scholarly journals Interferon receptor-deficient mice are susceptible to eschar-associated rickettsiosis

2020 ◽  
Author(s):  
Thomas P. Burke ◽  
Patrik Engström ◽  
Cuong J. Tran ◽  
Dustin R. Glasner ◽  
Diego A. Espinosa ◽  
...  
Keyword(s):  
Human Disease ◽  
Inbred Mice ◽  
Spotted Fever ◽  
Clinical Feature ◽  
Spotted Fever Group ◽  
Rickettsia Parkeri ◽  
Live Attenuated Vaccine ◽  
Interferon Receptor ◽  
Disseminated Disease ◽  
Deficient Mice

AbstractRickettsia are arthropod-borne pathogens that cause severe human disease worldwide. The spotted fever group (SFG) pathogen Rickettsia parkeri elicits skin lesion (eschar) formation in humans after tick bite. However, intradermal inoculation of inbred mice with millions of bacteria fails to elicit eschar formation or disseminated disease, hindering investigations into understanding eschar-associated rickettsiosis. Here, we report that intradermal infection of mice deficient for both interferon receptors (Ifnar-/-Ifngr-/-) with R. parkeri causes eschar formation, recapitulating the hallmark clinical feature of human disease. Intradermal infection with doses that recapitulate tick infestation caused eschar formation and lethality, including with as few as 10 bacteria. Using this model, we found that the actin-based motility protein Sca2 is required for R. parkeri dissemination from the skin to internal organs and for causing lethal disease, and that the abundant R. parkeri outer membrane protein OmpB contributes to eschar formation. We also found that immunizing mice with sca2 and ompB mutant R. parkeri protects against subsequent rechallenge with wild-type bacteria, revealing live-attenuated vaccine candidates. Thus, interferon receptor-deficient mice are a tractable model to investigate rickettsiosis, bacterial virulence factors, and immunity. Our results suggest that differences in interferon signaling in the skin between mice and humans may explain the discrepancy in susceptibility to SFG Rickettsia.

scholarly journals Interferon receptor-deficient mice are susceptible to eschar-associated rickettsiosis

eLife ◽  
2021 ◽  
Vol 10 ◽  
Author(s):  
Thomas P Burke ◽  
Patrik Engström ◽  
Cuong J Tran ◽  
Ingeborg M Langohr ◽  
Dustin R Glasner ◽  
...  
Keyword(s):  
Inbred Mice ◽  
Skin Lesions ◽  
Human Infection ◽  
Interferon Signaling ◽  
Internal Organs ◽  
Rickettsia Parkeri ◽  
Live Attenuated Vaccine ◽  
Motility Factor ◽  
Disseminated Disease ◽  
Deficient Mice

Arthropod-borne rickettsial pathogens cause mild and severe human disease worldwide. The tick-borne pathogen Rickettsia parkeri elicits skin lesions (eschars) and disseminated disease in humans; however, inbred mice are generally resistant to infection. We report that intradermal infection of mice lacking both interferon receptors (Ifnar1-/-;Ifngr1-/-) with as few as 10 R. parkeri elicits eschar formation and disseminated, lethal disease. Similar to human infection, eschars exhibited necrosis and inflammation, with bacteria primarily found in leukocytes. Using this model, we find that the actin-based motility factor Sca2 is required for dissemination from the skin to internal organs, and the outer membrane protein OmpB contributes to eschar formation. Immunizing Ifnar1-/-;Ifngr1-/- mice with sca2 and ompB mutant R. parkeri protects against rechallenge, revealing live-attenuated vaccine candidates. Thus, Ifnar1-/-;Ifngr1-/- mice are a tractable model to investigate rickettsiosis, virulence factors, and immunity. Our results further suggest that discrepancies between mouse and human susceptibility may be due to differences in interferon signaling.

scholarly journals Susceptibility of Inbred Mice to Rickettsia parkeri

2012 ◽  
Vol 80 (5) ◽  
pp. 1846-1852 ◽  
Author(s):  
Britton J. Grasperge ◽  
Kathryn E. Reif ◽  
Timothy D. Morgan ◽  
Piyanate Sunyakumthorn ◽  
Joseph Bynog ◽  
...  
Keyword(s):  
Inbred Mice ◽  
Spotted Fever ◽  
Inbred Mouse ◽  
Transmission Model ◽  
Mouse Strains ◽  
Spotted Fever Group ◽  
Limited Information ◽  
Rickettsia Parkeri ◽  
Content Type ◽  
Boutonneuse Fever

