FIG. 6.

Poor transduction of G₀ PHSC is not improved by immediate rescue with cytokines (CTX). (A) PHSC were maintained in the presence or absence of cytokines for 48 h prior to transduction. Immediately following transduction with concentrated HIV-eGFP(VSV G), all cells were placed into cytokine-containing medium, and 72 h later they were analyzed for enhanced GFP (EGFP) expression. Left column, PI histogram; right column, GFP histogram. Percentages of positive cells are indicated. (B) A separate experiment similar to the one for panel A was performed, except that one population of cells was never exposed to cytokines. After transduction, PHSC were stained for Pyronin Y (PY) and Hoechst 33342 and then analyzed by flow cytometry. Note that PHSC which had been rescued with cytokines were actively cycling, with a majority of cells being Pyronin Y positive, and yet they had a low transduction rate. (C) PHSC maintained in the presence or absence of cytokines for 48 h were mock transduced or transduced with ultracentrifuge-concentrated NL4-3-CMV-AP(VSV G). After transduction, all populations were refed with complete medium containing cytokines and 72 h later were stained overnight for HPAP activity by using BCIP-NBT. Shown are the average percent transductions for two independent experiments. Note that this vector (which contains all of the accessory HIV gene products) poorly transduced G₀ PHSC.