Browsing by Author "Bayih, Abebe Genetu"

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    Differential Immune Response against Recombinant Leishmania donovani Peroxidoxin 1 and Peroxidoxin 2 Proteins in BALB/c Mice
    (2015-08-25) Daifalla, Nada S.; Bayih, Abebe Genetu; Gedamu, Lashitew
    We assessed the immune response against recombinant proteins of two related, albeit functionally different, peroxidoxins from Leishmania donovani: peroxidoxin 1 (LdPxn1) and peroxidoxin 2 (LdPxn2) in BALB/c mice. We also evaluated the effect of coadministration of TLR agonists (CpG ODN and GLA-SE) on the antigen-specific immune response. Immunization with recombinant LdPxn1 alone induced a predominantly Th2 type immune response that is associated with the production of high level of IgG1 and no IgG2a isotype while rLdPxn2 resulted in a mixed Th1/Th2 response characterized by the production of antigen-specific IgG2a in addition to IgG1 isotype. Antigen-stimulated spleen cells from mice that were immunized with rLdPxn1 produced low level of IL-10 and IL-4 and no IFN-γ, whereas cells from mice immunized with rLdPxn2 secreted high level of IFN-γ, low IL-4, and no IL-10. Coadministration of CpG ODN or GLA-SE with rLdPxn1 skewed the immune response towards a Th 1 type as indicated by robust production of IgG2a isotype. Furthermore, the presence of TLR agonists together with rLdPxn1 antigen enhanced the production of IFN-γ and to a lesser extent of IL-10. TLR agonists also enhanced a more polarized Th 1 type immune response against rLdPxn2.
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    Evaluation of the Efficacy of Fusion or Combination Leishmania Donovani Peroxidoxin 1 and Superoxide Dismutase B1 Vaccine Candidates against Leishmaniasis in BALB/c Mice: Role of Granulocyte Macrophage Colony Stimulating Factor.
    (2013-09-09) Bayih, Abebe Genetu; Gedamu, Lashitew
    Leishmaniasis is a vector-borne infectious disease that affects millions of people worldwide. Human leishmaniasis appears in three major clinical forms, cutaneous (CL), mucocutaneous (MCL), and visceral leishmaniasis (VL). Visceral leishmaniasis is the deadliest form with a mortality rate of about 100% in untreated clinically overt cases. The fact that people who are cured from CL develop durable protective immunity to re-infection has led to the assumption that developing effective vaccine to the disease should be feasible. However, there is no universally effective vaccine yet. Previous studies in our lab have demonstrated that amastigote-specific Leishmania donovani peroxidoxin 1 (LdPxn1) and iron superoxide dismutase B1 (LdFeSODB1) induce specific immune response and partially protect BALB/c mice when administered together with adjuvants. In this study, it was hypothesized that fusing these antigens or using them in a form of cocktail vaccine would further increase the immunogenicity and protective efficacy of the antigens. In addition, two forms of immunization strategies were compared; heterologous DNA/protein prime-boost and homologous protein/protein immunizations. Murine granulocyte macrophage colony-stimulating factor (mGMCSF) adjuvant was used in tandem fusion with the DNA vaccines. Generally, the fusion/cocktail vaccine significantly increased immunogenicity of the vaccines in both immunization protocols. However, the high immunogenicity result was not directly reflected in the protection. In DNA/protein approach, the fusion vaccine was found to be more protective than LdFeSODB1 but not LdPxn1. In protein/protein immunization, the cocktail vaccine showed lower protection than each of the individual antigens. As demonstrated by multiparameter flow cytometry, the increased immunogenicity and protection in DNA/protein immunization was correlated to induction of significantly higher number of antigen-specific CD4+ helper T cells that individually express IFN-γ, TNF-α, and IL-2 cytokines. In addition, the presence of mGMCSF adjuvant in DNA antigens generally increased immunogenicity and protective efficacy of individual or fusion vaccines as compared with the corresponding antigens without mGMCSF. Taken together, these results suggest that heterologous DNA/protein immunization with the fusion vaccine in the presence of mGMCSF adjuvant is more efficacious than protein/protein immunization with the cocktail vaccine.
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    Immune Response and Protective Efficacy of a Heterologous DNA-Protein Immunization with Leishmania Superoxide Dismutase B1
    (2017-11-22) Bayih, Abebe Genetu; Daifalla, Nada S.; Gedamu, Lashitew
    Growing evidence shows that antioxidant proteins of Leishmania could be used as vaccine candidates. In this study, we report the efficacy of Leishmania donovani iron superoxide dismutase B1 (LdFeSODB1) as a vaccine antigen in BALB/c mice in a DNA-protein prime-boost immunization regimen in the presence or absence of murine granulocyte macrophage colony stimulating factor (mGMCSF) DNA adjuvant. The expression study confirmed that LdFeSODB1 is expressed in mammalian cells and mGMCSF fusion mediates the secretion of the recombinant protein. Heterologous immunization with LdFeSODB1 induced a strong antibody- and cell-mediated immune response in mice. Immunization triggered a mixed Th1/Th2 response as evidenced by the ratio of IgG2a to IgG1. Antigen-stimulated spleen cells from the immunized mice produced high level IFN-γ. Multiparametric flow cytometry data showed that immunization with LdFeSODB1 induced significantly higher expression of TNF-α or IL-2 by antigen-stimulated T cells. Eight weeks after L. major infection, immunization with the antigen shifted the immune response to a more Th1 type than the controls as demonstrated by IgG2a/IgG1 ratio. Moreover, IFN-γ production by antigen-stimulated spleen cells from immunized mice remained high. The footpad swelling experiment showed that immunization with LdFeSODB1 resulted in partial protection of mice from a high dose L. major infection.