in PASC for up to 15 months post-infection is highly relevant, as the amplification of trigger proteins to make microclots as part of the clotting mechanism means that miniscule (and highly substoichiometric) amounts of suitable triggers can suffice [ 26 , 47 ]. This alone is sufficient to account for the chronic nature of such diseases.…”

The Multifaceted Manifestations of Multisystem Inflammatory Syndrome during the SARS-CoV-2 Pandemic

“…In general, the factors related to the development of PASC-C and PASC-A appear to be identical. Factors leading to PASC include the following: effects from acute SARS-CoV-2 injury in one or multiple organs; persistent reservoirs of SARS-CoV-2; reactivation of neurotrophic pathogens, such as herpesviruses, due to COVID-19 causing immune dysregulation; ongoing activity of primed immune cells; autoimmunity due to molecular mimicry between pathogen and host proteins [ 73 , 74 ]; the appearance of antibodies specific to ACE2 [ 75 ]; and an elevated number of monocytes containing SARS-CoV-2 S1 protein in both severe COVID-19 and PASC patients [ 76 ]. Another feature is significant differences between innate (NK cells, LD neutrophils, and CXCR3+ monocytes) and adaptive (T helper, T follicular helper, and regulatory T cells) immune populations in convalescent individuals compared to healthy controls.…”