Benidipine impairs innate immunity converting sublethal to lethal infections in a murine model of spotted fever rickettsiosis.

Spotted fever group rickettsiae are tick-borne obligate intracellular bacteria that infect microvascular endothelial cells. Humans and mammalian infection results in endothelial cell barrier dysfunction and increased vascular permeability. We previously demonstrated that treatment of Rickettsia parkeri-infected cells with the calcium channel blocker benidipine significantly delayed vascular barrier permeability. Thus, we hypothesized that benidipine, known to be safe and effective for other clinical processes, could reduce rickettsia-induced vascular permeability in vivo in an animal model of spotted fever rickettsiosis. Based on liver, lung and brain vascular FITC-dextran extravasation studies, benidipine did not reliably impact vascular permeability. However, it precipitated a deleterious effect on responses to control sublethal R. parkeri infection. Animals treated with benidipine alone had no clinical signs or changes in histopathology and splenic immune cell distributions. Benidipine-treated infected animals had marked increases in tissue and blood bacterial loads, more extensive inflammatory histopathologic injury, and changes in splenic architecture and immune cell distributions potentially reflecting diminished Ca2+ signaling, reduced innate immune cell activation, and loss of rickettsial propagation control. Impaired T cell activation by R. parkeri antigen in the presence of benidipine was confirmed in vitro with the use of NKT cell hybridomas. The unexpected findings stand in stark contrast to recent discussions of the benefits of calcium channel blockers for viral infections and chronic infectious or inflammatory diseases. A role for calcium channel blockers in exacerbation of human rickettsiosis and acute inflammatory infections should be evaluated by a retrospective review of patient's outcomes and medications.

Clinical characteristics of and antibody response to spotted fever group rickettsial infections in South India: Case series and serological cohort study.

OBJECTIVE: The clinical and serological characteristics of spotted fever group rickettsial (SFGR) infections in South Asia are poorly understood. We studied the clinical presentation and the IgM/IgG response in cases enrolled at two health care centres in South India. METHOD: We enrolled 77 patients. Fifty-seven of these patients were recruited at a tertiary care centre, the remaining 20 at a community hospital (secondary care level). Diagnostic tests included IgM and IgG enzyme-linked immunosorbent assay and polymerase chain reaction. Over a period of 1 year, 41 cases were followed up for repeated sero-analysis. RESULTS: Median age was 9 years (range 1-79). A rash was present in 74% of cases (57/77). In cases aged <15 years, rash was present in 94% (44/47) vs. 43% (13/30) in cases aged ≥15 years. An eschar was found in two cases (3%). Severe infection or complications occurred in 10 cases (13%). These included central nervous system infection (6/77, 8%), kidney injury (3/77, 4%), shock (3/77, 4%), lung involvement (2/77, 3%) and peripheral gangrene (2/77, 3%). IgM antibody levels increased faster after fever onset than IgG antibodies, peaking at 50 and 60 days, respectively. After the peak, IgM and IgG levels showed a slow decline over one year with less than 50% of cases showing persistent IgG antibody levels. CONCLUSION: Spotted fever group rickettsial infections in South India may be under-diagnosed, as many cases may not develop a rash. The proportion of cases developing severe infection seems lower than for scrub typhus in this region. IgG seroprevalence may substantially underestimate the proportion in a population with past SFGR infection.

Linfadenopatía transmitida por garrapatas, una enfermedad emergente en Europa / Tick-borne lymphadenopathy, an emergent disease in Europe

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Activation of Mechanistic Target of Rapamycin (mTOR) in Human Endothelial Cells Infected with Pathogenic Spotted Fever Group Rickettsiae.

Attributed to the tropism for host microvascular endothelium lining the blood vessels, vascular inflammation and dysfunction represent salient features of rickettsial pathogenesis, yet the details of fundamentally important pathogen interactions with host endothelial cells (ECs) as the primary targets of infection remain poorly appreciated. Mechanistic target of rapamycin (mTOR), a serine/threonine protein kinase of the phosphatidylinositol kinase-related kinase family, assembles into two functionally distinct complexes, namely mTORC1 (Raptor) and mTORC2 (Rictor), implicated in the determination of innate immune responses to intracellular pathogens via transcriptional regulation. In the present study, we investigated activation status of mTOR and its potential contributions to host EC responses during Rickettsia rickettsii and R. conorii infection. Protein lysates from infected ECs were analyzed for threonine 421/serine 424 phosphorylation of p70 S6 kinase (p70 S6K) and that of serine 2448 on mTOR itself as established markers of mTORC1 activation. For mTORC2, we assessed phosphorylation of protein kinase B (PKB or Akt) and protein kinase C (PKC), respectively, on serine 473 and serine 657. The results suggest increased phosphorylation of p70 S6K and mTOR during Rickettsia infection of ECs as early as 3 h and persisting for up to 24 h post-infection. The steady-state levels of phospho-Akt and phospho-PKC were also increased. Infection with pathogenic rickettsiae also resulted in the formation of microtubule-associated protein 1A/1B-light chain 3 (LC3-II) puncta and increased lipidation of LC3-II, a response significantly inhibited by introduction of siRNA targeting mTORC1 into ECs. These findings thus yield first evidence for the activation of both mTORC1 and mTORC2 during EC infection in vitro with Rickettsia species and suggest that early induction of autophagy in response to intracellular infection might be regulated by this important pathway known to function as a central integrator of cellular immunity and inflammation.

