Alternative Enzyme Protection Assay To Overcome the Drawbacks of the Gentamicin Protection Assay for Measuring Entry and Intracellular Survival of Staphylococci

ABSTRACTPrecise enumeration of living intracellular bacteria is the key step to estimate the invasion potential of pathogens and host immune responses to understand the mechanism and kinetics of bacterial pathogenesis. Therefore, quantitative assessment of host-pathogen interactions is essential for development of novel antibacterial therapeutics for infectious disease. The gentamicin protection assay (GPA) is the most widely used method for these estimations by counting the CFU of intracellular living pathogens. Here, we assess the longstanding drawbacks of the GPA by employing an antistaphylococcal endopeptidase as a bactericidal agent to kill extracellularStaphylococcus aureus. We found that the difference between the two methods for the recovery of intracellular CFU ofS. aureuswas about 5 times. We prove that the accurate number of intracellular CFU could not be precisely determined by the GPA due to the internalization of gentamicin into host cells during extracellular bacterial killing. We further demonstrate that lysostaphin-mediated extracellular bacterial clearance has advantages for measuring the kinetics of bacterial internalization on a minute time scale due to the fast and tunable activity and the inability of protein to permeate the host cell membrane. From these results, we propose that accurate quantification of intracellular bacteria and measurement of internalization kinetics can be achieved by employing enzyme-mediated killing of extracellular bacteria (enzyme protection assay [EPA]) rather than the host-permeative drug gentamicin, which is known to alter host physiology.

Download Full-text

Initial Characterization of the Two ClpP Paralogs ofChlamydia trachomatisSuggests Unique Functionality for Each

Journal of Bacteriology ◽

10.1128/jb.00635-18 ◽

2018 ◽

Vol 201 (2) ◽

Cited By ~ 5

Author(s):

Nicholas A. Wood ◽

Krystal Y. Chung ◽

Amanda M. Blocker ◽

Nathalia Rodrigues de Almeida ◽

Martin Conda-Sheridan ◽

...

Keyword(s):

Host Cells ◽

Developmental Cycle ◽

Intracellular Bacteria ◽

Clp Protease ◽

Content Type ◽

Sexually Transmitted ◽

Obligate Intracellular ◽

Developmental Form ◽

Obligate Intracellular Bacteria

ABSTRACTMembers ofChlamydiaare obligate intracellular bacteria that differentiate between two distinct functional and morphological forms during their developmental cycle, elementary bodies (EBs) and reticulate bodies (RBs). EBs are nondividing small electron-dense forms that infect host cells. RBs are larger noninfectious replicative forms that develop within a membrane-bound vesicle, termed an inclusion. Given the unique properties of each developmental form of this bacterium, we hypothesized that the Clp protease system plays an integral role in proteomic turnover by degrading specific proteins from one developmental form or the other.Chlamydiaspp. have five uncharacterizedclpgenes,clpX,clpC, twoclpPparalogs, andclpB. In other bacteria, ClpC and ClpX are ATPases that unfold and feed proteins into the ClpP protease to be degraded, and ClpB is a deaggregase. Here, we focused on characterizing the ClpP paralogs. Transcriptional analyses and immunoblotting determined that these genes are expressed midcycle. Bioinformatic analyses of these proteins identified key residues important for activity. Overexpression of inactiveclpPmutants inChlamydiaspp. suggested independent function of each ClpP paralog. To further probe these differences, we determined interactions between the ClpP proteins using bacterial two-hybrid assays and native gel analysis of recombinant proteins. Homotypic interactions of the ClpP proteins, but not heterotypic interactions between the ClpP paralogs, were detected. Interestingly, protease activity of ClpP2, but not ClpP1, was detectedin vitro. This activity was stimulated by antibiotics known to activate ClpP, which also blocked chlamydial growth. Our data suggest the chlamydial ClpP paralogs likely serve distinct and critical roles in this important pathogen.IMPORTANCEChlamydia trachomatisis the leading cause of preventable infectious blindness and of bacterial sexually transmitted infections worldwide. Chlamydiae are developmentally regulated obligate intracellular pathogens that alternate between two functional and morphologic forms, with distinct repertoires of proteins. We hypothesize that protein degradation is a critical aspect to the developmental cycle. A key system involved in protein turnover in bacteria is the Clp protease system. Here, we characterized the two chlamydial ClpP paralogs by examining their expression inChlamydiaspp., their ability to oligomerize, and their proteolytic activity. This work will help understand the evolutionarily diverse Clp proteases in the context of intracellular organisms, which may aid in the study of other clinically relevant intracellular bacteria.

