Journal Article

Evaluation of prime and prime-boost immunization strategies in BALB/c mice inoculated with Leishmania infantum transfected with toxic plasmids

Janaína Soares Rocha, Francisca, Flóro e Silva, Marina, Fernanda Araújo, Thalita, Ruiz Abánades, Daniel, Esteves Zorgi, Nahiara, Augusto Sanches Roque, Guilherme, Giorgio, Selma

2022

Overview

•Leishmania infantum is the etiologic agent of zoonotic visceral leishmaniasis, which can be fatal.•Visceral leishmaniasis treatment may be toxic, and resistance has been reported.•There are currently no vaccines available for humans.•Transgenic L. infantum could be an excellent vaccine candidate.•Prime-boosted mice have shown maximized protection. The etiologic agents of visceral leishmaniasis are Leishmania infantum and Leishmania donovani. Despite the variety of drugs available to treat leishmaniasis, most lead to serious adverse effects, and resistance to these drugs has been reported. Currently, no leishmaniasis vaccine is available for humans. That is why the group developed transgenic L. infantum promastigote lines, which express toxic proteins after differentiation into amastigotes. That is why group developed the pFL-AMA plasmid and transfected it into L. Infantum promastigotes. This plasmid was expressed only in the amastigote form of the parasite. Sequences encoding toxic proteins (active bovine trypsin and egg avidin) were inserted in this plasmid, and the transfected parasites died after the differentiation process. In this study, two immunization protocols were performed in BALB/c mice: prime and prime-boost immunization prior to challenge with the wild-type L. infantum (WT). The parasite burdens in the spleen, liver, and bone marrow were evaluated to verify immunological protection. Histopathological analysis of the spleen and liver and the humoral immune response were also performed. The data showed that the parasite burden was reduced in prime-boosted mice in the spleen, liver, and bone marrow, indicating that mice immunized with two doses of the transfected parasites were satisfactorily protected. High levels of IgG, IgG1, and IgG2a antibodies were observed, as well as the presence of anti-inflammatory cytokine Interleukine-10 and pro-inflammatory cytokine Tumor Necrosis Factor-α (TNF-α) and Interferon-γ (IFN – γ) suggesting a Th1/Th2 mix response, in addition to the presence of multinucleated giant cells in the spleen and lymphocyte infiltration in the liver. Therefore, L. infantum transfected with a toxic plasmid is an excellent vaccine candidate against visceral leishmaniasis and the application of a boost before the challenge promotes greater protection against WT L. infantum infection.

• Publisher: Elsevier Ltd,Elsevier Limited
• Subject: Allergy and Immunology / Amastigotes / Antibodies / Avidin / Bone marrow / cattle / Cloning / Cytokines / Differentiation / Drug dosages / Drug resistance / Drugs / eggs / Etiology / Experiments / Genes / Genetic engineering / genetically modified organisms / Giant cells / Group dynamics / histopathology / humoral immunity / Immune response / Immune response (humoral) / Immune system / Immunization / Immunoglobulin G / Immunological protection / Immunology / Immunosuppressive agents / Infections / Inflammation / Interferon / Leishmania donovani / Leishmania infantum / Leishmaniainfantum / Liver / Lymphocytes / Lymphocytes T / Metastases / necrosis / neoplasms / Parasites / Parasitic diseases / Plasmids / Promastigotes / Proteins / Spleen / toxicity / Transgenic Leishmania / Trypsin / Tumor necrosis factor-α / Vaccine / Vaccines / Vector-borne diseases / Visceral leishmaniasis / γ-Interferon