Tetravalent Rabies-Vectored Filovirus and Lassa Fever Vaccine Induces Long-term Immunity in Nonhuman Primates

BACKGROUND

The objective of this study is to evaluate the immunogenicity of adjuvanted monovalent rabies virus (RABV)-based vaccine candidates against Ebola virus (FILORAB1), Sudan virus (FILORAB2), Marburg virus (FILORAB3), Lassa virus (LASSARAB1), and combined trivalent vaccine candidate (FILORAB1-3) and tetravalent vaccine candidate (FILORAB1-3 and LASSARAB) in nonhuman primates.

METHODS

Twenty-four Macaca fascicularis were randomly assigned into 6 groups of 4 animals. Each group was vaccinated with either a single adjuvanted vaccine, the trivalent vaccine, or the tetravalent vaccine at days 0 and 28. We followed the humoral immune responses for 1 year by antigen-specific enzyme-linked immunosorbent assays and RABV neutralization assays.

RESULTS

High titers of filovirus and/or Lassa virus glycoprotein-specific immunoglobulin G were induced in the vaccinated animals. There were no significant differences between immune responses in animals vaccinated with single vaccines vs trivalent or tetravalent vaccines. In addition, all vaccine groups elicited strong rabies neutralizing antibody titers. The antigen-specific immune responses were detectable for 1 year in all groups.

CONCLUSIONS

In summary, this study shows the longevity of the immune responses up to 365 days for a pentavalent vaccine-against Ebola virus, Sudan virus, Marburg virus, Lassa virus, and RABV-using a safe and effective vaccine platform.

Rabies-based vaccine induces potent immune responses against Nipah virus

Nipah Virus (NiV) is a re-emerging zoonotic pathogen in the genus Henipavirus of the Paramyxoviridae family of viruses. NiV is endemic to Bangladesh and Malaysia and is highly fatal to both livestock and humans (human case fatality rate = 74.5%). Currently, there is no approved vaccine against NiV on the market. The goal of this study was to use a recombinant RABV vector expressing NiV glycoprotein (NiV G) to develop a bivalent candidate vaccine against NiV disease and rabies virus (RABV) disease, which is also a significant health burden in the regions where NiV is endemic. The rabies vector is a well-established vaccine strain that lacks neurovirulence and can stably expresses foreign antigens that are immunogenic in various animal models. Mice inoculated intranasally with the live recombinant RABV/NiV vaccine (NIPARAB) showed no signs of disease. To test the immunogenicity of the vaccine candidate, groups of C57BL/6 mice were immunized intramuscularly with a single dose of live vaccine particles or two doses of chemically inactivated viral particles. Both vaccination groups showed NiV G-specific seroconversion, and the inactivated (INAC) vaccine group yielded higher titers of NiV G-specific antibodies. Furthermore, cross-reactivity of NiV G-specific immune sera against Hendra virus (HeV), was confirmed by immunofluorescence (IF) and indirect ELISA against soluble recombinant HeV glycoprotein (HeV G). Both live and killed vaccines induced neutralizing antibodies. These results indicate that NIPARAB may be used as a killed virus vaccine to protect humans against NiV and RABV, and possibly as a preventative measure against HeV as well.

A Recombinant Rabies Virus Expressing the Marburg Virus Glycoprotein Is Dependent upon Antibody-Mediated Cellular Cytotoxicity for Protection against Marburg Virus Disease in a Murine Model

Marburg virus (MARV) is a filovirus related to Ebola virus (EBOV) associated with human hemorrhagic disease. Outbreaks are sporadic and severe, with a reported case mortality rate of upward of 88%. There is currently no antiviral or vaccine available. Given the sporadic nature of outbreaks, vaccines provide the best approach for long-term control of MARV in regions of endemicity. We have developed an inactivated rabies virus-vectored MARV vaccine (FILORAB3) to protect against Marburg virus disease. Immunogenicity studies in our labs have shown that a Th1-biased seroconversion to both rabies virus and MARV glycoproteins (GPs) is beneficial for protection in a preclinical murine model. As such, we adjuvanted FILORAB3 with glucopyranosyl lipid adjuvant (GLA), a Toll-like receptor 4 agonist, in a squalene-in-water emulsion. Across two different BALB/c mouse challenge models, we achieved 92% protection against murine-adapted Marburg virus (ma-MARV). Although our vaccine elicited strong MARV GP antibodies, it did not strongly induce neutralizing antibodies. Through both in vitro and in vivo approaches, we elucidated a critical role for NK cell-dependent antibody-mediated cellular cytotoxicity (ADCC) in vaccine-induced protection. Overall, these findings demonstrate that FILORAB3 is a promising vaccine candidate for Marburg virus disease.IMPORTANCE Marburg virus (MARV) is a virus similar to Ebola virus and also causes a hemorrhagic disease which is highly lethal. In contrast to EBOV, only a few vaccines have been developed against MARV, and researchers do not understand what kind of immune responses are required to protect from MARV. Here we show that antibodies directed against MARV after application of our vaccine protect in an animal system but fail to neutralize the virus in a widely used virus neutralization assay against MARV. This newly discovered activity needs to be considered more when analyzing MARV vaccines or infections.

