Caspase-2 mediates a Brucella abortus RB51-induced hybrid cell death having features of apoptosis and pyroptosis

Brucella rough RB51 infection activates P53-Slc7a11-Gpx4/GSH pathway to induce ferroptosis to attenuate the intracellular survival on macrophages

B. abortus is a facultative intracellular bacterium that replicates within macrophages. Intracellular survival is one of the important indexes to evaluate the virulence of Brucella. Ferroptosis is a type of programmed cell death induced by the accumulation of free iron, reactive oxygen species (ROS), and toxic lipid peroxides, play roles on cancers, cardiovascular diseases, and inflammatory diseases. In this study, we found that Brucella rough strain RB51 induced ferroptosis on macrophages with reduced levels of host glutathione and glutathione peroxidase 4 (Gpx4), together with increased ferrous iron, lipid peroxidation, and ROS. The inhibitor ferrostatin-1 significantly reduced the ferroptosis of RB51-infected macrophages, confirming that ferroptosis occurred during infection with Brucella RB51. Furthermore, we found that RB51 infection induced ferroptosis is regulated by P53-Slc7a11-Gpx4/GSH signal pathway. Inhibiting P53 decreased the levels of ROS and lipid peroxidation, while the levels of Slc7a11, Gpx4 and GSH were rescued. More importantly, inhibiting ferroptosis by different ferroptosis inhibitors increased the intracellular survival of Brucella RB51, indicating ferroptosis functions on the attenuation of Brucella intracellular survival. Collectively, our observations demonstrate that Brucella RB51 infection induces ferroptosis on macrophages, which is regulated by P53-Slc7a11-Gpx4/GSH signal pathway and functions on the attenuation of intracellular survival of Brucella.

Evasion of host defense by Brucella

Brucella , an adept intracellular pathogen, causes brucellosis, a zoonotic disease leading to significant global impacts on animal welfare and the economy. Regrettably, there is currently no approved and effective vaccine for human use. The ability of Brucella to evade host defenses is essential for establishing chronic infection and ensuring stable intracellular growth. Brucella employs various mechanisms to evade and undermine the innate and adaptive immune responses of the host through modulating the activation of pattern recognition receptors (PRRs), inflammatory responses, or the activation of immune cells like dendritic cells (DCs) to inhibit antigen presentation. Moreover, it regulates multiple cellular processes such as apoptosis, pyroptosis, and autophagy to establish persistent infection within host cells. This review summarizes the recently discovered mechanisms employed by Brucella to subvert host immune responses and research progress on vaccines, with the aim of advancing our understanding of brucellosis and facilitating the development of more effective vaccines and therapeutic approaches against Brucella .

Validation of the Intermolecular Disulfide Bond in Caspase-2

Caspases are a family of proteins involved in cell death. Although several caspase members have been well characterized, caspase-2 remains enigmatic. Caspase-2 has been implicated in several phenotypes, but there has been no consensus in the field about its upstream activating signals or its downstream protein targets. In addition, the unique ability of caspase-2 to form a disulfide-bonded dimer has not been studied in depth. Herein, we investigate the disulfide bond in the context of inducible dimerization, showing that disulfide bond formation is dimerization dependent. We also explore and review several stimuli published in the caspase-2 field, test ferroptosis-inducing stimuli, and study in vivo infection models. We hypothesize that the disulfide bond will ultimately prove to be essential for the evolved function of caspase-2. Proving this will require the discovery of cell death phenotypes where caspase-2 is definitively essential.

ER stress induces caspase-2-tBID-GSDME-dependent cell death in neurons lytically infected with herpes simplex virus type 2

Neurotropic viruses, including herpes simplex virus (HSV) types 1 and 2, have the capacity to infect neurons and can cause severe diseases. This is associated with neuronal cell death, which may contribute to morbidity or even mortality if the infection is not controlled. However, the mechanistic details of HSV-induced neuronal cell death remain enigmatic. Here, we report that lytic HSV-2 infection of human neuron-like SH-SY5Y cells and primary human and murine brain cells leads to cell death mediated by gasdermin E (GSDME). HSV-2-induced GSDME-mediated cell death occurs downstream of replication-induced endoplasmic reticulum stress driven by inositol-requiring kinase 1α (IRE1α), leading to activation of caspase-2, cleavage of the pro-apoptotic protein BH3-interacting domain death agonist (BID), and mitochondria-dependent activation of caspase-3. Finally, necrotic neurons released alarmins, which activated inflammatory responses in human iPSC-derived microglia. In conclusion, lytic HSV infection in neurons activates an ER stress-driven pathway to execute GSDME-mediated cell death and promote inflammation.

