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EV02, a Phase I Trial to Assess the Safety and Immunogenicity of DNA-C followed by NYVAC-C in an Open, Randomized Comparison to NYVAC-C Alone in Healthy Volunteers at Low Risk of HIV Infection
Pierre-Alexandre Bart*1, A Harari1, C Cellerai1, D Ciuffreda1, T Barber2, W Stöhr3, S McCormack3, G Pantaleo1, J Weber2, and EUROVACC Prgm
1Ctr Hosp Univ Vaudois Lausanne, Switzerland; 2Imperial Coll, London, UK; and 3Med Res Council Clin Trials Unit, London, UK
Background: EV02 is a randomized trial to assess the
safety of DNA-C and the immunological impact of DNA-C priming on vaccination
with NYVAC-C. The same recombinant HIV DNA, consisting of a gag-pol-nef polyprotein and env derived from the Chinese R5 HIV clade C virus (97CN54), is inserted in the NYVAC-C and
DNA-C vaccines.
Methods: We successfully immunized 35 healthy low-risk
HIV-negative volunteers with 1 mL NYVAC-C at weeks 20
and 24. Of the total, 20 received 4 mg DNA-C intramuscularly at week 0 and 4. Interferon-g
(IFN-γ) ELISpot assays were performed on cryo-preserved peripheral blood mononuclear cells (PBMC) at
weeks 0, 5, 20, 24, 26, 28, and 48 with 8 pools of 49-61 peptides (15-mers
overlapping by 11) encompassing the gag-pol-nef
and env regions of HIV-1. Only ELISpot assays with a background <50 SFU/106
PBMC were considered and responses were regarded as positive only if >4-fold
above background and >55 SFU/106 PBMC.
Results: Vaccine-specific responses were generated in 6
of 15 subjects in the NYVAC alone arm, and in 18 of 20 subjects in the
DNA+NYVAC arm (p = 0.003). At week 48,
only 3 (20%) subjects from the NYVAC-alone arm remained positive, in contrast
to 16 subjects (80%) of the DNA+NYVAC arm (p
= 0.0006). Env responses prevailed in both groups
(>65%) but gag, pol, and nef
responses were also observed. The average magnitude of the ELISpot
responses was significantly higher in the DNA+NYVAC arm than in the NYVAC-alone
arm at any time point of the study (week 26, peak of response: 492±79 vs 148±26 SFU/106 PBMC, p = 0.01). Analysis of the breadth of
the env responses in 9 subjects from the DNA+NYVAC
group showed a median of 4 distinct epitopes, most of
which had never been described. Furthermore, flow cytometry
experiments in 13 subjects from the DNA+NYVAC group demonstrated that 6
subjects had both CD4/CD8 T-cell responses, while 7 had only CD4 T-cell
responses. Similar proportions were observed in the NYVAC-alone group.
Surprisingly, >80% of subjects with an env-specific
CD8 T-cell response recognized the same new epitope
(HLA-A*01-YSENSSEYY). Polychromatic flow cytometry
assays have shown that all CD4/CD8 T-cell responses were highly polyfunctional, ie, able to degranulate and to proliferate, and to secrete interleukin-2
and tumor necrosis factor-α, in addition to IFN-γ.
Conclusions: After 48 weeks of follow-up,
the vaccines appear safe and well tolerated. The DNA+NYVAC combination is
highly immunogenic (>90% responders) and induces vigorous immune responses
(500 SFU/106 cells) and polyfunctional CD4
and CD8 T-cell responses lasting in time (80% responders at week
48).
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