Central tolerance shapes the neutralizing B cell repertoire against a persisting virus in its natural host.

Viral mimicry of host cell structures has been postulated to curtail the B cell receptor (BCR) repertoire against persisting viruses through tolerance mechanisms. This concept awaits, however, experimental testing in a setting of natural virus-host relationship. We engineered mouse models expressing a monoclonal BCR specific for the envelope glycoprotein of lymphocytic choriomeningitis virus (LCMV), a naturally persisting mouse pathogen. When the heavy chain of the LCMV-neutralizing antibody KL25 was paired with its unmutated ancestor light chain, most B cells underwent receptor editing, a behavior reminiscent of autoreactive clones. In contrast, monoclonal B cells expressing the same heavy chain in conjunction with the hypermutated KL25 light chain did not undergo receptor editing but exhibited low levels of surface IgM, suggesting that light chain hypermutation had lessened KL25 autoreactivity. Upon viral challenge, these IgMlow cells were not anergic but up-regulated IgM, participated in germinal center reactions, produced antiviral antibodies, and underwent immunoglobulin class switch as well as further affinity maturation. These studies on a persisting virus in its natural host species suggest that central tolerance mechanisms prune the protective antiviral B cell repertoire.

The sound of silent RNA in tuberculosis and the lncRNA role on infection.

Tuberculosis (TB) is one of the leading causes of death worldwide, and Diabetes Mellitus is one of the major comorbidities (TB/DM) associated with the disease. A total of 103 differentially expressed ncRNAs have been identified in the TB and TB/DM comparisons. A machine learning algorithm was employed to identify the most informative lncRNAs: ADM-DT, LINC02009, LINC02471, SOX2-OT, and GK-AS1. These lncRNAs presented substantial accuracy in classifying TB from HC (AUCs >0.85) and TB/DM from HC (AUCs >0.90) in the other three countries. Genes with significant correlations with the five lncRNAs enriched common pathways in Brazil and India for both TB and TB/DM. This suggests that lncRNAs play an important role in the regulation of genes related to the TB immune response.

Another tick bites the dust: exploring the association of microbial composition with a broad transmission competence of tick vector species.

IMPORTANCE: Some tick species are competent to transmit more than one pathogen while other species are, until now, known to be competent to transmit only one single or any pathogen. Such a difference in vector competence for one or more pathogens might be related to the microbiome, and understanding what differentiates these two groups of ticks could help us control several diseases aiming at the bacteria groups that contribute to such a broad vector competence. Using 16S rRNA from tick species that could be classified into these groups, genera such as Rickettsia and Staphylococcus seemed to be associated with such a broad vector competence. Our results highlight differences in tick species when they are divided based on the number of pathogens they are competent to transmit. These findings are the first step into understanding the relationship between one single tick species and the pathogens it transmits.

The alarmin interleukin-33 promotes the expansion and preserves the stemness of Tcf-1+ CD8+ T cells in chronic viral infection.

T cell factor 1 (Tcf-1) expressing CD8+ T cells exhibit stem-like self-renewing capacity, rendering them key for immune defense against chronic viral infection and cancer. Yet, the signals that promote the formation and maintenance of these stem-like CD8+ T cells (CD8+SL) remain poorly defined. Studying CD8+ T cell differentiation in mice with chronic viral infection, we identified the alarmin interleukin-33 (IL-33) as pivotal for the expansion and stem-like functioning of CD8+SL as well as for virus control. IL-33 receptor (ST2)-deficient CD8+ T cells exhibited biased end differentiation and premature loss of Tcf-1. ST2-deficient CD8+SL responses were restored by blockade of type I interferon signaling, suggesting that IL-33 balances IFN-I effects to control CD8+SL formation in chronic infection. IL-33 signals broadly augmented chromatin accessibility in CD8+SL and determined these cells' re-expansion potential. Our study identifies the IL-33-ST2 axis as an important CD8+SL-promoting pathway in the context of chronic viral infection.

Screening organic repellent compounds against Lutzomyia longipalpis (Diptera: Psychodidae) present in plant essential oils: Bioassay plus an in silico approach.

