Biology subjects

Brown, G. D.

Publications and source records attributed to Brown, G. D..

At least 19 recordsLinked to original sources

bioRxiv2026

A double-blinded, placebo-controlled field trial of an OspA-based oral reservoir targeted vaccine against Borrelia burgdorferi

Lyme disease, caused by Borrelia burgdorferi and transmitted by Ixodes scapularis ticks, remains a significant vector-borne illness in the United States. Small mammal reservoirs, particularly Peromyscus leucopus, play a critical role in B. burgdorferi maintenance. Here we conducted a five-year, randomized, double-blinded, placebo-controlled field trial deploying an oral OspA-based reservoir targeted vaccine (RTV) across seven Maryland sites. Bayesian modeling provided estimates of vaccine impact on mouse anti-OspA antibody levels, nymphal tick infection prevalence (NIP), mouse infection rates, and seroconversion to B. burgdorferi in hunting dogs. RTV sites exhibited an estimated 10.5% proportional increase in protective murine anti-OspA antibody levels and a 15.4% reduction in NIP by year five. We also found a lower infection prevalence in mouse blood fed nymphal ticks (9.8%). RTV sites exhibited modest decreases in mouse infection prevalence and dog seroconversion rates were similar between groups. Our results indicate that anti-OspA antibody in vaccinated-infected P. leucopus reduced B. burgdorferi summertime larval infection prevalence, measured as NIP reductions the following spring. This suggests that OspA-based oral RTV reduces B. burgdorferi transstadial transmission within tick populations. Our findings advance development of reservoir targeted solutions for Lyme disease prevention. Further evaluation of impacts on incidental hosts is needed.

microbiology↗

bioRxiv2026

Dectin-2-dependent adaptive immunity governs intestinal clearance of systemic Candida albicans

Effective immunity to Candida albicans requires coordination between innate recognition and induction of adaptive CD4 T cell responses. While the C-type lectin receptor Clec4n (Dectin-2) is known to drive Th17 polarization, its role in shaping tissue-specific adaptive responses remains incompletely understood. Here, we used an OT-II antigen-specific CD4 T cell transfer model combined with OVA-expressing Candida albicans to dissect the function of Dectin-2 during systemic infection. We found that Dectin-2 is dispensable for antigen presentation and CD4 T cell priming in gut-draining lymph nodes. Moreover, we show that Dectin-2-deficient mice fail to control fungal growth in the intestinal mucosa, despite elevated local production of IL-17A and GM-CSF. The increased susceptibility of the Dectin-2-deficient mice was associated with impaired neutrophil activation in the intestinal mucosa. These findings identify a tissue-specific checkpoint role for Dectin-2, linking balanced adaptive Th17 cytokine responses to granulocyte function, and revealing a previously unappreciated mechanism required for anti-fungal immune regulation at intestinal mucosal surface.

immunology↗

bioRxiv2025

Comprehensive Mapping of the Virus and Host Factors that Guide the Paths of HIV-1 Escape from a Therapeutic

HIV-1 resistance to therapeutics can emerge through diverse mutational routes, yet the determinants guiding pathway selection in vivo remain unclear. Through comprehensive screening, we identified 18 mutations in the HIV-1 Env protein that enhance resistance to the FDA-approved small-molecule therapeutic temsavir. We then examined their occurrence in HIV-infected individuals who developed resistance on therapy. Only a subset of the resistance-enhancing mutations emerged in vivo. On-treatment mutation frequencies correlated with their spontaneous emergence rates in temsavir-untreated individuals, and were governed by two parameters: (i) Probability of mutation appearance, determined by number and type of nucleotide changes required, and (ii) Probability of mutation persistence, determined by Env functional and immune fitness. Notably, non-neutralizing antibodies commonly-elicited in HIV-infected individuals restricted emergence of multiple resistant forms, driving convergence to a narrow set of escape routes. These findings establish a quantitative framework for predicting therapeutic resistance and reveal how host-immunity constrains viral evolution during treatment.

microbiology↗

bioRxiv2025

Clec7a-mediated regulation of Killer-like Lectin Receptor expression controls T cell immunity

