Akkermansia muciniphila-induced trained immune phenotype increases bacterial intracellular survival and attenuates inflammation

The initial exposure to pathogens and commensals confers innate immune cells the capacity to respond distinctively upon a second stimulus. This training capacity might play key functions in developing an adequate innate immune response to the continuous exposure to bacteria. However, the mechanisms involved in induction of trained immunity by commensals remain mostly unexplored. A. muciniphila represents an attractive candidate to study the promotion of these long-term responses. Here, we show that priming of macrophages with live A. muciniphila enhances bacterial intracellular survival and decreases the release of pro- and anti-inflammatory signals, lowering the production of TNF and IL-10. Global transcriptional analysis of macrophages after a secondary exposure to the bacteria showed the transcriptional rearrangement underpinning the phenotype observed compared to acutely exposed cells, with the increased expression of genes related to phagocytic capacity and those involved in the metabolic adjustment conducing to innate immune training. Accordingly, key genes related to bacterial killing and pro-inflammatory pathways were downregulated. These data demonstrate the importance of specific bacterial members in the modulation of local long-term innate immune responses, broadening our knowledge of the association between gut microbiome commensals and trained immunity as well as the anti-inflammatory probiotic potential of A. muciniphila.

Mitochondrial dysfunction-associated microbiota establishes a transmissible refractory response to anti-TNF therapy during ulcerative colitis

Anti-TNF therapy can induce and maintain a remission status during intestinal bowel disease. However, up to 30% of patients do not respond to this therapy by mechanisms that are unknown. Here, we show that the absence of MCJ, a natural inhibitor of the respiratory chain Complex I, induces gut microbiota changes that are critical determinants of the lack of response in a murine model of DSS-induced inflammation. First, we found that MCJ expression is restricted to macrophages in human colonic tissue. Therefore, we demonstrate by transcriptomic analysis of colon macrophages from DSS-induced mice that MCJ-deficiency is linked to the expression of genes belonging to the FcγR signaling pathway and contains an anti-TNF refractory gene signature identified in ulcerative colitis patients. The gut microbial composition changes observed upon DSS treatment in the MCJ-deficient mice revealed the increased presence of specific colitogenic members, including Ruminococcus gnavus and Oscillospira, which could be associated with the non-response to TNF inhibitors. Further, we show that the presence of a microbiota associated resistance to treatment is dominant and transmissible to responsive individuals. Collectively, our findings underscore the critical role played by macrophage mitochondrial function in the gut ecological niche that can substantially affect not only the severity of inflammation but also the ability to successfully respond to current therapies.

Mitochondrial dysfunction promotes microbial composition that negatively impacts on ulcerative colitis development and progression

Recent evidence demonstrates potential links between mitochondrial dysfunction and inflammatory bowel diseases (IBD). In addition, bidirectional interactions between the intestinal microbiota and host mitochondria may modulate intestinal inflammation. We observed previously that mice deficient in the mitochondrial protein MCJ (Methylation-controlled J protein) exhibit increased susceptibility to DSS colitis. However, it is unclear whether this phenotype is primarily driven by MCJ-/- associated gut microbiota dysbiosis or by direct effects of MCJ-deficiency. Here, we demonstrate that fecal microbiota transplantation (FMT) from MCJ-deficient into germ-free mice was sufficient to confer increased susceptibility to colitis. Therefore, an FMT experiment by cohousing was designed to alter MCJ-deficient microbiota. The phenotype resulting from complex I deficiency was reverted by FMT. In addition, we determined the protein expression pathways impacted by MCJ deficiency, providing insight into the pathophysiology of IBD. Further, we used magnetic activated cell sorting (MACS) and 16S rRNA gene sequencing to characterize taxa-specific coating of the intestinal microbiota with Immunoglobulin A (IgA-SEQ) in MCJ-deficient mice. We show that high IgA coating of fecal bacteria observed in MCJ-deficient mice play a potential role in disease progression. This study allowed us to identify potential microbial signatures in feces associated with complex I deficiency and disease progression. This research highlights the importance of finding microbial biomarkers, which might serve as predictors, permitting the stratification of ulcerative colitis (UC) patients into distinct clinical entities of the UC spectrum.

