Expression of MIP-1α (CCL3) by a Recombinant Rabies Virus Enhances Its Immunogenicity by Inducing Innate Immunity and Recruiting Dendritic Cells and B Cells

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Rabies remains a public health threat in most parts of the world, and approximately 99% of the cases are transmitted by dogs. There is an urgent need to develop an efficacious and affordable vaccine to control canine-transmitted rabies in developing countries. Our previous studies demonstrate that overexpression of chemokines/cytokines such as CCL-3 (MIP-1␣) and granulocyte-macrophage colonystimulating factor (GM-CSF) can enhance the immunogenicity of rabies vaccines. In the present study, the chemokine CXCL13 was inserted into the genome of the recombinant rabies virus (rRABV) strain LBNSE, and the effect of the chemokine CXCL13 on the immunogenicity of RABV was investigated. It was found that LBNSE-CXCL13 recruited follicular helper T (Tfh) and germinal center (GC) B cells, promoted the formation of GCs, and increased the population of plasma cells in immunized mice. Further studies showed that mice immunized with LBNSE-CXCL13 produced more rabies virus-neutralizing antibodies (VNAs) and developed better protection than those immunized with the parent virus LBNSE or the GM-CSF-expressing RABV (LBNSE-GM-CSF). Collectively, these findings provide a better understanding of the role of CXCL13 expression in the immunogenicity of the RABV, which may help in designing more-efficacious rabies vaccines.IMPORTANCE Rabies is endemic in most parts of the world, and more effort is needed to develop affordable and effective vaccines to control or eliminate this disease. The chemokine CXCL13 recruits both Tfh and B cells, which is essential for the homing of Tfh cells and the development of B cell follicles. In this study, the effect of the overexpression of CXCL13 on the immunogenicity of the RABV was evaluated in a mouse model. We found that CXCL13 expression promoted humoral immunity by recruiting Tfh and GC B cells, facilitating the formation of GCs, and increasing the number of plasma cells. As expected, the overexpression of CXCL13 resulted in enhanced virus-neutralizing antibody (VNA) production and protection against a virulent RABV challenge. These findings provide a better understanding of the role of CXCL13 in RABV-induced immune responses, which will help in designing more efficacious rabies vaccines.KEYWORDS CXCL13, rabies virus, T follicular helper cells, germinal center B cells, humoral immunity R abies, a fatal and ancient neurological disease that occurs in both humans and warm-blooded animals (1, 2), still causes more than 59,000 human deaths every year and poses a potential threat to more than 3.3 billion people (3, 4). Its pathogen,

Section: Methodsmentioning

confidence: 99%

A Novel Rabies Vaccine Expressing CXCL13 Enhances Humoral Immunity by Recruiting both T Follicular Helper and Germinal Center B Cells

Zhao

Zhou

et al. 2017

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“…The inability of wild-type (wt) RABV to induce VNA responses also has been reported in other animal species, such as mice (10), dogs (11), and skunks (12). On the other hand, experimental infection with laboratory-attenuated RABV induces VNA responses in laboratory animals (10,(13)(14)(15)(16)(17). Although the mechanism(s) by which different RABVs induce different VNA responses are unknown, recent studies (18-21) indicate that laboratory-attenuated RABV activates, while wt RABV evades, the host innate immune responses, particularly interferon (IFN) and chemokines, in the central nervous system (CNS).…”

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confidence: 99%

“…On the other hand, experimental infection with laboratory-attenuated RABV induces VNA responses in laboratory animals (10,(13)(14)(15)(16)(17). Although the mechanism(s) by which different RABVs induce different VNA responses are unknown, recent studies (18-21) indicate that laboratory-attenuated RABV activates, while wt RABV evades, the host innate immune responses, particularly interferon (IFN) and chemokines, in the central nervous system (CNS).Innate immune genes, such as chemokines, have been cloned into RABV vectors to enhance the immune responses (10,14,15,22). It was found that the overexpression of these innate immune genes stimulated higher levels of VNA production and provided better protection by activating more dendritic cells (DCs) than the parental virus (10, 15) (14,17).…”

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confidence: 99%

The Inability of Wild-Type Rabies Virus To Activate Dendritic Cells Is Dependent on the Glycoprotein and Correlates with Its Low Level of theDe Novo-Synthesized Leader RNA

