Furthermore, to specifically understand if antibodies against the spike protein (S) enhance infection, we measured the anti-S IgG, IgA, and IgM responses and adapted retroviral-pseudotypes to measure virus neutralization with target cells expressing the ACE2 virus receptor and the Fc alpha receptor (FcαR) or Fc gamma receptor IIA (FcγRIIA). The gene discussed is ACE2; the disease is infection.