Francisella Tularensis Research Articles

Structural and biophysical properties of FopA, a major outer membrane protein of Francisella tularensis.

Francisella tularensis is an extremely infectious pathogen and a category A bioterrorism agent. It causes the highly contagious zoonosis, Tularemia. Currently, FDA approved vaccines against tularemia are unavailable. F. tularensis outer membrane protein A (FopA) is a well-studied virulence determinant and protective antigen against tularemia. It is a major outer membrane protein (Omp) of F. tularensis. However, FopA-based therapeutic intervention is hindered due to lack of complete structural information for membrane localized mature FopA. In our study, we established recombinant expression, monodisperse purification, crystallization and X-ray diffraction (~6.5 Å) of membrane localized mature FopA. Further, we performed bioinformatics and biophysical experiments to unveil its structural organization in the outer membrane. FopA consists of 393 amino acids and has less than 40% sequence identity to known bacterial Omps. Using comprehensive sequence alignments and structure predictions together with existing partial structural information, we propose a two-domain organization for FopA. Circular dichroism spectroscopy and heat modifiability assay confirmed FopA has a β-barrel domain consistent with alphafold2’s prediction of an eight stranded β-barrel at the N-terminus. Small angle X-ray scattering (SAXS) and native-polyacrylamide gel electrophoresis revealed FopA purified in detergent micelles is predominantly dimeric. Molecular density derived from SAXS at 31 Å shows putative dimeric N-terminal β-barrels surrounded by detergent corona and connected to C-terminal domains via flexible linker. Disorder analysis predicts N- and C-terminal domains are interspersed by a long intrinsically disordered region and alphafold2 predicts this region to be largely unstructured. Taken together, we propose a dimeric, two-domain organization of FopA in the outer membrane: the N-terminal β-barrel is membrane embedded, provides dimerization interface and tethers to membrane extrinsic C-terminal domain via long flexible linker. Structure determination of membrane localized mature FopA is essential to understand its role in pathogenesis and develop anti-tularemia therapeutics. Our results pave the way towards it.

Development and evaluation of a multiplex droplet digital polymerase chain reaction method for simultaneous detection of five biothreat pathogens

Biothreat agents pose a huge threat to human and public health, necessitating the development of rapid and highly sensitive detection approaches. This study establishes a multiplex droplet digital polymerase chain reaction (ddPCR) method for simultaneously detecting five high-risk bacterial biothreats: Yersinia pestis, Bacillus anthracis, Brucella spp., Burkholderia pseudomallei, and Francisella tularensis. Unlike conventional multiplex real-time PCR (qPCR) methods, the multiplex ddPCR assay was developed using two types of probe fluorophores, allowing the assay to perform with a common two-color ddPCR system. After optimization, the assay performance was evaluated, showing a lower limit of detection (LOD) (0.1–1.0 pg/μL) and good selectivity for the five bacteria targets. The multiplex assay’s ability to simultaneously detect two or more kinds of targets in a sample was also demonstrated. The assay showed strong sample tolerance when testing simulated soil samples; the LOD for bacteria in soil was 2 × 102–2 × 103 colony-forming unit (CFU)/100 mg soil (around 5–50 CFU/reaction), which was 10-fold lower than that of the single-target qPCR method. When testing simulated soil samples at bacterial concentrations of 2 × 103–2 × 104 CFU/100 mg soil, the assay presented a higher sensitivity (100%, 35/35) than that of the qPCR method (65.71%, 23/35) and a good specificity (100%, 15/15). These results suggest that the developed 5-plex ddPCR method is more sensitive than conventional qPCR methods and is potentially suitable for rapidly detecting or screening the five selected bacterial biothreats in suspicious samples.

