The Development of a Rabies Virus-Vectored Vaccine against Borrelia burgdorferi, Targeting BBI39.

Lyme disease (LD) is the most common tick-borne illness in the United States (U.S.), Europe, and Asia. Borrelia burgdorferi, a spirochete bacterium transmitted by the tick vector Ixodes scapularis, causes LD in the U.S. If untreated, Lyme arthritis, heart block, and meningitis can occur. Given the absence of a human Lyme disease vaccine, we developed a vaccine using the rabies virus (RABV) vaccine vector BNSP333 and an outer surface borrelial protein, BBI39. BBI39 was previously utilized as a recombinant protein vaccine and was protective in challenge experiments; therefore, we decided to utilize this protective antigen in a rabies virus-vectored vaccine against Borrelia burgdorferi. To incorporate BBI39 into the RABV virion, we generated a chimeric BBI39 antigen, BBI39RVG, by fusing BBI39 with the final amino acids of the RABV glycoprotein by molecular cloning and viral recovery with reverse transcription genetics. Here, we have demonstrated that the BBI39RVG antigen was incorporated into the RABV virion via immunofluorescence and Western blot analysis. Mice vaccinated with our BPL inactivated RABV-BBI39RVG (BNSP333-BBI39RVG) vaccine induced high amounts of BBI39-specific antibodies, which were maintained long-term, up to eight months post-vaccination. The BBI39 antibodies neutralized Borrelia in vaccinated mice when challenged with Borrelia burgdorferi by either syringe injection or infected ticks and they reduced the Lyme disease pathology of arthritis in infected mouse joints. Overall, the RABV-based LD vaccine induced more and longer-term antibodies compared to the recombinant protein vaccine. This resulted in lower borrelial RNA in RABV-based vaccinated mice compared to recombinant protein vaccinated mice. The results of this study indicate the successful use of BBI39 as a vaccine antigen and RABV as a vaccine vector for LD.

Sequential Combination of a Strong Interferon Inducer Viral Vector With Low Doses of Nivolumab Plus Ipilimumab Could Provide Functional Cure in Chronic Hepatitis B Virus infections: Technical Report Proposing a New Modality.

Based on the recommendation of the International Coalition to Eliminate hepatitis B virus (ICE-HBV), we intend to mimic the spontaneous resolution of HBV infection to achieve a functional cure of chronic hepatitis B virus (HBV) infection. To this end, we propose sequential targeting of the innate and adaptive host immune responses. Long-term suppression of HBV replication and hepatitis B surface antigen (HbsAg) production will be achieved first by inducing a strong innate immune response. The clinically validated viral superinfection therapy (SIT) will be administered, which employs an attenuated, non-lytic, double-stranded RNA (dsRNA) infectious bursal disease virus (IBDV) that provides an exceptionally strong interferon (IFN) response. Then, the exhausted HBV-specific T cell function will be restored by blocking the cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) and programmed cell death protein 1 (PD-1) receptors with immune checkpoint inhibitors (ICIs). In order to minimize any risk of toxicity, off-label low doses of nivolumab (0.5 mg/kg) plus ipilimumab (0.3 mg/kg) will be administered, the safety and efficacy of which has already been demonstrated in 131 unselected stage IV cancer patients. We predict that this combination therapy will provide sustained off-treatment virological and clinical responses during a relatively short treatment period.

Inclusion of cGAMP within virus-like particle vaccines enhances their immunogenicity.

Cyclic GMP-AMP (cGAMP) is an immunostimulatory molecule produced by cGAS that activates STING. cGAMP is an adjuvant when administered alongside antigens. cGAMP is also incorporated into enveloped virus particles during budding. Here, we investigate whether inclusion of cGAMP within viral vaccine vectors enhances their immunogenicity. We immunise mice with virus-like particles (VLPs) containing HIV-1 Gag and the vesicular stomatitis virus envelope glycoprotein G (VSV-G). cGAMP loading of VLPs augments CD4 and CD8 T-cell responses. It also increases VLP- and VSV-G-specific antibody titres in a STING-dependent manner and enhances virus neutralisation, accompanied by increased numbers of T follicular helper cells. Vaccination with cGAMP-loaded VLPs containing haemagglutinin induces high titres of influenza A virus neutralising antibodies and confers protection upon virus challenge. This requires cGAMP inclusion within VLPs and is achieved at markedly reduced cGAMP doses. Similarly, cGAMP loading of VLPs containing the SARS-CoV-2 Spike protein enhances Spike-specific antibody titres. cGAMP-loaded VLPs are thus an attractive platform for vaccination.

