A Role for the SmpB-SsrA System in Yersinia pseudotuberculosis Pathogenesis

Yersinia utilizes a sophisticated type III secretion system to enhance its chances of survival and to overcome the host immune system. SmpB (small protein B) and SsrA (small stable RNA A) are components of a unique bacterial translational control system that help maintain the bacterial translational machinery in a fully operational state. We have found that loss of the SmpB-SsrA function causes acute defects in the ability of Yersinia pseudotuberculosis to survive in hostile environments. Most significantly, we show that mutations in smpB-ssrA genes render the bacterium avirulent and unable to cause mortality in mice. Consistent with these observations, we show that the mutant strain is unable to proliferate in macrophages and exhibits delayed Yop-mediated host cell cytotoxicity. Correspondingly, we demonstrate that the smpB-ssrA mutant suffers severe deficiencies in expression and secretion of Yersinia virulence effector proteins, and that this defect is at the level of transcription. Of further interest is the finding that the SmpB-SsrA system might play a similar role in the related type III secretion system that governs flagella assembly and bacterial motility. These findings highlight the significance of the SmpB-SsrA system in bacterial pathogenesis, survival under adverse environmental conditions, and motility

Kdo Hydrolase Is Required for Francisella tularensis Virulence and Evasion of TLR2-Mediated Innate Immunity

ABSTRACT The highly virulent Francisella tularensis subsp. tularensis has been classified as a category A bioterrorism agent. A live vaccine strain (LVS) has been developed but remains unlicensed in the United States because of an incomplete understanding of its attenuation. Lipopolysaccharide (LPS) modification is a common strategy employed by bacterial pathogens to avoid innate immunity. A novel modification enzyme has recently been identified in F. tularensis and Helicobacter pylori. This enzyme, a two-component Kdo (3-deoxy-d-manno-octulosonic acid) hydrolase, catalyzes the removal of a side chain Kdo sugar from LPS precursors. The biological significance of this modification has not yet been studied. To address the role of the two-component Kdo hydrolase KdhAB in F. tularensis pathogenesis, a ΔkdhAB deletion mutant was constructed from the LVS strain. In intranasal infection of mice, the ΔkdhAB mutant strain had a 50% lethal dose (LD50) 2 log10 units higher than that of the parental LVS strain. The levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-1β (IL-1β) in bronchoalveolar lavage fluid were significantly higher (2-fold) in mice infected with the ΔkdhAB mutant than in mice infected with LVS. In vitro stimulation of bone marrow-derived macrophages with the ΔkdhAB mutant induced higher levels of TNF-α and IL-1β in a TLR2-dependent manner. In addition, TLR2−/− mice were more susceptible than wild-type mice to ΔkdhAB bacterial infection. Finally, immunization of mice with ΔkdhAB bacteria elicited a high level of protection against the highly virulent F. tularensis subsp. tularensis strain Schu S4. These findings suggest an important role for the Francisella Kdo hydrolase system in virulence and offer a novel mutant as a candidate vaccine

Early Interactions of Murine Macrophages with Francisella tularensis Map to Mouse Chromosome 19

ABSTRACT Differences among individuals in susceptibility to infectious diseases can be modulated by host genetics. Much of the research in this field has aimed to identify loci within the host genome that are associated with these differences. In mice, A/J (AJ) and C57BL/6J (B6) mice show differential susceptibilities to various pathogens, including the intracellular pathogen Francisella tularensis. Because macrophages are the main initial target during F. tularensis infection, we explored early interactions of macrophages from these two mouse strains with F. tularensis as well as the genetic factors underlying these interactions. Our results indicate that bacterial interactions with bone marrow-derived macrophages (BMDMs) during early stages of infection are different in the AJ and B6 strains. During these early stages, bacteria are more numerous in B6 than in AJ macrophages and display differences in trafficking and early transcriptional response within these macrophages. To determine the genetic basis for these differences, we infected BMDMs isolated from recombinant inbred (RI) mice derived from reciprocal crosses between AJ and B6, and we followed early bacterial counts within these macrophages. Quantitative trait locus (QTL) analysis revealed a locus on chromosome 19 that is associated with early differences in bacterial counts in AJ versus B6 macrophages. QTL analysis of published data that measured the differential susceptibilities of the same RI mice to an in vivo challenge with F. tularensis confirmed the F. tularensis susceptibility QTL on chromosome 19. Overall, our results show that early interactions of macrophages with F. tularensis are dependent on the macrophage genetic background

Evidence That Two ATP-Dependent (Lon) Proteases in Borrelia burgdorferi Serve Different Functions