Brucella abortus Rough-Type Mutant Induces Ferroptosis and More Oxidative Stress in Infected Macrophages

Brucella is an intracellular parasitic bacterium that uses multiple strategies to evade the host's defense mechanisms. However, how Brucella manipulates the host-induced oxidative stress and relevant biological processes are still poorly understood. In this study, a comparative transcriptome assay of macrophages infected with Brucella abortus S2308 and its rough mutant RB14 was performed to investigate the differentially expressed genes which might be associated with the pathogenic mechanism of Brucella. Our results showed that numerous host pro-oxidative and antioxidative stress genes were differentially expressed in macrophages infected with B. abortus S2308 and mutant RB14 at 4, 8, 24, and 48 h post-infection. Interestingly, we found that several ferroptosis-associated genes were differentially expressed during B. abortus RB14 infection. Moreover, we found that the rough mutant RB14-induced macrophage death was associated with reduced levels of host glutathione and glutathione peroxidase 4, together with increased free iron, lipid peroxidation, and ROS, all of which are important hallmarks of ferroptosis. The ferroptosis occurring during infection with RB14 was reduced by treatment with the inhibitor ferrostatin-1. However, B. abortus S2308 infection did not induce these hallmarks of ferroptosis. Taken together, our results demonstrate that ferroptosis is involved in rough B. abortus infection. Investigating how Brucella manipulates oxidative stress and ferroptosis in its host will be helpful to clarify the pathogenicity of B. abortus.

Brucella Outer Membrane Lipoproteins 19 and 16 Differentially Induce IL-18 Response or Pyroptosis in Human Monocytic Cells

BACKGROUND

Brucella species (B. spp.) are Gram-negative intracellular bacteria, causing severe inflammatory diseases in animals and humans. Two major lipoproteins (L19) and (L16) of Brucella outer membrane proteins (OMPs) were extensively explored in associating with inflammatory response of human monocytes (THP-1).

METHODS

Activated THP-1 cells induced with recombinant L19 and L16 were analyzed in comparison with unlipidated forms (U19 and U16) and lipopolysaccharide (LPS) of B. melitensis, respectively.

RESULTS

Secretion of inflammatory factors TNF-α, IL-6 and IL-1β was significantly increased from L19, L16 or both stimulated THP-1 cells. High secretion of IL-18 was detected only from L19-induced cells. Signaling of those cytokine responses was identified mainly through P38-MAPK pathway, and signaling of L19-induced IL-1β response was partly occurred via NF-κB. Exploration for different forms of IL-18 found that L19-induced production of active IL-18 (18 kD) was through up-regulating NLRP3 and activating caspase-1, while L16-induced production of inactive IL-18 fragments (15 kD and 16 kD) occurred through activating caspase-8/3. Additionally, L19 up-regulated phosphorylation of XIAP for inhibiting caspase-3 activity to cleave IL-18, while L16 activated caspase-3 for producing GSDME-N and leading to pyroptosis of THP-1 cells.

CONCLUSION

Brucella L19 and L16 differentially induce IL-18 response or pyroptosis in THP-1 cells, respectively.

VaximmutorDB: A Web-Based Vaccine Immune Factor Database and Its Application for Understanding Vaccine-Induced Immune Mechanisms

