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MBio Apr 2024We compared the growth characteristics of a virulent strain (Sheila Smith) to an attenuated stain (Iowa) and a non-pathogenic species () in primary human dermal...
We compared the growth characteristics of a virulent strain (Sheila Smith) to an attenuated stain (Iowa) and a non-pathogenic species () in primary human dermal microvascular endothelial cells (HDMEC). All replicated in Vero cells, however, only the Sheila Smith strain productively replicated in HDMECs. The Iowa strain showed minimal replication over a 24-h period, while lost viability and induced lysis of the HDMECs via a rapid programmed cell death response. Both the virulent and attenuated strains, but not , induced an interferon-1 response, although the response was of lesser magnitude and delayed in the Sheila Smith strain. IFN-β secretion correlated with increased host cell lysis, and treatment with anti-IFNAR2 antibody decreased lysis from Iowa-infected but not Sheila Smith-infected cells. Both Sheila Smith- and Iowa-infected cells eventually lysed, although the response from Sheila Smith was delayed and showed characteristics of apoptosis. We, therefore, examined whether reconstitution of the Iowa strain with two recently described putative virulence determinants might enhance survival of Iowa within HDMECs. Reconstitution with RARP2, which is inhibitory to anterograde trafficking through the Golgi apparatus, reduced IFN-β secretion but had no effect on cell lysis. RapL, which proteolytically processes surface exposed autotransporters and enhances replication of Iowa in Guinea pigs, suppressed both IFN-β production and host cell lysis. These findings suggest distinct mechanisms by which virulent spotted fever group rickettsiae may enhance intracellular survival and replication.IMPORTANCEWe examined a naturally occurring non-pathogenic rickettsial species, , a laboratory-attenuated strain (Iowa), and a fully virulent strain (Sheila Smith) for growth in human dermal microvascular endothelial cells. The two avirulent strains replicated poorly or not at all. Only the virulent Sheila Smith strain replicated. IFN-β production correlated with the inhibition of Iowa. Reconstitution of Iowa with either of two recently described putative virulence determinants altered the IFN-β response. A rickettsial ankyrin repeat protein, RARP2, disrupts the Golgi network and inhibits IFN-β secretion. An autotransporter peptidase, RapL, restores proteolytic maturation of outer membrane autotransporters and diminishes the IFN-β response to enhance cell survival and permit replication of the recombinant strain. These studies point the way toward discovery of mechanisms for innate immune response avoidance by virulent rickettsia.
Topics: Animals; Guinea Pigs; Humans; Chlorocebus aethiops; Endothelial Cells; Rickettsia; Rickettsia rickettsii; Rocky Mountain Spotted Fever; Type V Secretion Systems; Vero Cells; Virulence; Virulence Factors; Interferon-beta
PubMed: 38445878
DOI: 10.1128/mbio.03450-23 -
Microorganisms Jan 2024is an obligate intracellular pathogen that primarily targets endothelial cells (ECs), leading to vascular inflammation and dysfunction. Mechanistic target of rapamycin...
is an obligate intracellular pathogen that primarily targets endothelial cells (ECs), leading to vascular inflammation and dysfunction. Mechanistic target of rapamycin (mTOR) regulates several cellular processes that directly affect host immune responses to bacterial pathogens. Here, we infected ECs with two strains, avirulent (Iowa) and highly virulent Sheila Smith (SS) to identify differences in the kinetics and/or intensity of mTOR activation to establish a correlation between mTOR response and bacterial virulence. Endothelial mTOR activation with the highly virulent SS strain was significantly higher than with the avirulent Iowa strain. Similarly, there was increased LC3-II lipidation with the virulent SS strain compared with the avirulent Iowa strain of . mTOR inhibitors rapamycin and Torin2 significantly increased bacterial growth and replication in the ECs, as evidenced by a more than six-fold increase in rickettsia copy numbers at 48 h post-infection. Further, the knockdown of mTOR with Raptor and Rictor siRNA resulted in a higher rickettsial copy number and the altered expression of the pro-inflammatory cytokines interleukin (IL)-1α, IL-6, and IL-8. These results are the first to reveal that endothelial mTOR activation and the early induction of autophagy might be governed by bacterial virulence and have established the mTOR pathway as an important regulator of endothelial inflammation, host immunity, and microbial replication.