Download Full-text

Live-Cell Imaging of Phosphoinositide Dynamics and Membrane Architecture during Legionella Infection

mBio ◽

10.1128/mbio.00839-13 ◽

2014 ◽

Vol 5 (1) ◽

Cited By ~ 63

Author(s):

Stephen Weber ◽

Maria Wagner ◽

Hubert Hilbi

Keyword(s):

Host Cell ◽

Legionella Pneumophila ◽

Live Cell Imaging ◽

Cell Imaging ◽

Effector Proteins ◽

Host Cells ◽

Wild Type ◽

Host Cell Membrane ◽

Content Type ◽

Temporal And Spatial

ABSTRACTThe causative agent of Legionnaires’ disease,Legionella pneumophila, replicates in amoebae and macrophages in a distinct membrane-bound compartment, theLegionella-containing vacuole (LCV). LCV formation is governed by the bacterial Icm/Dot type IV secretion system that translocates ~300 different “effector” proteins into host cells. Some of the translocated effectors anchor to the LCV membrane via phosphoinositide (PI) lipids. Here, we use the soil amoebaDictyostelium discoideum, producing fluorescent PI probes, to analyze the LCV PI dynamics by live-cell imaging. Upon uptake of wild-type or Icm/Dot-deficientL. pneumophila, PtdIns(3,4,5)P3transiently accumulated for an average of 40 s on early phagosomes, which acquired PtdIns(3)Pwithin 1 min after uptake. Whereas phagosomes containing ΔicmTmutant bacteria remained decorated with PtdIns(3)P, more than 80% of wild-type LCVs gradually lost this PI within 2 h. The process was accompanied by a major rearrangement of PtdIns(3)P-positive membranes condensing to the cell center. PtdIns(4)Ptransiently localized to early phagosomes harboring wild-type or ΔicmT L. pneumophilaand was cleared within minutes after uptake. During the following 2 h, PtdIns(4)Psteadily accumulated only on wild-type LCVs, which maintained a discrete PtdIns(4)Pidentity spatially separated from calnexin-positive endoplasmic reticulum (ER) for at least 8 h. The separation of PtdIns(4)P-positive and ER membranes was even more pronounced for LCVs harboring ΔsidC-sdcAmutant bacteria defective for ER recruitment, without affecting initial bacterial replication in the pathogen vacuole. These findings elucidate the temporal and spatial dynamics of PI lipids implicated in LCV formation and provide insight into host cell membrane and effector protein interactions.IMPORTANCEThe environmental bacteriumLegionella pneumophilais the causative agent of Legionnaires’ pneumonia. The bacteria form in free-living amoebae and mammalian immune cells a replication-permissive compartment, theLegionella-containing vacuole (LCV). To subvert host cell processes, the bacteria secrete the amazing number of ~300 different proteins into host cells. Some of these proteins bind phosphoinositide (PI) lipids to decorate the LCV. PI lipids are crucial factors involved in host cell membrane dynamics and LCV formation. UsingDictyosteliumamoebae producing one or two distinct fluorescent probes, we elucidated the dynamic LCV PI pattern in high temporal and spatial resolution. Notably, the endocytic PI lipid PtdIns(3)Pwas slowly cleared from LCVs, thus incapacitating the host cell’s digestive machinery, while PtdIns(4)Pgradually accumulated on the LCV, enabling critical interactions with host organelles. The LCV PI pattern underlies the spatiotemporal configuration of bacterial effector proteins and therefore represents a crucial aspect of LCV formation.

Download Full-text

Auto-Assembling Detoxified Staphylococcus aureus Alpha-Hemolysin Mimicking the Wild-Type Cytolytic Toxin

Clinical and Vaccine Immunology ◽

10.1128/cvi.00091-16 ◽

2016 ◽

Vol 23 (6) ◽

pp. 442-450 ◽

Cited By ~ 6

Author(s):

Luigi Fiaschi ◽

Benedetta Di Palo ◽

Maria Scarselli ◽

Clarissa Pozzi ◽

Kelly Tomaszewski ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Staphylococcal Infection ◽

