Autoimmunity May Spark Thrombosis in Patients With Polycythemia Vera, Study Says

A new analysis of anti-endothelial cell antibodies (AECAs) in patients with polycythemia vera (PV) suggests that autoimmunity may be one mechanism by which thrombosis develops.

The study was published in Diagnostics.

The authors wrote that patients with PV are at higher risk of multiple types of thrombosis, including stroke, transient ischemic attack, and myocardial infarction, adding that thrombosis can occur at diagnosis or after; in some cases, it can even occur before diagnosis.

Several therapies have been proposed to reduce the risk of thrombosis, including hydroxyurea, low-dose aspirin, and vitamin K antagonists. Yet, the authors said the existing prevention methods are not universally effective and there is a significant unmet need to reliably prevent thrombosis.

The authors wrote that patients with PV not only experience thrombosis, but also report inflammation and autoimmunity. That is notable, because recent evidence suggests patients with PV and autoimmune and inflammatory disorders have a higher risk of thrombosis.

“Inflammation is caused by the activation of the JAK-STAT3 cytokine signal pathway, responsible for an increased production of inflammatory cytokines,” they noted. “Autoimmunity is caused by the activation of the JAK-STAT3 signaling pathway, responsible for a reduction in immunosuppressive Tregs and an increase in autoimmune Th17 cells.”

The authors said that in vasculitic diseases that have inflammation, autoimmunity, and thrombosis, such as Kawasaki disease and Henoch-Schönlein purpura, investigators have found AECAs and vascular thrombotic cytotoxicity. Yet, no similar analysis has been performed in patients with PV. They thus decided to measure AECAs in patients with PV and thrombosis using an enzyme-linked immunosorbent assay (ELISA) with human umbilical vein endothelial cells (HUVECs).

“To determine whether there was a pathogenic link between the presence of these autoantibodies and vascular damage, we examined AECA-containing sera from PV patients with thrombosis for binding of AECAs to cytokine-treated HUVECs and the antibody-dependent cellular cytotoxicity,” they explained.

The investigators analyzed samples from 60 patients with PV, using samples from 50 patients with blood disorders as controls.

Forty of the 60 patients with PV had thrombosis. The authors found these patients had a higher JAK2V617F allele burden, as well as higher Th17 cell counts and higher levels of interleukin-17. They also found a high AECA-immunoglobulin G ELISA ratio in patients with thrombosis; the ratio was normal in patients without thrombosis, they said. Patients with thrombosis had high endothelial leukocyte adhesion molecule-1, intracellular adhesion molecule-1, and von Willebrand factor antigen levels compared with those without thrombosis.

“AECA-positive sera from patients with thrombosis showed enhanced binding to cytokine-treated HUVEC and a positive antibody-dependent cellular cytotoxicity, suggesting that AECAs may contribute to vascular injury,” they wrote.

Taken together, the investigators said AECAs, allele burden, and thrombosis all appeared to be positively correlated. “These results suggest that autoimmunity may be an additional mechanism in PV thrombogenesis,” they concluded.

Physicians may want to measure AECAs in patients with PV, the authors added, particularly in those whose thrombosis persists following cytoreductive and antiplatelet treatment.

Reference

Cacciola R, Cacciola EG, Vecchio V, Cacciola E. Impact of anti-endothelial cell antibodies (aecas) in patients with polycythemia vera and thrombosis. Diagnostics (Basel). Published online April 25, 2022. doi:10.3390/diagnostics12051077