DELETION OF IMMUNOMODULATORY A44L, A46R AND C12L VIRAL GENES FROM MODIFIED VACCINIA ANKARA (MVA) GENOME: EFFECT ON ITS IMMUNOGENICITY

MARÍA P. HOLGADO; MAETO, CYNTHIA A; JULIANA FALIVENE; GHIGLIONE YANINA; MARÍA PAULA DEL MÉDICO ZAJAC; GABRIELA CALAMANTE; M. MAGDALENA GHERARDI

Congreso; HIV Research for Prevention 2014; 2014

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 viralgenes: A44L, implicated in synthesis of steroid hormones and A46R, which inhibits transduction signals from TLR (MVADA44L-A46R: MVAd); or including C12L deletion also (MVADC12L/DA44L-A46R: MVAt).Methods: C57Bl/6 mice were immunized with MVAwt or deleted MVAs (DMVAs). 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 IFNc 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 DMVAs induced significant increases in IFNc 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, DMVAs 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 IFNc was also improved by MVAt. The innate response analysis showed that mice who received MVAt produced higher levels of IFNc, IL6 and IL12 in DLNs compared toMVAwt.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.