Host Cells ◽

Wild Type ◽

Host Cell Membrane ◽

Content Type ◽

Single Particle Reconstruction ◽

Alpha Hemolysin ◽

Human Sera ◽

Membrane Spanning

ABSTRACTStaphylococcus aureusalpha-hemolysin (Hla) assembles into heptameric pores on the host cell membrane, causing lysis, apoptosis, and junction disruption. Herein, we present the design of a newly engineeredS. aureusalpha-toxin, HlaPSGS, which lacks the predicted membrane-spanning stem domain. This protein is able to form heptamers in aqueous solution in the absence of lipophilic substrata, and its structure, obtained by transmission electron microscopy and single-particle reconstruction analysis, resembles the cap of the wild-type cytolytic Hla pore. HlaPSGS was found to be impaired in binding to host cells and to its receptor ADAM10 and to lack hemolytic and cytotoxic activity. Immunological studies using human sera as well as sera from mice convalescent fromS. aureusinfection suggested that the heptameric conformation of HlaPSGS mimics epitopes exposed by the cytolytic Hla pore during infection. Finally, immunization with this newly engineered Hla generated high protective immunity against staphylococcal infection in mice. Overall, this study provides unprecedented data on the natural immune response against Hla and suggests that the heptameric HlaPSGS is a highly valuable vaccine candidate againstS. aureus.

Download Full-text

Orientia tsutsugamushi Nucleomodulin Ank13 Exploits the RaDAR Nuclear Import Pathway To Modulate Host Cell Transcription

mBio ◽

10.1128/mbio.01816-21 ◽

2021 ◽

Author(s):

Haley E. Adcox ◽

Amanda L. Hatke ◽

Shelby E. Andersen ◽

Sarika Gupta ◽

Nathan B. Otto ◽

...

Keyword(s):

Nuclear Import ◽

Scrub Typhus ◽

Bacterial Pathogen ◽

Host Cells ◽

Intracellular Bacteria ◽

Orientia Tsutsugamushi ◽

Microbial Protein ◽

Content Type ◽

Eukaryotic Gene Expression ◽

Eukaryotic Gene

Nucleomodulins are recently defined effectors used by diverse intracellular bacteria to manipulate eukaryotic gene expression and convert host cells into hospitable niches. How nucleomodulins enter the nucleus, their functional domains, and the genes that they modulate are incompletely characterized. Orientia tsutsugamushi is an intracellular bacterial pathogen that causes scrub typhus, which can be fatal. O. tsutsugamushi Ank13 is the first example of a microbial protein that coopts eukaryotic RaDAR (RanGDP-ankyrin repeats) nuclear import.

Download Full-text

Targeting Salmonella Typhimurium Invasion and Intracellular Survival Using Pyrogallol

Frontiers in Microbiology ◽

10.3389/fmicb.2021.631426 ◽

2021 ◽

Vol 12 ◽

Author(s):

Biruk Tesfaye Birhanu ◽

Eon-Bee Lee ◽

Seung-Jin Lee ◽

Seung-Chun Park

Keyword(s):

Inhibitory Concentration ◽

Minimum Bactericidal Concentration ◽

Efflux Pump ◽

Intracellular Survival ◽

Host Cells ◽

Intracellular Bacteria ◽

Intracellular Pathogen ◽

Intracellular Accumulation ◽

Protection Assay ◽

Serovar Typhimurium

Salmonella enterica serovar Typhimurium, an intracellular pathogen, evades the host immune response mechanisms to cause gastroenteritis in animals and humans. After invading the host cells, the bacteria proliferate in Salmonella-containing vacuole (SCV) and escapes from antimicrobial therapy. Moreover, Salmonella Typhimurium develops resistance to various antimicrobials including, fluoroquinolones. Treating intracellular bacteria and combating drug resistance is essential to limit the infection rate. One way of overcoming these challenges is through combination therapy. In this study, Pyrogallol (PG), a polyphenol, is combined with marbofloxacin (MAR) to investigate its effect on Salmonella Typhimurium invasion and intracellular survival inhibition. The Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of PG against Salmonella Typhimurium were 128 and 256 μg/mL, respectively. The lowest fractional inhibitory concentration (FIC) index for a combination of PG and MAR was 0.5. The gentamycin protection assay revealed that PG (30 μg/mL) alone and in combination with sub-MIC of MAR inhibited 72.75 and 76.18% of the invading bacteria in Caco-2 cells, respectively. Besides, the intracellular survival of Salmonella Typhimurium was reduced by 7.69 and 74.36% in treatment with PG alone and combined with sub-MIC of MAR, respectively, which was visualized by the confocal microscopy. PG has also shown to increase the intracellular accumulation of fluoroquinolone by 15.2 and 34.9% at 30 and 100 μg/mL concentration, respectively. Quantitative real-time PCR demonstrated PG suppressed the genetic expression of hilA, invF, sipB, and acrA by 14.6, 15.4, 13.6, and 36%, respectively. However, the downregulation of hilA, invF, sipB, and acrA increased to 80, 74.6, 78, and 70.1%, in combination with sub-MIC of MAR, respectively. Similarly, PG combined with MAR inhibited the expression of sdiA, srgE, and rck genes by 78.6, 62.8, and 61.8%, respectively. In conclusion, PG has shown antimicrobial activity against Salmonella Typhimurium alone and in combination with MAR. It also inhibited invasion and intracellular survival of the bacteria through downregulation of quorum sensing, invading virulence, and efflux pump genes. Hence, PG could be a potential antimicrobial candidate which could limit the intracellular survival and replication of Salmonella Typhimurium.

