Figure 5. Immunogenicity of different viral constructions measured by ELISPOT responses.

(A) Cryopreserved PBMCs from asymptomatic HIV seropositive individuals were tested for specific IFN-γ secreting T cells by in vitro stimulation with different HIV virions (WT+AT-2, ΔRT and ΔRT+AT-2). PBMCs were pulsed with 200 ng/ml p24 equivalents in all cases. The response elicited by WT+AT-2, ΔRT and ΔRT+AT-2 virions (mean ± SEM) is shown. The positivity threshold for each construct or antigen was defined as at least 50 SFC/10⁶ PBMC and at least twice that of the control medium. The magnitude of response differed significantly between stimuli (***p<0.001). (B) Four responder individuals were tested with different concentrations of WT+AT-2 and ΔRT virions (from 200 ng/ml to 5 µg/ml). The titration showed that the difference found between both stimuli was maintained, independently of the amount of virions used.