Assessing the safety and immunogenicity of recombinant vesicular stomatitis virus Ebola vaccine in healthy adults: a randomized clinical trial.

BACKGROUND: The 2013-2016 Ebola virus outbreak in West Africa was the most widespread in history. In response, alive attenuated recombinant vesicular stomatitis virus (rVSV) vaccine expressing Zaire Ebolavirus glycoprotein (rVSVΔG-ZEBOV-GP) was evaluated in humans. METHODS: In a phase 1, randomized, dose-ranging, observer-blind, placebo-controlled trial, healthy adults aged 18-65 years were randomized into 4 groups of 10 to receive one of 3 vaccine doses or placebo. Follow-up visits spanned 180 days postvaccination for safety monitoring, immunogenicity testing and any rVSV virus shedding. RESULTS: Forty participants were injected with rVSVΔG-ZEBOV-GP vaccine (n = 30) or saline placebo (n = 10). No serious adverse events related to the vaccine or participant withdrawals were reported. Solicited adverse events during the 14-day follow-up period were mild to moderate and self-limited, with the exception of injection-site pain and headache. Viremia following vaccination was transient and no longer detectable after study day 3, with no virus shedding in saliva or urine. All vaccinated participants developed serum immunoglobulin G (IgG), as measured by Ebola virus envelope glycoprotein-based enzyme-linked immunosorbent assay (ELISA). Immunogenicity was comparable across all dose groups, and sustained IgG titers were detectable through to the last visit, at study day 180. INTERPRETATION: In this phase 1 study, there were no safety concerns after a single dose of rVSVΔG-ZEBOV-GP vaccine. IgG ELISA showed persistent high titers at 180 days postimmunization. There was a period of reactogenicity, but in general, the vaccine was well tolerated. This study provides evidence of the safety and immunogenicity of rVSVΔG-ZEBOV-GP vaccine and importance of its further investigation. Trial registration: Clinical-Trials.gov no., NCT02374385.

Safety and Immunogenicity of an Accelerated Ebola Vaccination Schedule in People with and without Human Immunodeficiency Virus: A Randomized Clinical Trial.

The safety and immunogenicity of the two-dose Ebola vaccine regimen MVA-BN-Filo, Ad26.ZEBOV, 14 days apart, was evaluated in people without HIV (PWOH) and living with HIV (PLWH). In this observer-blind, placebo-controlled, phase 2 trial, healthy adults were randomized (4:1) to receive MVA-BN-Filo (dose 1) and Ad26.ZEBOV (dose 2), or two doses of saline/placebo, administered intramuscularly 14 days apart. The primary endpoints were safety (adverse events (AEs)) and immunogenicity (Ebola virus (EBOV) glycoprotein-specific binding antibody responses). Among 75 participants (n = 50 PWOH; n = 25 PLWH), 37% were female, the mean age was 44 years, and 56% were Black/African American. AEs were generally mild/moderate, with no vaccine-related serious AEs. At 21 days post-dose 2, EBOV glycoprotein-specific binding antibody responder rates were 100% among PWOH and 95% among PLWH; geometric mean antibody concentrations were 6286 EU/mL (n = 36) and 2005 EU/mL (n = 19), respectively. A total of 45 neutralizing and other functional antibody responses were frequently observed. Ebola-specific CD4+ and CD8+ T-cell responses were polyfunctional and durable to at least 12 months post-dose 2. The regimen was well tolerated and generated robust, durable immune responses in PWOH and PLWH. Findings support continued evaluation of accelerated vaccine schedules for rapid deployment in populations at immediate risk. Trial registration: NCT02598388 (submitted 14 November 2015).

Anti-AIDS agents 73: structure-activity relationship study and asymmetric synthesis of 3-O-monomethylsuccinyl-betulinic acid derivatives.

3-O-3'(or 2')-Methylsuccinyl-betulinic acid (MSB) derivatives were separated by using recycle HPLC. The structures of four isomers were assigned by NMR and asymmetric synthesis. 3-O-3'S-Methylsuccinyl-betulinic acid (3'S-MSB, 4) exhibited potent anti-HIV activity with an EC(50) value of 0.0087microM and a TI value of 6.3x10(3), which is comparable to the data for bevirimat (DSB, PA-457), a current clinical trials drug that was also derived from betulinic acid. The anti-HIV potency of 4 was slightly better than that of AZT.

Challenges, progress, and opportunities: proceedings of the filovirus medical countermeasures workshop.