ABSTRACTRickettsia parkeri, a member of the spotted fever groupRickettsia, is the causative agent of American boutonneuse fever in humans. Despite the increased recognition of human cases, limited information is available regarding the infection of invertebrate and vertebrate hosts for this emerging tick-borne disease. Toward the development of a viable transmission model and to further characterize the pathology associated withR. parkeriinfection, inbred mouse strains (A/J, BALB/c, C3H/HeJ, and C3H/HeN) were intravenously and intradermally inoculated with 105low-passage-numberR. parkeri(Portsmouth strain), and infection, gross pathology, and histopathology were scored. Additionally, a quantitative real-time PCR (qPCR) was performed to estimate rickettsial load in heart, lung, spleen, and liver tissues of infected mice at 19 days postinoculation. Of the A/J, BALB/c, and C3H/HeN mice, none displayed universal pathology consistent with sustained infection. Compared to age-matched control mice, the intravenously inoculated C3H/HeJ mice exhibited marked facial edema and marked splenomegaly upon gross examination, while the intradermally inoculated mice developed characteristic eschar-like lesions. The C3H/HeJ mice also exhibited the greatest concentrations of rickettsial DNA from heart, lung, liver, and spleen samples when examined by qPCR. The similarity of the pathology of human disease and sustained infection suggests that the C3H/HeJ strain of mice is a promising candidate for subsequent experiments to examine the tick transmission, dissemination, and pathology ofR. parkeririckettsiosis.

scholarly journals A streamlined method for transposon mutagenesis ofRickettsia parkeriyields numerous mutations that impact infection

2018 ◽  
Author(s):  
Rebecca L. Lamason ◽  
Natasha M. Kafai ◽  
Matthew D. Welch
Keyword(s):  
Host Cell ◽  
Virulence Factors ◽  
Vascular Endothelial Cells ◽  
Spotted Fever ◽  
Transposon Mutagenesis ◽  
Host Cells ◽  
Spotted Fever Group ◽  
Loss Of Function ◽  
Rickettsia Parkeri ◽  
Obligate Intracellular

AbstractThe rickettsiae are obligate intracellular alphaproteobacteria that exhibit a complex infectious life cycle in both arthropod and mammalian hosts. As obligate intracellular bacteria,Rickettsiaare highly adapted to living inside a variety of host cells, including vascular endothelial cells during mammalian infection. Although it is assumed that the rickettsiae produce numerous virulence factors that usurp or disrupt various host cell pathways, they have been challenging to genetically manipulate to identify the key bacterial factors that contribute to infection. Motivated to overcome this challenge, we sought to expand the repertoire of available rickettsial loss-of-function mutants, using an improvedmariner-based transposon mutagenesis scheme. Here, we present the isolation of over 100 transposon mutants in the spotted fever group speciesRickettsia parkeri. These mutants targeted genes implicated in a variety of pathways, including bacterial replication and metabolism, hypothetical proteins, the type IV secretion system, as well as factors with previously established roles in host cell interactions and pathogenesis. Given the need to identify critical virulence factors, forward genetic screens such as this will provide an excellent platform to more directly investigate rickettsial biology and pathogenesis.

scholarly journals Serosurvey on rickettsiae of the spotted fever group and Rickettsia bellii among dogs in the state of Goiás, Brazil

2020 ◽  
Vol 29 (2) ◽  
Author(s):  
Lucianne Cardoso Neves ◽  
Ana Laura Gonçalves Barreto ◽  
Mariana Xavier de Souza ◽  
Danieli Brolo Martins ◽  
Amália Regina Mar Barbieri ◽  
...  
Keyword(s):  
Spotted Fever ◽  
First Record ◽  
Immunofluorescence Assay ◽  
The State ◽  
Spotted Fever Group ◽  
Serum Samples ◽  
Rickettsia Parkeri ◽  
Serological Tests ◽  
Rickettsia Rickettsii ◽  
Rickettsia Bellii

