In a prospective multicentre trial, 68 healthy volunteers were randomised to receive, at weeks 0, 4 and 12, either a 0.5 ml IM (500 ¦Ìg of each lipopeptide; 35 volunteers) dose or a 0.1 ml ID (100 ¦Ìg of each lipopeptide; 33 volunteers) dose of the LIPO-4 vaccine, in the deltoid region of the non-dominant arm. All 68 volunteers received the first two vaccinations, and 44 volunteers in the ID group and 22 in the IM group received the third. We describe here the long-term CD8+ and CD4+ T-cell immune responses, up to 48 weeks after the first immunisation.
Response frequency was highest at week 14 for CD4+ T cells, at 85 % (28/33) for the IM group and 61 % (20/33) for the ID group (p = 0.027), and at week 48 for CD8+ T cells, at 36 % (12/33) for the ID group and 31 % (11/35) for the IM group (p = 0.67). Response rates tended to be lower for volunteers receiving the third vaccination boost, whether IM or ID. Finally, we also observed a striking change in the specificity of the CD8+ T-cell responses induced shortly (2 weeks) or several months (48 weeks) after LIPO-4 vaccination.
Lipopeptide vaccines elicited sustainable CD4+ and CD8+ T-cell responses, following IM or ID administration. CD8+ T-cell responses had shifted and expanded to different epitopes after one year of follow-up. These results should facilitate the design of the next generation of prime-boost trials with repeated doses of lipopeptide vaccines.