On August 22-23, 2013, agencies within the United States Department of Defense (DoD) and the Department of Health and Human Services (HHS) sponsored the Filovirus Medical Countermeasures (MCMs) Workshop as an extension of the activities of the Filovirus Animal Non-clinical Group (FANG). The FANG is a federally-recognized multi-Agency group established in 2011 to coordinate and facilitate U.S. government (USG) efforts to develop filovirus MCMs. The workshop brought together government, academic and industry experts to consider the needs for filovirus MCMs and evaluate the status of the product development pipeline. This report summarizes speaker presentations and highlights progress and challenges remaining in the field.

An interagency collaboration to facilitate development of filovirus medical countermeasures.

The Filovirus Animal Non-Clinical Group (FANG) is a US interdepartmental and interagency group established to support and facilitate the advanced development of filovirus Medical Countermeasures (MCM), both vaccines and therapeutics. It is co-led by one representative from the Department of Defense (DoD), the first author, and one from the Department of Health and Human Services (HHS), the second author. The FANG membership includes operational level program staff and Subject Matter Experts (SME) from performing organizations as well as scientific staff and program managers from DoD and HHS funding and regulatory agencies. Focus areas include animal models, assays, reagents, product manufacture and characterization, and other interagency product development issues that will support Food and Drug Administration (FDA) licensure of safe and effective filovirus MCMs. The FANG continues to develop strategies to address broadly applicable and interagency product development challenges relevant to filovirus MCM development. This paper summarizes FANG structure and accomplishments and is meant to heighten community awareness of this government-led collaborative effort.

Elevated temperature triggers human respiratory syncytial virus F protein six-helix bundle formation.

Human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infection in infants, immunocompromised patients, and the elderly. The RSV fusion (F) protein mediates fusion of the viral envelope with the target cell membrane during virus entry and is a primary target for antiviral drug and vaccine development. The F protein contains two heptad repeat regions, HR1 and HR2. Peptides corresponding to these regions form a six-helix bundle structure that is thought to play a critical role in membrane fusion. However, characterization of six-helix bundle formation in native RSV F protein has been hindered by the fact that a trigger for F protein conformational change has yet to be identified. Here we demonstrate that RSV F protein on the surface of infected cells undergoes a conformational change following exposure to elevated temperature, resulting in the formation of the six-helix bundle structure. We first generated and characterized six-helix bundle-specific antibodies raised against recombinant peptides modeling the RSV F protein six-helix bundle structure. We then used these antibodies as probes to monitor RSV F protein six-helix bundle formation in response to a diverse array of potential triggers of conformational changes. We found that exposure of 'membrane-anchored' RSV F protein to elevated temperature (45-55 degrees C) was sufficient to trigger six-helix bundle formation. Antibody binding to the six-helix bundle conformation was detected by both flow cytometry and cell-surface immunoprecipitation of the RSV F protein. None of the other treatments, including interaction with a number of potential receptors, resulted in significant binding by six-helix bundle-specific antibodies. We conclude that native, untriggered RSV F protein exists in a metastable state that can be converted in vitro to the more stable, fusogenic six-helix bundle conformation by an increase in thermal energy. These findings help to better define the mechanism of RSV F-mediated membrane fusion and have important implications for the identification of therapeutic strategies and vaccines targeting RSV F protein conformational changes.

Anti-AIDS agents 72. Bioisosteres (7-carbon-DCKs) of the potent anti-HIV lead DCK.

Three 9,10-di-O-(-)-camphanoyl-7,8,9,10-tetrahydro-benzo[h]chromen-2-one (7-carbon-DCK) analogs (3a-c) were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. All three new carbon bioisosteres of the anti-HIV lead DCK showed anti-HIV activity. Compound 3a had an EC(50) value of 0.068 microM, which was comparable to that of DCK in the same assay. The preliminary results indicated that 7-carbon-DCK analogs merit attention as potential HIV-1 inhibitors for further development into clinical trials candidates.

Rubrisandrins A and B, lignans and related anti-HIV compounds from Schisandra rubriflora.

Bioactivity-directed fractionation of an ethanolic extract of the fruits of Schisandra rubriflora led to the isolation and identification of dibenzocyclooctadiene lignans including the new lignans rubrisandrins A (1a + 1b) and B (2) and the known lignans gomisin J (3), (+/-)-gomisin M1 (4), (+)-gomisin M2 (5), schisanhenol (6), deoxyschisandrin, schisantherin B, schisandrin, tigloylgomisin P, gomisin O, angeloylgomisin P, and epigomisin O. Their structure and stereochemistry were determined by spectroscopic methods, including 2D-NMR techniques. Compounds 1 and 3-6 were active as anti-HIV agents. (+/-)-Gomisin M1 (4) exhibited the most potent anti-HIV activity, with EC50 and therapeutic index (TI) values of <0.65 microM and >68, respectively.

Determinants of activity of the HIV-1 maturation inhibitor PA-457.

