Tag Archives: Drug discovery

Transforming antibiotic resistance testing: a novel, rapid and affordable technique

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Thought LeadersDr. Sandor KasasResearch LeadEcole Polytechnique Fédérale de Lausanne

News Medical speaks with Dr. Sandor Kasas, a lead researcher at Ecole Polytechnique Fédérale de Lausanne in Switzerland. Here we discuss his recent development of a novel and highly efficient method for rapid antibiotic susceptibility testing using optical microscopy.

The new technique, known as Optical Nanomotion Detection (ONMD), is an extremely rapid, label-free, and single-cell sensitive method to test for antibiotic sensitivity. ONMD requires only a traditional optical microscope equipped with a camera or mobile phone. The simplicity and efficiency of the technique could prove to be a game changer in the field of antibiotic resistance.

Please can you introduce yourself, tell us about your career background, and what inspired your career in biology and medicine?

I graduated in medicine but never practiced in hospitals or medical centers. After my studies, I started working as an assistant in histology at the University of Fribourg in Switzerland. My first research projects included image processing, scanning tunneling, and atomic force microscopy.

Later, and for most of the rest of my scientific carrier, I focused primarily on the biological applications of AFM. For the past ten years, my research interest is about nanomotion, i.e., the study of oscillations at a nanometric scale of living organisms.

Image Credit: dominikazara/Shutterstock.comImage Credit: dominikazara/Shutterstock.com

You started working on biological applications of the atomic force microscope (AFM) in 1992. From your perspective, how has the antibiotic resistance landscape changed over the last two decades? What role has the advancement in technology played in furthering our understanding?

In the early ’90s, the AFM was mainly used for imaging. Later, AFM microscopists noticed that the instrument could also be used to explore the mechanical properties of living organisms. More recently, many “exotic” applications of the AFM have emerged, such as its use to weigh single cells or study their oscillations at the nanometric scale. In the 1990s, antibiotic resistance was not as serious a problem as today, but several teams were already using AFM to assess the effects of antibiotics on bacterial morphology.

The first investigations were limited to structural changes, but later, as the fields of application of AFM expanded, the instrument made it possible to monitor the mechanical properties of the bacterial cell wall upon exposure to antibiotics. In the 2010s, with G. Longo and G. Dietler, we demonstrated that AFM could also track nanoscale oscillations of living organisms. The very first application we had in mind was using the instrument to perform rapid antibiotic susceptibility testing.

We have therefore developed devices based on dedicated AFM technology to perform fast AST (i.e., in 2-4h). AFM-based nanomotion detection instruments are already implemented in medical centers in Switzerland, Spain, and Austria. However, this type of device has some drawbacks, including the need to fix the organism of interest on a cantilever. To overcome this limitation, we have developed with R. Willaert a nanomotion detector based on an optical microscope.

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Your most recent research has led to the development of a novel and highly efficient technique for rapid antibiotic susceptibility testing using optical microscopy. Please could you tell us why the development of rapid, affordable, and efficient testing methods is so important in the world of antimicrobial resistance?

Rapid antibiotic susceptibility testing could reduce the use of broad-spectrum antibiotics. Traditional ASTs based on replication rate require 24 hours (but up to 1 month in the case of tuberculosis) to identify the most effective antibiotic. Doctors prescribe broad-spectrum antibiotics between the patient’s admission to a medical center and the results of the AST.

These drugs quickly improve patients’ conditions but, unfortunately, promote resistance. A rapid AST that could identify the most suitable antibiotic within 2-4 hours would eliminate broad-spectrum antibiotics and increase treatment efficiency and reduce the development of resistant bacterial strains. Since bacterial resistance is a global problem, rapid ASTs should also be implemented in developing countries. Therefore, affordable and simple-to-use tests are needed.

Image Credit: Fahroni/Shutterstock.comImage Credit: Fahroni/Shutterstock.com

Were there any limitations and obstacles you faced in the research process? If so, how did you overcome them?

Antibiotic sensitivity detection with ONMD is very similar to the AFM-based technique. As long as the bacterium is alive, it oscillates; if the antibiotic is effective, it kills the micro-organism, and its oscillations stop. The first limitation we faced when developing the ONMD was our microscopes’ depth of field of view. To prevent the bacteria from leaving the focal plane of the optical microscope during the measurement, we had to constrain the microbes into microfluidic channels a few micrometers high.