Clec7a is a C-type lectin receptor (CLR) originally defined for its non-redundant role in anti-fungal immunity. Subsequent work has broadened this view, implicating Clec7a in host defense against diverse pathogens and in the pathogenesis of cancer, autoimmunity, neuroinflammation, and developmental disorders. How a single innate receptor orchestrates such wide-ranging outcomes remains unresolved. We previously demonstrated that dendritic cell (DC)-expressed Clec7a is required for protective anti-fungal immunity in the gastrointestinal tract through regulation of fungus-specific CD4 T cell responses. Here, we show that Clec7a controls the expression of multiple C-type lectins in DCs, including a cluster of killer lectin-like receptors (KLRs). Notably, we reveal that these KLRs directly regulate DC function and control CD4 T cell responses. These findings define a novel Clec7a-KLR axis that integrates innate and adaptive immunity, highlighting a regulatory pathway with broad relevance for immune homeostasis, inflammation, and host defense.

immunology↗

bioRxiv2025

KLRE1 shapes antifungal immunity by tuning dendritic cell and T cell activation through distinct heterodimeric partners

Dendritic cells (DCs) instruct adaptive immunity by integrating inflammatory cues to regulate co-signalling molecules and T cell activation. We recently discovered that the pattern recognition receptor Dectin-1 (Clec7a) controls expression of a network of killer lectin-like receptors (KLRs), including KLRI1 and KLRI2, which regulate adaptive immune responses. Here, we identify KLRE1 as a key regulator of DC phenotype and function, acting through distinct heterodimeric interactions with KLRI1 and KLRI2. KLRE1 is expressed by tissue-resident and bone marrow-derived DCs and is dynamically regulated by inflammatory signals, including fungal stimuli. Mechanistically, KLRE1:KLRI1 heterodimers promote DC activation, increasing CD40, CD80, CD86, and MHC-II, whereas KLRE1:KLRI2 heterodimers restrain activation. Differential regulation of KLRI1 and KLRI2 by inflammatory signals shapes heterodimer availability and immune outcomes under distinct conditions. Functionally, KLRE1 deficiency enhances DC activation and T cell responses in vitro and in vivo during Candida albicans infection. Strikingly, KLRI1- and KLRI2-deficient mice showed opposite survival outcomes during systemic candidiasis, despite similar fungal burdens, implicating KLRE1 heterodimers in disease tolerance rather than pathogen clearance. Protection in KLRI1-deficient mice was associated with a more balanced T cell response, whereas susceptibility to infection associated with KLRI2 deficiency resulted from increased T cell activation and migratory potential, leading to systemic inflammation and renal dysfunction. Thus, KLRE1 heterodimers fine-tune DC-driven T cell immunity, balancing protection and immunopathology during fungal infection.

immunology↗

bioRxiv2025

Antagonism between bacteriophages and macrophages decreases efficacy of a phage cocktail and increases bacteriophage resistance

Phage therapy, the use of viruses that infect bacteria (bacteriophages), is a promising complement to antibiotics during the antimicrobial resistance crisis, but treatment success is very variable. Evolution of bacterial resistance to bacteriophages and bacteriophage counter-resistance (coevolution) during therapy may explain some of this variation, the dynamics of which may be affected by interactions with the patients immune system. Here, we examine how a pathogenic bacterium, Pseudomonas aeruginosa coevolves with two clinically relevant bacteriophages (14-1 and PNM) when in the presence of macrophages (RAW 264.7 cell line). We show macrophages reduced the rate by which bacteria were killed by bacteriophages, likely by reducing bacteria-bacteriophage contact rates. Over evolutionary time-scales, macrophages increased the proportion of bacteriophage resistant bacteria compared to where macrophages were absent. These differences in resistance rates were likely driven by the early advantage in density offered by macrophages to bacteria, and exclusion of PNM from the bacteriophage cocktail which otherwise increased in frequency in the absence of macrophages. Consequently, macrophages significantly altered the short- and long-term efficacy of a bacteriophage cocktail. In line with a growing body of work, our results suggest that the patients immune system can reduce the efficacy of phage therapy, potentially driving variable outcomes in therapy success in patients. Significance statementPhage therapy, the use of viruses that infect bacteria (bacteriophages), is a promising complement to antibiotics during the antimicrobial resistance crisis. However, treatment success is very variable. One, often overlooked, variable is the immune system and how this influences bacteriophage efficacy, and how bacteria evolve resistance to bacteriophages. We find that macrophages reduce the rate by which bacteria are killed by bacteriophages. Resistance to bacteriophages also increased in the presence of macrophages, showing macrophages affect the short- and long-term efficacy of phage therapy. These results highlight the importance of the immune system in phage therapy, and the need for more research in this area.

