Christian Sergheraert

Methylation-dependent T cell immunity to Mycobacterium tuberculosis heparin-binding hemagglutinin

Although post-translational modifications of protein antigens may be important componenets of some B cell epitopes, the determinants of T cell immunity are generally nonmodified peptides. Here we show that methylation of the Mycobacterium tuberculosis heparin-binding hemagglutinin (HBHA) by the bacterium is essential for effective T cell immunity to this antigen in infected healthy humans and in mice. Methylated HBHA provides high levels of protection against M. tuberculosis challenge in mice, whereas nonmethylated HBHA does not. Protective immunity induced by methylated HBHA is comparable to that afforded by vaccination with bacille Calmette et Guérin, the only available anti-tuberculosis vaccine. Thus, post-translational modifications of proteins may be crucial for their ability to induce protective T cell-mediated immunity against infectious diseases such as tuberculosis.

Comparative efficiency of simple lipopeptide constructs for in vivo induction of virus-specific CTL

We have previously shown that virus-specific CTL responses can be elicited in vivo by injecting, without adjuvant, 12-40 amino acid-long peptides, modified in C-terminal position by a simple lipidic amino acid. In this paper, we have studied the chemical accessibility, and the ability to induce in mice a CTL response, of a series of lipopeptides derived from the HIV-1 env (312-327) or (302-335) sequences. We showed that a single modification of these peptides by a lipidic amino acid, preferably in C-terminal position, results in the ability to reproducibly induce, without adjuvant, a relevant CTL response. No clear discrimination appeared concerning the nature of the lipidic modification. Our findings indicate that modification of a relatively long peptide by a N epsilon-palmitoyl-L-Lysylamide can be achieved by conventional methods of synthesis and characterization, offering the possibility to develop low-cost synthetic vaccines in models in which the CTL component is of importance.

Design, synthesis and antimalarial activity of novel, quinoline-Based, zinc metallo-aminopeptidase inhibitors

PfA-M1, a neutral zinc aminopeptidase of Plasmodium falciparum, is a new potential target for the discovery of antimalarials. The design and synthesis of a library of 45 quinoline-based inhibitors of PfA-M1 is reported. The best inhibitor displays an IC(50) of 854 nM. The antimalarial activity on a CQ-resistant strain and the specificity towards mammalian aminopeptidase N are also discussed.

Trypanothione reductase inhibition/trypanocidal activity relationships in a 1,4-bis(3-aminopropyl)piperazine series

A series of symmetrically substituted 1,4-bis(3-aminopropyl)piperazines was synthesized and tested towards trypanothione reductase and for its in vitro trypanocidal potency. The most trypanocidal amongst them was found to be totally inactive towards the enzyme and thus constitutes a lead structure for the identification of new potential Trypanosoma cruzi target(s).

Parallel synthesis and anti-malarial activity of a sulfonamide library.

Solution-phase synthesis and evaluation of a library of 31 sulfonamides as inhibitors of a chloroquine-resistant strain of Plasmodium falciparum are described. The most potent compound displayed an activity 100-fold better than chloroquine. Experiments using a fluorescent sulfonamide derivative suggest that their site of action inside the parasite is different to that of chloroquine.

Potent and specific inhibitors of trypanothione reductase from Trypanosoma cruzi: bis(2-aminodiphenylsulfides) for fluorescent labeling studies

In order to optimise the activity of bis(2-aminodiphenylsulfides) upon trypanothione reductase (TR) from Trypanosoma cruzi, a new series of bis(2-aminodiphenylsulfides) possessing three side chains was synthesized. Various moieties were introduced at the end of the third side chain, including acridinyl or biotinyl moieties for fluorescent labeling studies. TR inhibition was improved: the most potent inhibitor (IC50 = 200 nM) was selective towards TR versus human glutathione reductase and corresponded to a single myristyl group. Compounds were also tested in vitro upon Trypanosoma cruzi and Leishmania infantum amastigotes, upon-Trapanosoma brucei trypomastigotes, and for their cytotoxicity upon human MRC-5 cells. In the presence of serum, acridine derivative was no longer detectable in mass spectrometry and its antitrypanosomal activity no longer observed. This transformation might explain the absence of correlation between the potent TR inhibition and the in vitro and in vivo antiparasitic activity with both of the first generation of 2-aminodiphenylsulfides.

Cloning of Plasmodium falciparum protein disulfide isomerase homologue by affinity purification using the antiplasmodial inhibitor 1,4-bis{3-[N-(cyclohexyl methyl)amino]propyl}piperazine 1

A series of 10 1,4‐bis(3‐aminopropyl)piperazine compounds was found to display antiplasmodial activity with 50% growth inhibition between 30 and 250 nM, on three Plasmodium falciparum strains differently sensitive to chloroquine. By affinity chromatography using one of these compounds, a 52‐kDa protein was isolated from P. falciparum, microsequenced and cloned. It corresponded to a single copy gene encoding a 453 amino acid protein displaying the typical features of protein disulfide isomerases, a thiol metabolizing enzyme belonging to the thiol: disulfide oxidoreductase superfamily, which was not previously described in malarial species.

Comparison of the Inhibition of Human and Trypanosoma cruzi Prolyl Endopeptidases

Prolyl endopeptidases (PEPs) have been found in numerous species. Inhibitors of human enzyme could correct cognitive deficits in Alzheimer patients while inhibition of Trypanosoma cruzi PEP could prevent invasion phase in Chagas disease. A structure-activity relationship study carried out in a tetrahydroisoquinoline series allowed to obtain potent competitive inhibitors superior to SUAM-1221. Besides, inhibitors expected to act according to an irreversible mechanism revealed to be superior to JPT-4819, for applications linked to human enzyme inhibition.

Antimalarial in-vivo activity of bis(9-amino-6-chloro-2-methoxyacridines)

In the fight against malaria, chemotherapy using bisacridines may represent an alternative method to overcoming chloroquine‐resistance. Eight bis(9‐amino‐6‐chloro‐2‐methoxyacri‐dines), in which acridine moieties were linked by polyamines substituted with a side chain, were tested for their in‐vivo activity upon mice infected by Plasmodium berghei. Three of the compounds revealed antimalarial activity but no relationship could be deduced from a comparison of in‐vitro and in‐vivo activities. N‐alkylation of the central amino group generated toxicity and, therefore, only compounds N‐acylated in this position can be selected as leads.

Synthesis and antimalarial activity of carbamate and amide derivatives of 4-anilinoquinoline

A series of 4-anilinoquinolines bearing an amino side chain linked to the aromatic ring with a carbamate or an amide bond were synthesized and evaluated for their antimalarial activity and their cytotoxicity upon MRC-5 cells. Among the 17 compounds, a majority was found to be active in the low nanomolar range against both chloroquine-sensitive and -resistant strains of Plasmodium falciparum in vitro with relative low cytotoxicity. Two compounds were then tested on mice infected by Plasmodium berghei and were found to exhibit reasonable in vivo activity.