In the Americas, Lutzomyia longipalpis is the most relevant sand fly species for the transmission of visceral leishmaniasis. For its vector control in Brazil, insecticide spraying has not shown persistent reduction in disease prevalence while some sand fly populations are reported resistant to the insecticides used in spraying. The usage of repellents and personal protection behavior can reduce vector borne diseases prevalence. Therefore, the search for new repellent compounds is needed to use together with insecticide spraying, especially from natural sources to overcome the resistance developed by some sand fly populations to the compounds commercially used. In silico strategies have been applied together with repellency bioassays successfully identifying new bioactive compounds from natural sources. Thus, the present study aimed to screen repellent potential of neem (Azadirachta indica), citronella (Cymbopogon winterianus), bushy matgrass (Lippia alba) and 'alecrim do mato' (Lippia thymoides) essential oils against L. longipalpis and to identify potential repellent compounds by chemical analysis and in silico approach. Plant essential oils were extracted from leaves and repellency bioassays were performed on volunteers using colony reared L. longipalpis. Aside from neem oil, all other tested essential oil has shown a reduced number of sand fly bites using higher concentrations. Chemical composition from oils was assessed and its compounds were screened on a pharmacophore model using odorant binding protein 1 (OBP1). All essential oils were majorly composed of either oxygenated monoterpenes, except for the oil extracted from neem which was composed of sesquiterpene hydrocarbons. Molecular docking was performed with the compounds that best superimposed in the OBP1 pharmacophore model, identifying those binding to OBP4, which is associated with insect repellency behavior. Citronellol, Citronellol acetate, Citronellal and Geranyl acetate showed similar interactions with OBP4 binding site as DEET. Thus, it is suggested that these compounds are able to bind to L. longipalpis OBP4 generating repellent behavior in sand flies.

Multiplex qPCR assay to determine Leishmania infantum load in Lutzomyia longipalpis sandfly samples.

The study aimed to develop a multiplex qPCR to detect Leishmania infantum load in different sandfly sample settings using Leishmania kDNA and sandfly vacuolar ATPase (VATP) subunit C as internal control gene. The amplification of Lutzomyia longipalpis VATP gene was evaluated together with Leishmania infantum kDNA in a multiplex reaction. The concentration of VATP gene oligonucleotides was adjusted until no statistically significant difference was observed between all multiplex standard curves and singleplex curves, that is, only kDNA amplification. Limit of detection (LoD) was measured using a probit model and a cut-off defined by receiver operating characteristic analysis. Limit of quantification (LoQ) was assessed by a linear model using the coefficient of variation threshold of 25%. After assuring VATP gene amplification, its primer-probe concentrations were best at 100 nM/10 nM, respectively. The cut-off Cq value for L. infantum kDNA was defined as 35.46 with 100% of sensitivity and specificity. A total of 95% LoD was determined to be of 0.162 parasites while LoQ was 5.858. Our VATP/kDNA multiplex qPCR assay shows that it can be used to evaluate both DNA integrity and determine L. infantum load in L. longipalpis even for low yielded samples, that is, individual midguts.

Vaccine-elicited CD4 T cells prevent the deletion of antiviral B cells in chronic infection.

Chronic viral infections subvert protective B cell immunity. An early type I interferon (IFN-I)-driven bias to short-lived plasmablast differentiation leads to clonal deletion, so-called "decimation," of antiviral memory B cells. Therefore, prophylactic countermeasures against decimation remain an unmet need. We show that vaccination-induced CD4 T cells prevented the decimation of naïve and memory B cells in chronically lymphocytic choriomeningitis virus (LCMV)-infected mice. Although these B cell responses were largely T independent when IFN-I was blocked, preexisting T help assured their sustainability under conditions of IFN-I-driven inflammation by instructing a germinal center B cell transcriptional program. Prevention of decimation depended on T cell-intrinsic Bcl6 and Tfh progeny formation. Antigen presentation by B cells, interactions with antigen-specific T helper cells, and costimulation by CD40 and ICOS were also required. Importantly, B cell-mediated virus control averted Th1-driven immunopathology in LCMV-challenged animals with preexisting CD4 T cell immunity. Our findings show that vaccination-induced Tfh cells represent a cornerstone of effective B cell immunity to chronic virus challenge, pointing the way toward more effective B cell-based vaccination against persistent viral diseases.