evolutionary biology↗

bioRxiv2024

Aspergillus-mediated allergic airway inflammation is triggered by dendritic cell recognition of a defined spore morphotype, a process that can be targeted via antifungal therapeutics.

BackgroundExposure to fungi, especially Aspergillus fumigatus (A.f.), can elicit potent allergic inflammation that triggers and worsens asthmatic disease. Dendritic cells (DCs), initiate allergic inflammatory responses to allergic stimuli. However, it is unclear if A.f. spores during isotropic growth (early spore swelling) can activate DCs to initiate allergic responses or if germination is required. This lack of basic understanding of how A.f. causes disease is a barrier to the development of new treatments. ObjectiveTo show that a precise A.f. morphotype stage during spore swelling can trigger DCs to mediate allergic inflammatory responses and ascertain if antifungal therapeutics can be effective at suppressing this process. MethodsWe employed an A.f. strain deficient in pyrimidine biosynthesis ({Delta}pyrG) to generate populations of A.f. spores arrested at different stages of isotropic growth (swelling) via temporal removal of uracil and uridine from growth media. These arrested spore stages were cultured with bone marrow derived DCs (BMDCs), and their activation measured via flow cytometry and ELISA to interrogate which growth stage was able to activate BMDCs. These BMDCs were then adoptively transferred into the airways, to assess if they were able to mediate allergic inflammation in naive recipient mice. Allergic airway inflammation in vivo was determined via flow cytometry, ELISA and qPCR. This system was also used to determine if antifungal drug (itraconazole) treatment could alter early stages of spore swelling and therefore BMDC activation and in vivo allergic inflammation upon adoptive transfer. ResultsWe found that A.f. isotropic growth is essential to trigger BMDC activation and mediate allergic airway inflammation. Furthermore, using time arrested A.f. stages, we found that least 3h in growth media enabled spores to swell sufficiently to activate BMDCs to elicit allergic airway inflammation in vivo. Incubation of germinating A.f. with itraconazole reduced spore swelling and partially reduced their ability to activate BMDCs to elicit in vivo allergic airway inflammation. ConclusionIn summary, our results have pinpointed the precise stage of A.f. development when germinating spores are able to activate DCs to mediate downstream allergic airway inflammation. Furthermore, we have identified that antifungal therapeutics can be effective in reducing the potential of A.f. spores to stimulate allergic responses, highlighting a potential mechanism by which antifungal treatment might help to prevent the development of fungal allergy.

immunology↗

bioRxiv2023

Within-Host Bayesian Joint Modeling of Longitudinal and Time-to-Event Data of Leishmania Infection

