Type III secretion systems (T3SSs) are protein transport nanomachines that are found in Gram-negative bacterial pathogens and symbionts. Resembling molecular syringes, T3SSs form channels that cross ...the bacterial envelope and the host cell membrane, which enable bacteria to inject numerous effector proteins into the host cell cytoplasm and establish trans-kingdom interactions with diverse hosts. Recent advances in cryo-electron microscopy and integrative imaging have provided unprecedented views of the architecture and structure of T3SSs. Furthermore, genetic and molecular analyses have elucidated the functions of many effectors and key regulators of T3SS assembly and secretion hierarchy, which is the sequential order by which the protein substrates are secreted. As essential virulence factors, T3SSs are attractive targets for vaccines and therapeutics. This Review summarizes our current knowledge of the structure and function of this important protein secretion machinery. A greater understanding of T3SSs should aid mechanism-based drug design and facilitate their manipulation for biotechnological applications.
Increasingly, fisheries researchers and managers seek or are compelled to “bridge” Indigenous knowledge systems with Western scientific approaches to understanding and governing fisheries. Here, we ...move beyond the all‐too‐common narrative about integrating or incorporating (too often used as euphemisms for assimilating) other knowledge systems into Western science, instead of building an ethic of knowledge coexistence and complementarity in knowledge generation using Two‐Eyed Seeing as a guiding framework. Two‐Eyed Seeing (Etuaptmumk in Mi’kmaw) embraces “learning to see from one eye with the strengths of Indigenous knowledges and ways of knowing, and from the other eye with the strengths of mainstream knowledges and ways of knowing, and to use both these eyes together, for the benefit of all,” as envisaged by Elder Dr. Albert Marshall. In this paper, we examine the notion of knowledge dichotomies and imperatives for knowledge coexistence and draw parallels between Two‐Eyed Seeing and other analogous Indigenous frameworks from around the world. It is set apart from other Indigenous frameworks in its explicit action imperative—central to Two‐Eyed Seeing is the notion that knowledge transforms the holder and that the holder bears a responsibility to act on that knowledge. We explore its operationalization through three Canadian aquatic and fisheries case‐studies that co‐develop questions, document and mobilize knowledge, and co‐produce insights and decisions. We argue that Two‐Eyed Seeing provides a pathway to a plural coexistence, where time‐tested Indigenous knowledge systems can be paired with, not subsumed by, Western scientific insights for an equitable and sustainable future.
SARS-CoV-2 infection can present with a broad clinical differential that includes many other respiratory viruses; therefore, accurate tests are crucial to distinguish true COVID-19 cases from ...pathogens that do not require urgent public health interventions. Co-circulation of other respiratory viruses is largely unknown during the COVID-19 pandemic but would inform strategies to rapidly and accurately test patients with respiratory symptoms.
This study retrospectively examined 298,415 respiratory specimens collected from symptomatic patients for SARS-CoV-2 testing in the three months since COVID-19 was initially documented in the province of Alberta, Canada (March-May, 2020). By focusing on 52,285 specimens that were also tested with the Luminex Respiratory Pathogen Panel for 17 other pathogens, this study examines the prevalence of 18 potentially co-circulating pathogens and their relative rates in prior years versus since COVID-19 emerged, including four endemic coronaviruses.
SARS-CoV-2 was identified in 2.2% of all specimens. Parallel broad multiplex testing detected additional pathogens in only 3.4% of these SARS-CoV-2-positive specimens: significantly less than in SARS-CoV-2-negative specimens (p < 0.0001), suggesting very low rates of SARS-CoV-2 co-infection. Furthermore, the overall co-infection rate was significantly lower among specimens with SARS-CoV-2 detected (p < 0.0001). Finally, less than 0.005% of all specimens tested positive for both SARS-CoV-2 and any of the four endemic coronaviruses tested, strongly suggesting neither co-infection nor cross-reactivity between these coronaviruses.
Broad respiratory pathogen testing rarely detected additional pathogens in SARS-CoV-2-positive specimens. While helpful to understand co-circulation of respiratory viruses causing similar symptoms as COVID-19, ultimately these broad tests were resource-intensive and inflexible in a time when clinical laboratories face unprecedented demand for respiratory virus testing, with further increases expected during influenza season. A transition from broad, multiplex tests toward streamlined diagnostic algorithms targeting respiratory pathogens of public health concern could simultaneously reduce the overall burden on clinical laboratories while prioritizing testing of pathogens of public health importance. This is particularly valuable with ongoing strains on testing resources, exacerbated during influenza seasons.
The human immune system consists of an intricate network of tightly controlled pathways, where proteases are essential instigators and executioners at multiple levels. Invading microbial pathogens ...also encode proteases that have evolved to manipulate and dysregulate host proteins, including host proteases during the course of disease. The identification of pathogen proteases as well as their substrates and mechanisms of action have empowered significant developments in therapeutics for infectious diseases. Yet for many pathogens, there remains a great deal to be discovered. Recently, proteomic techniques have been developed that can identify proteolytically processed proteins across the proteome. These “degradomics” approaches can identify human substrates of microbial proteases during infection in vivo and expose the molecular-level changes that occur in the human proteome during infection as an operational network to develop hypotheses for further research as well as new therapeutics. This Perspective Article reviews how proteases are utilized during infection by both the human host and invading bacterial pathogens, including archetypal virulence-associated microbial proteases, such as the Clostridia spp. botulinum and tetanus neurotoxins. We highlight the potential knowledge that degradomics studies of host–pathogen interactions would uncover, as well as how degradomics has been successfully applied in similar contexts, including use with a viral protease. We review how microbial proteases have been targeted in current therapeutic approaches and how microbial proteases have shaped and even contributed to human therapeutics beyond infectious disease. Finally, we discuss how, moving forward, degradomics research can greatly contribute to our understanding of how microbial pathogens cause disease in vivo and lead to the identification of novel substrates in vivo, and the development of improved therapeutics to counter these pathogens.