Abstract The purpose of this study was to do a serological survey on three rickettsial species: Rickettsia rickettsii and Rickettsia parkeri, two species of the spotted fever group (SFG) that are considered to be great importance for public health; and Rickettsia bellii, a species of unknown pathogenicity that infects a variety of human-biting ticks. Serum samples from 273 dogs were tested using the indirect immunofluorescence assay (IFA). A total of 52 samples (19.04%) were seropositive for at least one of the three Rickettsia spp. antigens. Thirty-eight (73.07%), twelve (23.07%) and one (1.92%) of these dogs showed homologous reactions to R. bellii, R. rickettsii and R. parkeri, respectively. Our results showed that the seroprevalence of Rickettsia spp. was relatively low. However, the positive serological tests indicated that these dogs had become infected by these agents at some point in their lives. Lastly, our study adds to the previous knowledge on the epidemiology of rickettsiosis in the state of Goiás by doing the first record of detection of anti-R. rickettsii, R. parkeri and R. bellii antibodies by IFA among dogs, thus indicating that these agents may be circulating in the dog population analyzed.

scholarly journals A biosafety level-2 dose-dependent lethal mouse model of spotted fever rickettsiosis: Rickettsia parkeri Atlantic Rainforest-like isolate

2018 ◽  
Author(s):  
Andrés Felipe Londoño ◽  
Nicole L. Mendell ◽  
David H. Walker ◽  
Donald H. Bouyer ◽  
Keyword(s):  
Mouse Model ◽  
Post Infection ◽  
Spotted Fever ◽  
Spotted Fever Group ◽  
Rickettsia Parkeri ◽  
Spotted Fever Group Rickettsia ◽  
Dose Dependent ◽  
Level 2 ◽  
Biosafety Level ◽  
Biosafety Level 2

Background The species of the Rickettsia genus is separated into four groups: the ancestral group, typhus group, transitional group and spotted fever group. Rickettsia parkeri, a spotted fever group Rickettsia, has been reported across the American continents as infecting several tick species and is associated with a relatively mild human disease characterized by eschar formation at the tick feeding site, fever, myalgia and rash. Currently several mouse models that provide a good approach to study the acute lethal disease caused by Rickettsia, but these models can only be performed in an animal biosafety level 3 laboratory. We present an alternative mouse model for acute lethal rickettsial disease, using R. parkeri and C3H/HeN mice, with the advantage that this model can be studied in an animal biosafety level 2 laboratory. Principal findings In the C3H/HeN mouse model, we determined that infection with 1x106 and 1x107 viable R. parkeri Atlantic Rainforest-like isolate produced dose-dependent severity, whereas infection with 1x108 viable bacteria resulted in a lethal illness. The animals became moribund on day five or six post-infection. The lethal disease was characterized by ruffled fur, erythema, labored breathing, decreased activity, and hunched back, which began on day three post-infection (p.i.) and coincided with the peak bacterial loads. Significant splenomegaly (on days three and five p.i.), neutrophilia (on days three and five p.i.), and thrombocytopenia (on days one, three and five p.i.) were observed. Significance The greatest advantage of this inbred mouse model is the ability to investigate immunity and pathogenesis of rickettsiosis with all the tools available at biosafety level 2.

scholarly journals Rickettsia parkeri: a Rickettsial pathogen transmitted by ticks in endemic areas for spotted fever rickettsiosis in southern Uruguay

2012 ◽  
Vol 54 (3) ◽  
pp. 131-134 ◽  
Author(s):  
José M. Venzal ◽  
Agustín Estrada-Peña ◽  
Aránzazu Portillo ◽  
Atilio J. Mangold ◽  
Oscar Castro ◽  
...  
Keyword(s):  
Dna Sequences ◽  
Spotted Fever ◽  
Rhipicephalus Sanguineus ◽  
Rickettsia Conorii ◽  
Spotted Fever Group ◽  
Rickettsia Parkeri ◽  
Molecular Tests ◽  
Glta Gene ◽  
Dna Pools ◽  
Human Infections