Determinants of resistance of <i>Francisella tularensis</i> to environmental stress

The review summarizes current literature data on the main structures and components of the tularemia microbe responsible for adaptation to the warm-blooded host macroorganism (susceptible animals, humans). According to scientific data, the successful survival of Francisella tularensis under stress conditions requires the interaction of all cellular structures of the microbe. Despite active research carried out in the field of studying the determinants and mechanisms of F. tularensis resistance, the reason for the high adaptive capacity with low variability of the tularemia pathogen has not been established. These studies are important for understanding the mechanisms of persistence and virulence of F. tularensis, as well as for further development of vaccines and diagnostic tests.

Toxoplasma gondii and Rickettsia spp. in ticks collected from migratory birds in the Republic of Korea

Migratory birds disperse ticks and associated tick-borne pathogens along their migratory routes. Four selected pathogens of medical importance (Coxiella burnetii, Rickettsia spp., Francisella tularensis, and Toxoplasma gondii) were targeted for detection in 804 ticks (365 pools) collected from migratory birds at Hong and Heuksan Islands in the Republic of Korea (ROK) from 2010 to 2011 and 2016. Toxoplasma gondii and Rickettsia spp., were detected in 1/365 (0.27%) and 34/365 (9.32%) pools of ticks, respectively. T. gondii and five rickettsial species were recorded in ticks collected from migratory birds for the first time in ROK. The five rickettsial species (R. monacensis, Candidatus Rickettsia longicornii, R. japonica, R. raoultii, and R. tamurae) were identified using sequence and phylogenetic analysis using ompA and gltA gene fragments. Rickettsia spp. are important pathogens that cause rickettsiosis in humans, with cases recorded in the ROK. These results provide important evidence for the potential role of migratory birds in the introduction and dispersal of T. gondii and Rickettsia spp. along their migratory routes and raise awareness of potential transmission of zoonotic tick-borne pathogens associated with migratory birds in the ROK.

Co-Occurrence of Francisella, Spotted Fever Group Rickettsia, and Midichloria in Avian-Associated Hyalomma rufipes.

The migratory behavior of wild birds contributes to the geographical spread of ticks and their microorganisms. In this study, we aimed to investigate the dispersal and co-occurrence of Francisella and spotted fever group Rickettsia (SFGR) in ticks infesting birds migrating northward in the African-Western Palaearctic region (AWPR). Birds were trapped with mist nests across the Mediterranean basin during the 2014 and 2015 spring migration. In total, 575 ticks were collected from 244 birds. We screened the ticks for the species Francisella tularensis, the genus Francisella, and SFGR by microfluidic real-time PCR. Confirmatory analyses and metagenomic sequencing were performed on tick samples that putatively tested positive for F. tularensis during initial screenings. Hyalomma rufipes was the most common tick species and had a high prevalence of Francisella, including co-occurrence of Francisella and SFGR. Metagenomic analysis of total DNA extracted from two H. rufipes confirmed the presence of Francisella, Rickettsia, and Midichloria. Average nucleotide identity and phylogenetic inference indicated the highest identity of the metagenome-assembled genomes to a Francisella-like endosymbiont (FLE), Rickettsia aeschlimannii, and Midichloria mitochondrii. The results of this study suggest that (i) FLE- and SFGR-containing ticks are dispersed by northbound migratory birds in the AWPR, (ii) H. rufipes likely is not involved in transmission of F. tularensis in the AWPR, and (iii) a dual endosymbiosis of FLEs and Midichloria may support some of the nutritional requirements of H. rufipes.

Neutrophil Survival Signaling During Francisella tularensis Infection.