Yang

Huang

Gnanadurai

et al. 2015

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Dendritic cells (DCs) are the most efficient antigen-presenting cells, playing a key role in the adaptive immune responses to viral infections. Our studies demonstrate that wild-type (wt) rabies virus (RABV) does not activate DCs. Adoptive transfer of DCs primed with wt RABV did not activate DCs, stimulate virus neutralizing antibodies (VNA), or protect recipients against challenge. However, adoptive transfer of DCs primed with laboratory-attenuated RABV resulted in DC activation, production of VNA, and protection against challenge. In vitro studies with recombinant RABV (laboratory-attenuated RABV expressing the glycoprotein or the phosphoprotein from wt RABV) demonstrate that DC activation is dependent on the glycoprotein and involves the IPS-1 pathway. Furthermore, binding to and entry into DCs by wt RABV is severely blocked, and the copy number of de novo-synthesized leader RNA was two logs lower in DCs infected with the wt than in DCs treated with laboratory-attenuated RABV. However, transient transfection of DCs with synthesized leader RNA from either wt or attenuated RABV is capable of activating DCs in a dose-dependent manner. Thus, the inability of wt RABV to activate DCs correlates with its low level of the de novo-synthesized leader RNA. IMPORTANCERabies remains a public health threat, with more than 55,000 fatalities each year around the world. Since DCs play a key role in the adaptive immune responses to viral infections, we investigated the ability of rabies virus (RABV) to activate DCs. It was found that the adoptive transfer of DCs primed with wt RABV did not activate DCs, stimulate VNA, or protect mice against lethal challenge. However, laboratory-attenuated RABV mediates the activation of DCs via the IPS-1 pathway and is glycoprotein dependent. We further show that wt RABV evades DC-mediated immune activation by inefficient binding/entry into DCs and as a result of a reduced level of de novo-synthesized leader RNA. These findings may have important implications in the development of efficient rabies vaccines. Despite the fact that rabies is one of the oldest human infectious diseases, it continues to present a public health threat by causing more than 55,000 human deaths every year around the globe (1). Its causative agent, rabies virus (RABV), belongs to the Rhabdoviridae family, and its genome encodes five structural proteins in the order of nucleoprotein (N), phosphoprotein (P), matrix protein (M), glycoprotein (G), and RNA-dependent RNA polymerase (RdRp; also termed large protein [L]) (2). Among these, RABV G is the only viral protein that is glycosylated and exposed on the surface of the virion (3). RABV G is responsible for binding to neurospecific receptors, such as the acetylcholine receptor and neural cell adhesion molecule (NCAM), for invasion into the nervous system (4, 5). Moreover, RABV G is the only protein capable of inducing virus-neutralizing antibodies (VNA) that are protective against rabies (6-8).It has been known for a long time that most of the human rabies patient...

“…Since the recent introduction of "reverse genetics" technology (12,13), new live attenuated RABV can be designed, for instance, by gene mutations (see reference 14), duplication or triplication of the RabG gene (15,16), or simultaneous expression of inserted cytokine genes to stimulate the innate immune response (17,18). Some of them are promising candidates of rabies vaccines due to their apathogenicity and improved immunogenicity in animal models.…”

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confidence: 99%

A New Rabies Vaccine Based on a Recombinant Orf Virus (Parapoxvirus) Expressing the Rabies Virus Glycoprotein

Amann

Rohde

Wulle

et al. 2013

The present study describes the generation of a new Orf virus (ORFV) recombinant, D1701-V-RabG, expressing the rabies virus (RABV) glycoprotein that is correctly presented on the surface of infected cells without the need of replication or production of infectious recombinant virus. One single immunization with recombinant ORFV can stimulate high RABV-specific virus-neutralizing antibody (VNA) titers in mice, cats, and dogs, representing all nonpermissive hosts for the ORFV vector. The protective immune response against severe lethal challenge infection was analyzed in detail in mice using different dosages, numbers, and routes for immunization with the ORFV recombinant. Long-term levels of VNA could be elicited that remained greater than 0.5 IU per ml serum, indicative for the protective status. Single applications of higher doses (10 7 PFU) can be sufficient to confer complete protection against intracranial (i.c.) challenge, whereas booster immunization was needed for protection by the application of lower dosages. Anamnestic immune responses were achieved by each of the seven tested routes of inoculation, including oral application. Finally, in vivo antibody-mediated depletion of CD4-positive and/or CD8-posititve T cell subpopulations during immunization and/or challenge infection attested the importance of CD4 T cells for the induction of protective immunity by D1701-V-RabG. This report demonstrates another example of the potential of the ORFV vector and also indicates the capability of the new recombinant for vaccination of animals.