Vaccines stimulate various immune factors critical to protective immune responses. However, a comprehensive picture of vaccine-induced immune factors and pathways have not been systematically collected and analyzed. To address this issue, we developed VaximmutorDB, a web-based database system of vaccine immune factors (abbreviated as “vaximmutors”) manually curated from peer-reviewed articles. VaximmutorDB currently stores 1,740 vaccine immune factors from 13 host species (e.g., human, mouse, and pig). These vaximmutors were induced by 154 vaccines for 46 pathogens. Top 10 vaximmutors include three antibodies (IgG, IgG2a and IgG1), Th1 immune factors (IFN-γ and IL-2), Th2 immune factors (IL-4 and IL-6), TNF-α, CASP-1, and TLR8. Many enriched host processes (e.g., stimulatory C-type lectin receptor signaling pathway, SRP-dependent cotranslational protein targeting to membrane) and cellular components (e.g., extracellular exosome, nucleoplasm) by all the vaximmutors were identified. Using influenza as a model, live attenuated and killed inactivated influenza vaccines stimulate many shared pathways such as signaling of many interleukins (including IL-1, IL-4, IL-6, IL-13, IL-20, and IL-27), interferon signaling, MARK1 activation, and neutrophil degranulation. However, they also present their unique response patterns. While live attenuated influenza vaccine FluMist induced significant signal transduction responses, killed inactivated influenza vaccine Fluarix induced significant metabolism of protein responses. Two different Yellow Fever vaccine (YF-Vax) studies resulted in overlapping gene lists; however, they shared more portions of pathways than gene lists. Interestingly, live attenuated YF-Vax simulates significant metabolism of protein responses, which was similar to the pattern induced by killed inactivated Fluarix. A user-friendly web interface was generated to access, browse and search the VaximmutorDB database information. As the first web-based database of vaccine immune factors, VaximmutorDB provides systematical collection, standardization, storage, and analysis of experimentally verified vaccine immune factors, supporting better understanding of protective vaccine immunity.

A rough Brucella mutant induced macrophage death depends on secretion activity of T4SS, but not on cellular Txnip- and Caspase-2-mediated signaling pathway

Brucella is a facultative intracellular bacterium, dividing into smooth- and rough-type Brucella. Smooth-type Brucella can dissociate into rough mutants with cytotoxicity for macrophages during infection, which is critical for Brucella egress and dissemination. However, the mechanism of cytotoxicity infected by rough Brucella is incomplete. In this study, we verified that a rough-type Brucella (RB14 strain) was cytotoxic for macrophages dependent on Type IV secretion system (T4SS). Two specific T4SS VirB4 and VirB11 mutants were constructed, which affect the secretion of T4SS effectors, but not the expression of T4SS components. Cytotoxicity analysis showed that RB14- induced macrophages death depends on T4SS secretion activity. In a further study, 15 reported T4SS effectors were evaluated in inducing macrophage death using over-expression and transfection methods, the results showed that 15 recombinant strains with over-expression of respective effector were not cytotoxicity. In addition, 10 effectors transfected individually, or co-transfected with five effectors barely induced macrophage death, suggesting that all 15 effectors were not associated with macrophage death. Besides, we also evaluated endoplasmic reticulum (ER) stress, Txnip- or Caspase-2 roles in RB14-induced macrophages death. The results showed that inhibition of ER stress, Caspase or Caspase-2 activation was not associated with RB14-infected macrophages death. The casp2 and txnip knockout cells also showed death when infected by the RB14 strain. In all, the RB14-induced macrophage death depends on the secretion activity of T4SS, but not on ER stress, Txnip- or Caspase-2 signal pathway. This study provides a deep insight for rough Brucella-induced macrophage death, which favors for elucidating Brucella infection lifecycle.

The involvement of regulated cell death forms in modulating the bacterial and viral pathogenesis

Apoptosis, necroptosis and pyroptosis represent three distinct types of regulated cell death forms, which play significant roles in response to viral and bacterial infections. Whereas apoptosis is characterized by cell shrinkage, nuclear condensation, bleb formation and retained membrane integrity, necroptosis and pyroptosis exhibit osmotic imbalance driven cytoplasmic swelling and early membrane damage. These three cell death forms exert distinct immune stimulatory potential. The caspase driven apoptotic cell demise is considered in many circumstances as anti-inflammatory, whereas the two lytic cell death modalities can efficiently trigger immune response by releasing damage associated molecular patterns to the extracellular space. The relevance of these cell death modalities in infections can be best demonstrated by the presence of viral proteins that directly interfere with cell death pathways. Conversely, some pathogens hijack the cell death signaling routes to initiate a targeted attack against the immune cells of the host, and extracellular bacteria can benefit from the destruction of intact extracellular barriers upon cell death induction. The complexity and the crosstalk between these cell death modalities reflect a continuous evolutionary race between pathogens and host. This chapter discusses the current advances in the research of cell death signaling with regard to viral and bacterial infections and describes the network of the cell death initiating molecular mechanisms that selectively recognize pathogen associated molecular patterns.

miR-1247-3p mediates apoptosis of cerebral neurons by targeting caspase-2 in stroke