Acute infectious purpura fulminans: a case series from India.

Acute infectious purpura fulminans is a serious, potentially fatal condition. We present a case series of 11 patients from March 2005 to March 2017, whose clinical symptoms were fever (100%), confusion (63.6%) and headache (55%), and whose common laboratory abnormalities were thrombocytopenia (100%), elevated alkaline phosphatase (70%) and anaemia (63.6%). Three patients (27%) developed gangrene and two presented in shock. Only one grew Neisseria meningitidis in cerebrospinal fluid (CSF) culture and another confirmed by latex agglutination and polymerase chain reaction in CSF. Five others had serology confirmed spotted fever rickettsioses (SFG). All received broad spectrum antibiotics; in 9/11 patients, this included doxycycline or azithromycin. The mean hospital stay was 10.2 days and overall mortality was 18.2%.

Cutaneous Immunoprofiles of Three Spotted Fever Group Rickettsia Cases.

Spotted fever group rickettsia (SFGR) can cause mild to fatal illness. The early interaction between the host and rickettsia in skin is largely unknown, and the pathogenesis of severe rickettsiosis remains an important topic. A surveillance of SFGR infection by PCR of blood and skin biopsy specimens followed by sequencing and immunohistochemical (IHC) detection was performed on patients with a recent tick bite between 2013 and 2016. Humoral and cutaneous immunoprofiles were evaluated in different SFGR cases by serum cytokine and chemokine detection, skin IHC staining, and transcriptome sequencing (RNA-seq). A total of 111 SFGR cases were identified, including 79 "Candidatus Rickettsia tarasevichiae," 22 Rickettsia raoultii, 8 Rickettsia sibirica, and 2 Rickettsia heilongjiangensis cases. The sensitivity to detect SFGR in skin biopsy specimens (9/24, 37.5%) was significantly higher than that in blood samples (105/2,671, 3.9%) (P < 0.05). As early as 1 day after the tick bite, rickettsiae could be detected in the skin. R. sibirica infection was more severe than "Ca Rickettsia" and R. raoultii infections. Increased levels of serum interleukin-18 (IL-18), IP10, and monokine induced by gamma interferon (MIG) and decreased levels of IL-2 were observed in febrile patients infected with R. sibirica compared to those infected with "Ca Rickettsia." RNA-seq and IHC staining could not discriminate between SFGR-infected and uninfected tick bite skin lesions. However, the type I interferon (IFN) response was differently expressed between R. sibirica and R. raoultii infections at the cutaneous interface. It is concluded that skin biopsy specimens were more reliable for the detection of SFGR infection in human patients although the immunoprofile may be complicated by immunomodulators induced by the tick bite.

Investigating the histopathological findings and immunolocalization of rickettsialpox infection in skin biopsies: A case series and review of the literature.

BACKGROUND: Recognition of rickettsialpox infection on skin biopsy can be challenging. The histopathology is non-specific and inconsistently described. We assess classic histopathologic features in confirmed cases and review the literature. METHODS: We searched for cases of "rickettsialpox" diagnosed between 2006 and 2018 with positive immunostaining for Spotted Fever Group Rickettsia species. Original slides were evaluated for vacuolar alterations, granulomatous inflammation, vasculitis, necrosis, fibrin thrombi, microvesiculation, papillary dermal edema, and extravasated red blood cells. All biopsies were stained for CD3, CD20, CD68, and myeloperoxidase. RESULTS: Six biopsy specimens were compiled, three of which were sampled from vesiculopapules, one from a maculopapule, and two from eschars. Vacuolar alterations and vasculitis were present in all specimens (6/6; 100%). Granulomatous inflammation was present in five specimens (5/6; 83.3%). Fibrin thrombi and red blood cells were seen in 3/6 (50%) of specimens. The eschars showed necrosis of the epidermis and superficial dermis (2/6, 33.3%). Only one specimen showed intraepidermal vesiculation and papillary dermal edema (1/6; 16.7%). All six specimens showed perivascular infiltration with CD3+ T-cells, and low amounts of CD20+ B-cells and neutrophils. Five of the six specimens (83.3%) showed significant levels of CD68+ histiocytes. CONCLUSION: The histopathology of rickettsialpox infection is septic lymphocytic and granulomatous vasculitis.