Sweet Drugs for Bad Bugs: A Glycomimetic Strategy against the DC-SIGN-Mediated Dissemination of SARS-CoV-2.

The C-type lectin receptor DC-SIGN is a pattern recognition receptor expressed on macrophages and dendritic cells. It has been identified as a promiscuous entry receptor for many pathogens, including epidemic and pandemic viruses such as SARS-CoV-2, Ebola virus, and HIV-1. In the context of the recent SARS-CoV-2 pandemic, DC-SIGN-mediated virus dissemination and stimulation of innate immune responses has been implicated as a potential factor in the development of severe COVID-19. Inhibition of virus binding to DC-SIGN, thus, represents an attractive host-directed strategy to attenuate overshooting innate immune responses and prevent the progression of the disease. In this study, we report on the discovery of a new class of potent glycomimetic DC-SIGN antagonists from a focused library of triazole-based mannose analogues. Structure-based optimization of an initial screening hit yielded a glycomimetic ligand with a more than 100-fold improved binding affinity compared to methyl α-d-mannopyranoside. Analysis of binding thermodynamics revealed an enthalpy-driven improvement of binding affinity that was enabled by hydrophobic interactions with a loop region adjacent to the binding site and displacement of a conserved water molecule. The identified ligand was employed for the synthesis of multivalent glycopolymers that were able to inhibit SARS-CoV-2 spike glycoprotein binding to DC-SIGN-expressing cells, as well as DC-SIGN-mediated trans-infection of ACE2+ cells by SARS-CoV-2 spike protein-expressing viruses, in nanomolar concentrations. The identified glycomimetic ligands reported here open promising perspectives for the development of highly potent and fully selective DC-SIGN-targeted therapeutics for a broad spectrum of viral infections.

Identification of Bioactive Compounds against Aedes aegypti (Diptera: Culicidae) by Bioassays and in Silico Assays.

Most of the hematophagous insects act as disease vectors, including Aedes aegypti, responsible for transmitting some of the most critical arboviruses globally, such as Dengue. The use of repellents based on natural products is a promising alternative for personal protection compared to industrial chemical repellents. In this study, the repellent effect of essential oils extracted from Lippia thymoides, Lippia alba, Cymbopogon winterianus, and Eucalyptus globulus leaves was evaluated. Essential oils used showed repellent activity against Ae. aegypti in laboratory bioassays, obtaining protection rates above 70 % from 3.75 mg/mL and higher concentration for all analyzed oils. GC/MS identified 57 constituents, which were used in the ligand-based pharmacophore model to expose compounds with requirements for repellents that modulate mosquitoes behavior through odorant-binding protein 1 Ae. aegypti. Ligand-based pharmacophore model approach results suggested that repellent activity from C. winterianus, L. alba, and L. thymoides essential oils' metabolites is related to Citronelal (QFIT=26.77), Citronelol (QFIT=11.29), Citronelol acetate (QFIT=52.22) and Geranil acetate (QFIT=10.28) with synergistic or individual activity. E. globulus essential oil's repellent activity is associated with Ledol (0.94 %; QFIT=41.95). Molecular docking was applied to understand the binding mode and affinity of the essential oils' data set at the protein binding site. According to molecular docking, Citronelol (ChemPLP=60.98) and geranyl acetate (ChemPLP=60.55) were the best-classified compounds compared to the others and they can be explored to develop new repellents.

Immune response dynamics and Lutzomyia longipalpis exposure characterize a biosignature of visceral leishmaniasis susceptibility in a canine cohort.

