Paper of the Month October 2015
Identification of broadly conserved cross-species protective Leishmania antigen and its responding CD4+ T cells.
Science Translational Medicine. 2015 Oct 21;7(310):310ra167. doi: 10.1126/scitranslmed.aac5477.
Mou Z, Li J, Boussoffara T, Rishi H, Hamana H, Ezzati P, Hu C, Yi W, Liu D, Khadem F, Okwor I, Jia P, Shitaoka K, Wang S, Ndao M, Petersen C, Chen J, Rafati S, Louzir H, Muraguchi A, Wilkins JA, Uzonna JE.
There is currently no clinically effective vaccine against leishmaniasis because of poor understanding of the antigens that elicit dominant T cell immunity. Using proteomics and cellular immunology, we identified a dominant naturally processed peptide (PEPCK335-351) derived from Leishmania glycosomal phosphoenolpyruvate carboxykinase (PEPCK). PEPCK was conserved in all pathogenic Leishmania, expressed in glycosomes of promastigotes and amastigotes, and elicited strong CD4(+) T cell responses in infected mice and humans. I-A(b)-PEPCK335-351 tetramer identified protective Leishmania-specific CD4(+) T cells at a clonal level, which comprised ~20% of all Leishmania-reactive CD4(+) T cells at the peak of infection. PEPCK335-351-specific CD4(+) T cells were oligoclonal in their T cell receptor usage, produced polyfunctional cytokines (interleukin-2, interferon-γ, and tumor necrosis factor), and underwent expansion, effector activities, contraction, and stable maintenance after lesion resolution. Vaccination with PEPCK peptide, DNA expressing full-length PEPCK, or rPEPCK induced strong durable cross-species protection in both resistant and susceptible mice. The effectiveness and durability of protection in vaccinated mice support the development of a broadly cross-species protective vaccine against different forms of leishmaniasis by targeting PEPCK.