A biosafety level-2 dose-dependent lethal mouse model of spotted fever rickettsiosis: Rickettsia parkeri Atlantic Rainforest strain.

BACKGROUND: The species of the Rickettsia genus are 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, regional lymphadenopathy, fever, myalgia and rash. Currently, there are several mouse models that provide good approaches 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 Atlantic Rainforest strain 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 strain organisms 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 posture, 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: Since R. parkeri is used at biosafety level 2, 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.

Vector Tick Transmission Model of Spotted Fever Rickettsiosis.

Many aspects of rickettsial infections have been characterized, including pathogenic and immune pathways and mechanisms of rickettsial survival within the vertebrate host and tick vector. However, very few studies are focused on the complex pathogen-vector-host interactions during tick feeding. Therefore, our objective was to develop a tick transmission model of the spotted fever group of rickettsial infections to study the initial events in disease development. The most appropriate strain of mouse was identified for evaluation as a transmission model, and the course of infection, bacterial levels, histopathologic changes, and antibody response during tick transmission in mice infested with Amblyomma maculatum ticks carrying the emerging pathogen, Rickettia parkeri, were studied. Results showed distinct clinical signs in C3H/HeN mice infected intravenously, leading to selection of this mouse strain for tick transmission studies. Active infection of animals was observed after tick vector transmission. The bacteria disseminated systemically and spread to several organs at 24 hours after tick attachment, with peak bacterial load at day 6 after tick attachment. Skin, lung, and liver showed the greatest pathologic changes, with inflammatory cellular infiltration and necrosis. These findings indicate the feasibility of using murine infection with R. parkeri by A. maculatum tick transmission as a model to study different aspects of the spotted fever group of rickettsial disease establishment.

[Fatal spotted fever in Salta province]. / Fiebre manchada de evolución fatal en la provincia de Salta.

We describe the case of a 17-year-old male patient living in Salta city who, 10 days after visiting a rural area in Salta province, was hospitalized for febrile seizures. Shortly after admission, he developed an exanthema followed by a multiple organ dysfunction that evolved to irreversible septic shock followed by death 48 hours after admission. Serological diagnosis -high IgM and IgG anti-Rickettsia spp. antibody titres as detected by indirect immunofluorescence- arrived post mortem. Spotted fever group rickettsioses are tick-borne diseases distributed worldwide and continue being under diagnosed in several countries mainly due to a low clinical suspicion. In the north-western provinces of Argentina there is also the limitation of not counting with a regional laboratory to perform the etiological diagnosis. This is crucial because the severe forms of the disease, which are commonly caused by R. rickettsii, have been already documented in the region. Given that spotted fevers have broadly unspecific febrile presentations and the components of the enzootic cycle are present even in geographic areas not yet considered to be endemic for tick borne diseases, their diagnosis should not be underestimated. If the adequate antibiotic treatment is administered timely, the prognosis of this group of life-threatening diseases improves drastically.

Fiebre manchada de evolución fatal en la provincia de Salta / Fatal spotted fever in Salta province

Describimos el caso de un varón de 17 años oriundo de la ciudad de Salta quien, 10 días después de visitar una zona rural de la provincia homónima, ingresó a nuestro hospital por convulsiones febriles. Durante la internación presentó exantema seguido de disfunción orgánica múltiple, la que evolucionó rápidamente hacia shock séptico irreversible y muerte a las 48 horas de su admisión. El diagnóstico serológico -altos títulos de IgM e IgG anti-Rickettsia spp. por inmunofluorescencia indirecta- arribó post mortem. Las rickettsiosis del grupo de las fiebres manchadas son transmitidas por garrapatas, tienen distribución global y en varios países continúan siendo subdiagnosticadas debido a una baja sospecha clínica. En las provincias del noroeste argentino se agrega la carencia de un laboratorio regional capacitado para efectuar el diagnóstico etiológico. Esta limitación es crítica porque en esa región del país ya ha sido documentada la presencia de las formas graves de la enfermedad, usualmente debidas a R. rickettsii. Dado que las fiebres manchadas se presentan como sindromes febriles inespecíficos y los componentes del ciclo enzoótico están presentes en vastas áreas geográficas, incluso en algunas aún no consideradas endémicas para rickettsiosis, su diagnóstico nunca debe ser subestimado. Con el tratamiento antibiótico adecuado instaurado en tiempo oportuno, el pronóstico de este grupo de enfermedades potencialmente mortales mejora en forma drástica.

