Microbial Pathogenesis

Mesenchymal stem cells (MSCs) are multipotent cells commonly derived from the bone marrow, adipose tissue and placenta. Human bone marrow derived MSCs migrate to a site of injury, release proinflammatory cytokines and modulate T-cell proliferation. At sites of injury, MSCs may well encounter bacterial pathogens most commonly the Gram positive pathogen Staphylococcus aureus. However, the precise molecular mechanism(s) of this interaction remain to be elucidated. In the present study we aim to show if a direct interaction occurs between S. aureus and bone marrow derived MSCs and identify if MSCRAMMs have a role in this interaction. We further aim to compare S. aureus interaction with cells that differentiate from MSCs, namely; osteoblasts, adipocytes and chondrocytes, since MSCs co-exist in the niche of these cells. Our results showed that S. aureus is able to interact with MSCs in the form of adhesion and invasion to the cells, and that this interaction is largely dependent on the expression of fibronecting-binding protein (FnBP) by S. aureus. We also showed that the same mechanism of interaction to osteoblasts, adipocytes and chondrocytes that are directly differentiated from the same MSCs. Finally, we have found that the presence of 10% FBS in the infection medium is essential as it helps in achieving the best specific bacterial-cell association with the least background association. The results reveals a mechanism of interaction between S. aureus and MSCs that could pave the way for therapeutic intervention that minimises the burden of infection in inflammatory diseases.

We identified the role of a conserved hypothetical protein (SSA_0451) in S. sanguinis that is involved in the virulence of infective endocarditis. An in vitro whole blood killing assay and rabbit endocarditis model studies revealed that the SSA_0451 mutant ({Delta}SSA_0451) was significantly less virulent than the wild-type (SK36) and its complementation mutant ({Delta}SSA_0451C). The mechanism underlying the SSA_0451 mutants reduced virulence in infective endocarditis was evidentially linked to oxidative stress and environmental stress. The genes related to the survival of S. sanguinis in an oxidative stress environment were downregulated in {Delta}SSA_0451, which affected its survival in blood. Our findings suggest that SSA_0451 is a novel IE virulence factor and a new target for drug discovery against IE. Author summaryThis study focused on SSA_0451, a conserved hypothetical protein in S. sanguinis, to explore its potential role as a virulence factor. Through in vitro whole blood killing assays and rabbit IE models, it was found that the SSA_0451 mutant exhibited reduced virulence compared to the wild-type and a complemented mutant. The study linked the mutants diminished virulence in IE to heightened susceptibility to oxidative and environmental stresses, supported by downregulation of genes crucial for oxidative stress survival in S. sanguinis. These findings identify SSA_0451 as a novel virulence factor in IE and propose it as a promising target for future drug development against this condition.

The antibiotic stress on bacteria leads to initiation of adaptive mechanisms, including exploiting the available opportunity, if any, for cell survival. In order to use the opportunity for survival while under threat, the microbe undergoes various mechanisms which are not completely known e.g. homologous recombination, horizontal gene transfer etc. Our aim is to understand the adaptive mechanism for cell survival during stress, especially antibiotic stress, in E. coli in the presence of opportunity. Understanding this mechanism in bacteria that gained resistance will help in identifying alternative survival pathways. By subjecting a recombination deficient ({Delta}RecA) strain of bacteria to antibiotic stress, we expected cell death, due to its inability to repair DNA damage (1, 2). Here we show that providing an opportunity in the form of an antibiotic resistance gene with homologous ends aids bacterial survival. There was 3-fold increase in cell envelope thickness along with 2.5-fold increase in phosphatidylethanolamine (PE) content, and enhanced antibiotic resistance to >4000{micro}g/mL (Kan). We observed genome-wide alteration of methylation pattern that lead to changes in transcriptome, proteome, lipidome, and metabolite level, thus, leading to morphological and physiological changes. We prove that global methylation helps in survival of bacteria under stress that changes essential pathways like energy, cell envelope, lipids, amino acids acid, etc. leading to over production of cell wall components including synthesis of PE. By inhibiting the activity of methyltransferase, it is noticed that there is reduction in PE synthesis in agreement with demethylation. This proves that the phenotypic changes are caused due to the global methylation, and also demonstrates that demethylation could be used as a strategy to prevent antibiotic resistance in microbes. One Sentence SummaryGlobal methylation determines the survival of bacteria to gain the antimicrobial resistance with an opportunity