At first Rickettsia conorii was implicated as the causative agent of spotted fever in Uruguay diagnosed by serological assays. Later Rickettsia parkeri was detected in human-biting Amblyomma triste ticks using molecular tests. The natural vector of R. conorii, Rhipicephalus sanguineus, has not been studied for the presence of rickettsial organisms in Uruguay. To address this question, 180 R. sanguineus from dogs and 245 A. triste from vegetation (flagging) collected in three endemic localities were screened for spotted fever group (SFG) rickettsiosis in southern Uruguay. Tick extracted DNA pools were subjected to PCR using primers which amplify a fragment of the rickettsial gltA gene. Positive tick DNA pools with these primers were subjected to a second PCR round with primers targeting a fragment of the ompA gene, which is only present in SFG rickettsiae. No rickettsial DNA was detected in R. sanguineus. However, DNA pools of A. triste were found to be positive for a rickettsial organism in two of the three localities, with prevalences of 11.8% to 37.5% positive pools. DNA sequences generated from these PCR-positive ticks corresponded to R. parkeri. These findings, joint with the aggressiveness shown by A. triste towards humans, support previous data on the involvement of A. triste as vector of human infections caused by R. parkeri in Uruguay.

scholarly journals Beyond the IFA: Revisiting the ELISA as a More Sensitive, Objective, and Quantitative Evaluation of Spotted Fever Group Rickettsia Exposure

Pathogens ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 88
Author(s):  
Navatha Alugubelly ◽  
John V. Stokes ◽  
Claire E. Cross ◽  
Anne-Marie L. Ross ◽  
Anna E. Crawford ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Signal To Noise Ratio ◽  
Spotted Fever ◽  
Clinical Signs ◽  
Enzyme Linked Immunosorbent Assay ◽  
Spotted Fever Group ◽  
Rickettsia Parkeri ◽  
Rickettsial Infections ◽  
Spotted Fever Group Rickettsia ◽  
Guinea Pig Model

Based on limited serological studies, at least 10% of the US population has been exposed to spotted fever group Rickettsia (SFGR) species. The immunofluorescence antibody assay (IFA) has been the gold standard for the serodiagnosis of rickettsial infections such as spotted fever rickettsiosis (SFR). However, the IFA is semi-quantitative and subjective, requiring a high level of expertise to interpret it correctly. Here, we developed an enzyme-linked immunosorbent assay (ELISA) for the serodiagnosis of Rickettsia parkeri infection in the guinea pig. Our ELISA is an objective, quantitative, and high-throughput assay that shows greater sensitivity and resolution in observed titers than the IFA. We methodically optimized relevant parameters in sequence for optimal signal-to-noise ratio and low coefficient of variation% values. We used a guinea pig model as it is a part of our overall research efforts to understand the immunological and clinical response to SFGR species after tick transmission. Guinea pigs are a useful model to study SFR and show clinical signs of SFR, such as fever and eschars. We anticipate that this assay will be easily adapted to other hosts, including humans and other SFGR species.

scholarly journals The Gulf Coast tick, Amblyomma maculatum (Ixodida: Ixodidae) and spotted fever group Rickettsia in the highly urbanized northeastern US

2021 ◽  
Author(s):  
Waheed I. Bajwa ◽  
Leonid Tsynman ◽  
Andrea M Egizi ◽  
Rafal Tokarz ◽  
Lauren P. Maestas ◽  
...  
Keyword(s):  
New York ◽  
Migratory Birds ◽  
Gulf Coast ◽  
Spotted Fever ◽  
Spotted Fever Group ◽  
Human Pathogens ◽  
Amblyomma Maculatum ◽  
Rickettsia Parkeri ◽  
Staten Island ◽  
Gulf Coast Tick

We report the multi-year collection of the Gulf Coast tick, Amblyomma maculatum Koch (Acaridae: Ixodida: Ixodidae) in Staten Island, New York City (NYC) as well as their detection in Brooklyn, NYC, and in Atlantic and Cumberland counties in southern NJ, USA. The first detections on all sites were of adults but in Freshkills Park on Staten Island larvae were collected in a following year. Based on known observations on birds of this tick species, it is likely A. maculatum are expanding north on migratory birds, which are now often seen in Freshkills Park. The presence of larvae indicates that adults are being successful at finding hosts in Staten Island. We describe the landscape features of the area in Staten Island where populations were highest and larvae were detected, which could have facilitated the establishment of A. maculatum. Notably, we also report the presence of human pathogens Rickettsia parkeri in 5/10 (50%) of adults tested and R. felis in 1/24 (4.17%) of larvae tested. In addition to established populations in Staten Island we found evidence of A. maculatum in NJ and other NYC boroughs, suggesting current or future establishment is possible. The failure thus far to detect established populations in these areas may be due to inherent difficulties in detecting low density, spatially heterogeneous incipient populations, which could require targeted surveillance efforts for this species. We discuss the consequences to public health of the establishment of A. maculatum and detection of two additional rickettsial pathogens in the densely populated Northeastern US.