Brain stroke is one of the leading causes of death worldwide. We explored a potential stroke-related role for a newly found microRNA, miR-1247-3p, and one of its target genes, caspase-2, predicted by TargetScanVert. In the present study, we found that miR-1247-3p was downregulated during ischemia/reperfusion (I/R) and that LV-miR-1247-3p overexpression attenuated brain impairment induced by I/R. Similar results were observed in neuro2a (N2a) cells treated with oxygen-glucose deprivation/reoxygenation (OGD/R). Caspase-2 was upregulated in the I/R and OGD/R model, while Z-VDVAD-FMK - the inhibitor of caspase-2-inhibited apoptosis of N2a cells induced by OGD/R. An miR-1247-3p mimic inhibited caspase-2 expression and attenuated apoptosis of N2a cells induced by OGD/R. Myocardin-related transcription factor-A (MRTF-A) overexpression upregulated miR-1247 and mature miR-1247-3p levels and attenuated apoptosis induced by OGD/R, whereas its anti-apoptotic function could be blocked by a miR-1247-3p inhibitor. Hence, we conclude that miR-1247-3p may protect cells during brain stroke. This study offers insights for the development of effective therapeutics for promoting the survival of cerebral neurons during brain I/R injury.

Caspase-2 mediates triglyceride (TG)-induced macrophage cell death

Triglyceride (TG) accumulation causes macrophage cell death, which affects the development of atherosclerosis. Here, we examined whether caspase-2 is implicated in TG-induced macrophage cell death. We found that caspase-2 activity is increased in TG-treated THP-1 macrophages, and that inhibition of caspase-2 activity drastically inhibits TG-induced cell death. We previously reported that TG-induced macrophage cell death is triggered by caspase-1, and thus investigated the relationship between caspase-2 and caspase-1 in TG-induced macrophage cell death. Inhibition of caspase-2 activity decreased caspase-1 activity in TG-treated macrophages. However, caspase-1 inhibition did not affect caspase-2 activity, suggesting that caspase-2 is upstream of caspase-1. Furthermore, we found that TG induces activation of caspase-3, -7, -8, and -9, as well as cleavage of PARP. Inhibition of caspase-2 and -1 decreased TG-induced caspase-3, -7, -8, and -9 activation and PARP cleavage. Taken together, these results suggest that TG-induced macrophage cell death is mediated via the caspase-2/caspase-1/apoptotic caspases/PARP pathways.

Brucella Rough Mutant Induce Macrophage Death via Activating IRE1α Pathway of Endoplasmic Reticulum Stress by Enhanced T4SS Secretion

Brucella is a Gram-negative facultative intracellular pathogen that causes the worldwide zoonosis, known as brucellosis. Brucella virulence relies mostly on its ability to invade and replicate within phagocytic cells. The type IV secretion system (T4SS) and lipopolysaccharide are two major Brucella virulence factors. Brucella rough mutants reportedly induce the death of infected macrophages, which is T4SS dependent. However, the underlying molecular mechanism remains unclear. In this study, the T4SS secretion capacities of Brucella rough mutant and its smooth wild-type strain were comparatively investigated, by constructing the firefly luciferase fused T4SS effector, BPE123 and VceC. In addition, quantitative real-time PCR and western blotting were used to analyze the T4SS expression. The results showed that T4SS expression and secretion were enhanced significantly in the Brucella rough mutant. We also found that the activity of the T4SS virB operon promoter was notably increased in the Brucella rough mutant, which depends on quorum sensing-related regulators of VjbR upregulation. Cell infection and cell death assays revealed that deletion of vjbR in the Brucella rough mutant absolutely abolished cytotoxicity within macrophages by downregulating T4SS expression. This suggests that up-regulation of T4SS promoted by VjbR in rough mutant ΔrfbE contribute to macrophage death. In addition, we found that the Brucella rough mutant induce macrophage death via activating IRE1α pathway of endoplasmic reticulum stress. Taken together, our study provide evidence that in comparison to the Brucella smooth wild-type strain, VjbR upregulation in the Brucella rough mutant increases transcription of the virB operon, resulting in overexpression of the T4SS gene, accompanied by the over-secretion of effecter proteins, thereby causing the death of infected macrophages via activating IRE1α pathway of endoplasmic reticulum stress, suggesting novel insights into the molecular mechanisms associated with Brucella rough mutant-induced macrophage cytotoxicity.