The host immune system plays a significant role in managing and clearing pathogen material during an infection, but this complex process presents numerous challenges from a modeling perspective. There are many mathematical and statistical models for these kinds of processes that take into account a wide range of events that happen within the host. In this work, we present a Bayesian joint model of longitudinal and time-to-event data of Leishmania infection that considers the interplay between key drivers of the disease process: pathogen load, antibody level, and disease. The longitudinal model also considers approximate inflammatory and regulatory immune factors. In addition to measuring antibody levels produced by the immune system, we adapt data from CD4+ and CD8+ T cell proliferation, and expression of interleukin 10, interferon-gamma, and programmed cell death 1 as inflammatory or regulatory factors mediating the disease process. The model is developed using data collected from a cohort of dogs naturally exposed to Leishmania infantum. The cohort was chosen to start with healthy infected animals, and this is the majority of the data. The model also characterizes the relationship features of the longitudinal outcomes and time of death due to progressive Leishmania infection. In addition to describing the mechanisms causing disease progression and impacting the risk of death, we also present the models ability to predict individual trajectories of Canine Leishmaniosis (CanL) progression. The within-host model structure we present here provides a way forward to address vital research questions regarding the understanding progression of complex chronic diseases such as Visceral Leishmaniasis, a parasitic disease causing significant morbidity worldwide. Author SummaryThe immune system is complex and its effectiveness against infection depends on a variety of host and pathogen factors. Despite numerous studies of Leishmania parasite infections, researchers are still discovering new connections between immune system components with hopes of better understanding how the immune system functions during Leishmania infection. The development of tools for understanding, preventing, and predicting Leishmania infection outcomes is the main goal of this work. We present a computational model made using field-collected data during canine Leishmania infections. The model considers the interplay between three main components: parasite load, antibody level, and disease severity. The model explores how key inflammatory and regulatory elements of the immune response affect these main components, including T cell proliferation and important cytokine expressions such as protective interferon-gamma (IFN-{gamma}) or inhibitory interleukin 10 (IL-10) [1]. Although the induction of CD4+ T helper 1 cell responses is considered essential for immunity against Leishmania, B cells and the production of Leishmania-specific antibodies have also been proposed to play an important role in disease progression [2]. In a simpler model, Pabon-Rodriguez et. al. [3] showed antibody levels are dependent on pathogen load and canine Leishmaniasis (CanL) disease presentation. These high levels of Leishmania specific antibodies are observed in subjects with visceral Leishmaniasis (VL) and other severe forms of Leishmanial disease, and there is accumulating evidence that B cells and antibodies correlate with pathology [4]. In Section 1, we introduce Canine Leishmaniasis and discuss the importance of host-pathogen interaction with the immune response. Next, in Section 2, we introduce the data collection study, the variables utilized in this model, and define the clinical signs of Leishmania infection. In addition, this section explains how the presented model was constructed based on different techniques. A summary of model parameters, model implementation details, convergence diagnostics, and sensitivity analysis are also included. In Section 3, we provide summary results of how different model variables interact with one another and disease progression forecasts. In Section 4, we discuss the results and provide further recommendations and considerations.

immunology↗

bioRxiv2023

The pathogenesis of experimental Emergomycosis in mice.

Emergomyces africanus is a recently identified thermally-dimorphic fungal pathogen that causes disseminated infection in people living with advanced HIV disease. Known as emergomycosis, this disseminated disease is associated with very high case fatality rates. Over the last decade, improved diagnostics and fungal identification in South Africa resulted in a dramatic increase in the number of reported cases. Although the true burden of disease is still unknown, emergomycosis is among the most frequently diagnosed dimorphic fungal infections in Southern Africa; and additional species in the genus have been identified on four continents. Little is known about the pathogenesis and the hosts immune response to this emerging pathogen. Therefore, we established a murine model of pulmonary infection using a clinical isolate, E. africanus (CBS 136260). Both conidia and yeast forms caused pulmonary and disseminated infection in mice with fungus subsequently isolated in culture from lung, spleen, liver, and kidney tissue. Wild-type C57BL/6 mice demonstrated a drop in body weight at two weeks post-infection, corresponding to a peak in fungal burden in the lung, spleen, liver, and kidney. An increase in pro-inflammatory cytokine production was detected in homogenized lung supernatants including IFN-{gamma}, IL-1{beta}, IL-6, IL12-p40 and IL-17 at three- and four-weeks post-infection. Rag-1-deficient mice, lacking mature T and B cells, had an increased fungal burden associated with reduced IFN-{gamma} production. Together our data support a protective T-helper type-1 immune response to E. africanus infection. This may provide a possible explanation for the susceptibility of only a subset of people living with advanced HIV disease despite hypothesized widespread environmental exposure. In summary, we have established a novel murine model of E. africanus disease providing critical insights into the host immune components required for eliminating the infection. Author summaryEmergomyces africanus is a thermally-dimorphic fungus that was recently described as the cause of disseminated infections in persons living with advanced HIV disease in South Africa, where emergomycosis is among the most frequently diagnosed dimorphic fungal diseases. Four additional Emergomyces species have been described causing serious infections around the world, and the infection has a high case fatality rate. Despite the seriousness of this infection, the pathophysiology, immunology, diagnosis, and optimal management of emergomycosis remain largely unknown, hampered by the absence of an animal model. Here, we established a mouse model of pulmonary and disseminated emergomycosis using a clinical isolate of E. africanus with the aim of investigating the host immune response. We found that infection spread from the lungs to other organs within two weeks. We describe the effector immune responses in immune-competent mice aiding in controlled infection. We also highlight the immune-modulating components lacking in immunocompromised mice that promote susceptibilty to infection. Our study provides new insights into the components of the host immune response required for controlling Emergomyces spp. infection.