The induction of macrophage death is regarded as a potential mechanism by which components secreted by Clostridium septicum are used to evade the innate immune response and cause tissue damage. This study aimed to determine the effect of partially purified fractions of extracellular proteins secreted by C. septicum on the death of mouse peritoneal macrophages. Elicited mouse peritoneal macrophages were incubated with partially purified fractions of proteins secreted by C. septicum into the culture medium. After incubation, we found that the protein fraction with a molecular weight [≥] 100 kDa caused significant cell death in macrophages, changed cell morphology, increased markers of apoptosis and autophagy, and increased the expression (protein and mRNA) of IL-10 and TNF Our data suggest that the proteins secreted by C. septicum (MW, [≥] kDa) induce cell death in macrophages by promoting autophagy- triggered apoptosis. This study may contribute to our understanding of the molecular mechanism of immune evasion by C. septicum at the infection site.

Aspergillus fumigatus exhibits autophagic and necroptotic process when its GPI anchor synthesis is suppressed. A putative kinase (AFUA_6G02590) is found to be overexpressed in response to GPI anchor suppression and identified as a RIP3-like protein, namely AfRip3. To elucidate its function, in this study a Afrip3-overexpressing strain OE-Afrip3 was constructed. Although OE-Afrip3 strain exhibited an increased cell death, neither apoptotic nor autophagic process was activated. Our evidences demonstrated that overexpression of Afrip3 gene in A. fumigatus only led to necroptosis, while the Afrip3-knockout mutant was unable to activate necroptotic process. Further analysis revealed that both JNK and SMase pathways were activated in OE-Afrip3 strain, by which an increase of reactive oxygen species (ROS) was induced. We also showed that expression of Afrip3 gene was induced by Ca2+. In addition, eEF1B{gamma} and adenylylsulfate kinase (ASK) were identified as potential candidates to interact with AfRip3. These results indicate that AfRip3 is a key modulator that activates necroptotic process in A. fumigatus, which can be induced by Ca2+ and in turn activate JNK (c-Jun NH2-terminal kinase) and SMase (sphingomyelinase) pathway. Our findings suggest that necroptotic pathway in A. fumigatus is distinct from that in mammalian cell and may provide a new strategy for development of anti-fungal drug. Author summaryAspergillus fumigatus is a human fungal pathogen and causes invasive aspergillosis (IA) in immunocompromised patients with high mortality (30-95%). Development of novel therapies is urgently needed. In this study, we confirm AfRip3 (AFUA_6G02590), a RIP3-like protein, is a key modulator that activates necroptotic process in A. fumigatus. We also find that cytosolic Ca2+ can induce the expression of Afrip3 and activated AfRip3 in turn activate JNK (c-Jun NH2-terminal kinase) and SMase (sphingomyelinase) pathway. Our findings suggest that necroptotic pathway in A. fumigatus is distinct from that in mammalian cell and may provide a new strategy for development of anti-fungal drug.

