Kinetics of severe dengue virus infection and development of gut pathology in mice.

IMPORTANCE: Dengue virus, an arbovirus, causes an estimated 100 million symptomatic infections annually and is an increasing threat as the mosquito range expands with climate change. Dengue epidemics are a substantial strain on local economies and health infrastructure, and an understanding of what drives severe disease may enable treatments to help reduce hospitalizations. Factors exacerbating dengue disease are debated, but gut-related symptoms are much more frequent in severe than mild cases. Using mouse models of dengue infection, we have shown that inflammation and damage are earlier and more severe in the gut than in other tissues. Additionally, we observed impairment of the gut mucus layer and propose that breakdown of the barrier function exacerbates inflammation and promotes severe dengue disease. This idea is supported by recent data from human patients showing elevated bacteria-derived molecules in dengue patient serum. Therapies aiming to maintain gut integrity may help to abrogate severe dengue disease.

Cell-Extrinsic Differentiation Block Mediated by EphA3 in Pre-Leukaemic Thymus Contributes to Disease Progression.

We recently characterised the NUP98-HOXD13 (NHD13) mouse as a model of T-cell pre-leukaemia, featuring thymocytes that can engraft in recipient animals and progress to T-cell acute lymphoblastic leukaemia (T-ALL). However, loss of this engraftment ability by deletion of Lyl1 did not result in any loss of leukemogenesis activity. In the present study, we observe that NHD13 thymocytes overexpress EPHA3, and we characterise thymocyte behaviour in NHD13 mice with deletion of EphA3, which show a markedly reduced incidence of T-ALL. Deletion of EphA3 from the NHD13 mice does not prevent the abnormal accumulation or transplantation ability of these thymocytes. However, upon transplantation, these cells are unable to block the normal progression of recipient wild type (WT) progenitor cells through the normal developmental pathway. This is in contrast to the EphA3+/+ NHD13 thymocytes, which block the progression of incoming WT progenitors past the DN1 stage. Therefore, EphA3 is not critical for classical self-renewal, but is essential for mediating an interaction between the abnormally self-renewing cells and healthy progenitors-an interaction that results in a failure of the healthy cells to differentiate normally. We speculate that this may orchestrate a loss of healthy cell competition, which in itself has been demonstrated to be oncogenic, and that this may explain the decrease in T-ALL incidence in the absence of EphA3. We suggest that pre-leukaemic self-renewal in this model is a complex interplay of cell-intrinsic and -extrinsic factors, and that multiple redundant pathways to leukaemogenesis are active.

Tea tree oil extract causes mitochondrial superoxide production and apoptosis as an anticancer agent, promoting tumor infiltrating neutrophils cytotoxic for breast cancer to induce tumor regression.

The antitumor activity of the tea tree oil (TTO) derived product, Melaleuca Alternifolia Concentrate (MAC) was characterized mechanistically at the molecular and cellular level. MAC was analyzed for its anticancer activity against human prostate (LNCaP) and breast (MCF-7) cancer cell lines growing in vitro. MAC (0.02-0.06% v/v) dose-dependently induced the intrinsic (mitochondrial) apoptotic pathway in both the LNCaP and MCF-7 cell lines, involving increased mitochondrial superoxide production, loss of mitochondrial membrane potential (MMP), caspase 3/7 activation, as well as the presence of TUNEL+ and cleaved-PARP+ cell populations. At concentrations of 0.01-0.04% v/v, MAC caused cell cycle arrest in the G0/1-phase, as well as autophagy. The in vivo anticancer actions of MAC were examined as a treatment in the FVB/N c-Neu murine model for spontaneously arising breast cancers. Intratumoral MAC injections (1-4% v/v) significantly suppressed tumor progression in a dose-dependent manner and was associated with greater levels of tumor infiltrating neutrophils exhibiting anticancer cytotoxic activity. Induction of breast cancer cell death by MAC via the mitochondrial apoptotic pathway was also replicated occurring in tumors treated in vivo. In conclusion, our data highlights the potential for the Melaleuca-derived MAC product inducing anticancer neutrophil influx, supporting its application as a novel therapeutic agent.

Manipulation of epithelial cell death pathways by Shigella.

Shigella, a major cause of bacterial dysentery, knows when it is not wanted. To generate and maintain its niche within host cells, this unwelcome guest injects several dozen virulence factors via a type 3 secretion system (T3SS). In this issue, Ashida et al (2020) have elucidated the role of two such factors from Shigella flexneri-OspC1 and OspD3-that together counteract apoptotic and necroptotic death pathways in colonised epithelial cells. As a result, Shigella can replicate to high levels within the colonic epithelium, leading to the substantial epithelial damage in shigellosis and efficient bacterial release for faecal transmission.

The NUP98-HOXD13 fusion oncogene induces thymocyte self-renewal via Lmo2/Lyl1.

T cell acute lymphoblastic leukaemia (T-ALL) cases include subfamilies that overexpress the TAL1/LMO, TLX1/3 and HOXA transcription factor oncogenes. While it has been shown that TAL1/LMO transcription factors induce self-renewal of thymocytes, whether this is true for other transcription factor oncogenes is unknown. To address this, we have studied NUP98-HOXD13-transgenic (NHD13-Tg) mice, which overexpress HOXA transcription factors throughout haematopoiesis and develop both myelodysplastic syndrome (MDS) progressing to acute myeloid leukaemia (AML) as well as T-ALL. We find that thymocytes from preleukaemic NHD13-Tg mice can serially transplant, demonstrating that they have self-renewal capacity. Transcriptome analysis shows that NHD13-Tg thymocytes exhibit a stem cell-like transcriptional programme closely resembling that induced by Lmo2, including Lmo2 itself and its critical cofactor Lyl1. To determine whether Lmo2/Lyl1 are required for NHD13-induced thymocyte self-renewal, NHD13-Tg mice were crossed with Lyl1 knockout mice. This showed that Lyl1 is essential for expression of the stem cell-like gene expression programme in thymocytes and self-renewal. Surprisingly however, NHD13 transgenic mice lacking Lyl1 showed accelerated T-ALL and absence of transformation to AML, associated with a loss of multipotent progenitors in the bone marrow. Thus multiple T cell oncogenes induce thymocyte self-renewal via Lmo2/Lyl1; however, NHD13 can also promote T-ALL via an alternative pathway.

The in vitro and in vivo antiviral properties of combined monoterpene alcohols against West Nile virus infection.

West Nile Virus (WNV) is a mosquito-borne flavivirus that can cause neuroinvasive disease in humans and animals for which no therapies are currently available. We studied an established combination of monoterpene alcohols (CMA) derived from Melaleuca alternifolia, against WNV infection. The in vitro results show that CMA exhibits virucidal activity, as well as reduces the viral titres and percentage of infected cells. The antiviral mechanism of action of CMA was studied. We found that CMA did not alter the intracellular pH, neither induced apoptosis, but did induce cell cycle arrest in the G0/G1-phase although that was not the antiviral mechanism. Furthermore, we tested CMA in vivo using IRF 3(-)(/)(-)/7(-/-)mice and it was found that CMA treatment significantly delayed morbidity due to WNV infection, reduced the loss of body weight and reduced the viral titres in brain. These findings suggest that CMA could be a therapeutic agent against WNV infection.