PubMed: 38399700
DOI: 10.3390/microorganisms12020296 -
Travel Medicine and Infectious Disease 2024Rickettsia is a zoonotic bacterial pathogen transmitted by vectors and has extensive reservoirs in animal and human populations. Rickettsiosis is a public health problem... (Review)
Review
SUBJECT
Rickettsia is a zoonotic bacterial pathogen transmitted by vectors and has extensive reservoirs in animal and human populations. Rickettsiosis is a public health problem all over the world. However, comprehensive information on the geographical distribution of different Rickettsia species, infection status of reservoirs, vectors, and human cases is lacking in most parts of the world. Therefore, this study aimed to investigate the geographical distribution of different Rickettsia species and their vectors in countries of the WHO-EMRO region.
METHODS
In this review study, a search was conducted for reports and published studies on Rickettsia species from WHO-EMRO region countries in various databases from 1995 to 2022. Finally, the reported status of human cases, reservoirs, and vectors associated with each species in different countries was documented.
RESULTS
Reports of infections related to the detection of Rickettsia species were only available for 15 out of 22 WHO-EMRO member countries. A total of twenty-four Rickettsia species, including R. sibrica, R. lusitaniae, R. africae, R. prowazekii, R. felis, R. typhi, R. rickettsii, R. aeschlimannii, R. conorii, R. massiliae, R. helvetica, R. monacensis, R. rhipicephali, R. bellii, R. asembonensis, R. hoogstraalii, R. andeanae, R. raoultii, R. asiatica, R. slovaca, R. australis, R. barbariae, Candidatus R. amblyommii, and Candidatus R. goldwasserii, were reported from WHO-EMRO member countries. Furthermore, human cases infected with six different Rickettsia species, including R. sibrica, R. prowazekii, R. felis, R. typhi, R. rickettsii, R. aeschlimannii, R. conorii, R. massiliae, and R. helvetica, were reported from these countries.
CONCLUSION
The vast diversity of Rickettsia vectors has contributed to the ongoing discovery of new Rickettsia species. Therefore, further research on the reservoir hosts of Rickettsia infections in the understudied WHO-EMRO region is crucial. This research sheds light on Rickettsia disease's epidemiology and transmission dynamics in this region.
Topics: Animals; Humans; Rickettsia; Rickettsia Infections; World Health Organization
PubMed: 38360158
DOI: 10.1016/j.tmaid.2024.102695 -
Microbiology Spectrum Apr 2024(), the causative agent of Rocky Mountain spotted fever (RMSF), is the most pathogenic member among spp. Previous studies have shown that tripartite motif-containing...
UNLABELLED
(), the causative agent of Rocky Mountain spotted fever (RMSF), is the most pathogenic member among spp. Previous studies have shown that tripartite motif-containing 56 (TRIM56) E3 ligase-induced ubiquitination of STING is important for cytosolic DNA sensing and type I interferon production to induce anti-DNA viral immunity, but whether it affects intracellular replication of remains uncharacterized. Here, we investigated the effect of TRIM56 on HeLa and THP-1 cells infected with . We found that the expression of TRIM56 was upregulated in the -infected cells, and the overexpression of TRIM56 inhibited the intracellular replication of , while replication was enhanced in the TRIM56-silenced host cells with the reduced phosphorylation of IRF3 and STING and the increased production of interferon-β. In addition, the mutation of the TRIM56 E3 ligase catalytic site impairs the inhibitory function against in HeLa cells. Altogether, our study discovers that TRIM56 is a host restriction factor of by regulating the cGAS-STING-mediated signaling pathway. This study gives new evidence for the role of TRIM56 in the innate immune response against intracellular bacterial infection and provides new therapeutic targets for RMSF.
IMPORTANCE
Given that () is the most pathogenic member within the genus and serves as the causative agent of Rocky Mountain spotted fever, there is a growing need to explore host targets. In this study, we examined the impact of host TRIM56 on infection in HeLa and THP-1 cells. We observed a significant upregulation of TRIM56 expression in -infected cells. Remarkably, the overexpression of TRIM56 inhibited the intracellular replication of , while silencing TRIM56 enhanced bacterial replication accompanied by reduced phosphorylation of IRF3 and STING, along with increased interferon-β production. Notably, the mutation of the TRIM56's E3 ligase catalytic site did not impede replication in HeLa cells. Collectively, our findings provide novel insights into the role of TRIM56 as a host restriction factor against through the modulation of the cGAS-STING signaling pathway.
Topics: Humans; Rickettsia rickettsii; Rocky Mountain Spotted Fever; Interferon Type I; HeLa Cells; Ubiquitin-Protein Ligases; Interferon-beta; Nucleotidyltransferases; Tripartite Motif Proteins
PubMed: 38358243
DOI: 10.1128/spectrum.03695-23 -
PloS One 2024Robust tick surveillance enhances diagnosis and prevention of tick-borne pathogens, yet surveillance efforts in the United States are highly uneven, resulting in large...