Immunization with a small fragment of the Schmallenberg virus nucleoprotein highly conserved across the Orthobunyaviruses of the Simbu serogroup reduces viremia in SBV challenged IFNAR-/- mice

Schmallenberg Virus (SBV), an arbovirus from the Peribunyaviridae family and Orthobunyavirus genus, was discovered in late 2011 in Germany and has been circulating in Europe, Asia and Africa ever since. The virus causes a disease associated with ruminants that includes fever, fetal malformation, drop in milk production, diarrhoea and stillbirths, becoming a burden for small and large farms. Building on previous studies on SBV nucleoprotein (SBV-N) as a promising vaccine candidate, we have investigated the possible protein regions responsible for protection. Based on selective truncation of domains designed from the available crystal structure of the SBV-N, we identified both the N-terminal domain (N-term; Met1 - Thr133) and a smaller fragment within (C4; Met1 - Ala58) as vaccine prototypes. Two injections of the N-term and C4 polypeptides protected mice knockout for type I interferon (IFN) receptors (IFNAR^-/-) challenged with virulent SBV, opposite to control groups that presented severe signs of morbidity and weight loss. Viremia analyses along with the presence of IFN-γ secreted from splenocytes re-stimulated with the N-terminal region of the protein corroborate that these two portions of SBV-N can be employed as subunit vaccines. Apart from both proteinaceous fragments being easily produced in bacterial cells, the C4 polypeptide shares a high sequence homology (∼87.1 %) with the corresponding region of nucleoproteins of several viruses of the Simbu serogroup, a group of Orthobunyaviruses that comprises SBV and veterinary pathogens like Akabane virus and human infecting viruses like Oropouche. Thus, we propose that this smaller fragment is better suited for vaccine nanoparticle formulation, and it paves the way to further research with other related Orthobunyaviruses.

Identification of novel conserved Ixodes vaccine candidates; a promising role for non-secreted salivary gland proteins

Ixodes ricinus and Ixodes scapularis are the main vectors for the causative agents of Lyme borreliosis and a wide range of other pathogens. Repeated tick-bites are known to lead to tick rejection; a phenomenon designated as tick immunity. Tick immunity is mainly directed against tick salivary gland proteins (TSGPs) and has been shown to partially protect against experimental Lyme borreliosis. TSGPs recognized by antibodies from tick immune animals could therefore be interesting candidates for an anti-tick vaccine, which might also block pathogen transmission. To identify conserved Ixodes TSGPs that could serve as a universal anti-tick vaccine in both Europe and the US, a Yeast Surface Display containing salivary gland genes of nymphal I. ricinus expressed at 24, 48 and 72 h into tick feeding was probed with either sera from rabbits repeatedly exposed for 24 h to I. ricinus nymphal ticks and/or sera from rabbits immune to I. scapularis. Thus, we identified thirteen TSGP vaccine candidates, of which ten were secreted. For vaccination studies in rabbits, we selected six secreted TSGPs, five full length and one conserved peptide. None of these proteins hampered tick feeding. In contrast, vaccination of guinea pigs with four non-secreted TSGPs - two from the current and two from a previous human immunoscreening - did significantly reduce tick attachment and feeding. Therefore, non-secreted TSGPs appear to be involved in the development of tick immunity and are interesting candidates for an anti-tick vaccine.

Mitochondrial bioenergetics boost macrophage activation, promoting liver regeneration in metabolically compromised animals

BACKGROUND AND AIMS

Hepatic ischemia-reperfusion injury (IRI) is the leading cause of early posttransplantation organ failure as mitochondrial respiration and ATP production are affected. A shortage of donors has extended liver donor criteria, including aged or steatotic livers, which are more susceptible to IRI. Given the lack of an effective treatment and the extensive transplantation waitlist, we aimed at characterizing the effects of an accelerated mitochondrial activity by silencing methylation-controlled J protein (MCJ) in three preclinical models of IRI and liver regeneration, focusing on metabolically compromised animal models.

APPROACH AND RESULTS

Wild-type (WT), MCJ knockout (KO), and Mcj silenced WT mice were subjected to 70% partial hepatectomy (Phx), prolonged IRI, and 70% Phx with IRI. Old and young mice with metabolic syndrome were also subjected to these procedures. Expression of MCJ, an endogenous negative regulator of mitochondrial respiration, increases in preclinical models of Phx with or without vascular occlusion and in donor livers. Mice lacking MCJ initiate liver regeneration 12 h faster than WT and show reduced ischemic injury and increased survival. MCJ knockdown enables a mitochondrial adaptation that restores the bioenergetic supply for enhanced regeneration and prevents cell death after IRI. Mechanistically, increased ATP secretion facilitates the early activation of Kupffer cells and production of TNF, IL-6, and heparin-binding EGF, accelerating the priming phase and the progression through G₁ /S transition during liver regeneration. Therapeutic silencing of MCJ in 15-month-old mice and in mice fed a high-fat/high-fructose diet for 12 weeks improves mitochondrial respiration, reduces steatosis, and overcomes regenerative limitations.

