In this study, comparing to her healthy sibling and the reference range of healthy population from 3 different districts in China: Beijing, Hong Kong and Shanghai26, 27, 28, the HIV+ twin had a significantly reduced count of CD4+ cells of <350 cells/microliter (Supplementary Table S1) and an abnormal CD4/CD8 cell ratio, suggesting that the HIV+ subject was at the moderate advanced stage of AIDS. This evidence concerns the gene CD4 and AIDS.