Robust tick surveillance enhances diagnosis and prevention of tick-borne pathogens, yet surveillance efforts in the United States are highly uneven, resulting in large surveillance vacuums, one of which spans the state of New Mexico. As part of a larger effort to fill this vacuum, we conducted both active and passive tick sampling in New Mexico, focusing on the southern portion of the state. We conducted active tick sampling using dragging and CO₂ trapping at 45 sites across Hidalgo, Doña Ana, Otero, and Eddy counties between June 2021 to May 2022. Sampling occurred intermittently, with at least one sampling event each month from June to October 2021, pausing in winter and resuming in March through May 2022. We also conducted opportunistic, passive tick sampling in 2021 and 2022 from animals harvested by hunters or captured or collected by researchers and animals housed in animal hospitals, shelters, and farms. All pools of ticks were screened for Rickettsia rickettsii, Rickettsia parkeri, Rickettsia amblyommatis, Ehrlichia ewingii, and Ehrlichia chaffeensis. Active sampling yielded no ticks. Passive sampling yielded 497 ticks comprising Carios kelleyi from pallid bats, Rhipicephalus sanguineus from dogs, mule deer, and Rocky Mountain elk, Otobius megnini from dogs, cats, horses, and Coues deer, Dermacentor parumapertus from dogs and black-tailed jackrabbits, Dermacentor albipictus from domesticated cats, mule deer and Rocky Mountain elk, and Dermacentor spp. from American black bear, Rocky Mountain elk, and mule deer. One pool of D. parumapterus from a black-tailed jackrabbit in Luna County tested positive for R. parkeri, an agent of spotted fever rickettsiosis. Additionally, a spotted fever group Rickettsia was detected in 6 of 7 C. kelleyi pools. Two ticks showed morphological abnormalities; however, these samples did not test positive for any of the target pathogens, and the cause of the abnormalities is unknown. Passive surveillance yielded five identified species of ticks from three domestic and six wild mammal species. Our findings update tick distributions and inform the public, medical, and veterinary communities of the potential tick-borne pathogens present in southern New Mexico.
Topics: Animals; Cats; Dogs; Horses; Vacuum; New Mexico; Deer; Rickettsia; Ehrlichia chaffeensis; Rhipicephalus sanguineus; Spotted Fever Group Rickettsiosis; Equidae
PubMed: 38295027
DOI: 10.1371/journal.pone.0292573 -
Pathogens (Basel, Switzerland) Dec 2023is a species of public health interest because it is associated with the transmission of the bacteria that causes Brazilian Spotted Fever (BSF). The use of repellents...
is a species of public health interest because it is associated with the transmission of the bacteria that causes Brazilian Spotted Fever (BSF). The use of repellents on humans is a prophylactic measure widely used to provide protection against a series of arthropod vectors, including mosquitoes and ticks. However, in Brazil, the effectiveness of commercial repellents against is little known. Therefore, it is necessary to carry out specific studies to evaluate the repellency of these commercial products, registered for use against mosquitoes, against the star tick. The main goal of the present work was to evaluate the effectiveness of six commercial repellents against . Unfed nymphs, aged between two and eight weeks, were tested against products based on DEET (OFF! and Repelex), Icaridin (Exposis and SBP), and IR3535 (Johnsons and Henlau). Three bioassays were conducted to evaluate tick behavior: (i) filter paper, (ii) fingertip, and (iii) field. All bases tested showed high repellent activity, differing significantly ( < 0.05) from the control. It was observed the formulation with DEET resulted in the best results in the filter paper bioassay. In the fingertip bioassay, the DEET base repelled a greater number of ticks compared to Icaridin. In the field bioassay, there was no significant difference between the Icaridin base and DEET, and both formulations differed from the control ( < 0.05). The six formulations tested showed significant percentages of repellency against ticks; however, for the fingertip and field bioassays, the products OFF!, Repelex, and Exposis were tested as they showed better performance in the filter paper test. OFF! showed the best percentage of repellency (100%), followed by Repelex (96.8%), and Exposis (93.1%), considering the two-hour period of the bioassay-field-test. Proving the effectiveness of repellents on the market against presented in this study is crucial, since this is the main ectoparasite of humans that can transmit when infected. The effectiveness of commercial insect repellents against other tick species that parasitize humans can also be explored.
