Recently, Koka et al. [36] reinforced our previous in vivo SCID-hu Bone repopulation study [20] by finding that erythroid, myeloid and megakaryocytoid in vitro colony-forming activity (CFA) of secondarily engrafted human CD34+ HSC/PC exposed to human immunodeficiency virus type 1 (HIV-1) infection in primary SCID-hu Thy/Liv grafts correlated with c-mpl expression. Here, MPL is linked to HIV-1 infection.