Transgenic 4-1BBL-engineered vaccine stimulates potent Gag-specific therapeutic and long-term immunity via increased priming of CD44＋CD62Lhigh IL-7R＋ CTLs with up- and downregulation of anti- and pro-apoptosis genes

Human immunodeficiency virus type-1 （HIV-1）-specific dendritic cell （DC） vaccines have been used in clinical trials. However, they have been found to only induce some degree of immune responses in these studies. We previously demonstrated that the HIV-1 Gag-specific Gag-Texo vaccine stimulated Gag-specific effector CD8＋ cytotoxic T lymphocyte （CTL） responses, leading to completely protective, but very limited, therapeutic immunity. In this study, we constructed a recombinant adenoviral vector, adenovirus （AdV）4-1BBL, which expressed mouse 4-1BB ligand （4-1BBL）, and generated transgenic 4-1BBL-engineered OVA-Texo/4.1BSL and Gag-Texo/4.1BSL vaccines by transfecting ovalbumin （OVA）-Texo and Gag-＇rexo cells with AdV4.1BBL, respectively. We demonstrate that the OVA-specific OVA-Texo/4.ZSSL vaccine stimulates more efficient OVA-specific CTL responses （3.26%） compared to OVA-Texo-activated responses （1.98%） in wild-type C57BIJ6 mice and the control OVA-TeXO/Nu, vaccine without transgenic 4-1BBL expression, leading to enhanced therapeutic immunity against 6-day established OVA-expressing B16 melanoma BL6-1OovA cells. OVA-Texo/4.1BBL-stimulated CTLs, which have a CD44＋CD62Lhigh IL-7R＋ phenotype, are likely memory CTL precursors, demonstrating prolonged survival and enhanced differentiation into memory CTLs with functional recall responses and long-term immunity against BL6-1OovA melanoma. In addition, we demonstrate that OVA-Texo/4_ZBBL-Stimulated CTLs up- and downregulate the expression of anti-apoptosis （Bcl2110, Naipl, No13, Pak7 and Tnfrsfllb） and pro-apoptosis （Casp12, Trp63 and Trp73） genes, respectively, by RT2 Profiler PCR array analysis. Importantly, the Gag-specific Gag-Texo/4.1BBL vaccine also stimulates more efficient Gag-specific therapeutic and long-term immunity against HLA-A2/Gag-expressing B 16 melanoma BL6-1OGag/A2 cells than the control Gag-TeXO/NuH vaccine in transgenic HLA-A2 mice. Taken together, our novel Gag-Texo/4-ZBBL vaccine, which is capable of stimulating potent Gag-specific therapeutic and long-term immunity, may represent a new immunotherapeutic vaccine for controlling HIV-1 infection.