The canonical ATP-dependent protease Lon participates in an assortment of biological processes in bacteria, including the catalysis of damaged or senescent proteins and short-lived regulatory proteins. Borrelia spirochetes are unusual in that they code for two putative ATP-dependent Lon homologs, Lon-1 and Lon-2. Borrelia burgdorferi, the etiologic agent of Lyme disease, is transmitted through the blood feeding of Ixodes ticks. Previous work in our laboratory reported that B. burgdorferi lon-1 is upregulated transcriptionally by exposure to blood in vitro, while lon-2 is not. Because blood induction of Lon-1 may be of importance in the regulation of virulence factors critical for spirochete transmission, the clarification of functional roles for these two proteases in B. burgdorferi was the object of this study. On the chromosome, lon-2 is immediately downstream of ATP-dependent proteases clpP and clpX, an arrangement identical to that of lon of Escherichia coli. Phylogenetic analysis revealed that Lon-1 and Lon-2 cluster separately due to differences in the NH2-terminal substrate binding domains that may reflect differences in substrate specificity. Recombinant Lon-1 manifested properties of an ATP-dependent chaperone-protease in vitro but did not complement an E. coli Lon mutant, while Lon-2 corrected two characteristic Lon-mutant phenotypes. We conclude that B. burgdorferi Lons -1 and -2 have distinct functional roles. Lon-2 functions in a manner consistent with canonical Lon, engaged in cellular homeostasis. Lon-1, by virtue of its blood induction, and as a unique feature of the Borreliae, may be important in host adaptation from the arthropod to a warm-blooded host

A multi-country test of brief reappraisal interventions on emotions during the COVID-19 pandemic.

The COVID-19 pandemic has increased negative emotions and decreased positive emotions globally. Left unchecked, these emotional changes might have a wide array of adverse impacts. To reduce negative emotions and increase positive emotions, we tested the effectiveness of reappraisal, an emotion-regulation strategy that modifies how one thinks about a situation. Participants from 87 countries and regions (n = 21,644) were randomly assigned to one of two brief reappraisal interventions (reconstrual or repurposing) or one of two control conditions (active or passive). Results revealed that both reappraisal interventions (vesus both control conditions) consistently reduced negative emotions and increased positive emotions across different measures. Reconstrual and repurposing interventions had similar effects. Importantly, planned exploratory analyses indicated that reappraisal interventions did not reduce intentions to practice preventive health behaviours. The findings demonstrate the viability of creating scalable, low-cost interventions for use around the world

Nephroprotective effect of apilarnil in lipopolysaccharide-induced sepsis through TLR4/NF-κB signaling pathway

© 2021 Elsevier Inc.Aims: In this study, we aimed to investigate the protective effect of apilarnil on kidney damage in the sepsis model induced by LPS. Main methods: 64 Sprague Dawley adult male rats were randomly divided into eight groups; control group, groups in which 0.2, 0.4 and 0.8 g/kg/bw apilarnil (API) was applied by oral gavage method for 10 days, LPS group in which 30 mg/kg/bw lipopolysaccharide (LPS) administered as intraperitoneally, groups in which LPS + 0.2, LPS+ 0.4 and LPS +0,8 API was applied. Six hour after the last administration the rats were anesthetized for euthanasia and kidney tissues were removed for RT-PCR analysis, immunohistochemical analysis and histopathologic analysis. Key finding: According to the results of RT-PCR expression levels of IL-6, IL-1β, NF-κB, TNF-α and TLR4 were significantly reduced in the LPS + 0,8 API group. Immunoreactivity of TLR4, pNF-κB and TNF-α levels in the LPS + 0.8 apilarnil group were significantly lower than in the LPS and LPS + 0.2 apilarnil groups. Histologically, compared to the LPS group the glomerular damage score tended to decrease in the LPS + 0,4 API and LPS+ 0,8 API groups, while the tubulointerstitial injury score decreased especially in the LPS + 0,8 API group. Significance: In the present study, 0,8 g/kg dose of apilarnil promoted potential renoprotective effects which were achieved, at least in part, by the modulation of important markers of the local immune response in the model of LPS-induced sepsis

