Now showing 1 - 10 of 12
  • Publication
    Reply to Dale and Shulman
    (Oxford University Press, 2019-01-29)
    Sikder, Suchandan
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    Rush, Catherine M
    ;
    Govan, Brenda L
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    Norton, Robert E
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    Cunningham, Madeleine W
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    McMillan, David J
    ;
    Sriprakash, Kadaba S
    ;
  • Publication
    Development of a diet-induced murine model of diabetes featuring cardinal metabolic and pathophysiological abnormalities of type 2 diabetes
    (The Company of Biologists Ltd, 2016-08-15)
    Morris, Jodie L
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    Bridson, Tahnee L
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    Alim, Md Abdul
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    Rush, Catherine M
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    Rudd, Donna M
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    Govan, Brenda L
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    The persistent rise in global incidence of type 2 diabetes (T2D) continues to have significant public health and economic implications. The availability of relevant animal models of T2D is critical to elucidating the complexity of the pathogenic mechanisms underlying this disease and the implications this has on susceptibility to T2D complications. Whilst many high-fat diet-induced rodent models of obesity and diabetes exist, growing appreciation of the contribution of high glycaemic index diets on the development of hyperglycaemia and insulin resistance highlight the requirement for animal models that more closely represent global dietary patterns reflective of modern society. To that end, we sought to develop and validate a murine model of T2D based on consumption of an energy-dense diet containing moderate levels of fat and a high glycaemic index to better reflect the aetiopathogenesis of T2D. Male C57BL/6 mice were fed an energy-dense (ED) diet and the development of pathological features used in the clinical diagnosis of T2D was assessed over a 30-week period. Compared with control mice, 87% of mice fed an ED diet developed pathognomonic signs of T2D including glucose intolerance, hyperglycaemia, glycosylated haemoglobin (HbA1c) and glycosuria within 30 weeks. Furthermore, dyslipidaemia, chronic inflammation, alterations in circulating leucocytes and renal impairment were also evident in ED diet-fed mice compared with mice receiving standard rodent chow. Longitudinal profiling of metabolic and biochemical parameters provide support of an aetiologically and clinically relevant model of T2D that will serve as a valuable tool for mechanistic and therapeutic studies investigating the pathogenic complications of T2D.
  • Publication
    Increased Neurotropic Threat from 'Burkholderia pseudomallei' Strains with a 'B mallei'-like Variation in the 'bimA' Motility Gene, Australia
    (Centers for Disease Control and Prevention (CDC), 2017)
    Morris, Jodie L
    ;
    Fane, Anne
    ;
    Sarovich, Derek S
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    Price, Erin P
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    Rush, Catherine M
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    Govan, Brenda L
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    Parker, Elizabeth
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    Mayo, Mark
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    Currie, Bart J
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    Neurologic melioidosis is a serious, potentially fatal form of Burkholderia pseudomallei infection. Recently, we reported that a subset of clinical isolates of B. pseudomallei from Australia have heightened virulence and potential for dissemination to the central nervous system. In this study, we demonstrate that this subset has a B. mallei-like sequence variation of the actin-based motility gene, bimA. Compared with B. pseudomallei isolates having typical bimA alleles, isolates that contain the B. mallei-like variation demonstrate increased persistence in phagocytic cells and increased virulence with rapid systemic dissemination and replication within multiple tissues, including the brain and spinal cord, in an experimental model. These findings highlight the implications of bimA variation on disease progression of B. pseudomallei infection and have considerable clinical and public health implications with respect to the degree of neurotropic threat posed to human health.
  • Publication
    A murine model of tuberculosis/type 2 diabetes comorbidity for investigating the microbiome, metabolome and associated immune parameters
    (John Wiley & Sons, Inc, 2021-06)
    Sathkumara, Harindra D
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    Eaton, Janet L
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    Field, Matt A
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    Govan, Brenda L
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    Kupz, Andreas
    Tuberculosis (TB) is one of the deadliest infectious diseases in the world. The metabolic disease type 2 diabetes (T2D) significantly increases the risk of developing active TB. Effective new TB vaccine candidates and novel therapeutic interventions are required to meet the challenges of global TB eradication. Recent evidence suggests that the microbiota plays a significant role in how the host responds to infection, injury and neoplastic changes. Animal models that closely reflect human physiology are crucial in assessing new treatments and to decipher the underlying immunological defects responsible for increased TB susceptibility in comorbid patients. In this study, using a diet-induced murine T2D model that reflects the etiopathogenesis of clinical T2D and increased TB susceptibility, we investigated how the intestinal microbiota may impact the development of T2D, and how the gut microbial composition changes following a very low-dose aerosol infection with Mycobacterium tuberculosis (Mtb). Our data revealed a substantial intestinal microbiota dysbiosis in T2D mice compared to non-diabetic animals. The observed differences were comparable to previous clinical reports in TB patients, in which it was shown that Mtb infection causes rapid loss of microbial diversity. Furthermore, diversity index and principle component analyses demonstrated distinct clustering of Mtb-infected non-diabetic mice vs. Mtb-infected T2D mice. Our findings support a broad applicability of T2D mice as a tractable small animal model for studying distinct immune parameters, microbiota and the immune-metabolome of TB/T2D comorbidity. This model may also enable answers to be found to critical outstanding questions about targeted interventions of the gut microbiota and the gut-lung axis.
  • Publication
    Anti-mycobacterial function of macrophages is impaired in a diet induced model of type 2 diabetes
    (Elsevier Ltd, 2017)
    Alim, Md Abdul
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    Sikder, Suchandan
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    Bridson, Tahnee L
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    Rush, Catherine M
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    Govan, Brenda L
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    Type 2 diabetes (T2D) is one of the major risk factors for tuberculosis (TB). In this study, a diet induced murine model of T2D (DIMT2D) was developed and characterized in the context of metabolic, biochemical and histopathological features following diet intervention. Mycobacterial susceptibility was investigated using Mycobacterium fortuitum as a surrogate. Phagocytic capability of alveolar macrophages and resident peritoneal macrophages were determined by in vitro assays using mycolic acid coated beads and M. fortuitum. Results demonstrated that bacillary loads were significantly higher in liver, spleen, and lungs of diabetic mice compared to controls. Higher inflammatory lesions and impaired cytokine kinetics (TNF-α, MCP-1, IL-12, IFN-γ) were also observed in diabetic mice. Macrophages isolated from diabetic mice had lower uptake of mycolic acid coated beads, reduced bacterial internalization and killing and altered cytokine responses (TNF-α, IL-6, MCP-1). This model will be useful to further investigate different facets of host-pathogen interactions in TB-T2D.
  • Publication
    Identification of defective early immune responses to Burkholderia pseudomallei infection in a diet-induced murine model of type 2 diabetes
    (Elsevier Masson, 2021-06)
    Morris, Jodie L
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    Govan, Brenda L
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    Rush, Catherine M
    ;

