Induction of Potentially Protective HIV-Specific T-Cell Responses In Vitro by Gag mRNA-Electroporated Dendritic Cells.

Human immunodeficiency virus type 1 (HIV-1) infection is characterized by dysfunction of HIV-1-specific T-lymphocytes. In order to suppress the virus and delay evolution to AIDS, antigen-loaded antigen-presenting cells, including dendritic cells (DC) might be useful to boost and broaden HIV-1-specific T-cell responses. Monocyte-derived DC from 15 untreated (“naive”) and 15 highly active anti-retroviral therapy (HAART)-treated HIV-1-infected patients were electroporated with codon-optimized (“humanized”) mRNA encoding consensus HxB-2 (hHxB-2) Gag protein. These DC were co-cultured for 1 week with autologous peripheral blood leucocytes (PBL). Potential expansion of specific T-cells was measured by comparing ELISPOT responses of PBL before and after co-culture, using a pool of overlapping peptides, spanning the HxB-2 Gag. Expansion of specific PBL after co-culture was noted for T cells producing interferon (IFN)-gamma, interleukin (IL)-2 and perforin (Wilcoxon signed rank test p<0.05, except for IL-2 in naive patients). From all HIV-1-seropositive persons tested, 12 HAART-treated and 12 naive patients match in absolute number of CD4+ T-cells. A comparison of the increase of the response between day 0 and after 1 week of stimulation between those two groups showed that the response was higher in HAART-treated subjects for IFN-gamma and IL-2 but not for perforin in comparison to untreated subjects. Examining purified CD4+ and CD8+ T-cells after co-culture revealed that HxB-2 Gag peptides induced IFN-gamma in both subsets, that IL-2 was only secreted by CD4+ T-cells and that perforin was dominantly secreted by CD8+ T-cells. Remarkably, the perforin response in the treatment-naive persons was negatively correlated with the peripheral blood absolute CD4+ and CD8+ T-cell count (respectively R=0.618, p=0.014; and R=0.529, p=0.043). Furthermore, the nadir absolute CD4+ T-cell count in HAART-treated subjects was positively correlated with the IL-2 response (R=0.521, p=0.046) and negatively correlated with the perforin response (R=0.588, p=0.021). In conclusion, DC from HAART-treated and therapy-naive subjects, electroporated with hHxB-2 gag mRNA have the capacity to induce secondary T-cell responses. In an earlier study (