CONCLUSIONS

Boosting mitochondrial activity by silencing MCJ could pave the way for a protective approach after major liver resection or IRI, especially in metabolically compromised, IRI-susceptible organs.

Uneven metabolic and lipidomic profiles in recovered COVID-19 patients as investigated by plasma NMR metabolomics

COVID-19 is a systemic infectious disease that may affect many organs, accompanied by a measurable metabolic dysregulation. The disease is also associated with significant mortality, particularly among the elderly, patients with comorbidities, and solid organ transplant recipients. Yet, the largest segment of the patient population is asymptomatic, and most other patients develop mild to moderate symptoms after SARS-CoV-2 infection. Here, we have used NMR metabolomics to characterize plasma samples from a cohort of the abovementioned group of COVID-19 patients (n = 69), between 3 and 10 months after diagnosis, and compared them with a set of reference samples from individuals never infected by the virus (n = 71). Our results indicate that half of the patient population show abnormal metabolism including porphyrin levels and altered lipoprotein profiles six months after the infection, while the other half show little molecular record of the disease. Remarkably, most of these patients are asymptomatic or mild COVID-19 patients, and we hypothesize that this is due to a metabolic reflection of the immune response stress.

The commensal bacterium Lactiplantibacillus plantarum imprints innate memory-like responses in mononuclear phagocytes

Gut microbiota is a constant source of antigens and stimuli to which the resident immune system has developed tolerance. However, the mechanisms by which mononuclear phagocytes, specifically monocytes/macrophages, cope with these usually pro-inflammatory signals are poorly understood. Here, we show that innate immune memory promotes anti-inflammatory homeostasis, using as model strains of the commensal bacterium Lactiplantibacillus plantarum. Priming of monocytes/macrophages with bacteria, especially in its live form, enhances bacterial intracellular survival and decreases the release of pro-inflammatory signals to the environment, with lower production of TNF and higher levels of IL-10. Analysis of the transcriptomic landscape of these cells shows downregulation of pathways associated with the production of reactive oxygen species (ROS) and the release of cytokines, chemokines and antimicrobial peptides. Indeed, the induction of ROS prevents memory-induced bacterial survival. In addition, there is a dysregulation in gene expression of several metabolic pathways leading to decreased glycolytic and respiratory rates in memory cells. These data support commensal microbe-specific metabolic changes in innate immune memory cells that might contribute to homeostasis in the gut.

A Catalogus Immune Muris of the mouse immune responses to diverse pathogens

Immunomodulation strategies are crucial for several biomedical applications. However, the immune system is highly heterogeneous and its functional responses to infections remains elusive. Indeed, the characterization of immune response particularities to different pathogens is needed to identify immunomodulatory candidates. To address this issue, we compiled a comprehensive map of functional immune cell states of mouse in response to 12 pathogens. To create this atlas, we developed a single-cell-based computational method that partitions heterogeneous cell types into functionally distinct states and simultaneously identifies modules of functionally relevant genes characterizing them. We identified 295 functional states using 114 datasets of six immune cell types, creating a Catalogus Immune Muris. As a result, we found common as well as pathogen-specific functional states and experimentally characterized the function of an unknown macrophage cell state that modulates the response to Salmonella Typhimurium infection. Thus, we expect our Catalogus Immune Muris to be an important resource for studies aiming at discovering new immunomodulatory candidates.

Oral vaccination stimulates neutrophil functionality and exerts protection in a Mycobacterium avium subsp. paratuberculosis infection model

Mycobacterium avium subsp. paratuberculosis (Map) causes paratuberculosis (PTB), a granulomatous enteritis in ruminants that exerts high economic impact on the dairy industry worldwide. Current vaccines have shown to be cost-effective against Map and in some cases confer beneficial non-specific effects against other pathogens suggesting the existence of trained immunity. Although Map infection is mainly transmitted by the fecal-oral route, oral vaccination has not been deeply studied. Therefore, the aim of this study was to compare the oral route with a set of mycobacterial and non-mycobacterial vaccines with a subcutaneously administered commercially available vaccine. Training effects on polymorphonuclear neutrophils (PMNs) and homologous and heterologous in vivo protection against Map were investigated in the rabbit infection model. Oral vaccination with inactivated or live vaccines was able to activate mucosal immunity as seen by elevation of serum IgA and the expression of IL4 in peripheral blood mononuclear cells (PBMCs). In addition, peripheral PMN phagocytosis against Map was enhanced by vaccination and extracellular trap release against Map and non-related pathogens was modified by both, vaccination and Map-challenge, indicating trained immunity. Finally, PBMCs from vaccinated animals stimulated in vitro with Map antigens showed a rapid innate activation cytokine profile. In conclusion, our data show that oral vaccination against PTB can stimulate neutrophil activity and both innate and adaptive immune responses that correlate with protection.