Establishment of Chronic Infection: Brucella's Stealth Strategy

Brucella is a facultative intracellular pathogen that causes zoonotic infection known as brucellosis which results in abortion and infertility in natural host. Humans, especially in low income countries, can acquire infection by direct contact with infected animal or by consumption of animal products and show high morbidity, severe economic losses and public health problems. However for survival, host cells develop complex immune mechanisms to defeat and battle against attacking pathogens and maintain a balance between host resistance and Brucella virulence. On the other hand as a successful intracellular pathogen, Brucella has evolved multiple strategies to evade immune response mechanisms to establish persistent infection and replication within host. In this review, we mainly summarize the "Stealth" strategies employed by Brucella to modulate innate and the adaptive immune systems, autophagy, apoptosis and possible role of small noncoding RNA in the establishment of chronic infection. The purpose of this review is to give an overview for recent understanding how this pathogen evades immune response mechanisms of host, which will facilitate to understanding the pathogenesis of brucellosis and the development of novel, more effective therapeutic approaches to treat brucellosis.

Cancer therapy in the necroptosis era

Necroptosis is a caspase-independent form of regulated cell death executed by the receptor-interacting protein kinase 1 (RIP1), RIP3, and mixed lineage kinase domain-like protein (MLKL). Recently, necroptosis-based cancer therapy has been proposed to be a novel strategy for antitumor treatment. However, a big controversy exists on whether this type of therapy is feasible or just a conceptual model. Proponents believe that because necroptosis and apoptosis use distinct molecular pathways, triggering necroptosis could be an alternative way to eradicate apoptosis-resistant cancer cells. This hypothesis has been preliminarily validated by recent studies. However, some skeptics doubt this strategy because of the intrinsic or acquired defects of necroptotic machinery observed in many cancer cells. Moreover, two other concerns are whether or not necroptosis inducers are selective in killing cancer cells without disturbing the normal cells and whether it will lead to inflammatory diseases. In this review, we summarize current studies surrounding this controversy on necroptosis-based antitumor research and discuss the advantages, potential issues, and countermeasures of this novel therapy.

Characterization and expression analysis of a caspase-2 in an invertebrate echinoderm sea cumber Apostichopus japonicus

Caspase-2 is the most evolutionarily conserved member of the caspase family which mediates the programmed cell death and plays crucial roles in key cellular processes. In this study, a caspase-2 homolog was identified and functionally characterized in sea cucumber Apostichopus japonicus, which we named AjCASP. The full-length cDNA consists of 2100 bp with an ORF encoding a protein of 378 amino acids. The deduced amino acid sequence shows that AjCASP consists of a conserved CARD-CASP2 domain and a CASs domain containing two active residues, two proteolytic cleavage residues, a substrate pocket and a dimer interface as well. In addition, a p20 large subunit with a characteristic five-peptide motif (QACRG) and a p10 small subunit in C-terminal were identified in CASs domain. Above data demonstrated that AjCASP is similar to CED-3 (the caspase-2 homolog of nematode Caenorhabditis elegans), which is further confirmed by phylogenetic tree analysis. AjCASP was ubiquitously expressed in sea cucumber and the obviously higher expression level was observed in coelomocyte, respiratory tree and intestine. Real-time PCR analyses further demonstrated that AjCASP was significantly induced by LPS. Taken together, these results strongly suggest that AjCASP is a caspase-2 homolog and it may be involved in invertebrate immune response, especially in eliminating and degrading invading pathogens.

Ontology-based representation and analysis of host-Brucella interactions

Background

Biomedical ontologies are representations of classes of entities in the biomedical domain and how these classes are related in computer- and human-interpretable formats. Ontologies support data standardization and exchange and provide a basis for computer-assisted automated reasoning. IDOBRU is an ontology in the domain of Brucella and brucellosis. Brucella is a Gram-negative intracellular bacterium that causes brucellosis, the most common zoonotic disease in the world. In this study, IDOBRU is used as a platform to model and analyze how the hosts, especially host macrophages, interact with virulent Brucella strains or live attenuated Brucella vaccine strains. Such a study allows us to better integrate and understand intricate Brucella pathogenesis and host immunity mechanisms.