immunology↗

bioRxiv2022

CRISPR-based tools for genetic manipulation in pathogenic Sporothrix species

Sporothrix brasiliensis is an emerging fungal pathogen frequently associated with zoonotic transmission of sporotrichosis. Although certain virulence factors have been proposed as potential sporotrichosis determinants, the scarcity of molecular tools for reverse genetics studies on Sporothrix has significantly impeded the dissection of mechanisms underlying the disease. Here, we demonstrate that PEG-mediated protoplast transformation is a powerful method for heterologous expression in S. brasiliensis, S. schenckii and S. chilensis. Combined with CRISPR/Cas9 gene editing, this transformation protocol allowed the deletion of the putative DHN-melanin synthase gene pks1, which is a proposed virulence factor of Sporothrix species. To improve in locus integration of deletion constructs, we deleted the KU80 homologue that is critical for non-homologous end-joining DNA repair. The use of S. brasiliensis {Delta}ku80 strains enhanced homologous-directed repair during transformation resulting in increased targeted gene deletion. In conclusion, our CRISPR/Cas9-based transformation protocol provides an efficient tool for targeted gene manipulation in Sporothrix species.

molecular biology↗

bioRxiv2022

Apolipoprotein E controls Dectin-1-dependent development of monocyte-derived alveolar macrophages upon pulmonary β-glucan-induced inflammatory adaptation

The lung is constantly exposed to the outside world and optimal adaptation of immune responses is crucial for efficient pathogen clearance. However, mechanisms which lead to the functional and developmental adaptation of lung-associated macrophages remain elusive. To reveal such mechanisms, we developed a reductionist model of environmental intranasal {beta}-glucan exposure, allowing for the detailed interrogation of molecular mechanisms of pulmonal macrophage adaptation. Employing single-cell transcriptomics, high dimensional imaging and flow cytometric characterization paired to in vivo and ex vivo challenge models, we reveal that pulmonary low-grade inflammation results in the development of Dectin-1 - Card9 signaling-dependent monocyte-derived macrophages (MoAM). MoAMs expressed high levels of CD11b, ApoE, Gpnmb and Ccl6, were glycolytic and produced large amounts of interleukin 6 upon restimulation. Myeloid cell specific ApoE ablation inhibited monocyte to MoAM differentiation dependent on M-CSF secretion, promoting MoAM cell death thus impeding MoAM maintenance. In vivo, {beta}-glucan-elicited MoAMs limited the bacterial burden of Legionella pneumophilia post infection and ameliorated fibrosis severity in a murine fibrosis model. Collectively these data identify MoAMs that are generated upon environmental cues and ApoE as an important determinant for lung immune resilience.

immunology↗

bioRxiv2022

Human Dectin-1 is O-glycosylated and serves as a ligand for C-type lectin receptor CLEC-2

C-type lectin receptors (CLRs) elicit immune responses upon recognition of glycoconjugates present on pathogens and self-components. While Dectin-1 is the best-characterized CLR recognizing {beta}-glucan on pathogens, the endogenous targets of Dectin-1 are not fully understood. Herein, we report that human Dectin-1 is a ligand for CLEC-2, another CLR expressed on platelets. Biochemical analyses revealed that Dectin-1 is a mucin-like protein as its stalk region is highly O-glycosylated. A sialylated core 1 glycan attached to the EDxxT motif of human Dectin-1, which is absent in mouse Dectin-1, provides a ligand moiety for CLEC-2. Strikingly, the expression of human Dectin-1 in mice rescued the lethality and lymphatic defect resulting from a deficiency of Podoplanin, a known CLEC-2 ligand. This finding is the first example of an innate immune receptor also functioning as a physiological ligand to regulate ontogeny upon glycosylation.

immunology↗

bioRxiv2022

Bayesian Hierarchical Model for Immune Responses to Leishmania - a tick borne Co-Infection Study