Probing an Ixodes ricinus salivary gland yeast surface display with tick-exposed human sera to identify novel candidates for an anti-tick vaccine

In Europe, Ixodes ricinus is the most important vector of human infectious diseases, most notably Lyme borreliosis and tick-borne encephalitis virus. Multiple non-natural hosts of I. ricinus have shown to develop immunity after repeated tick bites. Tick immunity has also been shown to impair B. burgdorferi transmission. Most interestingly, multiple tick bites reduced the likelihood of contracting Lyme borreliosis in humans. A vaccine that mimics tick immunity could therefore potentially prevent Lyme borreliosis in humans. A yeast surface display library (YSD) of nymphal I. ricinus salivary gland genes expressed at 24, 48 and 72 h into tick feeding was constructed and probed with antibodies from humans repeatedly bitten by ticks, identifying twelve immunoreactive tick salivary gland proteins (TSGPs). From these, three proteins were selected for vaccination studies. An exploratory vaccination study in cattle showed an anti-tick effect when all three antigens were combined. However, immunization of rabbits did not provide equivalent levels of protection. Our results show that YSD is a powerful tool to identify immunodominant antigens in humans exposed to tick bites, yet vaccination with the three selected TSGPs did not provide protection in the present form. Future efforts will focus on exploring the biological functions of these proteins, consider alternative systems for recombinant protein generation and vaccination platforms and assess the potential of the other identified immunogenic TSGPs.

Borrelia burgdorferi infection induces long-term memory-like responses in macrophages with tissue-wide consequences in the heart

Lyme carditis is an extracutaneous manifestation of Lyme disease characterized by episodes of atrioventricular block of varying degrees and additional, less reported cardiomyopathies. The molecular changes associated with the response to Borrelia burgdorferi over the course of infection are poorly understood. Here, we identify broad transcriptomic and proteomic changes in the heart during infection that reveal a profound down-regulation of mitochondrial components. We also describe the long-term functional modulation of macrophages exposed to live bacteria, characterized by an augmented glycolytic output, increased spirochetal binding and internalization, and reduced inflammatory responses. In vitro, glycolysis inhibition reduces the production of tumor necrosis factor (TNF) by memory macrophages, whereas in vivo, it produces the reversion of the memory phenotype, the recovery of tissue mitochondrial components, and decreased inflammation and spirochetal burdens. These results show that B. burgdorferi induces long-term, memory-like responses in macrophages with tissue-wide consequences that are amenable to be manipulated in vivo.

Lyme carditis is a manifestation of Lyme disease characterized by episodes of atrioventricular block and additional cardiomyopathies. This study describes the proteomic and transcriptomic changes in the heart upon infection with Borrelia burgdorferi, and identifies innate immune memory hallmarks specific to the response to the spirochete that are amenable to therapeutic manipulation.

A structurally unique Fusobacterium nucleatum tannase provides detoxicant activity against gallotannins and pathogen resistance

Colorectal cancer pathogenesis and progression is associated with the presence of Fusobacterium nucleatum and the reduction of acetylated derivatives of spermidine, as well as dietary components such as tannin-rich foods. We show that a new tannase orthologue of F. nucleatum (TanBF_nn ) has significant structural differences with its Lactobacillus plantarum counterpart affecting the flap covering the active site and the accessibility of substrates. Crystallographic and molecular dynamics analysis revealed binding of polyamines to a small cavity that connects the active site with the bulk solvent which interact with catalytically indispensable residues. As a result, spermidine and its derivatives, particularly N⁸ -acetylated spermidine, inhibit the hydrolytic activity of TanBF_nn and increase the toxicity of gallotannins to F. nucleatum. Our results support a model in which the balance between the detoxicant activity of TanBF_nn and the presence of metabolic inhibitors can dictate either conducive or unfavourable conditions for the survival of F. nucleatum.