Neutrophils are the most abundant and shortest-lived leukocytes in humans and tight regulation of neutrophil turnover via constitutive apoptosis is essential for control of infection and resolution of inflammation. Accordingly, aberrant neutrophil turnover is hallmark of many disease states. We have shown in previous work that the intracellular bacterial pathogen Francisella tularensis markedly prolongs human neutrophil lifespan. This is achieved, in part, by changes in neutrophil gene expression. Still unknown is the contribution of major neutrophil pro-survival signaling cascades to this process. The objective of this study was to interrogate the contributions of ERK and p38 MAP kinase, Class I phosphoinositide 3-kinases (PI3K), AKT, and NF-κB to neutrophil survival in our system. We demonstrate that both ERK2 and p38α were activated in F. tularensis-infected neutrophils, but only p38α MAPK was required for delayed apoptosis and the rate of cell death in the absence of infection was unchanged. Apoptosis of both infected and uninfected neutrophils was markedly accelerated by the pan-PI3K inhibitor LY2094002, but AKT phosphorylation was not induced, and neutrophil death was not enhanced by AKT inhibitors. In addition, isoform specific and selective inhibitors revealed a unique role for PI3Kα in neutrophil survival after infection, whereas only simultaneous inhibition of PI3Kα and PI3kδ accelerated death of the uninfected controls. Finally, we show that inhibition of NF-κB triggered rapid death of neutrophil after infection. Thus, we defined roles for p38α, PI3Kα and NF-κB delayed apoptosis of F. tularensis-infected cells and advanced understanding of Class IA PI3K isoform activity in human neutrophil survival.

Ecological niche and potential geographic distributions of Dermacentor marginatus and Dermacentor reticulatus (Acari: Ixodidae) under current and future climate conditions

Abstract. Dermacentor marginatus is a vector disease of both humans and animals and transmits the causative agents of Q fever (Coxiella burnetii) and the spotted fever group (Rickettsia raoultii and R. slovaca), as well as of Crimean–Congo hemorrhagic fever. Dermacentor reticulatus can transmit various pathogens such as Francisella tularensis, Babesia spp., tick encephalitis virus, Coxiella burnetii, Omsk hemorrhagic fever virus, and Rickettsia spp. and can cause serious skin lesions. Herein, ecological niche modeling (ENM) is used to characterize the niches of these two ticks and describe their potential distributional patterns under both current and future climate conditions, as a means of highlighting geographic distributional shifts that may be of public health importance. We assessed distributional implications of five general circulation models (GCMs), under two shared socio-economic pathways (SSP245 and SSP585) for the period 2041–2060. Predictions for D. marginatus showed broad suitable areas across western, central, and southern Europe, with potential for expansion in northern and eastern Europe. Dermacentor reticulatus has suitable areas across western, central, and northern Europe. Under future scenarios, new expansions were observed in parts of northern and eastern Europe and highland areas in central Europe. Despite broad overlap between the niches of the ticks, D. marginatus has a broader niche, which allows it to show greater stability in the face of the changing climate conditions. Areas of potential geographic distributional expansion for these species should be monitored for actual distributional shifts, which may have implications for public health in those regions.

Efficient multiplex CRISPR/Cpf1 (Cas12a) genome editing system in Aspergillus aculeatus TBRC 277

CRISPR/Cas technology is a versatile tool for genome engineering in many organisms, including filamentous fungi. Cpf1 is a multi-domain protein of class 2 (type V) RNA-guided CRISPR/Cas endonuclease, and is an alternative platform with distinct features when compared to Cas9. However, application of this technology in filamentous fungi is limited. Here, we present a single CRISPR/Cpf1 plasmid system in Aspergillus aculeatus strain TBRC 277, an industrially relevant cell factory. We first evaluated the functionality of three Cpf1 orthologs from Acidaminococcus sp. BV3L6 (AsCpf1), Francisella tularensis subsp. novicida U112 (FnCpf1), and Lachnospiraceae bacterium (LbCpf1), in RNA-guided site-specific DNA cleavage at the pksP locus. FnCpf1 showed the highest editing efficiency (93%) among the three Cpf1s. It was further investigated for its ability to delete a 1.7kb and a 0.5kb from pksP and pyrG genes, respectively, using two protospacers targeting these gene loci in a single crRNA array. Lastly, simultaneous editing of three sites within TBRC 277 genome was performed using three guide sequences targeting these two genes as well as an additional gene, kusA, which resulted in combined editing efficiency of 40%. The editing of the NHEJ pathway by targeting kusA to generate a NHEJ-deficient strain of A. aculeatus TBRC 277 improved gene targeting efficiency and yielded more precise gene-editing than that of using wild-type strain. This promising genome-editing system can be used for strain improvement in industrial applications such as production of valuable bioproducts.