Mechanisms of Innate Immune Activation by a Hybrid Alphavirus-Rhabdovirus Vaccine Platform.

Virus-like vesicles (VLV) are infectious, self-propagating alphavirus-vesiculovirus hybrid vaccine vectors that can be engineered to express foreign antigens to elicit a protective immune response. VLV are highly immunogenic and nonpathogenic in vivo, and we hypothesize that the unique replication and structural characteristics of VLV efficiently induce an innate antiviral response that enhances immunogenicity and limits replication and spread of the vector. We found that VLV replication is inhibited by interferon (IFN)-α, IFN-γ, and IFN-λ, but not by tumor necrosis factor-α. In cell culture, VLV infection activated IFN production and expression of IFN-stimulated genes (ISGs), such as MXA, ISG15, and IFI27, which were dependent on replication of the evolved VLV-encoded Semliki Forest virus replicon. Knockdown of the pattern recognition receptors, retinoic acid-inducible gene I and melanoma differentiation-associated protein 5 or their intermediary signaling protein mitochondrial antiviral-signaling protein (MAVS) blocked IFN production. Furthermore, ISG expression in VLV-infected cells was dependent on IFN receptor signaling through the Janus kinase (JAK) tyrosine kinases and phosphorylation of the STAT1 protein, and JAK inhibition restored VLV replication in otherwise uninfectable cell lines. This work provides new insight into the mechanism of innate antiviral responses to a hybrid virus-based vector and provides the basis for future characterization of the platform's safety and adjuvant-like effects in vivo. [Figure: see text].

Induction of Tier 1 HIV Neutralizing Antibodies by Envelope Trimers Incorporated into a Replication Competent Vesicular Stomatitis Virus Vector.

A chimeric vesicular stomatitis virus with the glycoprotein of the lymphocytic choriomeningitis virus, VSV-GP, is a potent viral vaccine vector that overcomes several of the limitations of wild-type VSV. Here, we evaluated the potential of VSV-GP as an HIV vaccine vector. We introduced genes for different variants of the HIV-1 envelope protein Env, i.e., secreted or membrane-anchored, intact or mutated furin cleavage site or different C-termini, into the genome of VSV-GP. We found that the addition of the Env antigen did not attenuate VSV-GP replication. All HIV-1 Env variants were expressed in VSV-GP infected cells and some were incorporated very efficiently into VSV-GP particles. Crucial epitopes for binding of broadly neutralizing antibodies against HIV-1 such as MPER (membrane-proximal external region), CD4 binding site, V1V2 and V3 loop were present on the surface of VSV-GP-Env particles. Binding of quaternary antibodies indicated a trimeric structure of VSV-GP incorporated Env. We detected high HIV-1 antibody titers in mice and showed that vectors expressing membrane-anchored Env elicited higher antibody titers than vectors that secreted Envs. In rabbits, Tier 1A HIV-1 neutralizing antibodies were detectable after prime immunization and titers further increased after boosting with a second immunization. Taken together, VSV-GP-Env is a promising vector vaccine against HIV-1 infection since this vector permits incorporation of native monomeric and/or trimeric HIV-1 Env into a viral membrane.

New developments in rabies vaccination.

Current rabies vaccines are safe and, when administered properly, they are highly effective. In addition, they elicit long-lasting immunity, with virus-neutralising antibody titres persisting for years after vaccination. However, current regimens require multiple doses to achieve high neutralising titres and they are costly, which means that it is difficult for developing countries, where rabies deaths are highest, to implement widespread vaccination. New innovations are the only way to reduce rabies disease to acceptable rates. Numerous preclinical and clinical studies are under way, testing novel vaccines, adjuvants and injection methods. Research into the use of live vaccines and alternative vaccine vectors is ongoing, while attempts to develop DNA vaccines have so far failed to match the immunogenicity and neutralising capability of traditional vaccines. The development of molecular adjuvants that induce faster, stronger immune responses with less antigen has yielded exciting preclinical results and appears to edge us closer to a better rabies vaccine. However, steep challenges remain: molecular adjuvants require administration with live vaccines, and differences in species specificity of immune molecules complicate development. Over all, the array of research undertaken over the past decade is impressive and encouraging, but most new vaccines have yet to be tested in clinical trials, and the viability of such experimental vaccines in the global market remains to be seen. Only a vaccine that outperforms currently available vaccines in every area will have a chance at widespread adoption. Nevertheless, the authors are confident that some vaccine candidates will meet these criteria.