Microfabrication of such devices is relatively straightforward in an academic environment, but we were looking for simpler solutions. One option for constructing such a device is to use 10-micron double-sided rubber tape. It allows you to “build” a microfluidic chamber in 5 minutes with two glass coverslips and a puncher.

Another challenge was nanoscale motion detection. For this purpose, we used freely available cross-correlation algorithms that achieve sub-pixel resolution. (i.e., a few nanometers). We first developed the ONMD for larger organisms, such as yeast cells, and expanded the method to bacteria. This further development took us around two years.

You worked alongside Dr. Ronnie Willaert, a professor of structural biology at Vrije Universiteit Brussel, on developing this new rapid AST technique. How did your areas of expertise and research backgrounds complement each other in developing ONMD?

R. Willaert is an expert in yeast microbiology and microfluidics, while our team in Lausanne is primarily involved in AFM-based nanomotion detection and applying AFM to clinically relevant problems. The two teams were supported by a joint grant from the Swiss National Science Foundation and the Research Foundation Flanders (FWO) which enabled the development of the method.

The field of antimicrobial resistance requires a high level of international collaboration, with everyone working together to achieve a common goal. With antimicrobial resistance rising to dangerously high levels in all parts of the world, how important is collaboration in this field?

Our project required expertise in various fields, such as microbiology, microscopy, microfluidics, programming, and data processing. In the development of rapid AST instruments and many others, only a multidisciplinary approach and close collaboration between teams with complementary expertise is today the only path to success.

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You and Dr. Willaert have said, ‘The simplicity and efficiency of the method make it a game-changer in the field of AST.’ Can you please expand on what makes ONMD a game changer in the AST field and what implications this research could have in clinical and research settings?

As mentioned earlier, bacterial resistance is a global health problem. Rapid AST should also be easily implemented in developing countries to limit the spread of resistant strains. The cheaper and simpler the technique, the more likely it is to be used on a large scale. We are convinced that the ONMD approach can meet these requirements. ONMD could also be used for drug discovery or basic research.

While we recognize the importance of rapid AST, what next steps must be taken before this technique can be used globally in research and clinical landscapes?

For fundamental research, there are no other important developments to be made. Any reasonably equipped research center can implement the technique and use it. Regarding implementing the technique in developing countries or extreme environments, stand-alone devices have to be used, which have yet to be manufactured.

There is a rapidly expanding need for efficient AST globally; however, the need for affordable, accessible, and simple techniques are of grave importance in developing countries disproportionately affected by antibiotic resistance due to existing global health disparities. Could this rapid AST technique be utilized in low-middle-income countries to slow the growing spread of multi-resistant bacteria? What would this mean for global health?

We are confident that ONMD-based AST testing can soon be implemented in research centers in both developed and developing countries. However, accreditation by the health authorities is necessary to use it as a standard diagnostic tool; this process can take several years, depending on the government health policy.

What’s next for you and your research? Are you involved in any exciting upcoming projects?

We want to develop a self-contained device for extreme environments. It would consist of a small microscope equipped with a camera and a data processing unit. The microfluidic part of the device could contain different antibiotics ready to be tested.

The ONMD technique could also monitor contamination levels in enclosed environments such as submarines, spacecraft, and space stations. One of our recent projects is funded by the European Space Agency (ESA) to develop a rapid antifungal susceptibility test that could work in microgravity. Additionally, ONMD could be used for even more exciting projects, such as chemistry-independent life detection in the search for extraterrestrial life.

Where can readers find more information?

