scholarly journals Contributions of lipopolysaccharide and the type IVB secretion system to Coxiella burnetii vaccine efficacy and reactogenicity

npj Vaccines ◽  
2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Carrie M. Long ◽  
Paul A. Beare ◽  
Diane C. Cockrell ◽  
Jonathan Fintzi ◽  
Mahelat Tesfamariam ◽  
...  

AbstractCoxiella burnetii is the bacterial causative agent of the zoonosis Q fever. The current human Q fever vaccine, Q-VAX®, is a fixed, whole cell vaccine (WCV) licensed solely for use in Australia. C. burnetii WCV administration is associated with a dermal hypersensitivity reaction in people with pre-existing immunity to C. burnetii, limiting wider use. Consequently, a less reactogenic vaccine is needed. Here, we investigated contributions of the C. burnetii Dot/Icm type IVB secretion system (T4BSS) and lipopolysaccharide (LPS) in protection and reactogenicity of fixed WCVs. A 32.5 kb region containing 23 dot/icm genes was deleted in the virulent Nine Mile phase I (NMI) strain and the resulting mutant was evaluated in guinea pig models of C. burnetii infection, vaccination-challenge, and post-vaccination hypersensitivity. The NMI ∆dot/icm strain was avirulent, protective as a WCV against a robust C. burnetii challenge, and displayed potentially altered reactogenicity compared to NMI. Nine Mile phase II (NMII) strains of C. burnetii that produce rough LPS, were similarly tested. NMI was significantly more protective than NMII as a WCV; however, both vaccines exhibited similar reactogenicity. Collectively, our results indicate that, like phase I LPS, the T4BSS is required for full virulence by C. burnetii. Conversely, unlike phase I LPS, the T4BSS is not required for vaccine-induced protection. LPS length does not appear to contribute to reactogenicity while the T4BSS may contribute to this response. NMI ∆dot/icm represents an avirulent phase I strain with full vaccine efficacy, illustrating the potential of genetically modified C. burnetii as improved WCVs.

mBio ◽  
2011 ◽  
Vol 2 (4) ◽  
Author(s):  
Paul A. Beare ◽  
Stacey D. Gilk ◽  
Charles L. Larson ◽  
Joshua Hill ◽  
Christopher M. Stead ◽  
...  

ABSTRACTCentral to Q fever pathogenesis is replication of the causative agent,Coxiella burnetii, within a phagolysosome-like parasitophorous vacuole (PV) in mononuclear phagocytes.C. burnetiimodulates PV biogenesis and other host cell functions, such as apoptotic signaling, presumably via the activity of proteins delivered to the host cytosol by a Dot/Icm type IVB secretion system (T4BSS). In this study, we utilized aC. burnetiistrain carrying IcmD inactivated by theHimar1transposon to investigate the requirements for Dot/Icm function inC. burnetiiparasitism of human THP-1 macrophage-like cells. TheicmD::Tn mutant failed to secrete characterized T4BSS substrates, a defect that correlated with deficient replication, PV development, and apoptosis protection. Restoration of type IVB secretion and intracellular growth of theicmD::Tn mutant required complementation withicmD,-J, and-B, indicating a polar effect of the transposon insertion on downstreamdot/icmgenes. Induction oficmDJBexpression at 1 day postinfection resulted inC. burnetiireplication and PV generation. Collectively, these data prove that T4BSS function is required for productive infection of human macrophages byC. burnetii. However, illustrating the metabolic flexibility ofC.burnetti, theicmD::Tn mutant could replicate intracellularly when sequestered in a PV generated by wild-type bacteria, where Dot/Icm function is provided intrans, and within a phenotypically similar PV generated by the protozoan parasiteLeishmania amazonensis, where host cells are devoid of Dot/Icm T4BSS effector proteins.IMPORTANCECoxiella burnetii, the cause of human Q fever, is the only bacterial pathogen known to replicate in a vacuole resembling a phagolysosome. The organism manipulates host macrophages to promote the biogenesis of a vacuolar compartment permissive for growth. By analogy to the well-established cellular microbiology ofLegionella pneumophila, the Dot/Icm type IVB secretion system ofC. burnetiiis implicated as a critical virulence factor in host cell modification that delivers proteins with effector functions directly into the host cell cytosol. Using new genetic tools, we verify that Dot/Icm function is essential for productive infection of human macrophages byC. burnetii. Interestingly, despite the production of homologous secretion systems,L. pneumophilaandC. burnetiihave strikingly different temporal requirements for Dot/Icm function during their respective infectious cycles.


mBio ◽  
2013 ◽  
Vol 4 (1) ◽  
Author(s):  
Justin A. McDonough ◽  
Hayley J. Newton ◽  
Scott Klum ◽  
Rachel Swiss ◽  
Hervé Agaisse ◽  
...  