Chemical synthesis and immunological evaluation of new generation multivalent anticancer vaccines based on a Tn antigen analogue

Tumor associated carbohydrate antigens (TACAs), such as the Tn antigen, have emerged as key targets for the development of synthetic anticancer vaccines. However, the induction of potent and functional immune responses has been challenging and, in most cases, unsuccessful. Herein, we report the design, synthesis and immunological evaluation in mice of Tn-based vaccine candidates with multivalent presentation of the Tn antigen (up to 16 copies), both in its native serine-linked display (Tn-Ser) and as an oxime-linked Tn analogue (Tn-oxime). The high valent vaccine prototypes were synthesized through a late-stage convergent assembly (Tn-Ser construct) and a versatile divergent strategy (Tn-oxime analogue), using chemoselective click-type chemistry. The hexadecavalent Tn-oxime construct induced robust, Tn-specific humoral and CD4⁺/CD8⁺ cellular responses, with antibodies able to bind the Tn antigen on the MCF7 cancer cell surface. The superior synthetic accessibility and immunological properties of this fully-synthetic vaccine prototype makes it a compelling candidate for further advancement towards safe and effective synthetic anticancer vaccines.

Exploiting structure-activity relationships of QS-21 in the design and synthesis of streamlined saponin vaccine adjuvants

We report the design, synthesis, immunological evaluation, and conformational analysis of new saponin variants as promising vaccine adjuvants. These studies have provided expedient synthetic access to streamlined adjuvant-active saponins and yielded molecular-level insights into saponin conformation that correlated with their in vivo adjuvant activities.

Regulation of macrophage activity by surface receptors contained within Borrelia burgdorferi-enriched phagosomal fractions

Macrophages mediate the elimination of pathogens by phagocytosis resulting in the activation of specific signaling pathways that lead to the production of cytokines, chemokines and other factors. Borrelia burgdorferi, the causative agent of Lyme disease, causes a wide variety of pro-inflammatory symptoms. The proinflammatory capacity of macrophages is intimately related to the internalization of the spirochete. However, most receptors mediating this process are largely unknown. We have applied a multiomic approach, including the proteomic analysis of B. burgdorferi-containing phagosome-enriched fractions, to identify surface receptors that are involved in the phagocytic capacity of macrophages as well as their inflammatory output. Sucrose gradient protein fractions of human monocyte-derived macrophages exposed to B. burgdorferi contained the phagocytic receptor, CR3/CD14 highlighting the major role played by these proteins in spirochetal phagocytosis. Other proteins identified in these fractions include C-type lectins, scavenger receptors or Siglecs, of which some are directly involved in the interaction with the spirochete. We also identified the Fc gamma receptor pathway, including the binding receptor, CD64, as involved both in the phagocytosis of, and TNF induction in response to B. burgdorferi in the absence of antibodies. The common gamma chain, FcγR, mediates the phagocytosis of the spirochete, likely through Fc receptors and C-type lectins, in a process that involves Syk activation. Overall, these findings highlight the complex array of receptors involved in the phagocytic response of macrophages to B. burgdorferi.

Macrophages eliminate infecting microorganisms through the concerted action of surface receptors and signaling molecules. As a consequence, these cells produce a series of soluble factors that participate in the inflammatory response during infections. The composition of the full complement of receptors that participate in the recognition and internalization of the causative agent of Lyme disease, Borrelia burgdorferi, is largely unknown. We have analyzed the protein composition of phagosomes containing B. burgdorferi from human macrophages and identified a series of surface proteins that may be involved in the process. Through the use of gene silencing techniques, we have determined the participation of several of these receptors both in the internalization of the bacterium and the subsequent inflammatory response. Among these, we have identified the Fc gamma receptor pathway as involved in this process in the absence of antibodies. We have also identified receptors that are directly involved in the attachment of B. burgdorferi, while others seem to have an accessory role in the internalization and/or induction of proinflammatory cytokines in response to the spirochete. These data clarify the complex array of interactions between macrophages and B. burgdorferi and shed light on the overall response to this infectious agent.

