Abstract
MVA is an attenuated vector that still retains immunomodulatory genes. We have previously reported its optimization after deleting the C12L gene, coding for the IL-18 binding-protein. Here, we analyzed the immunogenicity of MVA vectors harboring the simultaneous deletion of A44L, related to steroid synthesis and A46R, a TLR-signaling inhibitor (MVAΔA44L-A46R); or also including a deletion of C12L (MVAΔC12L/ΔA44L-A46R). The absence of biological activities of the deleted genes in the MVA vectors was demonstrated. Adaptive T-cell responses against VACV epitopes, evaluated in spleen and draining lymph-nodes of C57Bl/6 mice at acute/memory phases, were of higher magnitude in those animals that received deleted MVAs compared to MVAwt. MVAΔC12L/ΔA44L-A46R generated cellular specific memory responses of higher quality characterized by bifunctionality (CD107a/b+/IFN-γ+) and proliferation capacity. Deletion of selected genes from MVA generated innate immune responses with higher levels of determining cytokines related to T-cell response generation, such as IL-12, IFN-γ, as well as IL-1β and IFN-β. This study describes for the first time that simultaneous deletion of the A44L, A46R and C12L genes from MVA improved its immunogenicity by enhancing the host adaptive and innate immune responses, suggesting that this approach comprises an appropriate strategy to increase the MVA vaccine potential.
Highlights
Modified Vaccinia Ankara Virus (MVA) was originally developed as a vaccine for smallpox in primary chicken embryo fibroblasts (CEF) through serial passages of Chorioallantois Vaccinia virus Ankara (CVA)
The removal of the A44L, A46R and C12L genes from deleted MVAs was firstly corroborated by specific PCR
Afterwards, in order to verify the absence of mRNA expression of the different genes, we performed RT-PCRs with RNA extracted from CEFs previously infected with parental (MVAwt) or the deleted viruses (MVA∆A44L-A46R and MVA∆C12L/∆A44L-A46R), using specific primers detailed in Materials and Methods
Summary
Modified Vaccinia Ankara Virus (MVA) was originally developed as a vaccine for smallpox in primary chicken embryo fibroblasts (CEF) through serial passages of Chorioallantois Vaccinia virus Ankara (CVA) After this process, MVA lost its capacity to replicate in vivo in mammalian cells, restricting its productive replication to certain permissive cell-lines, such as BHK-21 [1,2,3]. Despite the loss of several immunomodulatory genes, MVA still preserves genes directed to evade the host immune response [17], the directed deletion from the MVA genome of these genes can constitute a strategy to improve its immunogenicity This proof of concept was demonstrated previously, e.g., after deleting the gene encoding an interleukin-1β binding-protein [18], and after the removal of the A41L gene encoding for a chemokine binding-protein [19]. Our group described that the deletion of the C12L gene from MVA genome, encoding for the interleukin-18 (IL-18)
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