Biology subjects

Chua, B. Y.

Publications and source records attributed to Chua, B. Y..

6 recordsLinked to original sources

bioRxiv2025

A refined low-dose murine model of Mycobacterium ulcerans infection to assess integrated immune networks in Buruli ulcer pathogenesis

Mycobacterium ulcerans, the causative agent of Buruli ulcer, is a slow-growing zoonotic pathogen with distinctive pathogenesis linked primarily to its toxin mycolactone. Recent research has shown that the M. ulcerans infectious dose is very low (<10 colony forming units [CFU]). Buruli ulcer animal infection models traditionally use bacterial challenge doses in the range 104 - 106 CFU; a range orders of magnitude higher than natural infection. These large doses represent an unrealistic challenge for vaccine trials and studies of immunity. Here, we address this issue and describe a murine tail infection model in two genetically distinct mouse strains (BALB/c and C57BL/6) using quality-controlled, M. ulcerans challenge doses (10 - 20 CFU and 100 CFU). Over 24-weeks, we assessed host responses to infection by measuring >70 clinical, immunological and microbiological parameters. Principal findings included a 100% infection rate even at the lowest bacterial challenge, but with a dose-dependent delay in lesion onset and disease progression for both mouse strains. Bacterial growth kinetics were similar between mouse strains. There was a difference in immune profiles between mouse strains and between low (10 CFU) versus high (100 CFU) bacterial challenge doses. C57BL/6 mice exhibited more robust systemic cellular responses and more rapid lesion onset compared to BALB/c mice. There were dose-dependent cytokine and chemokine differences in C57BL/6 mice, while BALB/c mice displayed similar responses across both doses. Antibody responses were only detected late in the infection and were associated with the high-dose inoculum in both strains. Machine learning and other statistical analyses highlighted the importance of activated CD8+ T cells and dendritic cells in the immune response to low-dose infection in C57BL/6 mice. Murine low-dose M. ulcerans infection models provide confidence for future human Buruli ulcer challenge trials and will inform the development of effective vaccines and therapeutics.

microbiology↗

bioRxiv2023

Evidence for vagal sensory neural involvement in influenza pathogenesis and disease

Influenza A virus (IAV) is a common respiratory pathogen and a global cause of significant and often severe morbidity. Although inflammatory immune responses to IAV infections are well described, little is known about how neuroimmune processes contribute to IAV pathogenesis. In the present study, we employed surgical, genetic, and pharmacological approaches to manipulate pulmonary vagal sensory neuron innervation and activity in the lungs to explore potential crosstalk between pulmonary sensory neurons and immune processes. Intranasal inoculation of mice with H1N1 strains of IAV resulted in stereotypical antiviral lung inflammation and tissue pathology, changes in breathing, loss of body weight and other clinical signs of severe IAV disease. Unilateral cervical vagotomy and genetic ablation of pulmonary vagal sensory neurons had a moderate effect on the pulmonary inflammation induced by IAV infection, but significantly worsened clinical disease presentation. Inhibition of pulmonary vagal sensory neuron activity via inhalation of the charged sodium channel blocker, QX-314, resulted in a moderate decrease in lung pathology, but again this was accompanied by a paradoxical worsening of clinical signs. Notably, vagal sensory ganglia neuroinflammation was induced by IAV infection and this was significantly potentiated by QX-314 administration. This vagal ganglia hyperinflammation was characterized by alterations in IAV-induced host defense gene expression, increased neuropeptide gene and protein expression, and an increase in the number of inflammatory cells present within the ganglia. These data suggest that pulmonary vagal sensory neurons play a role in the regulation of the inflammatory process during IAV infection and suggest that vagal neuroinflammation may be an important contributor to IAV pathogenesis and clinical presentation. Targeting these pathways could offer therapeutic opportunities to treat IAV-induced morbidity and mortality. Author summaryInfluenza viruses are a common respiratory pathogen that represent a constant and pervasive threat to human health. Although the inflammatory and immune responses to influenza viral infections are well described, little is known about the role the nervous system plays in the formation and progression of disease. The lungs receive a rich supply of sensory nerve fibers from the vagus nerve. These nerves are critical for protecting the lungs against harmful stimuli and play an important defence role against pathogens, including viruses. Here we use several complex animal models to demonstrate the impact lung sensory neurons have on influenza viral infection and disease outcome. We demonstrate that ablation of lung sensory neurons and inhibition of their neural activity significantly worsens the clinical outcome in mice infected with influenza virus, however with only a moderate impact on lung pathology. Interestingly, when the activity of these neurons is inhibited during influenza viral infection, this drives a hyper neuroinflammatory response within the vagal sensory ganglia, where their cell bodies are located. Our work provides new insights into how these lung sensory neurons are involved in influenza viral infections and may offer therapeutic opportunities to treat influenza-induced morbidity and mortality.

