Cross-Protective Immunity to Leishmania amazonensis is Mediated by CD4+ and CD8+ Epitopes of Leishmania donovani Nucleoside Hydrolase Terminal Domains

Abstract

The nucleoside hydrolase (NH) of Leishmania donovani (NH36) is a phylogenetic marker of high homology among Leishmania parasites. In mice and dog vaccination, NH36 induces a CD4+ T cell-driven protective response against Leishmania chagasi infection directed against its C-terminal domain (F3). The C-terminal and N-terminal domain vaccines also decreased the footpad lesion caused by Leishmania amazonensis. We studied the basis of the crossed immune response using recombinant generated peptides covering the whole NH36 sequence and saponin for mice prophylaxis against L. amazonensis. The F1 (amino acids 1–103) and F3 peptide (amino acids 199–314) vaccines enhanced the IgG and IgG2a anti-NH36 antibodies to similar levels. The F3 vaccine induced the strongest DTH response, the highest proportions of NH36-specific CD4+ and CD8+ T cells after challenge and the highest expression of IFN-γ and TNF-α. The F1 vaccine, on the other hand, induced a weaker but significant DTH response and a mild enhancement of IFN-γ and TNF-α levels. The in vivo depletion with anti-CD4 or CD8 monoclonal antibodies disclosed that cross-protection against L. amazonensis infection was mediated by a CD4+ T cell response directed against the C-terminal domain (75% of reduction of the size of footpad lesion) followed by a CD8+ T cell response against the N-terminal domain of NH36 (57% of reduction of footpad lesions). Both vaccines were capable of inducing long-term cross-immunity. The amino acid sequence of NH36 showed 93% identity to the sequence of the NH A34480 of L. amazonensis, which also showed the presence of completely conserved predicted epitopes for CD4+ and CD8+ T cells in F1 domain, and of CD4+ epitopes differing by a single amino acid, in F1 and F3 domains. The identification of the C-terminal and N-terminal domains as the targets of the immune response to NH36 in the model of L. amazonensis infection represents a basis for the rationale development of a bivalent vaccine against leishmaniasis.

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

“…In fact, the amino acid sequence of L. donovani NH36 shows high identity with the NH sequences of L. major (95–96%) (11, 30), L. mexicana (93%), L. infantum chagasi (99%), L. infantum (99%), Leishmania tropica (97%), Leishmania braziliensis (84%) (31), and L. amazonensis (93%) (12). …”

F1 Domain of the Leishmania (Leishmania) donovani Nucleoside Hydrolase Promotes a Th1 Response in Leishmania (Leishmania) infantum Cured Patients and in Asymptomatic Individuals Living in an Endemic Area of Leishmaniasis

“…We recently described that the in silico- predicted epitopes of L. (L.) donovani -NH36 are highly conserved in the nucleoside hydrolase of L. amazonensis (24). This justifies the high cross-protection obtained against L. (L.) amazonensis infection of mice, after vaccination with F1 and F3 (23–25).…”

“…In spite of that difference, the F1 domain, which induced a CD8 + T-cell-mediated protection against cutaneous leishmaniasis of mice (22, 24, 25), shares important epitopes for the generation of a Th1 and CD8 + T-cell responses of human VL patients infected with L. (L.) infantum chagasi from Sergipe, Brazil (28). However, while L. (L.) infantum chagasi is the etiological agent of VL in America, the disease is caused by L. (L.) infantum in Europe.…”