Figure 4.

(a) Lymphoproliferative (LP) response to gag p24 induced by in vitro stimulation of PBMC from HIV-seropositive donor 604 with LFn-NG. This donor did not have any detectable LP response to gag when fresh PBMC were tested against recombinant HIV-1 p24 protein (not shown). Stimulation was by adherent autologous PBMC treated with nothing (i), PHA (ii), LFn-p24 + PA (iii), or LFn-NG + PA (iv). Stimulated cultures contained approximately 95% CD4 T cells. LPA was performed by testing proliferation to autologous EBV-transformed B cells infected with recombinant vaccinia expressing lacZ (vsc8), gag (vDK1), or nef (vnef). (b) In vitro translocation of LFn-p24. LFn, full-length LF, full-length EF, and LFn-p24 were tested for translocation in the presence of PA. Bars represent the percent of bound protein internalized into CHO-K1 cells. (c) In vitro cytotoxicity of LF and LFn fusion proteins in the presence or the absence of PA in a macrophage cell line. (i) Cultures were exposed to PA only (◊) at concentrations of 0.1–3.2 μg/ml, LF only (○), or both (□) at a 2:1 ratio by weight. The LD₅₀ for native LT is 0.4 μg/ml LF plus 0.2 μg/ml PA. (ii) Although □ represents the cytotoxic effect of LF in the presence of PA, LFn-p24 (○) and LFn-NG (◊) in the presence of PA showed no significant effect. The effect of PA alone is represented with ▵.