Molecular survey on the presence of arthropod-borne bacteria and protozoans in roe deer (Capreolus capreolus) and ticks from Central Italy

Environmental changes, due to climatic emergency and to anthropogenic activities severely impact on the epidemiology of vector borne diseases, mostly when transmitted by ticks. The data about the distribution of microorganisms responsible for them in roe deer (Capreolus capreolus) population living in Italy are scanty and completely lacking in Tuscany, so a molecular survey was carried out to estimate the prevalence of some zoonotic tick-borne pathogens in roe deer, and ticks removed from them, living in areas of Central Italy with high risk of arthropod exposure. Spleen samples from 72 roe deer were tested by PCR for Anaplasma phagocytophilum, Borrelia burgdorferi s.l., Francisella tularensis and piroplasms. Moreover, 345 ticks were removed from 65 roe deer, morphologically or molecularly identified and grouped into 162 pools that were submitted to PCR for detecting the same pathogens. Forty-six (63.88%) roe deer were positive for at least one investigated pathogen: 43 (59.72%) for A. phagocytophilum, 2 (2.78%) for Babesia capreoli, 1 (1.39%) for B. burgdorferi, and 1 (1.39%) for Babesia sp. No animals were PCR positive for F. tularensis. All ticks were identified as Ixodes ricinus. Seventy-six (46.91%) tick pools showed DNA of one or more pathogens: 66 (40.74%) were positive for A. phagocytophilum, 22 (13.58%) for B. burgodorferi s.l., 6 (3.70%) for B. venatorum and 3 (1.85%) for B. capreoli. No pools were positive for F. tularensis. Two or three pathogens were detected in 23 (14.19%) pools.

A case report of ulceroglandular tularemia caused by Francisella tularensis subsp. Holarctica in Iran

BackgroundTularemia is a zoonotic disease that has been reported in many countries of the Northern Hemisphere. However, in some countries, such as Iran, this disease has been neglected by the health care system, and it is under-reported. Case presentationHere we report an unusual case of ulceroglandular tularemia occurring in a 35-year-old woman who presented with a skin lesion of the left flank, inguinal lymphadenopathy, and an abdominal abscess. The serological and real-time PCR tests for tularemia were positive for this patient, and infection by Francisella tularensis subsp. holarctica was confirmed. ConclusionsIt is necessary to implement various educational programs to increase the awareness of physicians with tularemia.

Arginine Catabolism and Polyamine Biosynthesis Pathway Disparities Within Francisella tularensis Subpopulations.

Francisella tularensis is a highly infectious zoonotic pathogen with as few as 10 organisms causing tularemia, a disease that is fatal if untreated. Although F. tularensis subspecies tularensis (type A) and subspecies holarctica (type B) share over 99.5% average nucleotide identity, notable differences exist in genomic organization and pathogenicity. The type A clade has been further divided into subtypes A.I and A.II, with A.I strains being recognized as some of the most virulent bacterial pathogens known. In this study, we report on major disparities that exist between the F. tularensis subpopulations in arginine catabolism and subsequent polyamine biosynthesis. The genes involved in these pathways include the speHEA and aguAB operons, along with metK. In the hypervirulent F. tularensis A.I clade, such as the A.I prototype strain SCHU S4, these genes were found to be intact and highly transcribed. In contrast, both subtype A.II and type B strains have a truncated speA gene, while the type B clade also has a disrupted aguA and truncated aguB. Ablation of the chromosomal speE gene that encodes a spermidine synthase reduced subtype A.I SCHU S4 growth rate, whereas the growth rate of type B LVS was enhanced. These results demonstrate that spermine synthase SpeE promotes faster replication in the F. tularensis A.I clade, whereas type B strains do not rely on this enzyme for in vitro fitness. Our ongoing studies on amino acid and polyamine flux within hypervirulent A.I strains should provide a better understanding of the factors that contribute to F. tularensis pathogenicity.