  • Villalba MI, Rossetti E, Bonvallat A, Yvanoff C, Radonicic V, Willaert RG*, Kasas S.*.Simple optical nanomotion method for single-bacterium viability and antibiotic response testing. PNAS 2023, May 2;120(18):e2221284120. doi: 10.1073/pnas.2221284120. Epub 2023 Apr 24. PMID: 37094120. * Contributed equally. https://doi.org/10.1073/pnas.2221284120
  • Radonicic, V.; Yvanoff, C.; Villalba, M.I.; Devreese, B.; Kasas, S.; Willaert, R.G. Single-Cell Optical Nanomotion of Candida albicans in Microwells for Rapid Antifungal Susceptibility Testing. Fermentation 2023, 9:365. https://doi.org/10.3390/fermentation9040365
  • Parmar P, Villalba MI, Horii Huber AS, Kalauzi A, Bartolić D, Radotić K, Willaert RG, MacFabe DF and Kasas S. Mitochondrial nanomotion measured by optical microscopy. Front. Microbiol. 2023, 14:1133773. https://doi.org/10.3389/fmicb.2023.1133773
  • Starodubtseva MN, Irina A. Chelnokova IA, Shkliarava NM, Villalba MI, Tapalski DV, Kasas S, Willaert RG. Modulation of the nanoscale motion rate of Candida albicans by X-rays. Front. Microbiol. 2023, 14:1133027. https://doi.org/10.3389/fmicb.2023.1133027
  • Radonicic V, Yvanoff C, Villalba MI, Kasas S, Willaert RG. The Dynamics of Single-Cell Nanomotion Behaviour of Saccharomyces cerevisiae in a Microfluidic Chip for Rapid Antifungal Susceptibility Testing. Fermentation. 2022; 8(5):195. https://doi.org/10.3390/fermentation8050195

About Dr. Sandor Kasas

Nanomotion is a fascinating and novel approach to observing living organisms.

Our team focuses almost exclusively on recording the nanomotion of bacterial mitochondria and mammalian cells with optical and AFM-based devices.

Recently, we demonstrated that the technique could be used not only for fast antimicrobial sensitivity testing but also to explore the metabolism of unicellular organisms. We hope our efforts will permit us to expand the application domains of ONMD.

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New compound with antibacterial activity shows promising results within one hour in laboratory trials

Resistance to antibiotics is a problem that alarms the medical and scientific community. Bacteria resistant to three different classes of antibiotics, known as multi-drug resistant (MDR) bacteria, are far from rare. Some are even resistant to all currently available treatments and are known as pan-drug resistant (PDR). They are associated with dangerous infections and listed by the World Health Organization (WHO) as priority pathogens for drug development with maximum urgency.

An article published in a special issue of the journal Antibiotics highlights a compound with antibacterial activity that presented promising results within one hour in laboratory trials.

The study was led by Ilana Camargo, last author of the article, and conducted during the doctoral research of first author Gabriela Righetto at the Molecular Epidemiology and Microbiology Laboratory (LEMiMo) of the University of São Paulo’s São Carlos Institute of Physics (IFSC-USP) in Brazil.

The compound we discovered is a new peptide, Pln149-PEP20, with a molecular framework designed to enhance its antimicrobial activity and with low toxicity. The results can be considered promising insofar as the trials involved pathogenic bacteria associated with MDR infections worldwide.”

Adriano Andricopulo, co-author of the article

Although novel antibacterial drugs are urgently needed, the pharmaceutical industry is notoriously uninterested in pursuing them, mainly because research in this field is time-consuming and costly, requiring very long lead times to bring viable active compounds to market.

The Center for Innovation in Biodiversity and Drug Discovery (CIBFar), a Research, Innovation and Dissemination Center (RIDC) set up and funded by FAPESP, looks for molecules that can be used to combat multidrug-resistant bacteria.

Camargo and Andricopulo are researchers at CIBFar, as are two other co-authors who study promising bactericidal compounds: Leila Beltramini and José Luiz Lopes.

For over a decade, the group formed by the collaboration between Beltramini and Lopes has analyzed Plantaricin 149 and its analogs. Plantaricins are substances produced by the bacterium Lactobacillus plantarum to combat other bacteria.

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Lactobacillus plantarum is commonly found in nature, especially in anaerobic plant matter, and in many fermented vegetable, meat and dairy products.

In the case of Plantaricin 149, Japanese researchers were the first to report its bactericidal action (in 1994) and since then scientists have been interested in obtaining more efficient synthetic analogs (molecules with small structural differences). In 2007, one of the first projects completed by the CIBFar team showed that the peptide inhibits pathogenic bacteria such as Listeria spp. and Staphylococcus spp. They then began studying synthetic analogs with stronger bactericidal activity than the original (causing more damage to the membrane of the combated microorganisms).

