Background:  In a therapeutic immunization study of acutely infected subjects (QUEST), ART treatment was combined with an HIV-recombinant canarypox vaccine (vCP1452) alone or in addition to RemuneÔ. We previously showed in vaccines versus placebo arms at the end of immunization (24 weeks post-Remune) a significant induction of CD4 and CD8 interferon-gamma (IFN-g) -producing cells that were not correlated to viremia levels at 24 weeks post-stopping ART. No viremia level difference was found between immunized versus placebo arms at 24 weeks post stopping ART. Since interleukin-2 (IL-2) might be required for protection we further analyzed multifunctional T cells producing IL-2 before and after ART discontinuation.

Methods:  We assessed by multicolor intra-cellular cytokine (IL-2 and IFN-g), 20 QUEST subjects (mean viral load = 3.8, range 1.69 to 5.24 log HIV copies/mL) with available samples and positive responses by IFN-g ELISpot against p24 and pools of gag and nef peptides, and staining against the same antigens at week 24 post Remune and post ART.

Results:  The IFN-g production against HIV gag-nef was confirmed to be mediated by HIV-specific CD4 cells (24 weeks post Remune:  8 of 9 cases, 89%; 24 weeks post ART:  10 of 11, 91%) and CD8 T cells (24 weeks post Remune:  8 of 8, 100%; 24 weeks post ART:  10 of 12, 83%). An HIV-specific IL-2 secretion was also observed in CD4 (24 weeks post Remune:  6 of 9, 67%; 24 weeks post ART:  7 of 10, 70%), and CD8 cells (24  weeks post Remune:  8 of 8, 100%; 24 weeks post ART:  7 of 9, 78%). Double-cytokine IFN-g⁺IL-2⁺ CD4 cells were detected at 24 weeks post Remune in 2 of 9 (22 %) subjects and at 24 weeks post ART in 2 of 12 (17%), and CD8 cells in 4 of 8 (50%) and 4 of 10 (40%) subjects, with very low frequencies of IFN-g⁺IL-2⁺ CD4 cells. Both IFN-g⁺IL-2⁺ and single IL-2⁺ CD4 and CD8 T cells were present in low and high viral load at 24 weeks post ART. For IFN-g⁺ and IL-2 secretion by HIV-specific T cells pre- and post-stopping HAART, see the table.

Conclusions:  In this early treated, acutely infected population with and without therapeutic vaccines, treated both with IFN-g- and IL-2-producing CD4 and CD8 T cells, responses to HIV were detected during and after HAART stop. Bi-functional HIV-specific CD4 and CD8 T cells producing IL-2 and IFN-γ⁺IL-2⁺ were also detected in subjects with low and high viral load post-stopping ART. This suggests that early treatment for acute infection with or without vaccines may preserve these responses even in subjects with high viral load rebound.