BACKGROUND: Reports have shown correlations between the immune response to vector saliva and Leishmaniasis outcome. We followed dogs in an endemic area for two years characterizing resistance or susceptibility to canine visceral leishmaniasis (CVL) according to Leishmania infantum diagnosis and clinical development criteria. Then, we aimed to identify a biosignature based on parasite load, serum biological mediators' interactions, and vector exposure intensity associated with CVL resistance and susceptibility. METHODOLOGY/PRINCIPAL FINDINGS: A prospective two-year study was conducted in an area endemic for CVL. Dogs were evaluated at 6-month intervals to determine infection, clinical manifestations, immune profile, and sandfly exposure. CVL resistance or susceptibility was determined upon the conclusion of the study. After two years, 78% of the dogs were infected with L. infantum (53% susceptible and 47% resistant to CVL). Susceptible dogs presented higher splenic parasite load as well as persistence of the parasite during the follow-up, compared to resistant ones. Susceptible dogs also displayed a higher number of correlations among the investigated biological mediators, before and after infection diagnosis. At baseline, anti-saliva antibodies, indicative of exposure to the vector, were detected in 62% of the dogs, reaching 100% in one year. Higher sandfly exposure increased the risk of susceptibility to CVL by 1.6 times (CI: 1.11-2.41). We identified a discriminatory biosignature between the resistant and susceptible dogs assessing splenic parasite load, interaction of biological mediators, PGE2 serum levels and intensity of exposure to sandfly. All these parameters were elevated in susceptible dogs compared to resistant animals. CONCLUSIONS/SIGNIFICANCE: The biosignature identified in our study reinforces the idea that CVL is a complex multifactorial disease that is affected by a set of factors which are correlated and, for a better understanding of CVL, should not be evaluated in an isolated way.

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.

Effects of larval rearing substrates on some life-table parameters of Lutzomyia longipalpis sand flies.

Sand flies are the insects responsible for transmitting Leishmania parasites, the causative agents of leishmaniasis in humans. However, the effects of sand fly breeding sites on their biology and ecology remain poorly understood. Herein, we studied how larval nutrition associated with putative breeding sites of the sand fly Lutzomyia longipalpis affects their oviposition, development, microbiome, and susceptibility to Leishmania by rearing L. longipalpis on substrates collected from an endemic area for leishmaniasis in Brazil. The results showed that female L. longipalpis select the oviposition site based on its potential to promote larval maturation and while composting cashew leaf litter hindered the development, larvae reared on chicken feces developed rapidly. Typical gut microbial profiles were found in larvae reared upon cashew leaf litter. Adult females from larvae reared on substrate collected in chicken coops were infected with Leishmania infantum, indicating that they were highly susceptible to the parasite. In conclusion, the larval breeding sites can exert an important role in the epidemiology of leishmaniasis.

The tibiocalcaneal bundle of the deltoid ligament - Prevalence and variations.

INTRODUCTION: A precise understanding of the anatomy of the multiple bundles of the deltoid ankle ligament might have clinical impact. The most relevant deltoid anatomical series report a variable frequency of the tibiocalcaneal ligament, possibly the most important bundle to be reconstructed in medial ankle insufficiency. Our purpose was to access the deltoid's tibiocalcaneal ligament morphology in a large anatomical study as well as to perform a historical literature review on the reasons for its variable prevalence. MATERIALS AND METHODS: Forty-three ankle specimen were dissected to describe the prevalence of superficial and deep deltoid bundles, with special attention to the tibiocalcaneal ligament and its variants. RESULTS: All ankles had distinct deep and superficial bundles. In all 43 ankles the tibionavicular and tibiospring ligaments were clearly identified. The superficial posterior tibiotalar ligament was identified in 38 ankles (88%). The deep anterior tibiotalar bundle was identified in 35 ankles (81%). The deep posterior tibiotalar bundle was identified in all ankles. The tibiocalcaneal ligament was identified in 33 ankles (77%). In ten ankles there wasn't a direct bundle between the tibia and the sustentaculum tali. In all of these, however, we found some fibers spanning the gap between the tibiospring ligament and the sustentaculum tali. CONCLUSION: The tibiocalcaneal ligament is present in most specimens. In those in which we could not identify a direct bundle between the tibia and the calcareous we found a variant of the tibiospring ligament that connects to the sustentaculum tali.

Longitudinal profiling of the vaccination coverage in Brazil reveals a recent change in the patterns hallmarked by differential reduction across regions.

