Japanese Encephalitis Virus Vaccination Elicits Cross-Reactive HLA-Class I-Restricted CD8 T Cell Response Against Zika Virus Infection.

Japanese encephalitis virus (JEV) exposure or vaccination could elicit cross-reactive CD8 T cell immunity against heterologous flaviviruses in humans. In addition, cross-reactive CD8 T cells induced by dengue virus (DENV) have been shown to play a protective role against Zika virus (ZIKV). However, how JEV exposure or vaccination affects ZIKV infection in humans remains unclear. In this report, epitope prediction algorithms were used to predict the cross-reactive CD8 T cell epitope restricted to human HLA between JEV and ZIKV. We found that these predicted CD8 T cell epitopes are immunogenic and cross-reactive in humanized HLA transgenic mice. Moreover, JEV vaccine immunization provided cross-protection against ZIKV infection. Furthermore, CD8 T cells were involved in the protection against ZKIV infection in vivo. Our results have an important clinical implication that vaccination with JEV SA14-14-2 may provide protection against ZIKV infection in humans.

Pre-existing heterologous T-cell immunity and neoantigen immunogenicity.

Neoantigens are tumor-specific mutated proteins that are exempt from central tolerance and are therefore capable of efficiently eliciting effective T-cell responses. The identification of immunogenic neoantigens in tumor-specific mutated proteins has promising clinical implications for cancer immunotherapy. However, the factors that may contribute to neoantigen immunogenicity are not yet fully understood. Through molecular mimicry of antigens arising during cancer progression, the gut microbiota and previously encountered pathogens potentially have profound impacts on T-cell responses to previously unencountered tumor neoantigens. Here, we review the characteristics of immunogenic neoantigens and how host exposure to microbes may affect T-cell responses to neoantigens. We address the hypothesis that pre-existing heterologous memory T-cell immunity is a major factor that influences neoantigen immunogenicity in individual cancer patients. Accumulating data suggest that differences in individual histories of microbial exposure should be taken into account during the optimisation of algorithms that predict neoantigen immunogenicity.

Synthesis and Biological Evaluation of Hapten-Clicked Analogues of The Antigenic Peptide Melan-A/MART-126(27L)-35.

A click-chemistry-based approach was implemented to prepare peptidomimetics designed in silico and made from aromatic azides and a propargylated GIGI-mimicking platform derived from the altered Melan-A/MART-126(27L)-35 antigenic peptide ELAGIGILTV. The CuI -catalyzed Huisgen cycloaddition was carried out on solid support to generate rapidly a first series of peptidomimetics, which were evaluated for their capacity to dock at the interface between the major histocompatibility complex class-I (MHC-I) human leucocyte antigen (HLA)-A2 and T-cell receptors (TCRs). Despite being a weak HLA-A2 ligand, one of these 11 first synthetic compounds bearing a p-nitrobenzyl-triazole side chain was recognized by the receptor proteins of Melan-A/MART-1-specific T-cells. After modification of the N and C termini of this agonist, which was intended to enhance HLA-A2 binding, one of the resulting seven additional compounds triggered significant T-cell responses. Thus, these results highlight the capacity of naturally circulating human TCRs that are specific for the native Melan-A/MART-126-35 peptide to cross-react with peptidomimetics bearing organic motifs structurally different from the native central amino acids.

Isolation of an Anti-Tumour Disintegrin: Dabmaurin-1, a Peptide Lebein-1-Like, from Daboia mauritanica Venom.

In the soft treatment of cancer tumours, consequent downregulation of the malignant tissue angiogenesis constitutes an efficient way to stifle tumour development and metastasis spreading. As angiogenesis requires integrin-promoting endothelial cell adhesion, migration, and vessel tube formation, integrins represent potential targets of new therapeutic anti-angiogenic agents. Our work is a contribution to the research of such therapeutic disintegrins in animal venoms. We report isolation of one peptide, named Dabmaurin-1, from the hemotoxic venom of snake Daboia mauritanica, and we evaluate its potential anti-tumour activity through in vitro inhibition of the human vascular endothelial cell HMECs functions involved in tumour angiogenesis. Dabmaurin-1 altered, in a dose-dependent manner, without any significant cytotoxicity, HMEC proliferation, adhesion, and their mesenchymal migration onto various extracellular matrix proteins, as well as formation of capillary-tube mimics on MatrigelTM. Via experiments involving HMEC or specific cancers cells integrins, we demonstrated that the above Dabmaurin-1 effects are possibly due to some anti-integrin properties. Dabmaurin-1 was demonstrated to recognize a broad panel of prooncogenic integrins (αvß6, αvß3 or αvß5) and/or particularly involved in control of angiogenesis α5ß1, α6ß4, αvß3 or αvß5). Furthermore, mass spectrometry and partial N-terminal sequencing of this peptide revealed, it is close to Lebein-1, a known anti-ß1 disintegrin from Macrovipera lebetina venom. Therefore, our results show that if Dabmaurin-1 exhibits in vitro apparent anti-angiogenic effects at concentrations lower than 30 nM, it is likely because it acts as an anti-tumour disintegrin.