Zika virus (ZIKV) have become a global health problem over the past decade due to the extension of the geographic distribution of ZIKV of Asian genotype. Epidemics of Asian ZIKV have been associated with developmental disorders in humans. ZIKV of African lineage would have an epidemic potential associated to fetal pathogenicity requiring a greater attention towards the most recently isolated viral strains from West Africa. In the present study, an infectious molecular clone GUINEA-18 has been obtained from viral strain ZIKV-15555 that had been sequenced from an individual infected by ZIKV in Guinea in 2018. A molecular clone-based comparative study between GUINEA-18 and viral clone MR766MC from historical African ZIKV strain MR766 revealed a lower replication rate for GUINEA-18 associated to a weaker cytotoxicity and reduced innate immune system activation in Vero E6, A549 and HCM3 cell lines. Analysis of chimeric viruses between MR766MC and GUINEA-18 stressed the importance NS1/NS4B proteins with a particular focus for NS4B on GUINEA-18 replication properties. ZIKV has developed strategies to prevent cytoplasmic stress granule formation which occurs in response to virus infection. Study of G3BP protein showed that GUINEA-18 but not MR766MC was efficient to inhibit stress granule assembly in A549 cells subjected to a physiological stressor. GUINEA-18 depends on NS1/NS4B proteins for suppressing stress granule response to environmental stress. The involvement of GUINEA-18 NS1/NS4B proteins on virus replication capability and host-cell responses to ZIKV infection raises the question of the importance of nonstructural proteins in the pathogenicity of contemporary viral strains from West Africa. AUTHOR SUMMARYMost of studies having for objectives to understand the biology of Zika virus (ZIKV) were carried out using epidemic viral strains of Asian lineage. It is now admitted that ZIKV of African genotype would have also a great epidemic potential associated a high risk of fetal pathogenicity. Today, it is urgent to improve our knowledge on recently isolated ZIKV strains in West Africa. In our study, we used the sequence of viral strain from an individual infected by ZIKV in Guinea in 2018 to generate an infectious molecular clone. Analysis of viral clone highlighted the preponderant role of NS1/NS4B proteins in virus replication strategy and cell interactions with a particular focus on ZIKV-specific stress granule formation blockade. We believe that our data will improve our knowledge on the biology of contemporary West Africa ZIKV opening perspectives towards a better understanding on the pathogenicity of African viral strains.

Brucella abortus is a pathogen that survives in macrophages. Several virulence factors participate in this process, including the open reading frame (ORF) BAB1_0270 codifying of a Zinc-dependent metalloproteinase. Here, its contribution in the process of intracellular adaptation was analyzed by infecting RAW264.7 macrophages with the mutant B. abortus {Delta}270 strain. Results showed that this Zinc-dependent metalloproteinase is a cytoplasmic protein that conforms an operon with a transcriptional regulator, which may constitute a type II toxin-antitoxin system. Functionally, this Zinc-dependent metalloproteinase participated neither in the adherence nor the initial intracellular traffic of B. abortus in macrophages. Nevertheless, its deletion significantly increased the co-localization of B. abortus {Delta}270 with phagolysosomal cathepsin D, reducing both its co-localization with calnexin, present in endoplasmic reticulum derived vesicles, and its intracellular replication within macrophages. Besides, B. abortus {Delta}270-infected macrophages produced significantly higher levels of TNF-, IL-6, CD80 and CD86 than B. abortus 2308, even when several genes involved in virulence (vjbR, hutC, bvrR, virB1) were up-regulated in this mutant. Finally, its deletion significantly reduced the capacity of B. abortus {Delta}270 to adapt, grow and express several virulence factors under acidic conditions. Based on these results, we discuss the role of this Zinc-dependent metalloproteinase in the regulation of the virulence of this pathogen, concluding that it contributes significantly to the intracellular adaptation of B. abortus 2308 during the infection of macrophages. Author summaryBrucella abortus is the causative agent of the brucellosis, a highly contagious diseases. A Zinc-dependent metalloproteinase contributes significantly in the intracellular survival. Here, we demonstrate that this metalloproteinase has homology with ImmA/IrrE proteases, which are involved in the bacterial resistance to hostile environment. Furthermore, it conforms a gene pair with a transcriptional regulator, being required by B. abortus to escape from phagolysosomes, to achieve the endoplasmic reticulum and replicate within macrophages. Its deletion from B. abortus stimulated the macrophages, which produced higher levels of pro-inflammatory cytokines and co-stimulatory proteins. This pathogen showed a reduced ability to adapt and grow under acidic conditions, which would negatively affect its escape from phagolysosomes and consequently, stimulating macrophages. Therefore, this work describes how this Zinc-dependent metalloproteinase significantly contributes in the intracellular adaptation of B. abortus 2308 in macrophages.

