Isotype class analysis of anti-spike antibodies revealed progression of IgA seroconversion in HD patients from t1 to t2 (41.3%; 95%CI 33.5–49.5 at t1, 83.9%; 95%CI 77.0–89.0 at t2, p = 2.27 × 10−13), reaching values similar to the control cohort (p = 0.3612). The gene discussed is CD79A; the disease is Huntington disease.