Download Full-text

Construction of Aminoglycoside-Sensitive Burkholderia cenocepacia Strains for Use in Studies of Intracellular Bacteria with the Gentamicin Protection Assay

Applied and Environmental Microbiology ◽

10.1128/aem.03024-09 ◽

2010 ◽

Vol 76 (10) ◽

pp. 3170-3176 ◽

Cited By ~ 51

Author(s):

Mohamad A. Hamad ◽

Alexander M. Skeldon ◽

Miguel A. Valvano

Keyword(s):

Efflux Pump ◽

Opportunistic Pathogen ◽

Multidrug Resistant ◽

Eukaryotic Cell ◽

Burkholderia Cenocepacia ◽

Intracellular Bacteria ◽

Raw 264.7 ◽

Protection Assay ◽

Intracellular Infection ◽

Gentamicin Protection Assay

ABSTRACT Burkholderia cenocepacia is a multidrug-resistant opportunistic pathogen that infects the airways of patients with cystic fibrosis (CF) and can survive intracellularly in macrophages and epithelial cells. The gentamicin protection assay, which relies on the poor ability of gentamicin or other aminoglycosides to permeate eukaryotic cell membranes, is traditionally employed to quantify intracellular bacteria. However, the high resistance of these bacteria to aminoglycosides hampers the use of the gentamicin protection assay to investigate intracellular infection by B. cenocepacia. Here, we report the construction of gentamicin-sensitive strains of B. cenocepacia carrying a deletion of the BCAL1674, BCAL1675, and BCAL1676 genes that form an operon encoding an AmrAB-OprA-like efflux pump. We show that bacteria carrying this deletion are hypersensitive to gentamicin and also delay phagolysosomal fusion upon infection of RAW 264.7 murine macrophages, as previously demonstrated for the parental strain. We also demonstrate for the first time that low concentrations of gentamicin can be used to effectively kill extracellular bacteria and reliably quantify the intracellular infection by B. cenocepacia, which can replicate in RAW 264.7 macrophages.

Download Full-text

Mimicry of the Pathogenic Mycobacterium VacuoleIn VitroElicits the Bacterial Intracellular Phenotype, Including Early-Onset Macrophage Death

Infection and Immunity ◽

10.1128/iai.01120-10 ◽

2011 ◽

Vol 79 (6) ◽

pp. 2412-2422 ◽

Cited By ~ 8

Author(s):

Julie Early ◽

Luiz E. Bermudez

Keyword(s):