neuroscience↗

bioRxiv2020

Prophylactic intranasal administration of a TLR2 agonist reduces upper respiratory tract viral shedding in a SARS-CoV-2 challenge ferret model

Respiratory viruses such as coronaviruses represent major ongoing global threats, causing epidemics and pandemics with huge economic burden. Rapid spread of virus through populations poses an enormous challenge for outbreak control. Like all respiratory viruses, the most recent novel human coronavirus SARS-CoV-2, initiates infection in the upper respiratory tract (URT). Infected individuals are often asymptomatic, yet highly infectious and readily transmit virus. A therapy that restricts initial replication in the URT has the potential to prevent progression of severe lower respiratory tract disease as well as limiting person-to-person transmission. We show that prophylactic intra-nasal administration of the TLR2/6 agonist INNA-051 in a SARS-CoV-2 ferret infection model effectively reduces levels of viral RNA in the nose and throat. The results of our study support clinical development of a therapy based on prophylactic TLR2/6 innate immune activation in the URT to reduce SARS-CoV-2 transmission and provide protection against COVID-19.

immunology↗

bioRxiv2020

High antibody titres induced by protein subunit vaccines against Buruli ulcer using Mycobacterium ulcerans antigens Hsp18 and MUL_3720

BackgroundMycobacterium ulcerans is the causative agent of a debilitating skin and soft tissue infection known as Buruli ulcer (BU). There is no vaccine against BU. The purpose of this study was to investigate the vaccine potential of two previously described immunogenic M. ulcerans proteins, MUL_3720 and Hsp18, using a mouse tail infection model of BU. MethodsRecombinant versions of the two proteins were each electrostatically coupled with a previously described lipopeptide adjuvant. Seven C57BL/6 and seven BALB/c mice were vaccinated and boosted with each of the formulations. Vaccinated mice were then challenged with M. ulcerans via subcutaneous tail inoculation. Vaccine performance was assessed by time-to-ulceration compared to unvaccinated mice. ResultsThe MUL_3720 and Hsp18 vaccines induced high titres of antigen-specific antibodies that were predominately subtype IgG1. However, all mice developed ulcers by day-40 post-M. ulcerans challenge. No significant difference was observed in the time-to-onset of ulceration between the experimental vaccine groups and unvaccinated animals. ConclusionsThese data align with previous vaccine experiments using Hsp18 and MUL_3720 that indicated these proteins may not be appropriate vaccine antigens. This work highlights the need to explore alternative vaccine targets and different approaches to understand the role antibodies might play in controlling BU.

microbiology↗

bioRxiv2019

Vaccine-specific immune responses against Mycobacterium ulcerans infection in a low-dose murine challenge model