Toddler With Fever and Limp.

Toddler With Fever and Limp.

The intracellular pathogen Francisella tularensis escapes from adaptive immunity by metabolic adaptation.

Intracellular pathogens lose many metabolic genes during their evolution from free-living bacteria, but the pathogenic consequences of their altered metabolic programs on host immunity are poorly understood. Here, we show that a pathogenic strain of Francisella tularensis subsp. tularensis (FT) has five amino acid substitutions in RibD, a converting enzyme of the riboflavin synthetic pathway responsible for generating metabolites recognized by mucosal-associated invariant T (MAIT) cells. Metabolites from a free-living strain, F. tularensis subsp. novicida (FN), activated MAIT cells in a T-cell receptor (TCR)-dependent manner, whereas introduction of FT-type ribD to the free-living strain was sufficient to attenuate this activation in both human and mouse MAIT cells. Intranasal infection in mice showed that the ribD FT-expressing FN strain induced impaired Th1-type MAIT cell expansion and resulted in reduced bacterial clearance and worsened survival compared with the wild-type free-living strain FN. These results demonstrate that F. tularensis can acquire immune evasion capacity by alteration of metabolic programs during evolution.

In silico functional and structural characterization revealed virulent proteins of Francisella tularensis strain SCHU4.

Francisella tularensis is a pathogenic, aerobic gram-negative coccobacillus bacterium. It is the causative agent of tularemia, a rare infectious disease that can attack skin, lungs, eyes, and lymph nodes. The genome of F. tularensis has been sequenced, and ~16% of the proteome is still uncharacterized. Characterizations of these proteins are essential to find new drug targets for better therapeutics. In silico characterization of proteins has become an extremely important approach to determine the functionality of proteins as experimental functional elucidation is unable to keep pace with the current growth of the sequence database. Initially, we have annotated 577 Hypothetical Proteins (HPs) of F. tularensis strain SCHU4 with seven bioinformatics tools which characterized them based on the family, domain and motif. Out of 577 HPs, 119 HPs were annotated by five or more tools and are further screened to predict their virulence properties, subcellular localization, transmembrane helices as well as physicochemical parameters. VirulentPred predicted 66 HPs out of 119 as virulent. These virulent proteins were annotated to find the interacting partner using STRING, and proteins with high confidence interaction scores were used to predict their 3D structures using Phyre2. The three virulent proteins Q5NH99 (phosphoserine phosphatase), Q5NG42 (Cystathionine beta-synthase) and Q5NG83 (Rrf2-type helix turn helix domain) were predicted to involve in modulation of cytoskeletal and innate immunity of host, H2S (hydrogen sulfide) based antibiotic tolerance and nitrite and iron metabolism of bacteria. The above predicted virulent proteins can serve as novel drug targets in the era of antibiotic resistance.

A challenging case of Francisella Tularensis: teenager’s massive lymphoadenopathy caused by an uncommon infectious disease.

A challenging case of Francisella Tularensis: teenager’s massive lymphoadenopathy caused by an uncommon infectious disease.

Metabolic Reprogramming Mediates Delayed Apoptosis of Human Neutrophils Infected With Francisella tularensis.

