P41.07
Background: MVA still retains genes involved in host immune response evasion. We have previously reported the optimization of its vaccine potential after removing the C12L gene, coding an IL18 binding protein. Here we analyze the immunogenicity of MVA vectors harboring the simultaneous deletion of two viral genes: A44L, implicated in synthesis of steroid hormones and A46R, which inhibits transduction signals from TLR (MVAΔA44L-A46R: MVAd); or including C12L deletion also (MVAΔC12L/ΔA44L-A46R: MVAt).
Methods: C57Bl/6 mice were immunized with MVAwt or deleted MVAs (ΔMVAs). We evaluated the adaptive T-cell response to VV (Vaccinia Virus) epitopes at acute (7 dpi) and memory phases (45 dpi) in spleen and draining lymph nodes (DLNs). The amount of IFNγ and IL2 producing cells was measured by ELISPOT. We studied the percentage of specific cytotoxic CD8 T-cells by flow cytometry, and the response of memory T-cells among specific proliferating CD8 T-cells. To study the innate response, we immunized mice with MVAwt or MVAt and pattern of cytokines produced were evaluated between 0-24 hpi.
Results: At 7 dpi both ΔMVAs induced significant increases in IFNγ anti-VV CD8 and CD4-T cells vs MVAwt (1.5 to two-fold, p<0.01;2.5 to five-fold, p<0.01 respectively), and IL2 anti-VV CD8 T-cells (up to five-fold higher; p<0.01). Notably, ΔMVAs still elicited a higher response than MVAwt at 45 dpi (p<0.05). Proliferating anti-VV CD8 T-cells were augmented from 1% (MVAwt) to 3% (MVAt). Moreover, this vector elicited a higher proportion of specific TCM compared to MVAwt (45% vs 20%). The percentage of specific cytotoxic CD8 T-cells secreting IFNγ was also improved by MVAt. The innate response analysis showed that mice who received MVAt produced higher levels of IFNγ, IL6 and IL12 in DLNs compared to MVAwt.
Conclusions: The deletion of interrelated immunomodulatory genes from MVA genome is a proper approach to improve its vaccine potential and it is a helpful tool that could contribute in the development of an HIV vaccine.