    Co-occurrence of bacterial infections with type 2 diabetes (T2D) is a global problem. Melioidosis caused by Burkholderia pseudomallei is 10 times more likely to occur in patients with T2D, than in normoglycemic individuals. Using an experimental model of T2D, we observed that greater susceptibility in T2D was due to differences in proportions of infiltrating leucocytes and reduced levels of MCP-1, IFN-γ and IL-12 at sites of infection within 24 h post-infection. However, by 72 h the levels of inflammatory cytokines and bacteria were markedly higher in visceral tissue and blood in T2D mice. In T2D, dysregulated early immune responses are responsible for the greater predisposition to B. pseudomallei infection.

  • Publication
    Anti-streptococcal antibody and T-cell interactions with vascular endothelial cells initiate the development of rheumatic carditis
    (Oxford University Press, 2020-02) ;
    Rush, Catherine M
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    Govan, Brenda L
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    Lim, Md A
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    The role of group A streptococcal and Streptococcus dysgalactiae subspecies equisimilis M-protein specific Abs and T-cells in endothelial cell activation was investigated using cultured rat aortic endothelial cells, and in a rat model of autoimmune valvulitis. Heat inactivated serum and mononuclear cells from streptococcal M-protein immunized rats independently induced upregulation of the endothelial cell adhesion molecules, vascular cell adhesion molecule (VCAM)-1 and intercellular adhesion molecule (ICAM)-1 in cultured cells. We also observed T-cell migration across endothelial cell monolayers incubated with serum from M-protein-immunized rats. Furthermore, we observed VCAM-1 and ICAM-1 expression in the myocardium of rats injected with M-protein compared to control animals. These observations support the contention that initial interactions between streptococcal M-protein specific Abs and/or T-cells with the heart endothelium lead to endothelial cell activation followed by transmigration of M-protein specific T-cells into heart tissue leading to an inflammatory process that leads to carditis in rheumatic fever and rheumatic heart disease.

