In HIV infection, the accessory viral protein Nef links HIV to Btk through the SH3 domain by cell‐based fluorescence detection.31 In addition, in HIV‐1‐infected cells, Btk is significantly up‐regulated in its phosphorylated form, and Btk knockdown by small interfering RNA (siRNA) results in the death of infected cells but not uninfected cells. The gene discussed is BTK; the disease is HIV infectious disease.