Rickettsia parkeri with a Genetically Disrupted Phage Integrase Gene Exhibits Attenuated Virulence and Induces Protective Immunity against Fatal Rickettsioses in Mice

Arroyave, Esteban; Hyseni, Ilirjana; Burkhardt, Nicole Y.; Kuo, Yong Fang; Munderloh, Ulrike G.; Fang, Rong

doi:10.3390/pathogens10070819

Cited by 9 publications

(8 citation statements)

References 49 publications

(59 reference statements)

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“…The presence of dead macrophages suggests that R. parkeri was likely transmitted from the tick to the guinea pig skin, where macrophages would have phagocytosed the rickettsial pathogen, then ultimately undergone cell death. Conversely, several studies show survival of infected macrophages or macrophage-like cells, using in vitro systems with R. parkeri-infected cells, such as differentiated THP-1 cells or murine primary cell lines [20,21]. Histopathology of human eschars confirms macrophages in infiltrates after tick transmission [22,23].…”

Section: Leukocyte Infiltration Assaysmentioning

confidence: 99%

Skin in the Game: An Assay to Monitor Leukocyte Infiltration in Dermal Lesions of a Guinea Pig Model for Tick-Borne Rickettsiosis

et al. 2022

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Intact, the skin typically serves as an effective barrier to the external world; however, once pathogens have breached this barrier via a wound, such as a tick bite, the surrounding tissues must recruit immune cells from the blood to neutralize the pathogen. With innate and adaptive immune systems being similar between the guinea pig and human systems, the ability of guinea pigs to show clinical signs of many infectious diseases, and the large size of guinea pigs relative to a murine model, the guinea pig is a valuable model for studying tick-borne and other pathogens that invade the skin. Here, we report a novel assay for assessing guinea pig leukocyte infiltration in the skin. Briefly, we developed an optimized six-color/eight-parameter polychromatic flow cytometric panel that combines enzymatic and mechanical dissociation of skin tissue with fluorescent antibody staining to allow for the immunophenotyping of guinea pig leukocytes that have migrated into the skin, resulting in inflammation. We designed this assay using a guinea pig model for tick-borne rickettsiosis to further investigate host–pathogen interactions in the skin, with preliminary data demonstrating immunophenotyping at skin lesions from infected ticks. We anticipate that future applications will include hypothesis testing to define the primary immune cell infiltrates responding to exposure to virulent, avirulent tick-borne rickettsiae, and tick-borne rickettsiae of unknown virulence. Other relevant applications include skin lesions resulting from other vector-borne pathogens, Staphylococcus aureus infection, and Buruli ulcer caused by Mycobacterium ulcerans.

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Section: Leukocyte Infiltration Assaysmentioning

confidence: 99%

Skin in the Game: An Assay to Monitor Leukocyte Infiltration in Dermal Lesions of a Guinea Pig Model for Tick-Borne Rickettsiosis

et al. 2022

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“…Rickettsia parkeri is a low virulence rickettsial species of the spotted fever group, phylogenetically closely related to R. rickettsii . Recently, a Rickettsia parkeri mutant RPATATE_0245:pLoxHimar (named 3A2) was generated by inserting a modified pLoxHimar transposon into the gene encoding a phage integrase protein [ 99 ]. The safety, immunogenicity and efficacy of this rickettsial mutant was evaluated as a live-attenuated vaccine candidate.…”

Section: Prospects For a Live Attenuated Vaccinementioning

confidence: 99%

“…Although we speculate that an immune response, induced by a successful vaccine and required for conferring complete protection against severe RMSF, would be consistent with protective immunity against primary infection, a deeper understanding of vaccine-induced immunity against R. rickettsii would facilitate the development of a licensed vaccine. The complete protection against lethal infection with R. parkeri or R. conorii conferred by R. parkeri mutant 3A2 results from both potent Rickettsia -specific antibody response and Th1 effector cytokines in sera [ 99 ].…”

Section: Prospects For a Live Attenuated Vaccinementioning

confidence: 99%

“…Further, the mutant strain was barely detectable in the organs of infected mice at 4 days post-infection despite inducing strong immunogenic type-I cellular and B-cell responses comparable to those observed in mice infected with the wild-type strain. Most interestingly, mice immunized with a single dose of the mutant demonstrated complete protection against challenge inoculations with wild type R. parkeri and R. conorii , thus providing proof of concept for utilizing live attenuated rickettsial strains/mutants for the development of vaccines against rickettsioses [ 99 ].…”

