ACE-2-like Enzymatic Activity in Anti-SARS-CoV-2 Spike Protein Monoclonal Antibodies

Many people are affected by post-acute sequelae of COVID-19 (PASC/long COVID, LC). LC has severely affected public health. Features of LC including blood pressure dysregulation, coagulopathies, hyperinflammation, and neuropsychiatric complaints. Mechanisms responsible for LC pathogenesis are not clear. The receptor for SARS-CoV-2 is human angiotensin converting enzyme 2 (ACE2), which binds SARS-CoV-2 spike protein receptor-binding domain (RBD) to initiate infection. We hypothesized that some people produce anti-RBD antibodies that sufficiently resemble ACE2 structure to have ACE2-like catalytic activity. Those antibodies, ACE2-like abzymes, may contribute to LC pathogenesis. We previously showed that ACE2-like activity was associated with immunoglobulin in some people with acute and convalescent COVID-19. ACE2-like catalytic activity correlated with blood pressure changes following moderate exercise challenge in convalescents. We screened human monoclonal antibodies (mAbs) against SARS-CoV-2 spike protein from 4 sources. We identified 4 human mAbs with ACE2-like catalytic activity. The activity was not inhibited by MLN-4760, a compound that inhibits native human ACE2, nor by EDTA, unlike native ACE2, a Zinc metalloprotease, but was inhibited by an overlapping pool of Spike peptides. Enzyme kinetic studies showed that the mAbs had lower Vmax and <i>Km</i> values than ACE2. The data suggested that the antibodies cleave angiotensin II via a different mechanism than ACE2. Identification of mAbs with ACE2-like catalytic activity supports the hypothesis that antibodies induced by SARS-CoV-2 infection could help mediate the pathogenesis of COVID-19 and LC, and more generally, the hypothesis that catalytic antibodies induced by infectious agents can contribute to disease pathogenesis.