Deletion of three viral genes from MVA genome related with host immune response evasion improved its immunogenicity by modifying the innate immune response and improving the specific adaptive response against VV epitopes.

HOLGADO, M.P.; MAETO, C.; FALIVENE, J.; ; DEL MEDICO ZAJAC, M.P.; CALAMANTE, G.; DEL MÉDICO ZAJAC, M.P.; PASCUTTI, F.; GHERARDI, M.M. Y CALAMANTE, G.

Mar del Plata

Congreso; LXII Reunión Anual de la Sociedad Argentina de Inmunología.; 2014

Sociedad Argentina de Inmunología

Modified Vaccinia Ankara (MVA) still keeps genes involved in host immune response evasion. Previously we reported the optimization of MVA vaccine potential after deleting the C12L gene coding an IL18 binding protein. Here we study the immunogenicity of MVA vectors harboring a simultaneous deletion of two viral genes: A44L, involved in synthesis of steroid hormones and A46R, which inhibit transduction signals from TLR receptors (MVAΔA44L-A46R:MVAd); or with an additional deletion: C12L (MVAΔC12L/ΔA44L-A46R:MVAt). C57Bl/6 mice were intramuscularly immunized with MVAwt or deleted MVAs (ΔMVAs). We evaluated the adaptive T cell response to VV (Vaccinia Virus) epitopes at acute (7dpi) and memory phases (45dpi) in spleen and draining lymph nodes. The amount of IFNg and IL2 producing cells was measured by ELISPOT. Percentage of cytotoxic CD8-T cells was analyzed by flow cytometry as well as memory T cell responses among proliferating T cells. To study the innate response, inflammatory cytokines were quantified by ELISA after 4,20 and 30 hours post-immunization (hpi). Compared with MVAwt at 7dpi both ΔMVAs induced significant increases in the IFNg anti-VV CD8 and CD4-T cells, and IL2 anti-VV CD8-T cells. Importantly, these increments were maintained at 45dpi, thus proliferating anti-VV T-cells were augmented from 3% (MVAwt) to 6% (MVAt) for CD8-T cells, and 1% to 7% for CD4-T cells. Moreover, this vector elicited a higher proportion of specific CD8-TCM(37%) and TEM(25%) compared to MVAwt (TCM:20%,TEM:11%) as well as for CD4-T cells (TCM:37%,TEM:16% and TCM:8%,TEM:2% respectively). Also, ΔMVAs induced a higher percentage of specific cytotoxic+/IFNg+CD8-T cells than MVAwt. The innate response analysis showed that MVAt yield higher levels of IFNgand IL12 at 20 and 30 hpi compared to MVAwt. Simultaneous deletion of specific viral genes from the MVA genome with related functions as A46R and C12L, is an adequate strategy to improve the vaccine potential of this vector