PubMed: 38276155
DOI: 10.3390/pathogens13010009 -
Parasites & Vectors Jan 2024Spotted fever group Rickettsia (SFGR) is the largest group of Rickettsia species of clinical and veterinary importance emerging worldwide. Historically, SFGR cases were...
BACKGROUND
Spotted fever group Rickettsia (SFGR) is the largest group of Rickettsia species of clinical and veterinary importance emerging worldwide. Historically, SFGR cases were linked to Rickettsia rickettsii, the causal agent of Rocky Mountain spotted fever; however, recently discovered species Rickettsia parkeri and Rickettsia amblyommatis have been shown to cause a wide range of clinical symptoms. The role of R. amblyommatis in SFGR eco-epidemiology and the possible public health implications remain unknown.
METHODS
This study evaluated statewide tick surveillance and land-use classification data to define the eco-epidemiological relationships between R. amblyommatis and R. parkeri among questing and feeding ticks collected across South Carolina between 2021 and 2022. Questing ticks from state parks and feeding ticks from animal shelters were evaluated for R. parkeri and R. amblyommatis using reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) on pooled samples. A Bayesian multivariable logistic regression model for pool testing data was used to assess associations between R. parkeri or R. amblyommatis infection and land-use classification variables among questing ticks. The Spearman correlation was used to evaluate the relationship between the two tested pathogens.
RESULTS
The infection prevalence for R. amblyommatis was 24.8% (23.4-26.3%) among questing ticks, and 39.5% (37.4-42.0%) among feeding ticks; conversely, for R. parkeri it was 19.0% (17.6-20.5%) among questing ticks and 22.4% (20.3-24.5%) among feeding ticks. A negative, refractory correlation was found between the species, with ticks significantly more likely to contain one or the other pathogen, but not both simultaneously. The Bayesian analysis revealed that R. amblyommatis infection was positively associated with deciduous, evergreen, and mixed forests, and negatively associated with hay and pasture fields, and emergent herbaceous wetlands. Rickettsia parkeri infection was positively associated with deciduous, mixed, and evergreen forests, herbaceous vegetation, cultivated cropland, woody wetlands, and emergent herbaceous wetlands, and negatively associated with hay and pasture fields.
CONCLUSIONS
This is the first study to evaluate the eco-epidemiological factors driving tick pathogenicity in South Carolina. The negative interactions between SFGR species suggest the possible inhibition between the two pathogens tested, which could have important public health implications. Moreover, land-use classification factors revealed environments associated with tick pathogenicity, highlighting the need for tick vector control in these areas.
Topics: Animals; Ticks; Acari; South Carolina; Bayes Theorem; Rickettsia; Rickettsia Infections; Ixodidae
PubMed: 38273414
DOI: 10.1186/s13071-023-06099-z -
Frontiers in Microbiology 2023is an obligate, intracellular pathogen and the causative agent of Rocky Mountain spotted fever (RMSF). RMSF is an important zoonotic disease due to its high fatal...
INTRODUCTION
is an obligate, intracellular pathogen and the causative agent of Rocky Mountain spotted fever (RMSF). RMSF is an important zoonotic disease due to its high fatal outcome in humans. The difficulty of clinical diagnosis due to the low sensitivity and specificity of current diagnostic methods are a principal setback. We reported the development of a new method for the detection of in human and tick DNA samples using loop-mediated isothermal amplification (LAMP), as well as the validation of the LAMP test for in field samples of infected ticks and humans, determining the diagnostic sensitivity and specificity, as well as the reproducibility of the test.
METHODS
This technique uses hydroxy naphthol blue (HNB) as an indicator of the formation of magnesium pyrophosphate, a marker for the presence of DNA. Here, we used a putative gene as a target for three pairs of primers that specifically amplify DNA by hairpin-based isothermal amplification technique (LAMP).
RESULTS AND DISCUSSION
The sensitivity of the assay was ~1.6-3 pg, which is 10 times more sensitive than PCR. To determine the diagnostics specificity and sensitivity, 103 human DNA samples and 30 tick DNA samples were evaluated. For the human samples, a sensitivity for HNB of 93%, a specificity of 70% and a k of 0.53 were obtained. For electrophoresis the sensitivity was 97% with a specificity of 58% and a k of 0.42. For tick samples, a sensitivity of 80% was obtained, a specificity of 93% for HNB and for electrophoresis the sensitivity and specificity were 87%. The k for both was 0.73. The degree of concordance between HNB and electrophoresis was 0.82 for humans and for ticks, it was 0.87. The result is obtained in shorter time, compared to a PCR protocol, and is visually interpreted by the color change. Therefore, this method could be a reliable tool for the early diagnosis of rickettsiosis.