Acanthamoeba castellanii is an amphizoic free-living amoeba as it can be found in humans and in the environment. This amoeba represents an important reservoir of pathogenic microorganisms. Persistence of A. castellanii in the environment or in humans is allowed by the ability of the vegetative form to differentiate under cysts when surrounding conditions are unfavorable. In this study, we investigate the role of the ACA1_383450 gene during encystment of A. castellanii. This gene encodes a putative G-protein coupled receptor, which shares homology with human GPR107 and murine GPR108. Expression of the ACA1_383450 gene is transiently repressed at the early phase of encystment and its overexpression affects encystment of A. castellanii. This study reveals a new Acanthamoeba gene which could affect the encystment process. HighlightsO_LIThe ACA1_383450 gene encodes for a putative G-protein coupled receptor (GPCR). C_LIO_LIThe ACA1_383450 mRNA levels are down-regulated during the early phase of encystment. C_LIO_LIOverexpression of the ACA1_383450 gene affects formation of cysts. C_LI

Raf Kinase Inhibitor Protein (RKIP) is an important regulator of MAPK signaling pathway in multicellular eukaryotes. Plasmodium falciparum RKIP (PfRKIP) is a putative phosphatidylethanolamine binding protein (PEBP) that shares limited similarity with Homo sapiens RKIP (HsRKIP). Interestingly, critical components of MAPK pathway are not expressed in malaria parasite and the physiological function of PfRKIP remains unknown. PfRKIP is expressed throughout the asexual schizogony with maximum expression in late schizonts. Interestingly, PfRKIP and HsRKIP show pH dependent differential interaction profiles with various lipids. At physiological pH, PfRKIP show interaction with PE and lipids containing phosphorylated phosphatidylinositol group; however, HsRKIP show no interaction under the same conditions. Mutation of conserved residues in the PEBP domain of PfRKIP decreases its interaction with PI(3)P. Furthermore, our results suggest that PfRKIP leads to increase in the autophosphorylation of PfCDPK1 that leads to transphosphorylation of substrates by PfCDPK1. Using various in vitro and in vivo experiments we have demonstrated the interaction of PfRKIP with PfCDPK1 and have also identified key residues in PfRKIP that play important role in this interaction. Interestingly, locostatin, a specific inhibitor of mammalian RKIP increased the interaction of PfRKIP with PfCDPK1 that perhaps leads to the sequestration of PfCDPK1 in a heterodimeric complex. Importantly, treatment of malaria parasite with locostatin shows dose dependent inhibition of parasite growth. This study suggests that specific inhibitors that modify PfRKIP leading to increase in its interaction with PfCDPK1 may be designed and explored as novel anti-malarial compounds to inhibit malaria parasite growth.

Sphingosine-1-phosphate (S1P) a bioactive lipid is produced in its primary reservoir, erythrocytes by an enzyme Sphingosine kinase-1 (SphK-1). The activation of such kinases and the subsequent S1P generation and secretion in the blood serum represent a major regulator of many cellular signaling cascades. Orthologue of sphingosine kinases 1 and 2 (SphK-1 and 2) that catalyze the phosphorylation of sphingosine generating S1P are not present in malaria parasite. The malaria parasite, Plasmodium falciparum, is an intracellular obligatory organism that reside in the human erythrocyte during its blood stage life cycle and orchestrates many metabolic interactions with host for its survival. Given the regulatory role of S1P, we targeted host SphK-1 by a generic pharmacological inhibitor N,N-Dimethyl-sphingosine (DMS) and analyzed growth of intra-erythrocytic parasite. We found that reducing S1P levels by inhibiting host SphK-1 activity led to halted parasite growth and ultimately cell death. Reduced intracellular S1P levels were attributed to decreased glycolysis marked by the low uptake of glucose by parasite and by less production of lactate, a byproduct of glycolysis. Reduced glycolysis was mediated by decrease translocation of the glycolytic enzyme, Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) to the cytosol of infected erythrocytes and cell death. Knocking down of erythrocyte SphK-1 is not lethal to the host and being a host encoded enzyme, targeting it with safe and specific drugs will not lead to the problem of resistance; thus, SphK-1 represents a potent target for the development of therapeutics against intra-erythrocytic P. falciparum.\n\nAuthor SummaryErythrocytes membrane enzyme Sphingosine kinase-1 (SphK-1) produces Sphingosine-1-phosphate (S1P) a bioactive lipid by phosphorylation of Sphingosine (Sph). S1P generated by activation of SphK is prosurvival signal and regulate cell growth. The malaria parasite, Plasmodium falciparum, is an intracellular obligatory pathogen that reside in erythrocyte during its blood stage life cycle and orchestrates many metabolic interactions with its host erythrocytes for survival. Orthologue of SphK-1/ 2 are not present in malaria parasite, therefore treatment with SphK inhibitor targeted host SphK-1 and led to reduced S1P level. The reduction in host S1P led to halted parasite growth and cell death. Furthermore, reduced erythrocyte S1P levels led to decreased glycolysis marked by the low uptake of glucose by parasite and by less production of lactate. Erythrocyte SphK-1 being a host encoded enzyme, is resistance safe and represents a potent target for the development of therapeutics against intra-erythrocytic P. falciparum.