While many Bayesian state-space models for infectious disease processes focus on population infection dynamics (e.g., compartmental models), in this work we examine the evolution of infection processes and the complexities of the immune responses within the host using these techniques. We present a joint Bayesian state-space model to better understand how the immune system contributes to the control of Leishmania infantum infections over the disease course. We use longitudinal molecular diagnostic and clinical data of a cohort of dogs to describe population progression rates and present evidence for important drivers of clinical disease. Among these results, we find evidence for the importance of co-infection in disease progression. We also show that as dogs progress through the infection, parasite load is influenced by their age, ectoparasiticide treatment status, and serology. Furthermore, we present evidence that pathogen load information from an earlier point in time influences its future value and that the size of this effect varies depending on the clinical stage of the dog. In addition to characterizing the processes driving disease progression, we predict individual and aggregate patterns of Canine Leishmaniasis progression. Both our findings and the application to individual-level predictions are of direct clinical relevance, presenting possible opportunities for application in veterinary practice and motivating lines of additional investigation to better understand and predict disease progression. Finally, as an important zoonotic human pathogen, these results may support future efforts to prevent and treat human Leishmaniosis. 1 AUTHOR SUMMARYThe immune system is a complex network that involves organs, cells, and proteins working together with the main purpose of protecting the body against harmful microorganisms such as bacteria, viruses, fungi, and toxins. To explore and study the responses of the host immune system during the course of a disease, we modeled the interaction between pathogen load, antibody responses, and the clinical presentation of this complex system. Specifically, we focused on Canine Leishmaniasis (CanL), a vector-borne disease caused by a parasite that affects internal organs of the body and is known to be fatal if patients remain untreated. In addition, we also considered the impact of possible co-infections with other diseases, which could potentially interact with many disease processes and contribute to different outcomes for infected subjects. With CanL specifically, we consider the presence of Borrelia, Anaplasma, Ehrlichia,, and Heartworm. In general, one limitation in vaccination strategies is a focus on neutralizing antibodies, without incorporating the broader complexities of immune responses. Here, we explore this complexity by jointly considering the interaction between pathogen and antibody development with the purpose of improving our understanding of the processes of disease progression and natural immunity. In this paper, we present a Bayesian model specification for immune responses to a Leishmania infection considering a tick-borne co-infection study. The model implementation is based on the general vector autoregressive (VAR) model, adapted to the problem under study. While the methodology around Bayesian VAR models is not new in the literature, in this work we adapt the more general VAR approach in a parsimonious way to a particular subclass of longitudinal problems. We believe our defined Bayesian model is useful to clinicians and veterinarians to better understand the immune responses and Leishmania infection control over time, which makes this work a novel application of Bayesian VAR models. We present evidence that pathogen load information from an earlier point in time influences its future value and that the size of this effect varies depending on the CanL clinical stage of the dog. In addition to characterizing evidence for the processes driving disease progression, we predict individual and aggregate patterns of CanL progression. The structure of this paper starts in Section 2 with an introduction to CanL infection as well as a discussion of possible co-infection with other pathogens. In Section 3, we include a description of the motivating prospective study along with the measured individual-level variables, a definition of the clinical signs of leishmaniosis infection, and a description of the available data coming from the study. In addition, this section explains the dynamic process and corresponding model specification via Bayesian methodology and a statement of contribution. A summary of prior distributions for model parameters, model implementation details, and convergence diagnostics are also included. In Section 4, we provide summary results from the posterior distribution as well as a summary of the corresponding disease progression forecasts. In Section 5, we discuss the results and describe future considerations to improve and extend the model.

immunology↗

bioRxiv2022

Patterns of Volatility Across the Spike Protein Accurately Predict the Emergence of Mutations within SARS-CoV-2 Lineages