PubMed: 38260903
DOI: 10.3389/fmicb.2023.1276809 -
MSphere Feb 2024Rickettsiae are Gram-negative obligate intracellular parasites of numerous eukaryotes. Human pathogens of the transitional group (TRG), typhus group (TG), and spotted...
Rickettsiae are Gram-negative obligate intracellular parasites of numerous eukaryotes. Human pathogens of the transitional group (TRG), typhus group (TG), and spotted fever group (SFG) rickettsiae infect blood-feeding arthropods, have dissimilar clinical manifestations, and possess unique genomic and morphological attributes. Lacking glycolysis, rickettsiae pilfer numerous metabolites from the host cytosol to synthesize peptidoglycan and lipopolysaccharide (LPS). For LPS, O-antigen immunogenicity varies between SFG and TG pathogens; however, lipid A proinflammatory potential is unknown. We previously demonstrated that (TRG), (TG), and (SFG) produce lipid A with long 2' secondary acyl chains (C16 or C18) compared to short 2' secondary acyl chains (C12) in (SFG) lipid A. To further probe this structural heterogeneity and estimate a time point when shorter 2' secondary acyl chains originated, we generated lipid A structures for two additional SFG rickettsiae ( and ) utilizing fast lipid analysis technique adopted for use with tandem mass spectrometry (FLAT). FLAT allowed analysis of lipid A structure directly from host cell-purified bacteria, providing a substantial improvement over lipid A chemical extraction. FLAT-derived structures indicate SFG rickettsiae diverging after evolved shorter 2' secondary acyl chains. While 2' secondary acyl chain lengths do not distinguish pathogens from non-pathogens, analyses of LpxL late acyltransferases revealed discrete active sites and hydrocarbon rulers for long versus short 2' secondary acyl chain addition. Our collective data warrant determining lipid A inflammatory potential and how structural heterogeneity impacts lipid A-host receptor interactions.IMPORTANCEDeforestation, urbanization, and homelessness lead to spikes in Rickettsioses. Vector-borne human pathogens of transitional group (TRG), typhus group (TG), and spotted fever group (SFG) rickettsiae differ by clinical manifestations, immunopathology, genome composition, and morphology. We previously showed that lipid A (or endotoxin), the membrane anchor of Gram-negative bacterial lipopolysaccharide (LPS), structurally differs in (later-evolving SFG) relative to (basal SFG), (TG), and (TRG). As lipid A structure influences recognition potential in vertebrate LPS sensors, further assessment of lipid A structural heterogeneity is needed. Here, we sidestepped the difficulty of lipid A chemical extraction by utilizing fast lipid analysis technique adopted for use with tandem mass spectrometry, a new procedure for generating lipid A structures directly from host cell-purified bacteria. These data confirm that later-evolving SFG pathogens synthesize structurally distinct lipid A. Our findings impact interpreting immune responses to different pathogens and utilizing lipid A adjuvant or anti-inflammatory properties in vaccinology.
Topics: Humans; Lipid A; Lipopolysaccharides; Typhus, Epidemic Louse-Borne; Rickettsia; Spotted Fever Group Rickettsiosis
PubMed: 38259062
DOI: 10.1128/msphere.00609-23 -
Cureus Nov 2023Rocky Mountain spotted fever (RMSF) is a potentially lethal tick-borne disease caused by Rickettsia rickettsii, known for its tropism for vascular endothelial cells. Its...
Rocky Mountain spotted fever (RMSF) is a potentially lethal tick-borne disease caused by Rickettsia rickettsii, known for its tropism for vascular endothelial cells. Its classic symptoms include fever, headaches, and a rash, but atypical presentations can challenge diagnosis. We present the case of a 71-year-old male with fever, weakness, and hiccups, evolving into confusion. Laboratory findings showed severe hyponatremia, leukocytosis, and abnormal blood parameters. Initial management addressed sepsis and hyponatremia, leading to symptom improvement. Later, a fever of 106.5°F prompted ICU transfer, broad-spectrum antibiotics, and testing for tick-borne diseases. The patient reported tick exposure and received prophylactic doxycycline. Follow-up confirmed the RMSF diagnosis based on serological testing and clinical symptoms. This case highlights the diagnostic challenges posed by atypical RMSF presentations and underscores the importance of early detection and treatment to prevent complications.
PubMed: 38074000
DOI: 10.7759/cureus.48558