Severe malaria caused by Plasmodium falciparum poses a major global health problem with high morbidity and mortality. The P. falciparum harbours a family of pore forming proteins (PFPs), known as perforin like proteins (PLPs), which are structurally equivalent to prokaryotic PFPs. These PLPs are secreted from the parasites and by interacting to host cells they contribute to disease pathogenesis. The severe malaria pathogenesis is associated with dysfunction of various barrier cells including endothelial cells. A number of factors, including PLPs, secreted by parasite contribute to the host cell dysfunction. Here in, we tested the hypothesis that the PLPs mediate dysfunction of barrier cells and might have a role in disease pathogenesis. We analysed various dysfunction in barrier cells following rPLP2 exposure and demonstrate that it causes an increase in intracellular Ca2+ levels. Additionally, rPLP2 exposed barrier cells displayed features of cell death including Annexin/PI positivity, depolarized mitochondrial membrane potential and ROS generation. We further performed the time lapse video microscopy of barrier cells and found the treatment of rPLP2 triggers their membrane blebbing. The cytoplasmic localization of HMGB1, a marker of necrosis, further confirmed the necrotic type of cell death. This study highlights the role of parasite factor PLP in endothelial dysfunction and provides a rational for the design of adjunct therapies against severe malaria.

Intracellular membrane fusion is mediated by membrane-bridging complexes of soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). SNARE proteins are one of the key players in the vesicular transport. Several reports shed light on intracellular bacteria modulating host SNARE machinery to establish infection successfully. The critical SNAREs in macrophages responsible for phagosome maturation are Syntaxin 3 (STX3) and Syntaxin 4 (STX4). Salmonella actively modulates its vacuole membrane composition to escape lysosomal fusion. A report showed that Salmonella containing vacuole (SCV) harbors recycling endosomal SNARE Syntaxin 12 (STX12). However, the role of host SNAREs in SCV biogenesis and pathogenesis is unclear. Upon knockdown of STX3, we have observed a reduction in bacterial proliferation and is restored upon the overexpression of STX3. Post infected live-cell imaging of cells showed STX3 localises to the SCV membranes and thus might help in fusion of SCV with intracellular vesicles to acquire membrane for its division. We also found this interaction abrogated when we infected with SPI-2 encoded T3SS apparatus mutant (STM {Delta}ssaV) but not with SPI-1 encoded T3SS (STM{Delta} invC). These observations were also consistent in mice model of Salmonella infection. Together, these results shed a light on the effector molecules secreted through SPI-2 encoded by T3SS possibly involved in interaction with host SNARE STX3, which is essential to maintain the division of Salmonella in SCV and maintenance the principle single bacterium per vacuole. SynopsisSalmonella Typhimurium infection in murine macrophage leads to upregulation of host Syntaxin 3 both at transcript and protein levels at late stage of infection. Syntaxin 3 cross-talk with Salmonella containing vacuoles (SCVs) is essential for establishment of replicative niche in host macrophages. The cross-talk between STX3 and SCVs is Salmonella pathogenicity island 2 (SPI-2) dependent and is consistent in mice model of Salmonella Typhimurium infection.