Mutations in the spike glycoprotein of SARS-CoV-2 allow the virus to probe the sequence space in search of higher-fitness states. New sublineages of SARS-CoV-2 variants-of-concern (VOCs) continuously emerge with such mutations. Interestingly, the sites of mutation in these sublineages vary between the VOCs. Whether such differences reflect the random nature of mutation appearance or distinct evolutionary spaces of spike in the VOCs is unclear. Here we show that each position of spike has a lineage-specific likelihood for mutations to appear and dominate descendent sublineages. This likelihood can be accurately estimated from the lineage-specific mutational profile of spike at a protein-wide level. The mutability environment of each position, including adjacent sites on the protein structure and neighboring sites on the network of comutability, accurately forecast changes in descendent sublineages. Mapping of imminent changes within the VOCs can contribute to the design of immunogens and therapeutics that address future forms of SARS-CoV-2.

bioinformatics↗

bioRxiv2021

Maternal transfer of neutralizing antibodies to OspA after oral vaccination of the rodent reservoir

Lyme Disease presents unique challenges for public health efforts. We hypothesized that transfer of protective antibodies between mothers and offspring should occur after oral vaccination of C3H-HeN mice with E. coli overexpressing OspA. We present new evidence for maternal transfer of vaccine induced neutralizing anti-OspA IgG antibodies to mouse pups through ingestion of colostrum. Protective levels of OspA antibodies in pups were present from 2-5 weeks after birth and they persisted in some mice until 9 weeks of age. This was corroborated by detection of neutralizing antibodies in the serum of all pups at 2-3 weeks after birth and in some mice at 9 weeks of age. A clear association was found between robust antibody responses in mothers and the length of antibody persistence in the respective pups using a novel longitudinal Bayesian model. These factors are likely to impact the enzootic cycle of B. burgdorferi when reservoir targeted OspA-based vaccination interventions are implemented.

microbiology↗

bioRxiv2019

Gradual decrease in the inter-population diversity of HIV-1 Env among group M lineages worldwide

HIV-1 group M was transmitted to humans nearly one century ago. The virus has since diversified to form distinct clades, which spread to multiple regions worldwide. Of the different proteins encoded by HIV-1, the envelope glycoproteins (Envs) have diversified most rapidly in all infected populations. We compared the range of variants that emerged during the AIDS pandemic in diverse HIV-1 clades and distinct geographic regions. Our analyses focused on two components of Env that contain multiple epitopes of broadly-neutralizing antibodies: the glycan shield and apex domain. Interestingly, at each Env position, the amino acid in the inferred clade ancestor was replaced by a unique combination of emerging variants. Key antigenic sites and genetic signatures of vaccine protection have gradually evolved toward conserved frequency distributions (FDs) of all amino acids. FDs are specific for position and clade and are highly conserved in populations from different regions. Remarkably, founder effects of Env mutations in distinct clades and recently-infected regions were significantly reduced during the epidemic by evolution of each site toward the position-specific FD. These findings suggest that the selective pressures that guide evolution of Env are conserved in different populations. They are sufficiently strong to reduce founder effects at the clade and regional levels and have significantly altered the distribution of Env forms that circulate worldwide. Consequently, the intra-population diversity of the Env protein continues to increase whereas the inter-population diversity is gradually decreasing.\n\nImportanceThe Env protein of HIV-1 is the primary target in AIDS vaccine design. Due to frequent mutations, new Env variants continuously emerge in the population. The increasing number of Env forms and apparent randomness of the changes limit our ability to design broadly-effective vaccines. We examined the populations-level changes that occurred in Env during the AIDS epidemic. Each position of the molecule has evolved toward a specific combination of amino acids. Similar changes occurred in different HIV-1 subtypes and geographic regions toward the same sets of forms, often from distinct ancestral sequences. Such conserved patterns of evolution define a new framework for designing vaccines that are tailored to the unique combination of Env variants expected to circulate in each population.

evolutionary biology↗

bioRxiv2019

Mannan detecting C-type lectin receptor probes recognise immune epitopes with diverse chemical, spatial and phylogenetic heterogeneity in fungal cell walls