We describe the case of a 17-year-old male patient living in Salta city who, 10 days after visiting a rural area in Salta province, was hospitalized for febrile seizures. Shortly after admission, he developed an exanthema followed by a multiple organ dysfunction that evolved to irreversible septic shock followed by death 48 hours after admission. Serological diagnosis -high IgM and IgG anti-Rickettsia spp. antibody titres as detected by indirect immunofluorescence- arrived post mortem. Spotted fever group rickettsioses are tick-borne diseases distributed worldwide and continue being under diagnosed in several countries mainly due to a low clinical suspicion. In the north-western provinces of Argentina there is also the limitation of not counting with a regional laboratory to perform the etiological diagnosis. This is crucial because the severe forms of the disease, which are commonly caused by R. rickettsii, have been already documented in the region. Given that spotted fevers have broadly unspecific febrile presentations and the components of the enzootic cycle are present even in geographic areas not yet considered to be endemic for tick borne diseases, their diagnosis should not be underestimated. If the adequate antibiotic treatment is administered timely, the prognosis of this group of life-threatening diseases improves drastically.

Case Report: Typhoid Fever and Spotted Fever Group Rickettsiosis Presenting Concomitantly in an Indian Immigrant.

We present a rare case of an Indian immigrant suffering from concomitant infection of Salmonella typhi and spotted fever group Rickettsia. We discuss the scarce reports of dual infections from the developing world and the related diagnostic challenges.

Clinicopathological study on rickettsial spotted fever from south India.

In a prospective study conducted between November 2006 and April 2008 of 35 patients (male:female ratio 2:1) with proven rickettsial spotted fever, a generalised rash with involvement of palms and soles were seen in 80% of patients. Vasculitis on histopathology of rash was seen in 54%.

Diagnosis of Spotted Fever Group Rickettsioses in U.S. Travelers Returning from Africa, 2007-2016.

Spotted fever group rickettsioses (SFGRs), such as African tick bite fever (ATBF), are among the most commonly diagnosed diseases for ill travelers returning from southern Africa. We summarized demographic, clinical, and diagnostic features of imported SFGR cases in U.S. travelers returning from Africa who had laboratory specimens submitted to the Centers for Disease Control and Prevention. Diagnosis of SFGR was performed by indirect immunofluorescence antibody assay, immunohistochemical staining, polymerase chain reaction (PCR), or culture. Cases were defined as probable SFGR, confirmed SFGR, or confirmed ATBF. Clinical and epidemiological categorical variables were described as counts and proportions; continuous variables were described using geometric mean titers, median, and range. One hundred and twenty-seven patients satisfied laboratory criteria for confirmed or probable SFGR. Fever was the most common symptom (N = 88; 69%), followed by ≥ 1 eschars (N = 70; 55%). Paired serums were submitted for 36 patients (28%); 12 patients (33%) had nonreactive initial serum sample but converted to a titer ≥ 64 with the convalescent sample. Twenty-seven patients (21%) had infection with Rickettsia africae based on PCR analysis of eschar swab (N = 8) or biopsy (N = 23). Fifteen patients had eschar biopsy or swab samples and serum sample(s) submitted together; 9 (60%) had PCR-positive eschar results and nonreactive acute serology. Health-care providers should consider SFGR when evaluating patients for a febrile illness with eschar and compatible foreign travel history. Polymerase chain reaction testing of eschar biopsies or swabs provides a confirmed diagnosis in early stages of disease; eschar swabs or biopsies are an underutilized diagnostic technique.

Case Report: Family Cluster of Japanese Spotted Fever.

Spotted fever group rickettsioses are transmitted by several types of arthropods (including ticks, chiggers, fleas, and lice) and are distributed worldwide. Japanese spotted fever (JSF) was discovered as an emerging rickettsiosis in 1984. The annual number of cases has increased 3-fold during the last decade. In Japan, JSF has been mainly reported in an area with warm climate that borders the Pacific Ocean. We describe a family/neighborhood cluster of three cases of JSF in an area of Japan that had previously not been considered endemic.

Histology and Serum Cytokine Responses in an Imported Rickettsia slovaca Infection, Germany.

Rickettsia slovaca, a spotted fever group rickettsial pathogen, causes a syndrome consisting of scalp eschar and neck lymphadenopathy following tick bite. We analyzed the histologic skin reaction in the eschar, showing a prominent eosinophilic infiltration, as well as the presence of B lymphocytes and CD4- and CD8-positive T cells. Examination of the serum cytokine responses over time demonstrated an initial proinflammatory cytokine elevation followed by normalization.