Tuberculosis (TB) is a global health problem caused by Mycobacterium tuberculosis (MTB) infection. The main problem of TB treatment is the emergence of drug resistance, which can occur by inappropriate of antibiotic used. Isoniazid (INH) is the first-line anti-TB drug that inhibits mycolic acid synthesis, an important part of the mycobacterial cell wall. Mannose-capped lipoarabinomannan (ManLAM) is an essential cell wall part that plays a role as an immunomodulator and acts as a virulence factor. In this study, MTB clinical isolates with different drug resistant profiles were used to determine the expression of ManLAM related genes including pimB, mptA, mptC, dprE1, dprE2 and embC by qRT-PCR. Stress-related genes including hspX, tgs1, and sigE were determined by multiplex real-time PCR with probe assay. Sanger sequencing of ManLAM related genes and genes associated with drug resistance (inhA, katG, and rpoB) were analyzed. In response to INH, the expression pattern of ManLAM related genes was different among four strains. Interestingly, MDR-TB markedly up-regulated ManLAM related genes greater than others. Stress-related genes hspX and tgs1 were significantly upregulated in MDR response to INH, whereas sigE was significantly upregulated in MDR response to RIF and INH-R. DprE1 is crucial for MTB and it is a valuable target for anti-TB drugs. RIF-R and MDR isolates show C[->]T mutation at nucleotide position 459 of the dprE1 gene leading to the same amino acid at codon 153. Codon usage analysis for DprE1 showed that RIF-R and MDR preferred ACT codon over drug sensitive strains. This work provides the expression pattern of ManLAM related genes and stress responder genes, which are key factors in the interaction between MTB and host. Moreover, ManLAM is a possible factor that plays an important role in the adaptive mechanism and the drug resistance mechanism of mycobacteria. Author summaryThe adaptive mechanism of mycobacteria in response to stressors is an important strategy to promote their virulence and pathogenesis. This study determined the effect of antibiotic stress on Mycobacterium tuberculosis (MTB) focusing on mannose-capped lipoarabinomannan (ManLAM), which is one of the virulence factors that modulate host immune response. Multiplex real-time PCR with probe assay targeting stress responder genes and qRT-PCR targeting ManLAM related genes were performed. Isoniazid acts as a stressor to induce stress response in mycobacteria, as shown in the up-regulation of stress-related genes including hspX, tgs1, and sigE. The expression pattern of ManLAM related genes in drug resistant and drug sensitive-MTB in response to INH was different, causing a unique pattern. ManLAM related genes respond to isoniazid mostly in drug resistant strains and are present at high expression levels in INH-R and MDR. The results suggest that ManLAM is one factor involved in the adaptive mechanism of MTB response to antibiotic stress and probably associated with the emergence of MTB drug resistance. This work provides new insights into the adaptive mechanism of mycobacterial response to isoniazid that will improve understanding of how mycobacteria develop drug resistance.

Pseudorabies virus (PRV) is an immunosuppressive disease that causes significant damage to the pig industry. This study aimed to detect the effects of PRV on oxidative stress related factors and cell apoptosis in the spleen, providing a basis for the research on the pathogenesis of PRV in mice model. Pathological observation was performed by hematoxylin and eosin Y staining. Biochemical and Flow cytometry method were performed to determine the reactive oxygen species profile of the spleen post-infection and apoptosis detection. In addition, q-PCR and Western blot were adopted to measure the apoptotic conditions of the spleen infected with PRV. The results indicated that the ROS level in the PRV infection group was remarkedly increased (p<0 01) at a time-dependent pattern. Furthermore, the Malondialdehyde levels in the spleen of mice in the infection group increased significantly (p<0.01) in a time-dependent mode. However, the Catalase, Superoxide dismutase, and Glutathione activity and expression levels in the infection group were significantly decreased with the control group (p<0 01) in a time-dependent manner. Furthermore, the ratio of splenocyte apoptosis in the infection group significantly increased (p<0 05, p<0 01) in a time-dependent manner. In conclusion, PRV infection causes apoptosis of the spleen via oxidative stress in mice.