Early Onset ◽

Disease Process ◽

Host Cells ◽

Intracellular Bacteria ◽

Content Type ◽

Time Points ◽

Stepwise Reduction ◽

Trace Elemental ◽

Laboratory Tool

ABSTRACTMycobacterium aviumcomplex (MAC) within macrophages undergoes a phenotype change that allows for more efficient entry into surrounding host cells. We hypothesized that, by developing anin vitrosystem resembling the intravacuolar environment, one could generate insights into the mycobacterial intracellular phenotype. MAC was incubated in “elemental mixtures” that reproduce metal concentrations and pH in the vacuoles at different time points and then used to infect fresh macrophages. Incubation of MAC with the mixture corresponding to the vacuole environment 24 h postinfection infected macrophages at a significantly higher rate than bacteria that were incubated in Middlebrook 7H9 broth. Uptake occurred by macropinocytosis, similar to the uptake of bacteria passed through macrophages. Genes reported to be upregulated in intracellular bacteria, such asMav1365,Mav2409,Mav4487, andMav0996, were upregulated in MAC incubated in the 24-h elemental mixture. Like MAC obtained from macrophages, the vacuoles of bacteria from the 24-h elemental mixture were more likely to contain lysosome-associated membrane protein 1 (LAMP-1). A stepwise reduction scheme of the 24-h elemental mixture indicated that incubation in physiologically relevant concentrations of potassium chloride, calcium chloride, and manganese chloride was sufficient to induce characteristics of the intracellular phenotype. It was demonstrated that bacteria harboring the intracellular phenotype induced early-onset macrophage death more efficiently than bacteria grown in broth. This new trace elemental mixture mimicking the condition of the vacuole at different time points has the potential to become an effective laboratory tool for the study of the MAC andMycobacterium tuberculosisdisease process, increasing the understanding of the interaction with macrophages.

Download Full-text

Uptake of Helicobacter pylori Vesicles Is Facilitated by Clathrin-Dependent and Clathrin-Independent Endocytic Pathways

mBio ◽

10.1128/mbio.00979-14 ◽

2014 ◽

Vol 5 (3) ◽

Cited By ~ 29

Author(s):

Annelie Olofsson ◽

Lars Nygård Skalman ◽

Ikenna Obi ◽

Richard Lundmark ◽

Anna Arnqvist

Keyword(s):

Helicobacter Pylori ◽

Host Cell ◽

Host Cells ◽

Gastric Epithelial Cells ◽

Host Cell Membrane ◽

Content Type ◽

Effector Molecules ◽

Chemical Inhibition ◽

H Pylori ◽

Endocytic Pathways

ABSTRACTBacteria shed a diverse set of outer membrane vesicles that function as transport vehicles to deliver effector molecules and virulence factors to host cells.Helicobacter pyloriis a gastric pathogen that infects half of the world’s population, and in some individuals the infection progresses into peptic ulcer disease or gastric cancer. Here we report that intact vesicles fromH. pyloriare internalized by clathrin-dependent endocytosis and further dynamin-dependent processes, as well as in a cholesterol-sensitive manner. We analyzed the uptake ofH. pylorivesicles by gastric epithelial cells using a method that we refer to as quantification of internalized substances (qIS). The qIS assay is based on a near-infrared dye with a cleavable linker that enables the specific quantification of internalized substances after exposure to reducing conditions. Both chemical inhibition and RNA interference in combination with the qIS assay showed thatH. pylorivesicles enter gastric epithelial cells via both clathrin-mediated endocytosis and additional endocytic processes that are dependent on dynamin. Confocal microscopy revealed thatH. pylorivesicles colocalized with clathrin and dynamin II and with markers of subsequent endosomal and lysosomal trafficking. Interestingly, however, knockdown of components required for caveolae had no significant effect on internalization and knockdown of components required for clathrin-independent carrier (CLIC) endocytosis increased internalization ofH. pylorivesicles. Furthermore, uptake of vesicles by both clathrin-dependent and -independent pathways was sensitive to depletion, but not sequestering, of cholesterol in the host cell membrane suggesting that membrane fluidity influences the efficiency ofH. pylorivesicle uptake.IMPORTANCEBacterial vesicles act as long-distance tools to deliver toxins and effector molecules to host cells. Vesicles can cause a variety of host cell responses via cell surface-induced cell signaling or internalization. Vesicles of diverse bacterial species enter host cells via different endocytic pathways or via membrane fusion. With the combination of a fluorescence-based quantification assay that quantifies internalized vesicles in a large number of cells and either chemical inhibition or RNA interference, we show that clathrin-mediated endocytosis is the major pathway for uptake ofHelicobacter pylorivesicles and that lipid microdomains of the host cell membrane affect uptake of vesicles via clathrin-independent pathways. Our results provide important insights about membrane fluidity and its important role in the complex process that directs theH. pylorivesicle to a specific endocytic pathway. Understanding the mechanisms that operate in vesicle-host interactions is important to fully recognize the impact of vesicles in pathogenesis.

Download Full-text

The Hydrophilic Translocator for Vibrio parahaemolyticus, T3SS2, Is Also Translocated

Infection and Immunity ◽

10.1128/iai.00402-12 ◽

2012 ◽

Vol 80 (8) ◽

pp. 2940-2947 ◽

Cited By ~ 12

Author(s):

Xiaohui Zhou ◽

Jennifer M. Ritchie ◽

Hirotaka Hiyoshi ◽

Tetsuya Iida ◽

Brigid M. Davis ◽

...