Les vaccins actuels contre la rage sont sûrs et très efficaces lorsqu'ils sont administrés correctement. En outre, ils confèrent une immunité durable, avec le maintien de titres neutralisants d'anticorps plusieurs années après la vaccination. Néanmoins, les régimes actuels nécessitent l'administration de plusieurs doses pour obtenir des titres élevés d'anticorps neutralisants et ils sont onéreux, de sorte que la vaccination à grande échelle est difficile à mettre en oeuvre dans les pays en développement, pourtant les plus touchés par la mortalité par rage. Seule l'adoption de solutions innovantes permettra de ramener l'incidence de la rage à un niveau acceptable. De nombreuses études précliniques et cliniques sont en cours, visant à tester les innovations en matière de vaccins, de modes d'injection et d'adjuvants. La recherche sur l'utilisation de vaccins à virus vivant et sur de nouveaux vecteurs vaccinaux se poursuit, alors que les tentatives de développement de vaccins à ADN n'ont pas réussi jusqu'à présent à obtenir un effet immunogène ou des capacités de neutralisation virale équivalents à ceux des vaccins traditionnels. Les résultats d'essais précliniques sur de nouveaux adjuvants moléculaires induisant une réponse immune plus rapide et plus puissante avec moins d'antigène sont extrêmement prometteurs et semblent annoncer l'imminence de meilleurs vaccins contre la rage. Il subsiste toutefois d'importantes difficultés : les adjuvants moléculaires ne peuvent être administrés qu'avec des vaccins vivants et les différences de spécificité d'espèce des molécules immunes rendent le développement plus complexe. Globalement, les efforts déployés depuis une décennie par la recherche sont impressionnants et encourageants mais la plupart des nouveaux vaccins doivent encore être soumis à des essais cliniques ; d'autre part la viabilité de ces vaccins expérimentaux dans le marché mondial reste à démontrer. Seul un vaccin capable de surpasser les performances des vaccins actuels dans chaque domaine aura une chance d'être largement adopté. Les auteurs estiment cependant que certains vaccins candidats pourront satisfaire à ces exigences.

Las actuales vacunas antirrábicas son seguras y, si se administran debidamente, muy eficaces. Además, inducen inmunidad duradera, con títulos de anticuerpos neutralizantes que subsisten años después de la vacunación. Sin embargo, los regímenes actuales resultan costosos y exigen dosis múltiples para lograr títulos de neutralización elevados, lo que dificulta a los países en desarrollo, que son los más golpeados por la rabia, la implantación generalizada de la vacunación. El único camino para reducir la rabia a niveles aceptables pasa por la innovación. Están en marcha numerosos estudios preclínicos y clínicos en los que se ensayan vacunas, adyuvantes y métodos de inyección novedosos. También sigue adelante la investigación sobre el uso de vacunas vivas y vectores vacunales alternativos, mientras que ninguna de las tentativas realizadas hasta la fecha con vacunas de ADN ha deparado niveles de inmunogenicidad y capacidad de neutralización equiparables a los de las vacunas tradicionales. La obtención de adyuvantes moleculares que inducen una respuesta inmunitaria más rápida y vigorosa en presencia de menos cantidad de antígeno ha dado resultados preclínicos muy interesantes y poco a poco parece acercarnos al logro de una mejor vacuna antirrábica. Subsisten, empero, arduas dificultades: los adyuvantes moleculares solo funcionan si se administran con vacunas vivas, y las diferencias existentes entre las especies en cuanto a la especificidad de las moléculas inmunitarias complican las labores de desarrollo. Globalmente, el conjunto de investigaciones emprendidas en el último decenio es impresionante y alentador, pero la mayoría de las nuevas vacunas aún deben pasar por la fase de ensayo clínico, y está por ver qué viabilidad tienen estas vacunas experimentales en el mercado mundial. Solo una vacuna que supere a las actuales en todos los aspectos tiene posibilidades de ser adoptada a gran escala. Pese a todo, los autores expresan su confianza en que algunas de las vacunas candidatas cumplan estos criterios.

Recombinant Tri-Segmented Pichinde Virus as a Novel Live Viral Vaccine Platform.

Pichinde virus (PICV) is a nonpathogenic arenavirus with a bi-segmented RNA genome (L and S segments) that encodes four viral genes. We have developed a reverse genetics system to generate recombinant tri-segmented PICV (rP18tri) that packages three RNA segments (L, S1, and S2) and can encode up to two foreign genes. Using influenza virus HA and NP as model antigens, we show that the rP18tri vector can induce strong humoral and cell-mediated immunity, which further increases upon a booster dose. We propose that this novel rP18tri vector can be developed into a useful vaccine platform for other antigens, particularly when strong cellular immunity and prime-boost vaccination strategy are desired.