Src-dependent Tyrosine Phosphorylation of Non-muscle Myosin Heavy Chain-IIA Restricts Listeria monocytogenes Cellular Infection

Bacterial pathogens often interfere with host tyrosine phosphorylation cascades to control host responses and cause infection. Given the role of tyrosine phosphorylation events in different human infections and our previous results showing the activation of the tyrosine kinase Src upon incubation of cells with Listeria monocytogenes, we searched for novel host proteins undergoing tyrosine phosphorylation upon L. monocytogenes infection. We identify the heavy chain of the non-muscle myosin IIA (NMHC-IIA) as being phosphorylated in a specific tyrosine residue in response to L. monocytogenes infection. We characterize this novel post-translational modification event and show that, upon L. monocytogenes infection, Src phosphorylates NMHC-IIA in a previously uncharacterized tyrosine residue (Tyr-158) located in its motor domain near the ATP-binding site. In addition, we found that other intracellular and extracellular bacterial pathogens trigger NMHC-IIA tyrosine phosphorylation. We demonstrate that NMHC-IIA limits intracellular levels of L. monocytogenes, and this is dependent on the phosphorylation of Tyr-158. Our data suggest a novel mechanism of regulation of NMHC-IIA activity relying on the phosphorylation of Tyr-158 by Src.     

Aspergillus species producing ochratoxin A: isolation from vineyard soils and infection of Semillon bunches in Australia

AIMS: The incidence of toxigenicity among Australian isolates of Aspergillus niger and Aspergillus carbonarius was assessed. Aspergillus rot and concomitant production of ochratoxin A (OA) in bunches inoculated with A. carbonarius were also investigated. METHODS AND RESULTS: Aspergillus niger and A. carbonarius were isolated from vineyard soils. Aspergillus niger was more widespread than A. carbonarius, and two restriction fragment length polymorphism types of A. niger, N and T, were present. Three of 113 A. niger isolates and all 33 A. carbonarius isolates produced OA. Aspergillus carbonarius was inoculated onto Semillon bunches with and without damage in the month before harvest. Damaged berries at greater than 12.3 (o) Bx were particularly susceptible to Aspergillus rot and production of OA, which was concentrated in severely mouldy berries. CONCLUSIONS: OA in Australian grapes results mainly from infection of berries by A. carbonarius. It is concentrated in discoloured, shrivelled berries. The potential for Aspergillus rot and OA production appears to commence after veraison and increase with berry damage and ripeness. SIGNIFICANCE AND IMPACT OF THE STUDY: Minimizing damage to grapes between veraison and harvest significantly reduces Aspergillus rot and OA formation. Monitoring the extent of Aspergillus rot in bunches infected with toxigenic Aspergillus spp. may give some indication of OA contamination.     

Local oestrogen therapy modulates extracellular matrix and immune response in the vaginal tissue of post‐menopausal women with severe pelvic organ prolapse

This study investigates the effect of local oestrogen therapy (LET) on the expression of proteins participating in collagen/elastin biogenesis and immune markers in vaginal tissues of post‐menopausal women with severe pelvic organ prolapse (POP). Vaginal biopsies were collected from the anterior vaginal wall of informed and consented 52 post‐menopausal women with severe POP undergoing total hysterectomy. Twenty‐nine of the 52 women were treated with LET (in the form of vaginal oestrogen cream or tablet), while the remaining 23 untreated patients served as the controls. This study was approved by Sinai Health System REB. Vaginal tissue specimens were analysed for gene and protein expression using real‐time RT‐PCR and Luminex assays, protein localization and immune cell infiltration were assessed by immunohistochemistry. Forty‐four cytokines were detected. We found that LET application: (a) significantly increased (P < 0.05) gene and protein expression levels of extracellular matrix (ECM) structural proteins, collagen and elastin, as well as the expression of ECM maturation enzyme BMP1; (b) decreased protein expression level of ECM degradation enzymes MMP1, MMP2 and MMP3 accompanied by an increase in their tissue inhibitors, TIMP1 and TIMP4; (c) significantly increased (P < 0.05) the gene and protein expression levels of 14 vaginal cytokines involved in leucocyte infiltration, which was confirmed by immunohistochemistry. Our results indicate that LET plays an important role in the activation of immune system within the local vaginal environment, limiting the undesirable ECM degradation, which supports the strengthening of vaginal ECM in post‐menopausal women, therefore resisting menopause/age‐related changes and inducing urogenital tract tissue regeneration.     