Salmonella is a facultative intracellular pathogen that has co-evolved with its host and has also developed various strategies to evade the host immune responses. Salmonella recruits an array of virulence factors to escape from host defense mechanisms. Previously chitinase A (chiA) was found to be upregulated in intracellular Salmonella. Although studies show that chitinases and chitin binding proteins (CBP) of many human pathogens have a profound role in various aspects of pathogenesis, like adhesion, virulence and immune evasion, the role of chitinase in strict intravacuolar pathogen Salmonella has not yet been elucidated. In this study, we deciphered the role of chitinase of Salmonella in the pathogenesis of the serovars, Typhimurium and Typhi. Our data propose that ChiA mediated modification of the glycosylation on the epithelial cell surface facilitates the invasion of the pathogen into the epithelial cells. Further we found that ChiA aids in reactive nitrogen species (RNS) and reactive oxygen species (ROS) production in phagocytes, leading to MHCII downregulation followed by suppression of antigen presentation and antibacterial responses. In continuation of the study in animal model C. elegans, Salmonella Typhi ChiA was found to facilitate attachment to the intestinal epithelium, gut colonization and persistence by downregulating antimicrobial peptides.

To study the effect of Marp protein in Mycobacterium bovis to the acid resistance and growth performance, this research constructed a knockout mutant ({Delta}Marp) with mycobacteriophage, complemented strain ({Delta}MarpComp), and overexpressing strain (PmvRv3671) of the gene Rv3671c with pmv261 plasmid. Culturing them in standard 7H9 medium to the early logarithmic phase and transferring them into 7H9 medium at pH 6.6 and pH 5.0 and maintenance solution at pH 6.6 and pH 4.5. Likewise, macrophages Raw264.7 were infected with multiple infections at 10. The results showed that while they grew in 7H9 medium at pH 5.0 or pH 6.6 and maintenance buffer at pH 4.5, the lived number of over-expressing strain PmvRv3671 is more than wild-type strain M.bovis, {Delta}MarpComp and{Delta} Marp on the 14th day. After removing the effects of citrate solution, it can be found that the acid resistance abilities of them all are significantly lower on the 14th day than that on the 5th day. Using them infected Raw264.7 macrophages with IFN{gamma} stimulation, the growth rate of the PmvRv3671 is better than An5,{Delta} Marp and {Delta}MarpComp. In conclusion, Rv3671c over-expressing strain had shown a better growth ability than wild-type An5,{Delta} Marp and {Delta}MarpComp under acidic environment. When exposed to pH 4.5 citrate maintenance solution for a long time, acid resistance abilities of them all have become weaker.

Chikungunya virus (CHIKV) is a positive-sense, single-stranded RNA virus, belonging to the genus alphavirus in the family Togaviridae. The virus is spread by the Aedes species (sp.) mosquitoes in tropical and subtropical regions of the world. CHIKV causes Chikungunya fever (CHIKF), where the acute stage of infection is characterized by high fever, headache, rash, and polyarthralgia. In 30-40% of cases, patients develop a chronic stage with debilitating joint pain persisting for months to years imposing a burden on the population in terms of disability adjusted life years (DALY). Presently, no vaccines or treatment options are available for this infection. Prior investigations reveal that CHIKV infection is associated with bone pathology; however, the molecular mechanism underlying CHIKV-induced bone pathology remains poorly defined. Studies show that disruption of osteogenic differentiation and function of bone marrow-derived mesenchymal stem cells (BMMSCs) can lead to bone pathologies. However, to date pathogenesis of CHIKV infection in this context has not been studied. In the current study, we investigated the susceptibility of BMMSCs to CHIKV and studied the effect of infection on BMMSCs-derived osteogenic cells. To our knowledge, for the first time we report that CHIKV can productively infect BMMSCs. We observed a decrease in the intracellular and extracellular alkaline phosphatase (ALP) activity and reduction in calcium phosphate deposition in infected cells compared to mock-infected control. Thus, we conclude that CHIKV infects BMMSCs and disrupts function of osteogenic cells.\n\nImportanceAlthough studies have shown association of bone pathology and CHIKV infection, the pathogenesis of infection causing altered bone homeostasis is not fully understood. Here, we demonstrate for the first time that BMMSCs are susceptible to CHIKV infection. Furthermore, we observe that infection causes disruption in the function of BMMSC- derived osteogenic cells. Impaired function of these osteogenic cells will likely lead to a disruption in bone homeostasis and in part, provides a mechanism for the observed bone pathology associated with CHIKV pathogenesis.