Keyword(s):

Host Cell ◽

Vibrio Parahaemolyticus ◽

Diarrheal Disease ◽

Host Cells ◽

Cell Cytoplasm ◽

Host Cell Membrane ◽

Membrane Pore ◽

Content Type ◽

Bacterial Proteins ◽

Host Cell Cytoplasm

ABSTRACTThe pathogenesis of the diarrheal disease caused byVibrio parahaemolyticus, a leading cause of seafood-associated enteritis worldwide, is dependent upon a type III secretion system, T3SS2. This apparatus enables the pathogen to inject bacterial proteins (effectors) into the cytosol of host cells and thereby modulate host processes. T3SS effector proteins transit into the host cell via a membrane pore (translocon) typically formed by 3 bacterial proteins. We have identified the third translocon protein for T3SS2: VopW, which was previously classified as an effector protein for a homologous T3SS inV. cholerae. VopW is a hydrophilic translocon protein; like other such proteins, it is not inserted into the host cell membrane but is required for insertion of the two hydrophobic translocators, VopB2 and VopD2, that constitute the membrane channel. VopW is not required for secretion of T3SS2 effectors into the bacterial culture medium; however, it is essential for transfer of these proteins into the host cell cytoplasm. Consequently, deletion ofvopWabrogates the virulence ofV. parahaemolyticusin several animal models of diarrheal disease. Unlike previously described hydrophilic translocators, VopW is itself translocated into the host cell cytoplasm, raising the possibility that it functions as both a translocator and an effector.

Download Full-text

CRISPR/Cas9-Based Knockout of GNAQ Reveals Differences in Host Cell Signaling Necessary for Egress of Apicomplexan Parasites

mSphere ◽

10.1128/msphere.01001-20 ◽

2020 ◽

Vol 5 (6) ◽

pp. e01001-20

Author(s):

Paul-Christian Burda ◽

Hugo Bisio ◽

Jean-Baptiste Marq ◽

Dominique Soldati-Favre ◽

Volker T. Heussler

Keyword(s):

Host Cell ◽

Parasitophorous Vacuole ◽

Host Cells ◽

Infected Host ◽

Protein Subunit ◽

Host Cell Membrane ◽

Guanine Nucleotide Binding Protein ◽

Liver Stage ◽

Content Type ◽

Apicomplexan Parasites

ABSTRACTToxoplasma gondii and members of the genus Plasmodium are obligate intracellular parasites that leave their infected host cell upon a tightly controlled process of egress. Intracellular replication of the parasites occurs within a parasitophorous vacuole, and its membrane as well as the host plasma membrane need to be disrupted during egress, leading to host cell lysis. While several parasite-derived factors governing egress have been identified, much less is known about host cell factors involved in this process. Previously, RNA interference (RNAi)-based knockdown and antibody-mediated depletion identified a host signaling cascade dependent on guanine nucleotide-binding protein subunit alpha q (GNAQ) to be required for the egress of Toxoplasma tachyzoites and Plasmodium blood stage merozoites. Here, we used CRISPR/Cas9 technology to generate HeLa cells deficient in GNAQ and tested their capacity to support the egress of T. gondii tachyzoites and Plasmodium berghei liver stage parasites. While we were able to confirm the importance of GNAQ for the egress of T. gondii, we found that the egress of P. berghei liver stages was unaffected in the absence of GNAQ. These results may reflect differences between the lytic egress process in apicomplexans and the formation of host cell-derived vesicles termed merosomes by P. berghei liver stages.IMPORTANCE The coordinated release of apicomplexan parasites from infected host cells prior to reinvasion is a critical process for parasite survival and the spread of infection. While Toxoplasma tachyzoites and Plasmodium blood stages induce a fast disruption of their surrounding membranes during their egress from host cells, Plasmodium liver stages keep the host cell membrane intact and leave their host cell in host cell-derived vesicles called merosomes. The knockout of GNAQ, a protein involved in G-protein-coupled receptor signaling, demonstrates the importance of this host factor for the lytic egress of T. gondii tachyzoites. Contrastingly, the egress of P. berghei is independent of GNAQ at the liver stage, indicating the existence of a mechanistically distinct strategy to exit the host cell.

Download Full-text