The neglected tropical disease Buruli ulcer (BU) is an infection of subcutaneous tissue with Mycobacterium ulcerans. There is no effective BU vaccine. Here, we assessed an experimental prime-boost vaccine in a low-dose murine tail infection model. We used the enoyl-reductase (ER) domain of the M. ulcerans mycolactone polyketide synthases electrostatically coupled with a previously described TLR-2 agonist-based lipopeptide adjuvant, R4Pam2Cys. Mice were vaccinated and then challenged via tail inoculation with 14-20 colony forming units (CFU) of an engineered bioluminescent strain of M. ulcerans. Mice receiving either the experimental ER vaccine or Mycobacterium bovis Bacille Calmette-Guerin (BCG) were equally well protected, with both groups faring significantly better than non-vaccinated animals (p<0.05). A suite of 29 immune parameters were assessed in the mice at the end of the experimental period. Multivariate statistical approaches were then used to interrogate the immune response data to develop disease-prognostic models. High levels of IL-2 and low IFN-{gamma} produced in the spleen best predicted control of infection across all vaccine groups. Univariate logistic regression then revealed vaccine-specific profiles of protection. High titres of ER-specific IgG serum antibodies together with IL-2 and IL-4 in the draining lymph node (DLN) were associated with protection induced by the experimental ER vaccine. In contrast, high titres of IL-6, TNF-, IFN-{gamma} and IL-10 in the DLN and low IFN{gamma} titres in the spleen were associated with protection following BCG vaccination. This study suggests an effective BU vaccine must induce localized, tissue-specific immune profiles with controlled inflammatory responses at the site of infection.

immunology↗

bioRxiv2018

Bioluminscent Mycobacterium ulcerans, a tool to study host-pathogen interactions in a murine tail model of Buruli ulcer

Buruli ulcer is a neglected tropical disease caused by infection with Mycobacterium ulcerans. In this study we used a previously reported strain of M. ulcerans, genetically engineered to constitutively produce bioluminescence, to follow the progression of Buruli ulcer in mice using an in-vivo imaging (IVIS(R)) system. We aimed to characterize a mouse tail infection model for pathogenesis, as well as for pre-clinical vaccine and drug development research for Buruli ulcer. Immune parameters, such as antibody titers and cytokine levels, were determined throughout the course of the infection and histology specimens were examined for comparison with human pathology. Nine out of ten (90%) BALB/c mice infected subcutaneously with 105 M. ulcerans JKD8049 (containing pMV306 hsp16+luxG13) exhibited light emission from the site of infection over the course of the experiment indicating M. ulcerans growth in-vivo. Five out of ten (50%) animals developed clinical signs of disease. Antibody titers were overall low and their onset was late, as measured by responses to both heterogenous (bacterial whole cell lysate) and single antigen (Hsp18) targets. IFN-{gamma}, and IL-10 are reported to play a vital role in host control of Buruli ulcer and these cytokines were elevated in animals with pathology. For mice with advanced pathology, histology revealed clusters of acid-fast bacilli within subcutaneous tissue 300-400 m beneath the epidermis of the tail, with macrophage infiltration and granuloma-formation resembling human Buruli ulcer. This study has shown the utility of using bioluminescent M. ulcerans and IVIS(R) in a mouse tail infection model to study Buruli ulcer infection.\n\nAuthor summaryBuruli ulcer is one of the so called neglected tropical diseases. It is an infectious disease, mainly occurring in West Africa but also in Australia. It manifests as skin lesion and ulcer. Up to date, the way of transmission is inadequately understood. Also, there is no vaccine to protect against the disease. Buruli ulcer is treatable with a course of antibiotics that need to be given for the duration of two months. More laboratory research is needed to elucidate the mechanism of transmission, develop a vaccine and improve and shorten antibiotic therapy. For this, animal (mouse) models of disease are used. The aim of this study was to refine and improve the mouse tail infection model of Buruli ulcer. For this, we used a genetically modified Mycobacterium ulcerans strain that emits light. After infection of animals, light emitted from the bacteria was read out with an in-vivo imaging (IVIS) camera. This allowed us to monitor the location of bacteria in the living animal over time without the need to kill the animal. We also measured parameters of the immune system such as antibodies and cytokines as a baseline for future studies into immunology, vaccine development and pathology of Buruli ulcer. We successfully improved and characterized the mouse tail infection model in Buruli ulcer with the use of modern technology using light emitting bacteria and the IVIS camera.

microbiology↗