During the course of fungal infection, pathogen recognition by the innate immune system is critical to initiate efficient protective immune responses. The primary event that triggers immune responses is the binding of Pattern Recognition Receptors (PRRs), which are expressed at the surface of host immune cells, to Pathogen-Associated Molecular Patterns (PAMPs) located predominantly in the fungal cell wall. Most fungi have mannosylated PAMPs in their cell walls and these are recognized by a range of C-type lectin receptors (CTLs). However, the precise spatial distribution of the ligands that induce immune responses within the cell walls of fungi are not well defined. We used recombinant IgG Fc-CTLs fusions of three murine mannan detecting CTLs, including dectin-2, the mannose receptor (MR) carbohydrate recognition domains (CRDs) 4-7 (CRD4-7), and human DC-SIGN (hDC-SIGN) and the {beta}-1,3 glucan-binding lectin dectin-1 to map PRR ligands in the fungal cell wall. We show that epitopes of mannan-specific CTL receptors can be clustered or diffuse, superficial or buried in the inner cell wall. We demonstrate that PRR ligands do not correlate well with phylogenetic relationships between fungi, and that Fc-lectin binding discriminated between mannosides expressed on different cell morphologies of the same fungus. We also demonstrate CTL epitope differentiation during different phases of the growth cycle of Candida albicans and that MR and DC-SIGN labelled outer chain N-mannans whilst dectin-2 labelled core N-mannans displayed deeper in the cell wall. These immune receptor maps of fungal walls therefore reveal remarkable spatial, temporal and chemical diversity, indicating that the triggering of immune recognition events originates from multiple physical origins at the fungal cell surface.\n\nAuthor SummaryInvasive fungal infections remain an important health problem in immunocompromised patients. Immune recognition of fungal pathogens involves binding of specific cell wall components by pathogen recognition receptors (PRRs) and subsequent activation of immune defences. Some cell wall components are conserved among fungal species while other components are species-specific and phenotypically diverse. The fungal cell wall is dynamic and capable of changing its composition and organization when adapting to different growth niches and environmental stresses. Differences in the composition of the cell wall lead to differential immune recognition by the host. Understanding how changes in the cell wall composition affect recognition by PRRs is likely to be of major diagnostic and clinical relevance. Here we address this fundamental question using four soluble immune receptor-probes which recognize mannans and {beta}-glucan in the cell wall. We use this novel methodology to demonstrate that mannan epitopes are differentially distributed in the inner and outer layers of fungal cell wall in a clustered or diffuse manner. Immune reactivity of fungal cell surfaces did not correlate with relatedness of different fungal species, and mannan-detecting receptor-probes discriminated between cell surface mannans generated by the same fungus growing under different conditions. These studies demonstrate that mannan-epitopes on fungal cell surfaces are differentially distributed within and between the cell walls of fungal pathogens.

microbiology↗

bioRxiv2019

A bacterial endosymbiont enables fungal immune evasion during fatal mucormycete infection

Opportunistic infections by environmental fungi are a growing clinical problem, driven by an increasing population of people with immunocompromising conditions. Spores of the Mucorales order are ubiquitious in the environment but can also cause acute invasive infections in humans through germination and evasion of the mammalian host immune system. How they achieve this, and the evolutionary drivers underlying the acquisition of virulence mechanisms, are poorly understood. Here we show that a clinical isolate of Rhizopus microsporus contains a Ralstonia pickettii bacterial endosymbiont required for virulence in both zebrafish and mice, and that this endosymbiosis enables secretion of factors that potently suppress growth of the soil amoeba Dictyostelium discoideum, as well as their ability to engulf and kill other microbes. As amoebae are natural environmental predators of both bacteria and fungi, we propose this tri-kingdom interaction contributes to establishing the endosymbiosis, and acquisition of anti-phagocyte activity. Importantly, we show this activity also protects fungal spores from phagocytosis and clearance by human macrophages, and endosymbiont removal renders the fungal spores avirulent in vivo. Together, these findings describe a novel role for a bacterial endosymbiont in Rhizopus microsporus pathogenesis in animals, and suggest a mechanism of virulence acquisition through environmental interactions with amoebae. In briefHow environmental fungi evolved the mechanisms that enable them to cause opportunistic infections in humans is unclear. Here, we identify a novel tri-kingdom interaction, whereby a bacterial endosymbiont, living within a clinical isolate of the ubiquitous environmental fungus Rhizopus microsporus, causes the generation of a secreted activity that blocks the growth and predatory activity of amoebae. We suggest this provides a new evolutionary driver for the establishment of bacterial/fungal endosymbiosis and demonstrate this is critical for fungal pathogenicity in vivo.

microbiology↗