Leishmania donovani Nucleoside Hydrolase Terminal Domains in Cross-Protective Immunotherapy Against Leishmania amazonensis Murine Infection

Abstract

Nucleoside hydrolases of the Leishmania genus are vital enzymes for the replication of the DNA and conserved phylogenetic markers of the parasites. Leishmania donovani nucleoside hydrolase (NH36) induced a main CD4+ T cell driven protective response against L. chagasi infection in mice which is directed against its C-terminal domain. In this study, we used the three recombinant domains of NH36: N-terminal domain (F1, amino acids 1–103), central domain (F2 aminoacids 104–198), and C-terminal domain (F3 amino acids 199–314) in combination with saponin and assayed their immunotherapeutic effect on Balb/c mice previously infected with L. amazonensis. We identified that the F1 and F3 peptides determined strong cross-immunotherapeutic effects, reducing the size of footpad lesions to 48 and 64%, and the parasite load in footpads to 82.6 and 81%, respectively. The F3 peptide induced the strongest anti-NH36 antibody response and intradermal response (IDR) against L. amazonenis and a high secretion of IFN-γ and TNF-α with reduced levels of IL-10. The F1 vaccine, induced similar increases of IgG2b antibodies and IFN-γ and TNF-α levels, but no IDR and no reduction of IL-10. The multiparameter flow cytometry analysis was used to assess the immune response after immunotherapy and disclosed that the degree of the immunotherapeutic effect is predicted by the frequencies of the CD4+ and CD8+ T cells producing IL-2 or TNF-α or both. Total frequencies and frequencies of double-cytokine CD4 T cell producers were enhanced by F1 and F3 vaccines. Collectively, our multifunctional analysis disclosed that immunotherapeutic protection improved as the CD4 responses progressed from 1+ to 2+, in the case of the F1 and F3 vaccines, and as the CD8 responses changed qualitatively from 1+ to 3+, mainly in the case of the F1 vaccine, providing new correlates of immunotherapeutic protection against cutaneous leishmaniasis in mice based on T-helper TH1 and CD8+ mediated immune responses.

Vaccination with poly(D,L-lactide-co-glycolide) nanoparticles loaded with soluble <em>Leishmania</em> antigens and modified with a TNF&alpha;-mimicking peptide or monophosphoryl lipid A confers protection against experimental visceral leishmaniasis

“…Although protection against leishmaniasis depends more on the cellular than on the humoral immune response, it is worth noting that the skewing IgG subtypes observed at 4 months post-challenge are strong surrogates of protection, 45 which indicate the decrease of parasite load. [46][47][48] Protection against leishmaniasis is believed to be dependent upon IL-12 driven production of IFNγ, which drives the immune response towards a Th1-type phenotype. This process is suppressed during infection, and a successful immunization protocol should be able to activate the signal between antigen-presenting cells and T cells.…”

Leishmania donovani Nucleoside Hydrolase (NH36) Domains Induce T-Cell Cytokine Responses in Human Visceral Leishmaniasis

“…The development of successful protection or resistance to VL requires, the generation of potent and durable Th1 parasite-specific memory responses, characterized by the production of IFN-γ, IL-2, and TNF-α by multifunctional CD4 + T cells (4, 10–13). Additionally, the assessment of the balance between immunoregulatory mechanisms, including pro-inflammatory IFN-γ and TNF-α, and the secretion of IL-17 and the regulatory cytokine IL-10 (4, 8) is required.…”

“…After vaccination with the recombinant NH36 in the mouse model, we described the achievement of 88% prophylactic protection (26) and 91% cure of VL (28), and 65–81% cure of cutaneous leishmaniasis (CL) (13). …”

Protective or Detrimental? Understanding the Role of Host Immunity in Leishmaniasis

“…Highly conserved immunogenic proteins or epitopes between Leishmania spp. have the potential to confer cross-protection as demonstrated for L. donovani nucleoside hydrolase (NH36) and/or its recombinant fragments F1 (N-terminal domain) and F3 (C-terminal domain) formulated with saponin, which induced antigen-specific protection in BALB/c mice against L. amazonensis and L. braziliensis [157][158][159]. Other Leishmania proteins evaluated as vaccine candidates are reviewed in [160].…”