Section: Scope Of Rickettsial Mutants For Vaccine Developmentmentioning

confidence: 99%

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A Vaccine for Canine Rocky Mountain Spotted Fever: An Unmet One Health Need

et al. 2022

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Outbreaks of life-threatening Rocky Mountain spotted fever in humans and dogs associated with a canine-tick maintenance cycle constitute an important One Health opportunity. The reality of the problem has been observed strikingly in Mexico, Brazil, Colombia, and Native American tribal lands in Arizona. The brown dog tick, Rhipicephalus sanguineus sensu lato, acquires the rickettsia from bacteremic dogs and can maintain the bacterium transtadially to the next tick stage. The subsequent adult tick can then transmit infection to a new host, as shown by guinea pig models. These brown dog ticks maintain spotted fever group rickettsiae transovarially through many generations, thus serving as both vector and reservoir. Vaccine containing whole-killed R. rickettsii does not stimulate sufficient immunity. Studies of Rickettsia subunit antigens have demonstrated that conformationally preserved outer-membrane autotransporter proteins A and B are the leading vaccine candidates. The possibility of a potentially safe and effective live attenuated vaccine has only begun to be explored as gene knockout methods are applied to these obligately intracellular pathogens.

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“…Rickettsia (R.) rickettsii, R. conorii, and R. australis can cause life-threatening diseases. While R. parkeri is not life-threatening in humans (5)(6)(7)(8), the organism is used as a model for pathogenic SFGR in a low biosafety level (BSL2) setting (9). Microvascular endothelial cells (MECs) are the primary mammalian host target cells of SFGR infections (10,11).…”

Section: Introductionmentioning

confidence: 99%

Identification of common sequence motifs shared exclusively among selectively packed exosomal pathogenic microRNAs during rickettsial infections

Bei¹,

Qiu²,

Cockrell

et al. 2023

Preprint

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We previously reported that microRNA (miR)23a and miR30b are selectively sorted into rickettsia-infected, endothelial cell-derived exosomes (R-ECExos). Yet, the mechanism remains unknown. The number of cases of spotted fever rickettsioses has been increasing in recent years, and infections with these bacteria cause life-threatening diseases by targeting brain and lung tissues. Therefore, the aim of the present study is to continue to dissect the molecular mechanism underlying R-ECExos-induced barrier dysfunction of normal recipient microvascular endothelial cells (MECs), depending on their exosomal RNA cargos. Rickettsiae are transmitted to human hosts by the bite of an infected tick into the skin. In the present study we demonstrate that treatment with R-ECExos, which were derived from spotted fever group R parkeri infected human dermal MECs, induced disruptions of the paracellular adherens junctional protein VE-cadherin and breached the paracellular barrier function in recipient pulmonary MECs (PMECs) in an exosomal RNA-dependent manner. Similarly, we did not detect different levels of miRs in parent dermal MECs following rickettsial infections. However, we demonstrated that the microvasculopathy-relevant miR23a-27a-24 cluster and miR30b are selectively enriched in R-ECExos. Bioinformatic analysis revealed that common sequence motifs are shared exclusively among the exosomal, selectively-enriched miR23a cluster and miR30b at different levels. Taken together, these data warrant further functional identification and characterization of a single, bipartition, or tripartition among ACA, UCA, and CAG motifs that guide recognition of microvasculopathy-relevant miR23a-27a-24 and miR30b, and subsequently results in their selective enrichments in R-ECExos.

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Rickettsia parkeri with a Genetically Disrupted Phage Integrase Gene Exhibits Attenuated Virulence and Induces Protective Immunity against Fatal Rickettsioses in Mice

Cited by 9 publications

References 49 publications

Skin in the Game: An Assay to Monitor Leukocyte Infiltration in Dermal Lesions of a Guinea Pig Model for Tick-Borne Rickettsiosis

Skin in the Game: An Assay to Monitor Leukocyte Infiltration in Dermal Lesions of a Guinea Pig Model for Tick-Borne Rickettsiosis

A Vaccine for Canine Rocky Mountain Spotted Fever: An Unmet One Health Need

Identification of common sequence motifs shared exclusively among selectively packed exosomal pathogenic microRNAs during rickettsial infections

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