[Detection of neutralizing antibody against SARS-CoV-2 in a patient with X-linked agammaglobulinemia receiving immunoglobulin replacement therapy].

Patients with X-linked agammaglobulinemia (XLA) cannot produce antibodies. In this study, we investigated antibodies against SARS-CoV-2 in a man in his 40s with XLA who had no history of COVID-19 or vaccination against COVID-19. Even though his close contact mother contracted SARS-CoV-2, he had never been infected. We measured N-IgG and S-IgG antibodies, as well as neutralizing activity. Serum antibody titers were higher after administration of immunoglobulin, and the antibody titers of immunoglobulin preparations were high as well. Our data revealed that regular administration of immunoglobulins sufficiently increases virus-specific neutralizing antibody activity in patients with XLA.