A new antibiotic to fight antibiotic-resistant bacteria

Written By: Rebecca Tweedell

Original Article: Racine et al. Antimicrobial Agents and Chemotherapy 2018
The Gist of It:
In the early 1900s, nearly 1/3 of all deaths in the United States were caused by infectious diseases. Now, that has gone down to just 2% of deaths. One of the major reasons for this sharp decrease has been the discovery and use of antibiotics. Over time, the early antibiotics have been improved and optimized so that they work really well. However, today we rely on the same classes of antibiotics that we have been using since the 1970s. And with continued use of the same antibiotics, bacteria have been able to develop antibiotic resistance, meaning some of them can survive even in the presence of our best antibiotics. Infections with these antibiotic-resistant “super bugs” can lead to a long and difficult battle for the body that cannot always be won; antibiotic-resistant infections are fatal about 30% of the time. In light of the dangers of these antibiotic-resistant bacteria, there has been a lot of work to identify new antibiotics that can kill bacteria in new ways. Recently, researchers identified a new class of antibiotics known as the odilorhabdins. These antibiotics keep bacteria from making the proteins they need to grow, divide, and survive by sticking to the bacterial ribosome (the part of the bacterium responsible for making the proteins) and stopping it from working. While other classes of antibiotics also stop the protein-making process, the odilorhabdins stick to a unique place on the ribosome, which allows them to work even when the bacterium is already resistant to other antibiotics. Researchers from a collaboration between a biotechnology company called Nosopharm and the Emerging Antibiotic Resistance Unit at the University of Fribourg have been working with a specific odilorhabdin called NOSO-502. In a recent paper, they showed that NOSO-502 could successfully kill several different types of antibiotic-resistant bacteria in culture. Even more importantly, they tested NOSO-502 in mouse models of sepsis, lung infection, and upper urinary tract infection and found that the antibiotic could successfully kill bacteria in all these models. NOSO-502 could also protect the mice from dying in the normally fatal sepsis infection model. This is an important step toward being able to use NOSO-502 to treat infections in people. Adding new antibiotics like NOSO-502 to our arsenal will be critically important in the growing fight against antibiotic-resistant bacteria.
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Odilorhabdins like NOSO-502, can act as potent antibiotics by targeting a new place on the ribosome, preventing bacteria from making proteins.

The Nitty Gritty:
Racine et al. performed a series of in vitro and in vivo experiments to characterize the safety and efficacy of NOSO-502. They first determined the minimal inhibitory concentration (MIC) of NOSO-502 for a number of Gram-positive and Gram-negative reference strains; MIC values as low as 0.5 ug/mL were recorded. Furthermore, the MIC values against several recent clinical isolates, including carbapenem-, fluoroquinolone-, aminoglycoside-, and polymyxin B-resistant strains, were determined and found to be similar to values determined for the reference strains. The researchers also performed a suite of safety analyses with NOSO-502. Cytotoxicity was tested using human kidney tissue, human renal proximal tubular epithelial cells, HK-2 cells, and HepG2 cells; cardiotoxicity was tested using the automated patch clamp ether-a-go-go related gene potassium channel assay; and genotoxicity was tested using the micronucleus assay. In all assays, NOSO-502 exhibited no significant safety issues. Finally, they tested NOSO-502 in four different mouse models: a neutropenic sepsis infection model with E. coli EN122, an upper urinary tract infection model with E. coli UTI89, a neutropenic intraperitoneal sepsis infection model with E. coli ATCC BAA-2469, and a neutropenic lung infection model with K. pneumoniae NCTC 13442. In all four models, NOSO-502 significantly reduced the level of bacteria in all tested tissues compared to vehicle-treated controls.
Original Research Article:  Emilie Racine, Patrice Nordmann, Lucile Pantel, Matthieu Sarciaux, Marine Serri, Jessica Houard, Philippe Villain-Guillot, Anthony Demords, Carina Vingsbo Lundberg, and Maxime Gualtieri. “In vitro and in vivo characterization of NOSO-502, a novel inhibitor of bacterial translation.Antimicrobial Agents and Chemotherapy 62 (2018): e01016-18.

