Ebolavirus delta-peptide immunoadhesins inhibit marburgvirus and ebolavirus cell entry.

With the exception of Reston and Lloviu viruses, filoviruses (marburgviruses, ebolaviruses, and "cuevaviruses") cause severe viral hemorrhagic fevers in humans. Filoviruses use a class I fusion protein, GP(1,2), to bind to an unknown, but shared, cell surface receptor to initiate virus-cell fusion. In addition to GP(1,2), ebolaviruses and cuevaviruses, but not marburgviruses, express two secreted glycoproteins, soluble GP (sGP) and small soluble GP (ssGP). All three glycoproteins have identical N termini that include the receptor-binding region (RBR) but differ in their C termini. We evaluated the effect of the secreted ebolavirus glycoproteins on marburgvirus and ebolavirus cell entry, using Fc-tagged recombinant proteins. Neither sGP-Fc nor ssGP-Fc bound to filovirus-permissive cells or inhibited GP(1,2)-mediated cell entry of pseudotyped retroviruses. Surprisingly, several Fc-tagged Δ-peptides, which are small C-terminal cleavage products of sGP secreted by ebolavirus-infected cells, inhibited entry of retroviruses pseudotyped with Marburg virus GP(1,2), as well as Marburg virus and Ebola virus infection in a dose-dependent manner and at low molarity despite absence of sequence similarity to filovirus RBRs. Fc-tagged Δ-peptides from three ebolaviruses (Ebola virus, Sudan virus, and Taï Forest virus) inhibited GP(1,2)-mediated entry and infection of viruses comparably to or better than the Fc-tagged RBRs, whereas the Δ-peptide-Fc of an ebolavirus nonpathogenic for humans (Reston virus) and that of an ebolavirus with lower lethality for humans (Bundibugyo virus) had little effect. These data indicate that Δ-peptides are functional components of ebolavirus proteomes. They join cathepsins and integrins as novel modulators of filovirus cell entry, might play important roles in pathogenesis, and could be exploited for the synthesis of powerful new antivirals.

The novel tuberculosis vaccine, AERAS-402, induces robust and polyfunctional CD4+ and CD8+ T cells in adults.

RATIONALE: AERAS-402 is a novel tuberculosis vaccine designed to boost immunity primed by bacillus Calmette-Guérin (BCG), the only licensed vaccine. OBJECTIVES: We investigated the safety and immunogenicity of AERAS-402 in healthy Mycobacterium tuberculosis-uninfected BCG-vaccinated adults from a tuberculosis-endemic region of South Africa. METHODS: Escalating doses of AERAS-402 vaccine were administered intramuscularly to each of three groups of healthy South African BCG-vaccinated adults, and a fourth group received two injections of the maximal dose. Participants were monitored for 6 months, with all adverse effects documented. Vaccine-induced CD4(+) and CD8(+) T-cell immunity was characterized by an intracellular cytokine staining assay of whole blood and peripheral blood mononuclear cells. MEASUREMENTS AND MAIN RESULTS: AERAS-402 was well tolerated, and no vaccine-related serious adverse events were recorded. The vaccine induced a robust CD4(+) T-cell response dominated by cells coexpressing IFN-gamma, tumor necrosis factor-alpha, and IL-2 ("polyfunctional" cells). AERAS-402 also induced a potent CD8(+) T-cell response, characterized by cells expressing IFN-gamma and/or tumor necrosis factor-alpha, which persisted for the duration of the study. CONCLUSIONS: Vaccination with AERAS-402 is safe and immunogenic in healthy adults. The immunity induced by the vaccine appears promising: polyfunctional T cells are thought to be important for protection against intracellular pathogens such as Mycobacterium tuberculosis, and evidence is accumulating that CD8(+) T cells are also important. AERAS-402 induced a robust and durable CD8(+) T-cell response, which appears extremely promising. Clinical trial registered with www.sanctr.gov.za (NHREC no. 1381).

Discovery of dipiperidines as new antitubercular agents.

As part of our ongoing research effort to develop new therapeutics for treatment of tuberculosis (TB), we synthesized a combinatorial library of 10,358 compounds on solid support using a pool-and-split technique and tested the resulting compounds for activity against Mycobacteriumtuberculosis. Structure-activity relationship (SAR) evaluation identified new compounds with antitubercular activity, including a novel hit series that is structurally unrelated to any existing antitubercular drugs, dipiperidines. Dipiperidine representatives exhibited MIC values as low as 7.8microM, the ability to induce promoter Rv0341 activated in response to cell wall biosynthesis inhibition, relatively low nonspecific cellular toxicity in the range of 30-162microM, and logP values less than 4.

Identification of new diamine scaffolds with activity against Mycobacterium tuberculosis.

A diverse 5000-compound library was synthesized from commercially available diamines and screened for activity against Mycobacterium tuberculosis in vitro, revealing 143 hits with minimum inhibitory concentration (MIC) equal to or less than 12.5 microM. New prospective scaffolds with antitubercular activity derived from homo-piperazine, phenyl- and benzyl-substituted piperazines, 4-aminomethylpiperidine, 4-aminophenylethylamine, and 4,4'-methylenebiscyclohexylamine were identified. Compound SQ775 derived from homopiperazine and compound SQ786 derived from benzylpiperazine had potent antimicrobial activity against M. tuberculosis in experimental animals in vivo.

A recombinant adenovirus expressing immunodominant TB antigens can significantly enhance BCG-induced human immunity.

BACKGROUND: Despite the availability of Bacille Calmette Guérin (BCG) vaccines, Mycobacterium tuberculosis currently infects billions of people and millions die annually from tuberculosis (TB) disease. New TB vaccines are urgently needed. METHODS: We studied the ability of AERAS-402, a recombinant, replication-deficient adenovirus type 35 expressing the protective M. tuberculosis antigens Ag85A, Ag85B, and TB10.4, to boost BCG immunity in an area of low TB endemicity. RESULTS: In volunteers primed with BCG 3 or 6 months prior to AERAS-402 boosting, significant CD4(+) and CD8(+) T cell responses were induced. Ag85-specific responses were more strongly boosted than TB10.4-specific responses. Frequencies of TB-specific CD8(+) T cells reached>50 fold higher than pre-AERAS boosting levels, remarkably higher than reported in any previous human TB vaccine trial. Multiparameter flow cytometric assays demonstrated that AERAS-402-boosted CD4(+) and CD8(+) T cells were multifunctional, producing multiple cytokines and other immune effector molecules. Furthermore, boosted T cells displayed lymphoproliferative capacity, and tetramer analyses confirmed that antigen-specific CD8(+) T cells were induced. BCG and AERAS-402 vaccinations given 3 and 6 months apart appeared equivalent. CONCLUSIONS: Our results indicate that AERAS-402 is a promising TB vaccine candidate that can significantly enhance both CD4(+) and CD8(+) TB-specific T cell responses after BCG priming. ClinicalTrials.gov Identifier: NCT01378312.