Leishmania Major Centrin Gene-Deleted Parasites Generate Skin Resident Memory T-Cell Immune Response Analogous to Leishmanization

Abstract

Leishmaniasis is a vector-borne parasitic disease transmitted through the bite of a sand fly with no available vaccine for humans. Recently, we have developed a live attenuated Leishmania major centrin gene-deleted parasite strain (LmCen-/-) that induced protection against homologous and heterologous challenges. We demonstrated that the protection is mediated by IFN (Interferon) γ-secreting CD4+ T-effector cells and multifunctional T cells, which is analogous to leishmanization. In addition, in a leishmanization model, skin tissue-resident memory T (TRM) cells were also shown to be crucial for host protection. In this study, we evaluated the generation and function of skin TRM cells following immunization with LmCen-/- parasites and compared those with leishmanization. We show that immunization with LmCen-/- generated skin CD4+ TRM cells and is supported by the induction of cytokines and chemokines essential for their production and survival similar to leishmanization. Following challenge with wild-type L. major, TRM cells specific to L. major were rapidly recruited and proliferated at the site of infection in the immunized mice. Furthermore, upon challenge, CD4+ TRM cells induce higher levels of IFNγ and Granzyme B in the immunized and leishmanized mice than in non-immunized mice. Taken together, our studies demonstrate that the genetically modified live attenuated LmCen-/- vaccine generates functional CD4+ skin TRM cells, similar to leishmanization, that may play a crucial role in host protection along with effector T cells as shown in our previous study.

Deletion of MIF gene from live attenuated LdCen−/− parasites enhances protective CD4+ T cell immunity

“…The low levels of persistent antigens may be important for maintaining long term protection profile, as the generation of IFN-γ producing CD4 + T effector populations 25 , 78 , despite the difference between the survival profile of parasites used in leishmanization and immunization with attenuated parasites. Independently T CM and skin resident T RM memory T cells were also shown to play a role in protection in L. major mouse models 39 , 79 . Thus, it would be hard to discriminate the role of memory cell populations in a L. major infection model due to the presence of memory and effector populations and the kinetics of their actions following a challenge infection.…”

“…Accordingly, the protective immunity induced by LdCen −/− parasites has been shown to be mediated by Th1 dominant multifunctional CD4 + and CD8 + T cell populations that orchestrate the assembling of granulomas in the spleens followed by the parasiticidal activities mediated by nitric oxide 14 . Recent studies also showed that in a centrin deletion mutant of L. major , skin resident TRM (Tissue Resident Memory) cells also play an important role in protection 39 . Towards understanding the immune mechanisms that direct the development of Th1-type response following LdCen −/− immunization, studies investigated early interactions between LdCen −/− parasites and the innate immune cells.…”

CRISPR/Cas9-mediated deletion of a kinetoplast-associated gene attenuates virulence inLeishmania majorparasites

“…The Lm UMSBP +/- mutant promastigotes showed significant reduction in infection of macrophages and intracellular replication as intracellular amastigotes compared to the WT parasites. While we need parasite growth within the host cells to elicit the effector immune responses and development of memory T cells, this growth needs to be limited to guaranty parasite persistence without pathology (36). Two months following infection, the Lm UMSBP +/− parasites were not completely cleared from the spleen and lymphnodes, even a significantly reduction of the parasite load was observed compared to WT Lm infected mice.…”

Live attenuated-nonpathogenic Leishmania and DNA structures as promising vaccine platforms against leishmaniasis: innovations can make waves

“…LmCen −/− parasites represent an equally effective but safer alternative to leishmanization for the protection induced against L. major transmitted by sand fly bite ( Silvestre et al, 2008 ) and also cross protection against more virulent L. donovani ( Karmakar et al, 2022 ). In particular, mice immunized with LmCen −/− parasites compared to mice healed from L. major leishmanization, have generated a significantly higher pro-inflammatory immune response, characterized by CD4 + CD44 high Ly6C + T-bet + IFN-γ + effector T cells ( Zhang et al, 2020 ) and tissue resident memory (T RM ) T cell responses ( Ismail et al, 2022 ). This is the first report of a live attenuated formulation that enables Ly6C + T EFF and T RM induction without a compensatory reversion.…”