Decoding a new way that cancer hides from our immune system

Written By: Kaitlyn Sadtler

Original Article: Stanczak et al. JCI 2018
The Gist of It:
How does your body tell its own cells from bacterial cells? What’s more – how does it tell cancerous cells from healthy cells? It’s a tricky problem because cancerous cells and healthy cells are both technically your cells, just one is bad. There are many ways that your body protects itself from creating immune cells that will mistake its own healthy cells for dangerous invaders and attack them. If these systems go awry, on one side you can see autoimmune diseases, such as multiple sclerosis and type-1 diabetes, and on the other side, diseases such as cancer can evade detection as dangerous by masquerading as normal cells. So, figuring out how these cancer cells are evading detection by our immune system can help us find targets for new cancer therapeutics. In a recent paper out of the University Hospital Basel in Switzerland, researchers describe a way in which cancer cells are camouflaged as normal cells. When certain kinds of immune cells – T cells — enter a tumor, things can (generally) go one of two ways: either the T cells will recognize the cancer and kill the cells, or they will turn into what we call regulatory T cells. As the name suggests, these cells regulate the immune response, dampening inflammation – which is exactly what we don’t want when it comes to cancer. We want our T cells to see the cancer and attack it. Michal Stanczak and colleagues describe molecules known as Siglecs on T cells that are responsible for recognizing patterns in the proteins of normal cells so that the T cells know not to kill those cells – because they are us, or “self”. Cancer, which is still technically us, but a damaged/altered version, can make T cells increase the amount of Siglec they produce. This means that the T cells are being told that the cancer is their own body so therefore they shouldn’t attack it. These studies present a new potential target for cancer treatment; decreasing the amount of Siglecs in T cells can decrease cancer’s ability to hide from our immune system.

 

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When T Cells express high amounts of Siglec9, they can’t see that the cancer is dangerous, and do not act to defend against it.

The Nitty Gritty:
Stanczak et al. described a regulatory pathway by which tumor-infiltrating T cells upregulated Siglecs. These Siglecs, specifically Siglec-9, are acting as self-associated molecular pattern (SAMP) receptors which are associated with other regulatory markers such as PD-1 and TIM3. Such increases in Siglec-9 expression on tumor-infiltrating lymphocytes were noted in clinical samples from patients with non-small cell lung cancer, colorectal cancer, and ovarian cancer. By inducing Siglec-9 expression on CD4+ T cells in a murine MC38 model, researchers showed that expression of Siglec-9 on CD4+ T cells correlated with an increased tumor volume and growth rate compared to a wild type control. Furthermore, if cells were desialynated (either enzymatically or through knockout of a rate-limiting enzyme in the sialic acid biosynthesis pathway, UDP-N-acetylglucosamine-2-epimerase) CD8+ T cell-mediated cell killing was increased in vitro. This presents a putative new therapeutic target for cancer immunotherapies.
Original Research Article: Stanczak, Michal A., et al. “Self-associated molecular patterns mediate cancer immune evasion by engaging Siglecs on T cells.” The Journal of clinical investigation (2018).

Defend yourself!… against the common cold: how smoking can blunt your antiviral response

Written By: Padmini Pillai

Original Article: Mihaylova et al. Cell Reports 2018

The Gist of It:

As the cold season is upon us, it’s time we think about how to protect ourselves against rhinovirus, the most frequent cause of the common cold. Rhinovirus enters the respiratory tract through the nasal passages and can spread down to larger airways of the lungs called bronchi. Epithelial cells, which line the respiratory tract, can detect rhinovirus and trigger immune responses. Although nasal and bronchial epithelial cells can be infected by rhinovirus, a study published this week demonstrates that they respond to infection in different ways.
The authors obtained human nasal and bronchial airway epithelial cells and infected them with rhinovirus. After infection, nasal epithelial cells produced significantly more interferon, a key antiviral molecule that turns on a plethora of genes to stop the virus. On the other hand, bronchial cells produced less interferon but higher amounts of a molecule called NRF2. NRF2 protects cells against damage triggered by injury and inflammation, and is often found in large amounts in the lungs of smokers.
Therefore, immune responses by cell types in different parts of the respiratory tract, from the nose down to the lungs, react to stimuli differently. This makes sense — your nasal passage encounters many pathogens and serves as the entry point for viruses into the respiratory tract, as well as your frontline defense against them, so interferon is critical for protection there. Further down in the bronchi, the consequences of inflammation and damage to the delicate lining in large airways responsible for carrying oxygen into the body is far too great, so pathways preventing damage and promoting survival to bronchial cells are of utmost importance.
Interestingly, the authors also discovered that NRF2 inhibits antiviral responses. If nasal cells were exposed to an extract of cigarette smoke and then infected with rhinovirus, they saw increased NRF2 and enhanced viral replication.  So here’s the take-home message: cigarette smoking or exposure to other airway irritants such as car exhaust or environmental pollutants could inhibit your antiviral responses by turning on NRF2, making you susceptible to respiratory infections such as the common cold. Prior research from Dr. Ellen Foxman showed that lower temperatures in the nasal passage also inhibit production of interferon by nasal epithelial cells (looks like the old wives’ tale to cover your nose in the cold may be true!). So this winter, try to stay away from smokers and keep those nasal passages warm to protect yourself from the common cold!
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Different places in your airways respond differently to viruses — and in case you needed more evidence — don’t smoke! If you smoke you’re more vulnerable to viral infections.