Toward an Effective Ebola Virus Vaccine

Long-term control of viral outbreaks requires the use of vaccines to impart acquired resistance and ensuing protection. In the wake of an epidemic, established immunity against a particular disease can limit spread and significantly decrease mortality. Creation of a safe and efficacious vaccine against Ebola virus (EBOV) has proven elusive so far, but various inventive strategies are now being employed to counteract the threat of outbreaks caused by EBOV and related filoviruses. Here, we present a current overview of progress in the field of Ebola virus vaccine development.

An Inactivated Rabies Virus-Based Ebola Vaccine, FILORAB1, Adjuvanted With Glucopyranosyl Lipid A in Stable Emulsion Confers Complete Protection in Nonhuman Primate Challenge Models

The 2013-2016 West African Ebola virus (EBOV) disease outbreak was the largest filovirus outbreak to date. Over 28 000 suspected, probable, or confirmed cases have been reported, with a 53% case-fatality rate. The magnitude and international impact of this EBOV outbreak has highlighted the urgent need for a safe and efficient EBOV vaccine. To this end, we demonstrate the immunogenicity and protective efficacy of FILORAB1, a recombinant, bivalent, inactivated rabies virus-based EBOV vaccine, in rhesus and cynomolgus monkeys. Our results demonstrate that the use of the synthetic Toll-like receptor 4 agonist glucopyranosyl lipid A in stable emulsion (GLA-SE) as an adjuvant increased the efficacy of FILORAB1 to 100% protection against lethal EBOV challenge, with no to mild clinical signs of disease. Furthermore, all vaccinated subjects developed protective anti-rabies virus antibody titers. Taken together, these results support further development of FILORAB1/GLA-SE as an effective preexposure EBOV vaccine.

Preclinical Development of Inactivated Rabies Virus-Based Polyvalent Vaccine Against Rabies and Filoviruses

We previously described the generation of a novel Ebola virus (EBOV) vaccine based on inactivated rabies virus (RABV) containing EBOV glycoprotein (GP) incorporated in the RABV virion. Our results demonstrated safety, immunogenicity, and protective efficacy in mice and nonhuman primates (NHPs). Protection against viral challenge depended largely on the quality of the humoral immune response against EBOV GP.Here we present the extension and improvement of this vaccine by increasing the amount of GP incorporation into virions via GP codon-optimization as well as the addition of Sudan virus (SUDV) and Marburg virus (MARV) GP containing virions. Immunogenicity studies in mice indicate similar immune responses for both SUDV GP and MARV GP compared to EBOV GP. Immunizing mice with multiple antigens resulted in immune responses similar to immunization with a single antigen. Moreover, immunization of NHP with the new inactivated RABV EBOV vaccine resulted in high titer neutralizing antibody levels and 100% protection against lethal EBOV challenge when applied with adjuvant.Our results indicate that an inactivated polyvalent vaccine against RABV filoviruses is achievable. Finally, the novel vaccines are produced on approved VERO cells and a clinical grade RABV/EBOV vaccine for human trials has been produced.

Abstract 656: Discovery of MAbs against difficult GPCRs, ion channels, and transporters using the MPS Discovery Engine®

Integral membrane proteins are important drug targets and monoclonal antibodies (MAbs) directed against them are highly sought for therapeutic purposes. However, the complex structure of membrane protein targets makes the discovery of these MAbs especially challenging. To address this need, we have developed the MPS Discovery Engine® to enable the isolation, characterization, and engineering of monoclonal antibodies for challenging membrane protein targets, including GPCRs, ion channels, and transporters. MPS harnesses the strength of Integral's 10+ years of expertise in membrane protein expression and analysis, as well as proprietary technologies including Lipoparticles for high concentration membrane protein presentation and Shotgun Mutagenesis for comprehensive epitope mapping and MAb optimization. Integral Molecular currently has a pipeline of several dozen MAbs against complex membrane proteins that are involved in a variety of diseases, including cancer, inflammation, pain, and infectious diseases. There are currently no FDA-approved MAbs that target GPCRs, ion channels, or transporters, and MPS provides a pathway to these new and previously intractable targets.

Citation Format: Sharon H. Willis, Kimberly Mattia, Riley Payne, Moniquetta Hall, Manu Mabila, Christine Rettew, Joseph Couto, Rohan Keshwara, Cheryl Paes, Benjamin J. Doranz, Joseph Rucker. Discovery of MAbs against difficult GPCRs, ion channels, and transporters using the MPS Discovery Engine®. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 656. doi:10.1158/1538-7445.AM2015-656