Knock‐on community impacts of a novel vector: spillover of emerging DWV‐B from Varroa‐infested honeybees to wild bumblebees

Novel transmission routes can directly impact the evolutionary ecology of infectious diseases, with potentially dramatic effect on host populations and knock‐on effects on the wider host community. The invasion of Varroa destructor, an ectoparasitic viral vector in Western honeybees, provides a unique opportunity to examine how a novel vector affects disease epidemiology in a host community. This specialist honeybee mite vectors deformed wing virus (DWV), an important re‐emerging honeybee pathogen that also infects wild bumblebees. Comparing island honeybee and wild bumblebee populations with and without V. destructor, we show that V. destructor drives DWV prevalence and titre in honeybees and sympatric bumblebees. Viral genotypes are shared across hosts, with the potentially more virulent DWV‐B overtaking DWV‐A in prevalence in a current epidemic. This demonstrates disease emergence across a host community driven by the acquisition of a specialist novel transmission route in one host, with dramatic community level knock‐on effects.     

The estimated health impact of sodium reduction through food reformulation in Australia: A modeling study

BackgroundThe Australian Government recently established sodium targets for packaged foods to encourage voluntary reformulation to reduce population sodium consumption and related diseases. We modeled the health impact of Australia’s sodium reformulation targets and additional likely health gains if more ambitious, yet feasible sodium targets had been adopted instead.Methods and findingsUsing comparative risk assessment models, we estimated the averted deaths, incidence, and disability-adjusted life years (DALYs) from cardiovascular disease (CVD), chronic kidney disease (CKD) and stomach cancer after implementation of (a) Australia’s sodium targets (overall and by individual companies); (b) United Kingdom’s targets (that covers more product categories); and (c) an optimistic scenario (sales-weighted 25th percentile sodium content for each food category included in the UK program). We used nationally representative data to estimate pre- and post-intervention sodium intake, and other key data sources from the Global Burden of Disease study. Full compliance with the Australian government’s sodium targets could prevent approximately 510 deaths/year (95% UI, 335 to 757), corresponding to about 1% of CVD, CKD, and stomach cancer deaths, and prevent some 1,920 (1,274 to 2,600) new cases and 7,240 (5,138 to 10,008) DALYs/year attributable to these diseases. Over half (59%) of deaths prevented is attributed to reformulation by 5 market-dominant companies. Compliance with the UK and optimistic scenario could avert approximately an additional 660 (207 to 1,227) and 1,070 (511 to 1,856) deaths/year, respectively, compared to Australia’s targets. The main limitation of this study (like other modeling studies) is that it does not prove that sodium reformulation programs will prevent deaths and disease events; rather, it provides the best quantitative estimates and the corresponding uncertainty of the potential effect of the different programs to guide the design of policies.ConclusionsThere is significant potential to strengthen Australia’s sodium reformulation targets to improve its health impact. Promoting compliance by market-dominant food companies will be critical to achieving the potential health gains.

Kathy Trieu and colleagues model the estimated health impact of sodium reformulation targets in Australia.     

Mycobacteria employ two different mechanisms to cross the blood–brain barrier

Central nervous system (CNS) infection by Mycobacterium tuberculosis is one of the most devastating complications of tuberculosis, in particular in early childhood. In order to induce CNS infection, M. tuberculosis needs to cross specialised barriers protecting the brain. How M. tuberculosis crosses the blood–brain barrier (BBB) and enters the CNS is not well understood. Here, we use transparent zebrafish larvae and the closely related pathogen Mycobacterium marinum to answer this question. We show that in the early stages of development, mycobacteria rapidly infect brain tissue, either as free mycobacteria or within circulating macrophages. After the formation of a functionally intact BBB, the infiltration of brain tissue by infected macrophages is delayed, but not blocked, suggesting that crossing the BBB via phagocytic cells is one of the mechanisms used by mycobacteria to invade the CNS. Interestingly, depletion of phagocytic cells did not prevent M. marinum from infecting the brain tissue, indicating that free mycobacteria can independently cause brain infection. Detailed analysis showed that mycobacteria are able to cause vasculitis by extracellular outgrowth in the smaller blood vessels and by infecting endothelial cells. Importantly, we could show that this second mechanism is an active process that depends on an intact ESX‐1 secretion system, which extends the role of ESX‐1 secretion beyond the macrophage infection cycle.     

Molecular mechanisms of viral inhibitors of RIG-I-like receptors

Activation of innate immune signaling pathways through cytosolic RIG-I-like receptors (RLR) is a crucial response that is antagonized by many viruses. A variety of RNA-related pathogen-associated molecular patterns (PAMPS) have been identified and their role in RLR activation has been examined. Recent studies suggest that several virus-encoded components that antagonize RLR signaling interact with and inhibit the interferon (IFN)-α/β activation pathway using both RNA-dependent and RNA-independent mechanisms. The structural basis for these RLR inhibitory mechanisms, as well as the multifunctional nature of viral RLR antagonists, is reviewed in the context of recent biochemical and structural studies.