The Nitty Gritty:

The authors cultured primary human nasal and bronchial epithelial cells. After inoculation with rhinovirus 1b or transfection with the RIG-I ligand SLR14, nasal cells produced significantly more IFNλ1 and upregulated IFNβ and ISG expression. RNA-seq and ingenuity pathway analysis revealed that stimulation with SLR14 led to a dominant interferon response in nasal cells, while bronchial cells exhibited transcripts related to the NRF2 pathway. Knockdown of NRF2 in bronchial cells resulted in increased IFN and ISG expression. Pretreatment of nasal cells with the NRF2 activator sulforaphane significantly decreased interferon and ISG transcripts after SLR14 stimulation. siRNA knockdown of NRF2 in nasal cells inoculated with rhinovirus led to enhanced ISG induction and even stronger viral restriction. Nasal epithelial cells pretreated with cigarette smoking extract and inoculated with rhinovirus had higher viral tiers, increased expression of NRF2, and decreased expression of the ISG IFIT2. This study demonstrates two different defense mechanisms in airway epithelial cells from different regions of the respiratory tract and reveals that activation of NRF2 by oxidative stress can inhibit antiviral responses.
Original Research Article: Mihaylova, Valia T., et al. “Regional Differences in Airway Epithelial Cells Reveal Tradeoff between Defense against Oxidative Stress and Defense against Rhinovirus.” Cell Reports 24.11 (2018): 3000-3007.

Light-induced origami folding of millimeter sized objects

Written by: Ritu Raman

Original Article: Zhao et al. 2017

The Gist of It:

At some point in your life (maybe right after your class in school read “Sadako and the Thousand Paper Cranes”), you’ve probably experimented with origami. This ancient art of paper folding has recently garnered a lot of interest in the engineering community, because it’s a really well-established way of turning a simple 2D material into a complex 3D structure. This could potentially have a lot of applications, ranging from the design of futuristic spacecraft to tiny implantable medical devices. A recent paper, published in the open-access journal Science Advances, demonstrated a really elegant approach for manufacturing millimeter-scale origami structures with complex 3D shapes. The technique relies on a phenomenon known as “photopolymerization”, using light to turn a liquid material into a solid material. The transition from liquid to solid causes the material to shrink in total volume. In this study, the team projected light onto a vat of liquid, and the surface of the liquid closest to the light turned solid first. As time went on, the liquid deeper in the vat started turning solid as well. We can think of this as two layers, where layer 1 turns solid first and layer 2 turns solid next. When layer 2 starts to shrink, it pulls against layer 1, causing the whole two-layer solid to bend inward (see figure below). This shrinkage-induced bending can be used as “hinges” in a flat 2D pattern to turn it into a 3D shape. The team was able to use this simple technique to turn flat sheets into cubes, flowers, and even cranes! The method presented in this paper could be used by other engineers in future to build complex 3D devices for a variety of real-world applications. I’m really excited to see the problems they solve!
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Folding of 2D materials into 3D structures by using light to create origami

The Nitty Gritty:

Zhao et al. formulated a photo-sensitive liquid resin by mixing the biocompatible hydrogel polymer poly (ethylene glycol) diacrylate (PEGDA) with the photoinitiator phenylbis(2,4,6-trimethylbenzoyl) phosphine oxide (Irgacure 819). A photoabsorber, Sudan I, was used to regulate the depth of penetration of light into the liquid resin. This resin, similar to that used in a variety of papers on stereolithographic 3D printing, was then irradiated with an LED projecting ultraviolet light in the wavelength range at which Irgacure 819 is active. The team investigated the effect of light irradiation for different lengths of time on overall thickness of the polymerized material, as well as the resultant shrinkage-induced bending of the material. They conducted theoretical calculations to form a mathematical model for the internal stresses in the material as a resultant of light exposure, and matched their experimental data with great accuracy. With this predictive model, they were able to very precisely predict the folding behavior of printed structures, thus generating complex 3D shapes from 2D printed layers.
Original Research Article: Zhao, Z., Wu, J., Mu, X., Chen, H., Qi, H.J. and Fang, D., 2017. Origami by frontal photopolymerizationScience Advances3(4), p.e1602326.