ABSTRACTCoxiella burnetiiis an intracellular pathogen that replicates within a lysosome-like vacuole. A Dot/Icm type IVB secretion system is used byC. burnetiito translocate effector proteins into the host cytosol that likely modulate host factor function. To identify host determinants required forC. burnetiiintracellular growth, a genome-wide screen was performed using gene silencing by small interfering RNA (siRNA). Replication ofC. burnetiiwas measured by immunofluorescence microscopy in siRNA-transfected HeLa cells. Newly identified host factors included components of the retromer complex, which mediates cargo cycling between the endocytic pathway and the Golgi apparatus. Reducing the levels of the retromer cargo-adapter VPS26-VPS29-VPS35 complex or retromer-associated sorting nexins abrogatedC. burnetiireplication. Several genes, when silenced, resulted in enlarged vacuoles or an increased number of vacuoles withinC. burnetii-infected cells. Silencing of theSTX17gene encoding syntaxin-17 resulted in a striking defect in homotypic fusion of vacuoles containingC. burnetii, suggesting a role for syntaxin-17 in regulating this process. Lastly, silencing host genes needed forC. burnetiireplication correlated with defects in the translocation of Dot/Icm effectors, whereas, silencing of genes that affected vacuole morphology, but did not impact replication, did not affect Dot/Icm translocation. These data demonstrate thatC. burnetiivacuole maturation is important for creating a niche that permits Dot/Icm function. Thus, genome-wide screening has revealed host determinants involved in sequential events that occur duringC. burnetiiinfection as defined by bacterial uptake, vacuole transport and acidification, activation of the Dot/Icm system, homotypic fusion of vacuoles, and intracellular replication.IMPORTANCEQ fever in humans is caused by the bacteriumCoxiella burnetii. Infection withC. burnetiiis marked by its unique ability to replicate within a large vacuolar compartment inside cells that resembles the harsh, acidic environment of a lysosome. Central to its pathogenesis is the delivery of bacterial effector proteins into the host cell cytosol by a Dot/Icm type IVB secretion system. These proteins can interact with and manipulate host factors, thereby leading to creation and maintenance of the vacuole that the bacteria grow within. Using high-throughput genome-wide screening in human cells, we identified host factors important for several facets ofC. burnetiiinfection, including vacuole transport and membrane fusion events that promote vacuole expansion. In addition, we show that maturation of theC. burnetiivacuole is necessary for creating an environment permissive for the Dot/Icm delivery of bacterial effector proteins into the host cytosol.


2010 ◽  
Vol 311 (1) ◽  
pp. 61-69 ◽  
Author(s):  
John K. Morgan ◽  
Brandon E. Luedtke ◽  
Herbert A. Thompson ◽  
Edward I. Shaw

2021 ◽  
Vol 12 ◽  
Author(s):  
Alycia P. Fratzke ◽  
Sharon Jan ◽  
Jiin Felgner ◽  
Li Liang ◽  
Rie Nakajima ◽  
...  

Q fever is caused by the obligate intracellular bacterium, Coxiella burnetii, a designated potential agent of bioterrorism because of its route of transmission, resistance to disinfectants, and low infectious dose. The only vaccine licensed for human use is Q-VAX® (Seqirus, licensed in Australia), a formalin-inactivated whole-cell vaccine, which produces severe local and systemic reactogenic responses in previously sensitized individuals. Accordingly, the U.S. Food and Drug Administration and other regulatory bodies around the world, have been reluctant to approve Q-VAX for widespread use. To obviate these adverse reactions, we prepared recombinant protein subunit vaccine candidates containing purified CBU1910, CBU0307, CBU0545, CBU0612, CBU0891, and CBU1398 proteins and TLR triagonist adjuvants. TLR triagonist adjuvants combine different TLR agonists to enhance immune responses to vaccine antigens. We tested both the protective efficacy and reactogenicity of our vaccine candidates in Hartley guinea pigs using intratracheal infection with live C. burnetii. While all of our candidates showed varying degrees of protection during challenge, local reactogenic responses were significantly reduced for one of our vaccine candidates when compared with a formalin-inactivated whole-cell vaccine. Our findings show that subunit vaccines combined with novel TLR triagonist adjuvants can generate protective immunity to C. burnetii infection while reducing reactogenic responses.


