Analysis of the Antigenic and Prophylactic Properties of the Leishmania Translation Initiation Factors eIF2 and eIF2B in Natural and Experimental Leishmaniasis

Abstract

Different members of intracellular protein families are recognized by the immune system of the vertebrate host infected by parasites of the genus Leishmania. Here, we have analyzed the antigenic and immunogenic properties of the Leishmania eIF2 and eIF2B translation initiation factors. An in silico search in Leishmania infantum sequence databases allowed the identification of the genes encoding the α, β, and γ subunits and the α, β, and δ subunits of the putative Leishmania orthologs of the eukaryotic initiation factors F2 (LieIF2) or F2B (LieIF2B), respectively. The antigenicity of these factors was analyzed by ELISA using recombinant versions of the different subunits. Antibodies against the different LieIF2 and LieIF2B subunits were found in the sera from human and canine visceral leishmaniasis patients, and also in the sera from hamsters experimentally infected with L. infantum. In L. infantum (BALB/c) and Leishmania major (BALB/c or C57BL/6) challenged mice, a moderate humoral response against these protein factors was detected. Remarkably, these proteins elicited an IL-10 production by splenocytes derived from infected mice independently of the Leishmania species employed for experimental challenge. When DNA vaccines based on the expression of the LieIF2 or LieIF2B subunit encoding genes were administered in mice, an antigen-specific secretion of IFN-γ and IL-10 cytokines was observed. Furthermore, a partial protection against murine CL development due to L. major infection was generated in the vaccinated mice. Also, in this work we show that the LieIF2α subunit and the LieIF2Bβ and δ subunits have the capacity to stimulate IL-10 secretion by spleen cells from naïve mice. B-lymphocytes were identified as the major producers of this anti-inflammatory cytokine. Taking into account the data found in this study, it may be hypothesized that these proteins act as virulence factors implicated in the induction of humoral responses as well as in the production of the down-regulatory IL-10 cytokine, favoring a pathological outcome. Therefore, these proteins might be considered markers of disease.

A candidate vaccine for human visceral leishmaniasis based on a specific T cell epitope-containing chimeric protein protects mice against Leishmania infantum infection

“…However, none of these experimental vaccine candidates have satisfactorily progressed in human trials. Amongst such different vaccine approaches, recombinant protein-based vaccines have several significant advantages, such as stability, low cost, and standardized production 26 – 28 .…”

Improving the serodiagnosis of canine Leishmania infantum infection in geographical areas of Brazil with different disease prevalence

“…infantum coding regions: KMP-11 (Fuertes et al, 2001); H2A (Iborra et al, 2004); HSP83 (Angel et al, 1996); HSP70 (Souza et al, 2013); LiP2a and LiP2b (Iborra et al, 2007); LiP0 (Iborra et al, 2003). Gene expression and protein purification of the different his-tagged recombinant proteins were performed by affinity chromatography using Ni-NTA resin (Qiagen), under denaturant conditions as described (Garde et al, 2018). Proteins were stored at −20 °C in ELISA denaturant coating buffer (EDCB: 3 M urea, 0.5 M NaCl, 5 mM imidazol, 1 mM 2-mercaptoethanol in 20 mM Tris HCl pH 8).…”

Subcutaneous, Oral, and Intranasal Immunization of BALB/c Mice with Leishmania infantum K39 Antigen Induces Non-Protective Humoral Immune Response

“…Translation initiation factors eIF2 (LieIF2) and eIF2B (LieIF2B) are two intracellular antigens whose immunogenicity has also been characterized in L. infantum -infected BALB/c mice [ 24 ]. LieIF2B α, β, and γ subunits and LieIF2 α and β subunits induced mixed antibody responses, with immunoglobulins of both IgG1 and IgG2a subclasses detected, similar to what we reported for the rK39-HFBI antigen.…”