  • Publication
    Group G Streptococcus Induces an Autoimmune Carditis Mediated by Interleukin 17A and Interferon γ in the Lewis Rat Model of Rheumatic Heart Disease
    (Oxford University Press, 2018-07-15)
    Sikder, Suchandan
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    Williams, Natasha L
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    Sorenson, Alanna E
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    Alim, Md A
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    Vidgen, Miranda E
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    Moreland, Nicole J
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    Rush, Catherine M
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    Simpson, Robert S
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    Govan, Brenda L
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    Norton, Robert E
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    Cunningham, Madeleine W
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    McMillan, David J
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    Sriprakash, Kadaba S
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    Acute rheumatic fever and rheumatic heart disease (ARF/RHD) have long been described as autoimmune sequelae of Streptococcus pyogenes or group A streptococcal (GAS) infection. Both antibody and T-cell responses against immunodominant GAS virulence factors, including M protein, cross-react with host tissue proteins, triggering an inflammatory response leading to permanent heart damage. However, in some ARF/RHD-endemic regions, throat carriage of GAS is low. Because Streptococcus dysgalactiae subspecies equisimilis organisms, also known as β-hemolytic group C streptococci and group G streptococci (GGS), also express M protein, we postulated that streptococci other than GAS may have the potential to initiate or exacerbate ARF/RHD. Using a model initially developed to investigate the uniquely human disease of ARF/RHD, we have discovered that GGS causes interleukin 17A/interferon γ–induced myocarditis and valvulitis, hallmarks of ARF/RHD. Remarkably the histological, immunological, and functional changes in the hearts of rats exposed to GGS are identical to those exposed to GAS. Furthermore, antibody cross-reactivity to cardiac myosin was comparable in both GGS- and GAS-exposed animals, providing additional evidence that GGS can induce and/or exacerbate ARF/RHD.
  • Publication
    Design and Development of an Internationally Applicable Educational Video to Increase Community Awareness in Regions with High Prevalence of Melioidosis and Diabetes
    (American Society of Tropical Medicine and Hygiene, 2023-03)
    Maisrikrod, Shalisa C
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    Currie, Mathew
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    Govan, Brenda L
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    Norton, Robert E
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    Currie, Bart J
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    Mayo, Mark

    Melioidosis is a neglected tropical disease that causes high morbidity and mortality. Public health aware-ness is essential for both prevention and early detection of the infection. This project aimed to develop an internationally applicable educational tool to increase community awareness in regions with high prevalence of diabetes and melioido-sis. The animation was created with international collaboration. Sixty-four delegates from different cultural backgrounds participated in the survey to evaluate the animation. Feedback was positive, with 85% agreeing that they would use this video for public education and 82% agreeing that the video was culturally appropriate to them in the context of their region. The animation was refined after feedback. To supplement the 3-minute animation, a 13-minute film footage of interviews with clinicians, researchers and patients was also created. These materials have been made available online through the International Melioidosis Network and can be readily downloaded or subtitled in any language using publicly available software, demonstrating the utility of developing low-cost adaptable health education material targeted for widespread use internationally.

  • Publication
    Dysregulation of key cytokines may contribute to increased susceptibility of diabetic mice to Mycobacterium bovis BCG infection
    (Elsevier Ltd, 2019-03)
    Alim, Md Abdul
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    Sikder, Suchandan
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    Sathkumara, Harindra
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    Kupz, Andreas
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    Rush, Catherine M
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    Govan, Brenda L
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    Diabetes is one of the major co-morbidities contributing to the high global burden of tuberculosis (TB). The increased susceptibility of individuals with type 2 diabetes (T2D) to TB is multifactorial and may influence the efficacy of vaccines. This study was undertaken to determine the early immune responses that occur following infection with Mycobacterium bovis Bacille Calmette-Guérin (BCG) in a diet-induced murine model of T2D. The phagocytic capabilities of alveolar (AM) and resident peritoneal macrophages (RPM) were assessed using ex vivo assays. Compared to macrophages from non-diabetic mice, macrophages from diabetic animals showed decreased BCG uptake and killing and inflammatory cytokine production (TNF-α, MCP-1, IL-6, IL-1β). In vivo susceptibility to BCG was determined following intravenous infection and diabetic mice showed a trend towards increased mortality, higher bacterial burden in the lung, liver and spleen and increased inflammatory lesions compared to controls. Differences between tissue cytokines were observed as early as one day post-infection and by days 14 and 35, lung and liver TNF-α and IFN-γ levels were decreased in diabetic mice compared to controls. These results suggest that early dysregulated immune responses may influence the susceptibility of T2D mice to BCG infection.