Autoimmune Features of Post-COVID-19 Vaccination Syndrome and Their Impacts on the Renin–Angiotensin System

One of the most critical aspects of post-acute COVID-19 syndrome (PACS) and post-acute COVID-19 vaccination syndrome (PACVS) is the presence of autoantibodies. These autoantibodies are directed against various receptors in the autonomic and cardiovascular systems, including those targeting proteins of the renin–angiotensin system (RAS). The RAS plays a central role in regulating vascular homeostasis, inflammation, and endothelial function. During SARS-CoV-2 infection, the interaction of the spike (S) protein with angiotensin-converting enzyme 2 (ACE2) can alter the balance of the RAS, favoring an imbalance towards the ACE/Angiotensin II/AT1R axis, known for its pro-inflammatory, pro-thrombotic, and vasoconstrictive properties. Similar pathological mechanisms also come into play in response to vaccinations that use the S protein as an antigen. Studies conducted by other groups and us on patients with PACS and PACVS have revealed the presence of autoantibodies directed against these RAS components and the mechanisms by which these antibodies can worsen the clinical situation. In particular, anti-ACE2, presumably formed by the anti-idiotype network or molecular mimicry, is correlated with PACVS symptoms in many patients. Furthermore, the presence of anti-MAS1 antibodies can reduce the efficiency of the ACE2/Angiotensin-(1–7)/MAS1 axis, which normally acts as a counter-regulator. Considering this evidence, an analysis of RAS molecules and the autoantibodies implicated in reactions to them may be useful for evaluating a state of persistent dysregulation associated with post-vaccination symptoms such as asthenia, headache, skin edema and bruising, cardiovascular alterations, and neurovegetative manifestations. Finally, we offer insights into diagnosing these multifaceted syndromes and working hypotheses to guide research into possible therapeutic approaches.