Cross-protective immune responses against African horse sickness virus after vaccination with protein NS1 delivered by avian reovirus muNS microspheres and modified vaccinia virus Ankara

African horse sickness virus (AHSV) is an insect-borne pathogen that causes acute disease in horses and other equids. In an effort to improve the safety of currently available vaccines and to acquire new knowledge about the determinants of AHSV immunogenicity, new generation vaccines are being developed. In this work we have generated and tested a novel immunization approach comprised of nonstructural protein 1 (NS1) of AHSV serotype 4 (AHSV-4) incorporated into avian reovirus muNS protein microspheres (MS-NS1) and/or expressed using recombinant modified vaccinia virus Ankara vector (MVA-NS1). The protection conferred against AHSV by a homologous MS-NS1 or heterologous MS-NS1 and MVA-NS1 prime/boost was evaluated in IFNAR (-/-) mice. Our results indicate that immunization based on MS-NS1 and MVA-NS1 afforded complete protection against the infection with homologous AHSV-4. Moreover, priming with MS-NS1 and boost vaccination with MVA-NS1 (MS-MVA-NS1) triggered NS1 specific cytotoxic CD8 + T cells and prevented AHSV disease in IFNAR (-/-) mice after challenge with heterologous serotype AHSV-9. Cross-protective immune responses are highly important since AHS can be caused by nine different serotypes, which means that a universal polyvalent vaccination would need to induce protective immunity against all serotypes.

Identification of a highly active tannase enzyme from the oral pathogen Fusobacterium nucleatum subsp. polymorphum

BACKGROUND

Tannases are tannin-degrading enzymes that have been described in fungi and bacteria as an adaptative mechanism to overcome the stress conditions associated with the presence of these phenolic compounds.

RESULTS

We have identified and expressed in E. coli a tannase from the oral microbiota member Fusobacterium nucleatum subs. polymorphum (TanB_Fnp). TanB_Fnp is the first tannase identified in an oral pathogen. Sequence analyses revealed that it is closely related to other bacterial tannases. The enzyme exhibits biochemical properties that make it an interesting target for industrial use. TanB_Fnp has one of the highest specific activities of all bacterial tannases described to date and shows optimal biochemical properties such as a high thermal stability: the enzyme keeps 100% of its activity after prolonged incubations at different temperatures up to 45 °C. TanB_Fnp also shows a wide temperature range of activity, maintaining above 80% of its maximum activity between 22 and 55 °C. The use of a panel of 27 esters of phenolic acids demonstrated activity of TanB_Fnp only against esters of gallic and protocatechuic acid, including tannic acid, gallocatechin gallate and epigallocatechin gallate. Overall, TanB_Fnp possesses biochemical properties that make the enzyme potentially useful in biotechnological applications.

CONCLUSIONS

We have identified and characterized a metabolic enzyme from the oral pathogen Fusobacterium nucleatum subsp. polymorphum. The biochemical properties of TanB_Fnp suggest that it has a major role in the breakdown of complex food tannins during oral processing. Our results also provide some clues regarding its possible participation on bacterial survival in the oral cavity. Furthermore, the characteristics of this enzyme make it of potential interest for industrial use.

Microspheres-prime/rMVA-boost vaccination enhances humoral and cellular immune response in IFNAR(-/-) mice conferring protection against serotypes 1 and 4 of bluetongue virus

Bluetongue virus (BTV) is the causative agent of bluetongue disease (BT), which affects domestic and wild ruminants. At the present, 27 different serotypes have been documented. Vaccination has been demonstrated as one of the most effective methods to avoid viral dissemination. To overcome the drawbacks associated with the use of inactivated and attenuated vaccines we engineered a new recombinant BTV vaccine candidate based on proteins VP2, VP7, and NS1 of BTV-4 that were incorporated into avian reovirus muNS-Mi microspheres (MS-VP2/VP7/NS1) and recombinant modified vaccinia virus Ankara (rMVA). The combination of these two antigen delivery systems in a heterologous prime-boost vaccination strategy generated significant levels of neutralizing antibodies in IFNAR(-/-) mice. Furthermore, this immunization strategy increased the ratio of IgG2a/IgG1 in sera, indicating an induction of a Th1 response, and elicited a CD8 T cell response. Immunized mice were protected against lethal challenges with the homologous serotype 4 and the heterologous serotype 1 of BTV. All these results support the strategy based on microspheres in combination with rMVAs as a promising multiserotype vaccine candidate against BTV.

Defeating Bluetongue virus: new approaches in the development of multiserotype vaccines

Bluetongue virus (BTV) is a global threat to domestic and wild ruminants, causing massive economic losses throughout the world. New serotypes of the virus are rapidly emerging in different continents, unfortunately there is little cross-protection between BTV serotypes. The eradication of the virus from a region is particularly complicated in areas where multiple serotypes circulate for a long time. The present review summarizes the actual concerns about the spread of the virus and relevant approaches to develop efficient vaccines against BTV, in particular those focused on a multiserotype design.