Figure 3
Evaluation of the biological binding function of Hutat2:Fc and protective effects of Hutat2:Fc against HIV-1 Tat 86 -mediated toxicity in HTB-11 cells. (A) Specific binding of Hutat2:Fc to HIV-1 Tat. HIV-1 Tat86 (Clade B) loaded nitrocellular membranes (NCM) were incubated with cell culture supernatants collected from HR-Hutat2-transduced HTB-11 (HTB-Hutat2), U937 (U937-Hutat2), or hMDM (hMDM-Hutat2) at 4 °C overnight followed by incubation with rabbit anti-human IgG(H+L) and goat anti-rabbit IgG HRP conjugated antibodies. Specific binding was visualized by the color deposition on the NCM. The Tat86-loaded membrane incubated with rabbit anti-Tat serum served as a positive control (Pos Ctl) while incubated with cell culture supernatant from HR-A3H5 transduced HTB-11 served as a negative control (HTB-A3H5). The NCM loaded with Tat dilution buffer was used as a blank control (BLK Ctl). (B) Functional antagonization of Hutat2:Fc against HIV-1 Tat86-induced toxicity in HTB-11 cells by an MTT assay. The OD570 value of untreated HTB-11 cells was arbitrarily defined as 100% cell viability. The relative cell viability (%) was expressed as a percentage relative to the untreated control cells. The cell viability was significantly higher for the cells treated with the conditioned mediums from transduced cells releasing Hutat:Fc when compared to the cultures that received Tat86 (500 nM) alone (*P <0.01 for HTB-Hutat2 medium; # P <0.05 for U937-Hutat2 medium, and hMDM-Hutat2 medium). (C) Protection of HR-Hutat2 transduction against Tat86-induced toxicity by an MTT assay. No significant difference of cell viability was detected between normal and vector HR-Hutat2 transduced HTB-11 cells (HTB-Hutat2) (P >0.05). However, the cell viability of HTB-11 transduced with the vector HR-Hutat2 was significantly higher than that of HTB-A3H5 in the presence of HIV-1 Tat86 (500 nM) (*P <0.01). All experiments were performed in quadruplicate. Error bars denote the s.e.m.