3-O-(3',3'-dimethylsuccinyl) betulinic acid, also termed PA-457 or DSB, is a novel HIV-1 inhibitor that blocks virus maturation by disrupting cleavage of the capsid precursor, CA-SP1. To better define the molecular target for PA-457, we prepared a panel of mutant viruses with point deletions spanning the CA-SP1 cleavage domain and characterized each of these viruses for PA-457 sensitivity. Our results indicate that amino acid residues in the N-terminal half of SP1 serve as determinants of PA-457 activity, while residues in the C-terminal half of SP1 were not involved in compound activity. These findings support and extend previous observations that PA-457 is a specific inhibitor of CA-SP1 cleavage and identify the CA-SP1 domain as the primary viral determinant for this novel inhibitor of HIV-1 replication.

Direct evidence that C-peptide inhibitors of human immunodeficiency virus type 1 entry bind to the gp41 N-helical domain in receptor-activated viral envelope.

While it has been established that peptides modeling the C-helical region of human immunodeficiency virus type 1 gp41 are potent in vivo inhibitors of virus replication, their mechanism of action has yet to be determined. It has been proposed, but never directly demonstrated, that these peptides block virus entry by interacting with gp41 to disrupt the formation or function of a six-helix bundle structure. Using a six-helix bundle-specific monoclonal antibody with isolate-restricted Env reactivity, we provide the first direct evidence that, in receptor-activated viral Env, C-peptide entry inhibitors bind to the gp41 N-helical coiled-coil to form a peptide/protein hybrid structure and, in doing so, disrupt native six-helix bundle formation.

Anti-HIV agents. Part 55: 3'R,4'R-Di-(O)-(-)-camphanoyl-2',2'-dimethyldihydropyrano[2,3-f]chromone (DCP), a novel anti-HIV agent.

3'R,4'R-Di-O-(-)-camphanoyl-2',2'-dimethyldihydropyrano[2,3-f]chromone (DCP) (2) was designed and synthesized on the basis of a structure-activity relationship study of 3'R,4'R-di-O-(-)-camphanoyl-(+)-cis-khellactone DCK (1) and its analogues. DCP (2), a pyranochromone, and DCK (1), a pyranocoumarin, have different skeletons. Compound 2 showed potent in vitro inhibition of HIV-1 replication in H9 lymphocyte cells with an EC(50) of 6.78 x 10(-4) microM and TI of 14,500. These values are comparable with those for DCK (1) and better than those of AZT in the same assay.

Anti-HIV agents derived from the ent-kaurane diterpenoid linearol.

Twenty-six semisynthetic ent-kaurane derivatives of linearol (1) have been investigated for their anti-HIV effects. Five compounds (4, 7, 11, 25, and 26) showed significant activity against HIV replication in H9 lymphocyte cells with EC(50) values in the range <0.1-3.11 microg/mL. With TI values of 163 and 184, compounds 4 and 25 are especially promising for further development as potential anti-HIV agents.

Anti-AIDS agents. Part 56: Synthesis and anti-HIV activity of 7-thia-di-O-(-)-camphanoyl-(+)-cis-khellactone (7-thia-DCK) analogs.

Two thia-DCK analogs (3a,b) were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. Compound 3a showed potent anti-HIV activity with an EC50 value of 0.14 microM and a therapeutic index of 1110. However, the corresponding 6-tert-butyl-substituted compound (3b) showed no suppression. The bioassay results indicated that thia-DCK analogs merit attention as potential HIV-1 inhibitors.

3-O-Glutaryl-dihydrobetulin and related monoacyl derivatives as potent anti-HIV agents.

3-O-Acyl-betulin and -dihydrobetulin derivatives were prepared and evaluated for anti-HIV activity. 3-O-Glutaryl-dihydrobetulin (17) demonstrated extremely potent anti-HIV activity with an EC(50) value of 2 x 10(-5) microM and a TI value of 1.12 x 10(6). 3-O-(3',3'-Dimethylsuccinyl)- and 3-O-(3',3'-dimethylglutaryl)-dihydrobetulins (15, 16) were also potent anti-HIV compounds with EC(50) values of 0.0017 and 0.0013 microM, respectively, and TI values of 16,160 and 19,530, respectively.

Anti-AIDS agents. Part 58: synthesis and anti-HIV activity of 1-thia-di-O-(-)-camphanoyl-(+)-cis-khellactone (1-thia-DCK) analogues.

Two 1-thia-DCK analogues (9a and 9b) were synthesized and evaluated for inhibition of HIV-1 replication in H9 lymphocytes. Compound 9a showed excellent anti-HIV activity with an EC(50) value of 0.00012 microM and therapeutic index of 1408000. Compound 9b was less active with EC(50) and TI values of 3.11 microM and 62.3, respectively. The bioassay results indicated that thia-DCK analogues merit attention as potential HIV-1 inhibitors.