OBJECTIVE: Vaccination coverage is decreasing worldwide, favoring the potential reemergence of vaccine-preventable diseases. In this study, we performed a longitudinal characterization of vaccination coverage in Brazil and compared the profiles between the distinct regions in the country to test whether there has been a substantial change over the last 5 years. METHODS: De-identified publicly available data were retrieved from the repository of the Brazilian Ministry of Health, comprising detailed information on vaccination coverage in all age groups between 1994 and 2019. The vaccination coverage for the whole country and for each Brazilian region, by year, was examined, and a time-series pattern analysis was performed. RESULTS: A significant decrease in overall vaccination coverage across the country regions was observed between 2017 and 2019, especially in childhood immunization. A reduction in BCG, hepatitis B, influenza, and rotavirus vaccine coverage was observed. Conversely, vaccines against measles, mumps, rubella, varicella, and meningococcus showed an increase in coverage. Region-specific changes in vaccination patterns within the study period were observed. CONCLUSIONS: A substantial reduction in vaccination coverage was detected in Brazil, a country already highly susceptible to the emergence of epidemic infectious diseases. Continuing evaluation of the immunization program actions may help to improve vaccination coverage and prevent new epidemics.

Seroepidemiological survey of canine visceral leishmaniasis in a continental island of northeast Brazil / Investigação soroepidemiológica da leishmaniose visceral canina em uma ilha continental do Nordeste do Brasil

Introduction: Visceral leishmaniasis (VL) is endemic disease in the neighboring municipalities of the continental island Ilha de Maré, Salvador, Bahia, Brazil. Nevertheless, VL has not been reported in the island itself. Objective: the present study aimed to investigate the seroprevalence and clinical signs of Canine Visceral Leishmaniasis (CVL) and to identify the sand fly population present in the village of Botelho, Ilha de Maré. Methodology: sera of local dogs were tested for anti-Leishmania IgG by immunoassays (screening with TR DPP ™ rapid test and confirmatory with indirect ELISA, Bio-Manguinhos/Fiocruz) and an entomological survey was conducted to estimate and identify the phlebotomine fauna of the region. Results: seven out of 106 samples (6.6%) were positive using rapid test. These positive samples were sent to the Central Laboratory of Bahia for confirmation by indirect ELISA. However, all samples presentednegative results. Nine specimens of Pressatia choti, subfamily Phlebotominae were identified, being this species frequently found in areas with cutaneous leishmaniasis transmission in Brazil. Conclusion: although this work did not confirm the presence of CVL in Ilha de Maré, new serological and entomological studies in a larger area are required for the maintenance of the epidemiological surveillance in the emphasized insular area.

Introdução: Leishmaniose Visceral (LV) é uma doença endêmica em municípios vizinhos à Ilha de Maré, situada na plataforma continental do município de Salvador, Bahia, Brasil. Entretanto, casos de LV não tem sido notificados nesta Ilha. Objetivo: O presente trabalho objetivou investigar a soroprevalência e sinais clínicos de Leishmaniose Visceral Canina (LVC) e identificar a população de flebótomos presentes no povoado de Botelho, Ilha de Maré. Metodologia: soro de cães locais foram testados para IgG anti-Leishmania por imunoensaios (triagem com teste rápido TR DPP™ e confirmatório com Elisa Indireto, Bio-Manguinhos/Fiocruz) e uma investigação entomológica foi conduzida para estimar e identificar a fauna flebotomínea da região. Resultados: sete de 106 amostras (6,6%) foram positivas usando o teste rápido. As amostras positivas foram encaminhadas ao Laboratório Central da Bahia para a confirmação por ELISA indireto. Entretanto, essas amostras apresentaram resultado negativo. Foram encontrados nove exemplares da espécie Pressatia choti, subfamília Phlebotominae, espécie frequentemente encontrada em áreas de transmissão de leishmaniose cutânea no Brasil. Conclusão: apesar deste trabalho não ter confirmado a presença de LVC na Ilha de Maré, novos inquéritos sorológicos e analises entomológicas em uma maior área são necessários para a manutenção de uma vigilância epidemiológica na região insular em destaque.

Inactivated Rabies Virus-Based Ebola Vaccine Preserved by Vaporization Is Heat-Stable and Immunogenic Against Ebola and Protects Against Rabies Challenge.