Causative agents of pneumonia, gastroenteritis, typhoid fever, and plague all utilize a type III secretion system (T3SS) to directly inject proteins into human cells and cause disease. These ...bacterial pathogens are frequently resistant to antibiotics and novel treatment options are needed. The T3SS is essential for virulence and can be inhibited to prevent disease.
T3SS structure and assembly are introduced in this review, highlighting targets for T3SS-specific therapeutics. Promising inhibitors of type III secretion (T3S), their modes of action, and successful techniques for their identification are reviewed. T3S inhibitor research has focused on small molecules identified in high-throughput screens, although recently inhibitors have also been identified or engineered by rational design. Promising compounds have emerged that inhibit T3S and attenuate virulence in several pathogens, including an engineered antibody in clinical trials. T3S inhibitor research may yield effective treatments and prophylactics that are effective against a wide range of human pathogens.
More techniques are needed to identify the mode of action for compounds identified in high-throughput screens, a long-standing challenge. Although only a few groups have attempted rational design of inhibitors, the approach has seen initial success and mechanistic follow-up studies are greatly simplified.
•Medical school admission requirements do not match national vaccination guidelines.•Observed increase in requests for quantitative proof-of-immunity serology.•Quantitative serology titers should not ...be used for asymptomatic screening.•Labs are challenged to support admission requirements with inappropriate testing.•Med school admission requirements should be updated to match national guidelines.
To assess the guideline concordance of medical school requirements for students’ proof-of-immunity in the United States (US) and Canada.
National guidelines for healthcare worker proof-of-immunity to measles, mumps, rubella, and varicella were compared to admission requirements for 62 US and 17 Canadian medical schools.
All surveyed schools accepted at least one recommended form of proof-of-immunity, however, contrary to national guidelines, 16% of surveyed US schools asked for a serologic titer, and only 73–79% US schools accepted vaccination as the sole proof-of-immunity.
The requirement of numerical, non-standardized serologic testing highlights an oversight in medical school admissions documentation. The requirement for quantitative values to demonstrate immunity is not practical from a laboratory standpoint, and is not needed to show individual immunity to these vaccine-preventable diseases. Until a more standardized process is adopted, laboratories will need to provide clear documentation and direction for quantitative titer requests.
The human genome encodes ∼20 mitochondrial proteases, yet we know little of how they sculpt the mitochondrial proteome, particularly during important mitochondrial events such as the initiation of ...apoptosis. To characterize global mitochondrial proteolysis we refined our technique, terminal amine isotopic labeling of substrates, for mitochondrial SILAC (MS-TAILS) to identify proteolysis across mitochondria and parent cells in parallel. Our MS-TAILS analyses identified 45% of the mitochondrial proteome and identified protein amino (N)-termini from 26% of mitochondrial proteins, the highest reported coverage of the human mitochondrial N-terminome. MS-TAILS revealed 97 previously unknown proteolytic sites. MS-TAILS also identified mitochondrial targeting sequence (MTS) removal by proteolysis during protein import, confirming 101 MTS sites and identifying 135 new MTS sites, revealing a wobbly requirement for the MTS cleavage motif. To examine the relatively unknown initial cleavage events occurring before the well-studied activation of caspase-3 in intrinsic apoptosis, we quantitatively compared N-terminomes of mitochondria and their parent cells before and after initiation of apoptosis at very early time points. By identifying altered levels of >400 N-termini, MS-TAILS analyses implicated specific mitochondrial pathways including protein import, fission, and iron homeostasis in apoptosis initiation. Notably, both staurosporine and Bax activator molecule-7 triggered in common 7 mitochondrial and 85 cellular cleavage events that are potentially part of an essential core of apoptosis-initiating events. All mass spectrometry proteomics data have been deposited to the ProteomeXchange Consortium with the dataset identifier PXD009054.
To assess the burden of respiratory virus coinfections with severe acute respiratory coronavirus virus 2 (SARS-CoV-2), this study reviewed 4,818 specimens positive for SARS-CoV-2 and tested using ...respiratory virus multiplex testing. Coinfections with SARS-CoV-2 were uncommon (2.8%), with enterovirus or rhinovirus as the most prevalent target (88.1%). Respiratory virus coinfection with SARS-CoV-2 remains low 1 year into the coronavirus disease 2019 (COVID-19) pandemic.
Intestinal helminth infections occur predominantly in regions where exposure to enteric bacterial pathogens is also common. Helminth infections inhibit host immunity against microbial pathogens, ...which has largely been attributed to the induction of regulatory or type 2 (Th2) immune responses. Here we demonstrate an additional 3-way interaction in which helminth infection alters the metabolic environment of the host intestine to enhance bacterial pathogenicity. We show that an ongoing helminth infection increased colonization by Salmonella independently of T regulatory or Th2 cells. Instead, helminth infection altered the metabolic profile of the intestine, which directly enhanced bacterial expression of Salmonella pathogenicity island 1 (SPI-1) genes and increased intracellular invasion. These data reveal a novel mechanism by which a helminth-modified metabolome promotes susceptibility to bacterial coinfection.
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