Pathophysiological effects of long COVID-19 (auto)antibodies on fertility.

Molecular mimicry between foreign and self-antigens has long been recognized to initiate/exacerbate autoimmunity. Shared amino acid sequences have been found between SARS-CoV-2 Spike glycoprotein and human self-proteins, raising concerns about potential damages. We previously identified sequences with ≥5 identical residues shared by the SARS-CoV-2 Spike and spermatogenesis-associated proteins. One of these peptides was especially recognized by antibodies from infected, but not vaccinated individuals. Here, their pathogenic effects were explored in vivo. Injection of peptide antibodies into healthy male mice impaired fertility or delayed delivery time in fertile females, suggesting that cross-reactivity via molecular mimicry might affect the human reproductive system.