Long-term follow up of human T-cell responses to conserved HIV-1 regions elicited by DNA/simian adenovirus/MVA vaccine regimens.

BACKGROUND: Durability of vaccine-elicited immune responses is one of the key determinants for vaccine success. Our aim is to develop a vaccination strategy against the human immunodeficiency virus type 1 (HIV-1), which induces protective and durable CD8+ T-cell responses. The central theorem of our approach is to focus T cells on highly conserved regions of the HIV-1 proteome and this is achieved through the use of the first-generation conserved vaccine immunogen HIVconsv. This immunogen vectored by plasmid DNA, simian adenovirus and poxvirus MVA was tested in healthy, HIV-1-negative adults in UK and induced high magnitudes of HIVconsv-specific plurifunctional CD8+ T cells capable of in vitro HIV-1 inhibition. Here, we assessed the durability of these responses.

METHODS: Vaccine recipients in trial HIV-CORE 002 were invited to provide a blood sample at 1 and 2 years after vaccination. Their PBMCs were tested in IFN-γ ELISPOT, 25-analyte Luminex, CFSE proliferation and intracellular cytokine staining assays, the last enhanced by HLA-peptide dextramer analysis.

RESULTS: 12/12 (1 year) and 8/8 (2 years) returning subjects had median (range) of 990 (150-2495) and 763 (70-1745) IFN-γ SFU/106 PBMC specific for HIVconsv, respectively, and recognized 5 (1-6) out of 6 peptide pools at 2 years. Over one-half of the HIVconsv-specific cells expressed at least 3 functions IFN-γ, TNF-α and CD107a, and were capable of proliferation. Among dextramer-reactive cells, naïve, transitional, effector and terminally differentiated memory subsets were similarly represented.

CONCLUSIONS: First generation HIVconsv vaccine induced human T cells, which were plurifunctional and persisted for at least 2 years.

TRIAL REGISTRATION: ClinicalTrials.gov NCT01151319.