The pre-existing cellular immunity to Japanese encephalitis virus heterotypically protects mice from Zika virus infection.

Zika virus (ZIKV) and Japanese encephalitis virus (JEV) are closely related flaviviruses, ZIKV circulates in the population that has been JEV vaccinated in Southeast Asian countries. This alerts that a pre-existing immunity to JEV would impact ZIKV infection and/or pathogenesis. Herein we showed that the pre-existing immunity to JEV SA14-14-2 vaccination provided an ample protection against non-lethal or lethal dose of ZIKV infection in mice. This was in sharp contrast to the passive immunization of JEV antibodies, which failed to affect ZIKV infection or pathogenesis in mice, albeit these antibodies exhibited cross-reactivity and antibody dependent enhancement (ADE) of ZIKV infection in vitro. Furthermore, we determined that JEV vaccine-elicited CD8+ T cells were required to mediate the heterotypic protection of ZIKV infection, which cross-reacted to ZIKV E and NS5 antigens (E294-302 and NS52839-2848). Adoptive transfer of these CD8+ T cells could partially protect the mice from ZIKV challenge. Therefore, although short of epidemiological evidence, these results suggested that cross-reactive CD8+ T cells activated by JEV vaccination could protect potential ZIKV infection in human populations.

AaTX1, from Androctonus australis scorpion venom: purification, synthesis and characterization in dopaminergic neurons.

We have purified the AaTX1 peptide from the Androctonus australis (Aa) scorpion venom, previously cloned and sequenced by Legros and collaborators in a venom gland cDNA library from Aa scorpion. AaTX1 belongs to the α-Ktx15 scorpion toxins family (αKTx15-4). Characterized members of this family share high sequence similarity and were found to block preferentially IA-type voltage-dependent K(+) currents in rat cerebellum granular cells in an irreversible way. In the current work, we studied the effects of native AaTX1 (nAaTX1) using whole-cell patch-clamp recordings of IA current in substantia nigra pars compacta dopaminergic neurons. At 250 nM, AaTX1 induces 90% decrease in IA current amplitude. Its activity was found to be comparable to that of rAmmTX3 (αKTx15-3), which differs by only one conserved (R/K) amino acid in the 19th position suggesting that the difference between R19 and K19 in AaTX1 and AmmTX3, respectively, may not be critical for the toxins' effects. Molecular docking of both toxins with Kv4.3 channel is in agreement with experimental data and suggests the implication of the functional dyade K27-Y36 in toxin-channel interactions. Since AaTX1 is not highly abundant in Aa venom, it was synthesized as well as AmmTX3. Synthetic peptides, native AaTX1 and rAmmTX3 peptides showed qualitatively the same pharmacological activity. Overall, these data identify a new biologically active toxin that belongs to a family of peptides active on Kv4.3 channel.

Design, synthesis and evaluation of ß-lactam antigenic peptide hybrids; unusual opening of the ß-lactam ring in acidic media.

ß-Lactam peptides were envisioned as conformational constraints in antigenic peptides (APs). Three different ß-lactam tripeptides of varying flexibility were prepared in solution and incorporated in place of the central part of the altered melanoma associated antigenic peptide Leu(27)-Melan-A(26-35) using solid phase synthesis techniques. Upon TFA cleavage from the solid support, an unexpected opening of the ß-lactam ring occurred with conservation of the amide bond. After adaptation of the solid phase synthesis strategy, ß-lactam peptides were successfully obtained and both opened and closed forms were evaluated for their capacity to bind to the antigen-presenting class-I MHC HLA-A2 protein system. None of the closed ß-lactam peptides bound to HLA-A2, but their opened variants were shown to be moderate to good HLA-A2 ligands, one of them being even capable of stimulating a Melan-A-specific T cell line.

Crystal structures of HLA-A*0201 complexed with Melan-A/MART-1(26(27L)-35) peptidomimetics reveal conformational heterogeneity and highlight degeneracy of T cell recognition.

There is growing interest in using tumor associated antigens presented by class I major histocompatibility complex (MHC-I) proteins as cancer vaccines. As native peptides are poorly stable in biological fluids, researchers have sought to engineer synthetic peptidomimetics with greater biostability. Here, we demonstrate that antigenic peptidomimetics of the Melan-A/MART-1(26(27L)-35) melanoma antigen adopt strikingly different conformations when bound to MHC-I, highlighting the degeneracy of T cell recognition and revealing the challenges associated with mimicking native peptide conformation.