BACKGROUND: Ebola virus (EBOV) is a highly lethal member of the Filoviridae family associated with human hemorrhagic disease. Despite being a sporadic disease, it caused a large outbreak in 2014-2016 in West Africa and another outbreak recently in the Democratic Republic of Congo. Several vaccine candidates are currently in preclinical and clinical studies but none are stable without cold chain storage. METHODS: We used preservation by vaporization (PBV), a novel processing technology to heat-stabilize FiloRab1 (inactivated rabies-based Ebola vaccine), a candidate Ebola vaccine, and stored the vials at temperatures ranging from 4°C to 50°C for 10 days to 12 months. We immunized Syrian hamsters with the best long-term stable FiloRab1 PBV vaccines and challenged them with rabies virus (RABV). RESULTS: Syrian hamsters immunized with FiloRab1 PBV-processed vaccines stored at temperatures of 4°C and 37°C for 6 months, and at 50°C for 2 weeks, seroconverted against both RABV-G and EBOV-GP. Notably, all of the FiloRab1 PBV vaccines proved to be 100% effective in a RABV challenge model. CONCLUSIONS: We successfully demonstrated that the FiloRab1 PBV vaccines are stable and efficacious for up to 6 months when stored at temperatures ranging from 4°C to 37°C and for up to 2 weeks at 50°C.

Natural infection by Leishmania infantum in the Lutzomyia longipalpis population of an endemic coastal area to visceral leishmaniasis in Brazil is not associated with bioclimatic factors.

Visceral leishmaniasis (VL) is a zoonosis caused by the protozoan Leishmania infantum and in Brazil is transmitted mainly by the bite of Lutzomuyia longipalpis sand flies. Data about the presence, distribution, natural infection rate, seasonal and monthly dynamics of the vector population are important for optimizing the measures to control VL in endemic areas. This study aimed to identify sand fly fauna in an endemic area for VL to detect the prevalence of L. infantum infection in the Lu. longipalpis population and to elucidate the influence of bioclimatic factors on the monthly fluctuations of this vector. HP light traps were monthly set in the intradomicile and peridomicile of residences located in the central and beachfront areas of Camaçari, a VL endemic area. The sand fly collection was conducted in two periods: i) period 1-between December 2011 and November 2012 and ii) period 2-August 2014 and July 2015. Sand fly species were identified and detection of L. infantum infection by qPCR was performed in pools of female Lu. longipalpis. For the first time, the parasite load of positive pools was correlated with the number of Lu. longipalpis captured per month in both periods. Correlation analyses between the monthly fluctuation of the sand fly population and bioclimatic indices of the municipality in both collection periods were also performed. In both evaluated periods, more than 98% of the collected sand flies were Lu. longipalpis, confirming the predominance of this species in the region. It was captured mostly in the beachfront area in all months evaluated (99%). For the period 1, Leishmania DNA was detected in 81% of tested pools representing a minimal infection rate of 9.6%. In the period 2, 40% of the pools were positive with a minimal infection rate of 10.2%. Infected sand flies were only detected in the beachfront area in both periods. The parasite load was low and did not vary in the evaluated months despite the number of collected sand flies. No correlation was observed for climatic factors in both areas of Camaçari. These findings emphasize the high risk of Leishmania transmission in Camaçari regardless of the season and that other factors, aside from bioclimatic elements, are influencing the sand fly population monthly fluctuation.

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.

Non-neutralizing antibodies elicited by recombinant Lassa-Rabies vaccine are critical for protection against Lassa fever.

Lassa fever (LF), caused by Lassa virus (LASV), is a viral hemorrhagic fever for which no approved vaccine or potent antiviral treatment is available. LF is a WHO priority disease and, together with rabies, a major health burden in West Africa. Here we present the development and characterization of an inactivated recombinant LASV and rabies vaccine candidate (LASSARAB) that expresses a codon-optimized LASV glycoprotein (coGPC) and is adjuvanted by a TLR-4 agonist (GLA-SE). LASSARAB elicits lasting humoral response against LASV and RABV in both mouse and guinea pig models, and it protects both guinea pigs and mice against LF. We also demonstrate a previously unexplored role for non-neutralizing LASV GPC-specific antibodies as a major mechanism of protection by LASSARAB against LF through antibody-dependent cellular functions. Overall, these findings demonstrate an effective inactivated LF vaccine and elucidate a novel humoral correlate of protection for LF.