Kronik idiopatik ürtikerde otolog serum testi

The etiology of chronic urticaria cannot be identified in more than 75% of the patients even after an exhaustive search. However, recent studies indicate that autoimmune mechanisms may be involved in the etiology in patients with chronic idiopathic urticaria (CIU). In this study, 60 patients who presented to the allergy clinic with urticaria were studied to determine the positivity of the autologous serum test in CIU. Twenty-eight patients were diagnosed with CIU. Patients were injected with 5OuI autologous serum in the forearm intradermally. Histamine and normal saline were also injected as a positive and negative control, respectively. An area of skin redness that is at least 1.5 mm larger in diameter than that observed with saline was considered positive. The autologous serum test was positive in 82.1% of the patients with CIU. The urticaria symptoms were more severe and unresponsive to antihistaminic therapy in patients with a positive autologous serum test. Therefore, immunomodulatory therapies may be indicated in the CIU patients with a positive autologus serum test.In conclusion, the autologous serum test appears to be useful tool in CIU especially in identification of the patients who are unlikely to respond to the conventional antihistaminic therapy.Kronik ürtiker hastalarının % 75 inden fazlasında yoğun araştırmalara rağmen etiyoloji saptanamaz. Kronik idiopatik örtiker (KlU) tanısı konulan bu hastalarda otoimmun mekanizmaların ürtiker oluşumundan sorumlu olduğuna dair bulgular gün geçtikçe artmaktadır. KlU hastalarında otolog serum test pozitifliğini belirlemek amacı ile alerji polikliniğine ürtiker şikayeti He başvuran 60 hasta çalışmaya alınmıştır, 28 hastaya KlO tanısı konulmuştur. Hastalardan elde edilen serumlar ön kol fleksor bölümüne 50 /A. volümünde intradermal enjekte edilmiştir. Deri reaktivitesini belirlemek amacı He pozitif kontrol (histamin) ve negatif kontrol (serum fizyolojik) kullanılmıştır. Otolog serumun enjeksiyon yerinde serum fizyolojiğin oluşturduğundan 1,5 mm veya daha fazla kızarıklığın eşlik ettiği kabarıklık oluşması pozitif test reaksiyonu olarak yorumlanmıştır. Bu çalışmada KlU hastalarının %82.1'inde otolog serum testi pozitif bulunmuştur. Yapılan çalışmalarda otolog serum testi pozitif hastalarda semptomların daha şiddetli olduğu ve klasik antihistaminik tedavisine yanıt vermedikleri saptanmıştır. Bu nedenle otolog serum testi pozitif hastalarda immunomodülatör tedavilerin kullanılması gerekebilir. Sonuç olarak otolog serum testi, rutinde uygulanması gereken verilecek tedaviyi belirleyici test olarak önem kazanmaktadır

Glycoconjugate vaccine using a genetically modified O antigen induces protective antibodies to Francisella tularensis

: Francisella tularensis is the causative agent of tularemia, a category A bioterrorism agent. The lipopolysaccharide (LPS) O antigen (OAg) of F. tularensis has been considered for use in a glycoconjugate vaccine, but conjugate vaccines tested so far have failed to confer protection necessary against aerosolized pulmonary bacterial challenge. When F. tularensis OAg was purified under standard conditions, the antigen had a small molecular size [25 kDa, low molecular weight (LMW)]. Using milder extraction conditions, we found the native OAg had a larger molecular size [80 kDa, high molecular weight (HMW)], and in a mouse model of tularemia, a glycoconjugate vaccine made with the HMW polysaccharide coupled to tetanus toxoid (HMW-TT) conferred better protection against intranasal challenge than a conjugate made with the LMW polysaccharide (LMW-TT). To further investigate the role of OAg size in protection, we created an F. tularensis live vaccine strain (LVS) mutant with a significantly increased OAg size [220 kDa, very high molecular weight (VHMW)] by expressing in F. tularensis a heterologous chain-length regulator gene (wzz) from the related species Francisella novicida Immunization with VHMW-TT provided markedly increased protection over that obtained with TT glycoconjugates made using smaller OAgs. We found that protective antibodies recognize a length-dependent epitope better expressed on HMW and VHMW antigens, which bind with higher affinity to the organism

Diagnostic Value of Specific IgE Analysis in Latex Allergy

WOS: 000304485200009PubMed ID: 22398567Background: The precision of the methods used to diagnose latex allergy is of great importance due to false-positive results. Neither the skin prick test (SPT) nor the latex-specific IgE assay has 100% diagnostic accuracy. We analysed the diagnostic value of latex-specific IgE by the first-ever concomitant use of the SPT and nasal provocation test (NPT). Methods: Twenty-seven latex-sensitive patients (group 1), 46 aeroallergen-sensitive patients (group 2a) and 33 healthy subjects (group 2b) participated in the study. All groups underwent an SPT with latex and aeroallergens and an NPT with latex. Latex-specific IgE and total IgE levels were measured by the ImmunoCAP assay. Results: Latex-specific IgE was positive in 92.6, 30.4 and 9.1% of groups 1, 2a and 2b, respectively. The 11 aeroallergen-sensitive patients in group 1 and all of the patients in group 2a were predominantly sensitised to pollens (grass, weed and tree) and reacted to a lesser degree to house dust mite, moulds and animal dander. Combined pollinosis was remarkably more prevalent in patients with positive latex-specific IgE in group 2a than in those with negative latex-specific IgE (p = 0.001). The NPT was positive in 84.6% of group 1 and negative in all control subjects. The sensitivity, specificity, negative predictive value and positive predictive value of the latex-specific IgE assay were 90.9, 72.2, 96.3 and 50%, respectively. Conclusion: The high rate of false-positive results for latex-specific IgE by ImmunoCAP should be taken into account when making a diagnosis of latex allergy in patients with pollinosis, especially in those sensitised to more than one pollen species. Copyright (C) 2012 S. Karger AG, Base