scholarly journals Spotted fever group rickettsial infection in dogs and their ticks from domestic–wildlife interface areas in southeastern Brazil

2020 ◽  
Vol 29 (1) ◽  
Author(s):  
Sabrina Destri Emmerick Campos ◽  
Nathalie Costa da Cunha ◽  
Camila de Souza Cerqueira Machado ◽  
Niara Vanat Nadal ◽  
Eloy Silva Seabra Junior ◽  
...  
Keyword(s):  
Natural Infection ◽  
Spotted Fever ◽  
Rhipicephalus Sanguineus ◽  
Southeastern Brazil ◽  
Spotted Fever Group ◽  
Forest Fragments ◽  
Rickettsia Parkeri ◽  
Chain Reactions ◽  
Glta Gene ◽  
Pcr Targeting

Abstract Rickettsia rickettsii is the causative agent of Brazilian spotted fever (BSF), for which humans and dogs are both susceptible. Dogs are sentinels in serological surveys, however, canine disease is rarely reported. Therefore, we aimed to evaluate natural infection by spotted fever group (SFG) Rickettsia spp. in dogs and ticks collected from domiciles close to forest fragments, featuring domestic–wildlife interface areas. Samples from 115 dogs and 135 ixodids were assessed by polymerase chain reactions (PCR) targeting the gltA gene for Rickettsia spp. and the ompA gene for the SFG rickettsial species. One dog (0.87%; 1/115) was positive for R. rickettsii. This dog presented nonspecific laboratory and clinical abnormalities (thrombocytopenia, hyperproteinemia, lymph node enlargement, emaciation, anorexia, and lethargy). Rickettsia parkeri was identified in 2.96% (4/135) of the ticks (Amblyomma sculptum, A. aureolatum, and Rhipicephalus sanguineus). This study confirmed the presence of SFG bacteria in non-endemic and preserved locations, where domestic and wild populations interact. We reinforce the fact that the dog is susceptible to natural R. rickettsii infection. Although this is a rare finding, preventive measures should be taken against BSF in the studied areas. Finally, R. parkeri infection is possibly being demonstrated in A. sculptum for the first time.

Rickettsia spp. Infecting Lone Star Ticks (Amblyomma americanum) (Acari: Ixodidae) in Monmouth County, New Jersey

2020 ◽  
Vol 57 (3) ◽  
pp. 974-978 ◽  
Author(s):  
Andrea Egizi ◽  
Sydney Gable ◽  
Robert A Jordan
Keyword(s):  
New Jersey ◽  
Spotted Fever ◽  
Rocky Mountain ◽  
Amblyomma Americanum ◽  
Spotted Fever Group ◽  
Eastern United States ◽  
Rocky Mountain Spotted Fever ◽  
Rickettsia Parkeri ◽  
Monmouth County ◽  
Epidemiological Changes

Abstract Tick-borne rickettsiae are undergoing epidemiological changes in the eastern United States while human encounters with lone star ticks (Amblyomma americanum L.) have increased substantially. We used real-time polymerase chain reaction assays to test for three species of spotted fever group rickettsiae (SFGR) (Rickettsiales: Rickettsiaceae) in 1,858 nymphal A. americanum collected from Monmouth County, New Jersey, a coastal county with endemic Lyme disease and established tick surveillance. Out of the 1,858 tested, 465 (25.0%) were infected with Rickettsia amblyommatis Karpathy, a species of undetermined pathogenicity found frequently in A. americanum, while 1/1,858 (0.05%) contained Rickettsia rickettsii Brumpt, the agent of Rocky Mountain spotted fever. No ticks tested positive for mildly pathogenic Rickettsia parkeri Lackman, and no ticks were co-infected with multiple Rickettsia spp. Our results indicate that A. americanum could be involved in transmission of R. rickettsii to humans in New Jersey, albeit rarely. The much higher rates of R. amblyommatis infection are consistent with hypotheses that human sera reacting to this species could contribute to reports of mild SFGR cases.

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