Neutrophils (polymorphonuclear leukocytes, PMNs) have a distinctively short lifespan, and tight regulation of cell survival and death is imperative for their normal function. We demonstrated previously that Francisella tularensis extends human neutrophil lifespan, which elicits an impaired immune response characterized by neutrophil dysfunction. Herein, we extended these studies, including our transcriptional profiling data, and employed Seahorse extracellular flux analysis, gas chromatography-mass spectrometry metabolite analysis, flow cytometry and several other biochemical approaches to demonstrate that the delayed apoptosis observed in F. tularensis-infected neutrophils is mediated, in part, by metabolic reprogramming. Specifically, we show that F. tularensis-infected neutrophils exhibited a unique metabolic signature characterized by increased glycolysis, glycolytic flux and glucose uptake, downregulation of the pentose phosphate pathway, and complex glycogen dynamics. Glucose uptake and glycolysis were essential for cell longevity, although glucose-6-phosphate translocation into the endoplasmic reticulum was not, and we identify depletion of glycogen as a potential trigger of apoptosis onset. In keeping with this, we also demonstrate that ablation of apoptosis with the pan-caspase inhibitor Q-VD-OPh was sufficient to profoundly increase glycolysis and glycogen stores in the absence of infection. Taken together, our data significantly advance understanding of neutrophil immunometabolism and its capacity to regulate cell lifespan.

Differentiation of the Francsella tularensis subspecies by the INDEL typing method

Background. Francisella tularensis, the etiological agent of tularemia, belongs to the facultative intracellular pathogens that cause severe disease in humans and man species of animals, and is a category A bioterrorism agent. Currently, F. tularensis is divided into four subspecies: F. tularensis subsp. tularensis (nearctica), F. tularensis subsp. holarctica, F. tularensis subsp. mediasiatica, F. tularensis subsp novicida, which differ in their pathogenicity and geographical distribution. Historically, this division was due to the different distribution area of strains, their differences in biochemical activity and pathogenicity for different hosts. The biochemical identification of subspecies is very laborious and requires work with live cultures of the microorganism, which determines the need to develop new molecular genetic approaches for genotyping F. tularensis strains.The aim of this study is to develop a method for differentiating subspecies and individual groups of F. tularensis based on INDEL typing. Research objectives: creation of a local database of nucleotide sequences of F. tularensis strains of different subspecies, search for INDEL markers that are significant for the differentiation of subspecies of the causative agent of tularemia, designing primers for the detection of INDEL markers using PCR, optimization of the set of INDEL markers and elucidation of phylogenetic relationships between the studied strains based on the proposed INDEL typing method.Materials and methods. The local database of nucleotide sequences of F. tularensis strains of different subspecies for comparative analysis of F. tularensis genomes presented in the GenBank database was created using the author's software. Detection of INDEL markers in the genomes of strains of the local database was carried out using the GeneExpert program. Primer design and in silico PCR were performed using the Primer3Plus software and the proprietary VirtualPCR software. Cluster analysis and construction of a phylogenetic tree were performed using the GrapeTree program.Results and discussion. The implementation of the proposed five INDEL markers for genotyping of 29 studied strains of different subspecies from the GenBank database made it possible to detect 9 individual genotypes with a high diversity index (DI = 0.85). Not only the corresponding division of the tularensis, holarctica, mediasiatica, and novicida subspecies into different clusters was noted, but also the intraspecific division into groups of strains was observed. Differentiation of F. tularensis subspecies was confirmed in vitro for the collection of strains of different subspecies of the Collection of Living Cultures of the Rostov-on-Don Plague Control Researsh Institute.Conclusion. For the first time, the F. tularensis subspecies differentiation system based on the INDEL typing method has been developed, which allows in vitro identification of both F. tularensis subspecies (tularensis, holarctica, mediasiatica and novicida) and groups of strains within subspecies without the need for strain sequencing. The method is protected by a patent. The topology of the INDEL phylogenetic tree of genotypes of F. tularensis strains correlates with the patterns of evolution of the tularemia microbe presented earlier. The proposed method can be used for combined typing of F. tularensis strains together with MLVA or SNP typing

Mutational Switch-Backs Can Accelerate Evolution of Francisella to a Combination of Ciprofloxacin and Doxycycline.