Pathogens ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1223
Author(s):  
Carrie Mae Long

Q fever is a zoonotic disease caused by the intracellular pathogen Coxiella burnetii. This disease typically manifests as a self-limiting, febrile illness known as acute Q fever. Due to the aerosol transmissibility, environmental persistence, and infectivity of C. burnetii, this pathogen is a notable bioterrorism threat. Despite extensive efforts to develop next-generation human Q fever vaccines, only one vaccine, Q-Vax®, is commercially available. Q-Vax® is a phase I whole-cell vaccine, and its licensed use is limited to Australia, presumably due to the potential for a post-vaccination hypersensitivity response. Pre-clinical Q fever vaccine development is a major area of interest, and diverse approaches have been undertaken to develop an improved Q fever vaccine. Following a brief history of Q fever vaccine development, current approaches will be discussed along with future considerations for an improved Q fever vaccine.


2015 ◽  
Vol 83 (3) ◽  
pp. 1190-1198 ◽  
Author(s):  
Joseph G. Graham ◽  
Caylin G. Winchell ◽  
Uma M. Sharma ◽  
Daniel E. Voth

Coxiella burnetiicauses human Q fever, a zoonotic disease that presents with acute flu-like symptoms and can result in chronic life-threatening endocarditis. In human alveolar macrophages,C. burnetiiuses a Dot/Icm type IV secretion system (T4SS) to generate a phagolysosome-like parasitophorous vacuole (PV) in which to replicate. The T4SS translocates effector proteins, or substrates, into the host cytosol, where they mediate critical cellular events, including interaction with autophagosomes, PV formation, and prevention of apoptosis. Over 100C. burnetiiDot/Icm substrates have been identified, but the function of most remains undefined. Here, we identified a novel Dot/Icm substrate-encoding open reading frame (CbuD1884) present in allC. burnetiiisolates except the Nine Mile reference isolate, where the gene is disrupted by a frameshift mutation, resulting in a pseudogene. The CbuD1884 protein contains two transmembrane helices (TMHs) and a coiled-coil domain predicted to mediate protein-protein interactions. The C-terminal region of the protein contains a predicted Dot/Icm translocation signal and was secreted by the T4SS, while the N-terminal portion of the protein was not secreted. When ectopically expressed in eukaryotic cells, the TMH-containing N-terminal region of the CbuD1884 protein trafficked to the endoplasmic reticulum (ER), with the C terminus dispersed nonspecifically in the host cytoplasm. This new Dot/Icm substrate is now termed ElpA (ER-localizingproteinA). Full-length ElpA triggered substantial disruption of ER structure and host cell secretory transport. These results suggest that ElpA is a pathotype-specific T4SS effector that influences ER function duringC. burnetiiinfection.


2019 ◽  
Vol 87 (12) ◽  
Author(s):  
A. E. Gregory ◽  
E. J. van Schaik ◽  
K. E. Russell-Lodrigue ◽  
A. P. Fratzke ◽  
J. E. Samuel

ABSTRACT Coxiella burnetii, the etiological agent of Q fever, is a Gram-negative bacterium transmitted to humans by inhalation of contaminated aerosols. Acute Q fever is often self-limiting, presenting as a febrile illness that can result in atypical pneumonia. In some cases, Q fever becomes chronic, leading to endocarditis that can be life threatening. The formalin-inactivated whole-cell vaccine (WCV) confers long-term protection but has significant side effects when administered to presensitized individuals. Designing new vaccines against C. burnetii remains a challenge and requires the use of clinically relevant modes of transmission in appropriate animal models. We have developed a safe and reproducible C. burnetii aerosol challenge in three different animal models to evaluate the effects of pulmonary acquired infection. Using a MicroSprayer aerosolizer, BL/6 mice and Hartley guinea pigs were infected intratracheally with C. burnetii Nine Mile phase I (NMI) and demonstrated susceptibility as determined by measuring bacterial growth in the lungs and subsequent dissemination to the spleen. Histological analysis of lung tissue showed significant pathology associated with disease, which was more severe in guinea pigs. Infection using large-particle aerosol (LPA) delivery was further confirmed in nonhuman primates, which developed fever and pneumonia. We also demonstrate that vaccinating mice and guinea pigs with WCV prior to LPA challenge is capable of eliciting protective immunity that significantly reduces splenomegaly and the bacterial burden in spleen and lung tissues. These data suggest that these models can have appreciable value in using the LPA delivery system to study pulmonary Q fever pathogenesis as well as designing vaccine countermeasures to C. burnetii aerosol transmission.


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