Results

Different levels of host-Brucella interactions based on different host cell types and Brucella strains were first defined ontologically. Three important processes of virulent Brucella interacting with host macrophages were represented: Brucella entry into macrophage, intracellular trafficking, and intracellular replication. Two Brucella pathogenesis mechanisms were ontologically represented: Brucella Type IV secretion system that supports intracellular trafficking and replication, and Brucella erythritol metabolism that participates in Brucella intracellular survival and pathogenesis. The host cell death pathway is critical to the outcome of host-Brucella interactions. For better survival and replication, virulent Brucella prevents macrophage cell death. However, live attenuated B. abortus vaccine strain RB51 induces caspase-2-mediated proinflammatory cell death. Brucella-associated cell death processes are represented in IDOBRU. The gene and protein information of 432 manually annotated Brucella virulence factors were represented using the Ontology of Genes and Genomes (OGG) and Protein Ontology (PRO), respectively. Seven inference rules were defined to capture the knowledge of host-Brucella interactions and implemented in IDOBRU. Current IDOBRU includes 3611 ontology terms. SPARQL queries identified many results that are critical to the host-Brucella interactions. For example, out of 269 protein virulence factors related to macrophage-Brucella interactions, 81 are critical to Brucella intracellular replication inside macrophages. A SPARQL query also identified 11 biological processes important for Brucella virulence.

Conclusions

To systematically represent and analyze fundamental host-pathogen interaction mechanisms, we provided for the first time comprehensive ontological modeling of host-pathogen interactions using Brucella as the pathogen model. The methods and ontology representations used in our study are generic and can be broadened to study the interactions between hosts and other pathogens.

Electronic supplementary material

The online version of this article (doi:10.1186/s13326-015-0036-y) contains supplementary material, which is available to authorized users.

Endoplasmic Reticulum Stress Activates the Inflammasome via NLRP3- and Caspase-2-Driven Mitochondrial Damage

Endoplasmic reticulum (ER) stress is observed in many human diseases, often associated with inflammation. ER stress can trigger inflammation through nucleotide-binding domain and leucine-rich repeat containing (NLRP3) inflammasome, which might stimulate inflammasome formation by association with damaged mitochondria. How ER stress triggers mitochondrial dysfunction and inflammasome activation is ill defined. Here we have used an infection model to show that the IRE1α ER stress sensor regulates regulated mitochondrial dysfunction through an NLRP3-mediated feed-forward loop, independently of ASC. IRE1α activation increased mitochondrial reactive oxygen species, promoting NLRP3 association with mitochondria. NLRP3 was required for ER stress-induced cleavage of caspase-2 and the pro-apoptotic factor, Bid, leading to subsequent release of mitochondrial contents. Caspase-2 and Bid were necessary for activation of the canonical inflammasome by infection-associated or general ER stress. These data identify an NLRP3-caspase-2-dependent mechanism that relays ER stress to the mitochondria to promote inflammation, integrating cellular stress and innate immunity.

Proteomic analysis of detergent resistant membrane domains during early interaction of macrophages with rough and smooth Brucella melitensis

The plasma membrane contains discrete nanometer-sized domains that are resistant to non-ionic detergents, and which are called detergent resistant membrane domains (DRMDs) or lipid rafts. Exposure of host cells to pathogenic bacteria has been shown to induce the re-distribution of specific host proteins between DRMDs and detergent soluble membranes, which leads to the initiation of cell signaling that enable pathogens to access host cells. DRMDs have been shown to play a role in the invasion of Brucella into host macrophages and the formation of replicative phagosomes called Brucella-containing vacuoles (BCVs). In this study we sought to characterize changes to the protein expression profiles in DRMDs and to respective cellular pathways and networks of Mono Mac 6 cells in response to the adherence of rough VTRM1 and smooth 16 M B. melitensis strains. DRMDs were extracted from Mono Mac 6 cells exposed for 2 minutes at 4°C to Brucella (no infection occurs) and from unexposed control cells. Protein expression was determined using the non-gel based quantitative iTRAQ (Isobaric Tags for Relative and Absolute Quantitation) mass spectrometry technique. Using the identified iTRAQ proteins we performed enrichment analyses and probed constructed human biochemical networks for interactions and metabolic reactions. We identified 149 proteins, which either became enriched, depleted or whose amounts did not change in DRMDs upon Brucella exposure. Several of these proteins were distinctly enriched or depleted in DRMDs upon exposure to rough and smooth B. melitensis strains which results in the differential engagement of cellular pathways and networks immediately upon Brucella encounter. For some of the proteins such as myosin 9, small G protein signaling modulator 3, lysine-specific demethylase 5D, erlin-2, and voltage-dependent anion-selective channel protein 2, we observed extreme differential depletion or enrichment in DRMDs. The identified proteins and pathways could provide the basis for novel ways of treating or diagnosing Brucellosis.