Combination antimicrobial therapy has been considered a promising strategy to combat the evolution of antimicrobial resistance. Francisella tularensis is the causative agent of tularemia and in addition to being found in the nature, is recognized as a threat agent that requires vigilance. We investigated the evolutionary outcome of adapting the Live Vaccine Strain (LVS) of F. tularensis subsp. holarctica to two non-interacting drugs, ciprofloxacin and doxycycline, individually, sequentially, and in combination. Despite their individual efficacies and independence of mechanisms, evolution to the combination arose on a shorter time scale than evolution to the two drugs sequentially. We conducted a longitudinal mutational analysis of the populations evolving to the drug combination, genetically reconstructed the identified evolutionary pathway, and carried out biochemical validation. We discovered that, after the appearance of an initial weak generalist mutation (FupA/B), each successive mutation alternated between adaptation to one drug or the other. In combination, these mutations allowed the population to more efficiently ascend the fitness peak through a series of evolutionary switch-backs. Clonal interference, weak pleiotropy, and positive epistasis also contributed to combinatorial evolution. This finding suggests that the use of this non-interacting drug pair against F. tularensis may render both drugs ineffective because of mutational switch-backs that accelerate evolution of dual resistance.

Tularemia research activity: a bibliometric analysis between 1980 and 2020.

Tularemia disease attracts attention as an important contagious zoonosis that has increased its impact in recent years. The aim of the study is to analyze the publications on tularemia between 1980 and 2020. We performed literature retrieval in the Web of Science (WoS) on 22 September 2021. Search terms were "Francisella tularensis" and "Tularemia" in the article title for the period between January 1980 and December 2020. We determined the number of articles, keywords, countries, authors, and institutions for each publication. We visualized the data with the VOS viewer tool. After all inclusion and exclusion criteria were applied finally, 1688 articles were analyzed. The number of articles has increased in recent years. The three most productive countries in tularemia were the USA (777 articles 46.03%), Sweden (113 articles 6.69%), and Turkey (95 articles, 5.63%). Most of the articles were from the journal of Infection and Immunity(II), Plos one, Journal of Clinical Microbiology (JCM), Emerging Infectious Diseases (EID), and Vaccine. Sjostedt A. and Umea University-Sweden were the most influential author and institution. Productivity trend has been shown to increase in tularemia. High-income countries had a great influence on the literature in the field. Publications from the USA were in a high percentage among all articles. Related work may lead to the future direction of this dossier in the next years.

Increased M1 macrophage activity makes females more sensitive to Francisella tularensis infection

Abstract The intensity of the inflammatory response differs between males and females, with females having a stronger basal inflammatory response compared with males. This leads to differences in sensitivity to autoimmune and infectious diseases. Males tend to be more susceptible to infectious diseases whereas females tend to be more susceptible to autoimmune diseases. However, certain infectious diseases cause disease by over stimulating an inflammatory response resulting in dysregulation of cytokine production and generation of a cytokine storm. We hypothesized that the elevated basal inflammatory state of females would make them more susceptible to inflammatory infectious diseases such as Francisella tularensis. Indeed, survival and immunological studies demonstrated that females had a stronger innate immune response and were more likely to succumb to tularemic-disease compared with males. Importantly, this dichotomy was independent of hormonal signaling. We traced the source of this elevated inflammatory response to alterations in the M1 and M2 macrophage activation profile. In females, M1 macrophages were activated earlier than in males in response to inoculation. These M1 macrophages from female mice showed a stronger activation both in vivo and in vitro cultures. This was consistent in both mouse and human systems. Our results demonstrate that females possess a higher abundance of M1 macrophages and that these M1 macrophages are more inflammatory in response to F. tularensis infection. This suggests that the consequence of the dichotomy between the male and female inflammatory response is dependent upon the mechanism of disease triggered by infectious diseases. Supported by grants from the NIH (SC1 GM122699-01A1) and NSF (MRI 1626587).