African Swine Fever (ASF) has affected all pig breeds in North-East India since 2020, except Doom pigs, a unique indigenous breed from Assam and the closest progenitor to Indian wild pigs, resulting in significant economic losses for pig farmers in the region. Based on the complete sequences of the B646L (p72) gene, it has been determined that the virus responsible for the outbreak is ASFV genotype II. The further characterization of three complete sequences of the B646L (p72) gene established 100% identical with other existing sequences of different parts of the world as well as confirmed that there is no co-circulation of different genotypes of ASFV in India except genotype II. Present studies also corroborate that MYD88, LDHB and IFIT1 were important genes of the immune system involved in the pathogenesis of ASFV. The differential expression patterns of these genes in ASFV-infected survived, and healthy Doom breed pigs, compared to healthy control pigs, were studied to distinguish the expression pattern at different stages. The hardiness and ability of the Doom pig to withstand common pig diseases, along with its genetic resemblance to wild pigs, make it an ideal candidate for studying tolerance to ASFV infection. So, the present study investigates the natural resistance to ASF in Doom pigs from an endemic area in North-East India to support the proposition that Doom pigs can co-exist with virulent ASFVs recently break in North-East India. The results of this study also provide important molecular insights into the regulation of the ASFV-tolerant gene. ImportanceStudying the natural resistance to African Swine Fever (ASF) in Doom pigs from North-East India holds crucial importance. ASF has inflicted significant economic losses on pig farmers in the region, necessitating the identification and comprehension of factors contributing to resistance and tolerance in specific pig breeds such as Doom pigs. Understanding the molecular mechanisms and genetic factors associated with ASFV tolerance could help in breeding programs and the selection of resilient pig breeds, ultimately aiding in disease control efforts.

Leishmania genome encodes for two isoforms of myosin, but only Myosin XXI (Myo21), which is a novel form of myosin in that it contains two ubiquitin associated-like (UBA) domains towards the end of its tail structure, is expressed in both the promastigote and amastigote forms of this protozoan. Earlier studies have shown that in Leishmania promastigotes Myo21 besides localizing throughout the cell body and flagellum, it is prominently localized to the base of the flagellum. It has further been shown that this protein in the promastigotes plays an important role in regulating the cell morphology, motility, flagellum dynamics, growth and intracellular trafficking, As Myo21 depletion has been shown to result in reduced cell growth in culture, we considered it of interest to investigate whether the observed effect of Myo21 on the cell growth is mediated through its possible role in Leishmania cell division cycle. For this, we prepared heterozygous Myo21 mutants of Leishmania promastigotes (Myo21+/-cells) and then analyzed their morphology, growth and cell division cycle, using wild type Leishmania promastigotes (Myo21+/+ cells) as control. The cell division cycle was analyzed by employing flow cytometry and immunofluorescence microscopy. Flow cytometric analysis revealed that the G2/M to G1 phase transition in Myo21+/- cell is significantly delayed, as compared to Myo21+/+ cells. Immunofluorescence confocal microscopic analysis indicated that Myo21+/- cells encountered a significant delay in initiation of cytokinesis, which was mainly due to delay in the flagellar pocket division. Further analysis revealed that actin-based Myo21 motor is essentially required in the initiation phase of Leishmania cytokinesis.

BackgroundThe Clp proteases regulator, ClgR, is encoded in the Mycobacterium tuberculosis (Mtb) genome by Rv2745c gene (clgR). ClgR is required to clear damaged proteins, thereby preventing their accumulation in the cell. It also controls the availability of key enzymes or regulators via conditional degradation mechanism of proteolytic activity in Mtb [1,2]. MethodsIt has been previously reported that Mtb clgR gene is induced in a sigma factor SigH-dependent manner and a deletion mutant of clgR is susceptible to growth in a hypoxic environment. Whether hypoxia is indeed a restriction factor and ClgR is required for Mtb growth in that environment remains unelucidated. We began to address this hypothesis in the C57/BL6 mouse model of TB where Mtb infected lungs do not form granuloma and the lung environment is considerably non-hypoxic. ResultsOur results demonstrate that despite not having a deficit in growth in either murine lungs or primary macrophages, in comparison to wild type, the{Delta} clgR mutant failed to induce pulmonary pathology. ConclusionWe propose that ClgR is required for the pathogenesis of Mtb.