With the support of a scholarship from FAPESP, Righetto synthesized 20 analogs of Plantaricin 149, finding that Pln149-PEP20 had the best results so far and was also half the size of the original peptide. “The main advances in our research consist of the development of this smaller, more active and less toxic molecule, and the characterization of its action and propensity to develop resistance. It has proven to be highly promising in vitro – active against MDR bacteria and extensively resistant bacteria,” said Camargo, principal investigator for the project.

LEMiMo, the laboratory where the studies were conducted, has experience in characterizing bacterial isolates involved in outbreaks of hospital infections and holds a collection of bacteria selected for these trials in search of novel active compounds. The bacteria have the resistance profiles currently of greatest concern and were isolated during hospital outbreaks.

They are known in the scientific community by the term ESKAPE, an acronym for the scientific names of six highly virulent and antibiotic-resistant bacterial pathogens: Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter spp.

Further research can now be conducted to investigate the molecule’s action mechanism in more depth, to look for formulations, and possibly to develop an application. “In terms of the action mechanism, it’s also possible to use the cell morphology of the bacteria to identify cellular pathways affected by the peptide,” Righetto said. “As for optimization, the molecule can be functionalized by being linked to macrostructures, and the amino acid sequence can be modified.” Research is also needed on its cytotoxicity and on its selectivity (whether it affects healthy cells).

“We’re living in times of major global public health hazards due to a lack of antimicrobials that can be used to treat infections caused by extremely resistant bacteria. Antimicrobial peptides are targets of great interest for the development of novel candidate drugs. This novel molecule has the potential to be used as an innovative antimicrobial therapy, but further modifications and molecular optimizations still need to be investigated,” Andricopulo said.

Publication of the article also involved Harvard Medical School’s Infectious Disease Institute in Boston (USA) via researchers Paulo José Martins Bispo and Camille André.

Journal reference:

Righetto, G. M., et al. (2023). Antimicrobial Activity of an Fmoc-Plantaricin 149 Derivative Peptide against Multidrug-Resistant Bacteria. doi.org/10.3390/antibiotics12020391.

Reconstructing ancient bacterial genomes can revive previously unknown molecules – offering a potential source for new antibiotics

Microorganisms – in particular bacteria – are skillful chemists that can produce an impressive diversity of chemical compounds known as natural products. These metabolites provide the microbes major evolutionary advantages, such as allowing them to interact with one another or their environment and helping defend against different threats. Because of the diverse functions bacterial natural products have, many have been used as medical treatments such as antibiotics and anti-cancer drugs.

The microbial species alive today represent only a tiny fraction of the vast diversity of microbes that have inhabited Earth over the past 3 billion years. Exploring this microbial past presents exciting opportunities to recover some of their lost chemistry.

Directly studying these metabolites in archaeological samples is virtually impossible because of their poor preservation over time. However, reconstructing them using the genetic blueprints of long-dead microbes could provide a path forward.

We are a team of anthropologists, archaeogeneticists and biochemists who study ancient microbes. By generating previously unknown chemical compounds from the reconstructed genomes of ancient bacteria, our newly published research provides a proof of concept for the potential use of fossil microbes as a source of new drugs.

The cellular machinery producing bacterial natural products is encoded in genes that are typically in close proximity to one another, forming what are called biosynthetic gene clusters. Such genes are difficult to detect and reconstruct from ancient DNA because very old genetic material breaks down over time, fragmenting into thousands or even millions of pieces. The end result is numerous tiny DNA fragments less than 50 nucleotides long all mixed together like a jumbled jigsaw puzzle.

We sequenced billions of such ancient DNA fragments, then improved a bioinformatic process called de novo assembly to digitally order the ancient DNA fragments in stretches of up to 100,000 nucleotides long – a 2,000-fold improvement. This process allowed us to identify not only what genes were present, but also their order in the genome and the ways they differ from bacterial genes known today – key information to uncovering their evolutionary history and function.

This method allowed us to take an unprecedented look at the genomes of microbes living up to 100,000 years ago, including species not known to exist today. Our findings push back the previously oldest reconstructed microbial genomes by more than 90,000 years.

In the microbial genomes we reconstructed from DNA extracted from ancient tooth tartar, we found a gene cluster that was shared by a high proportion of Neanderthals and anatomically modern humans living during the Middle and Upper Paleolithic that lasted from 300,000 to 12,000 years ago. This cluster bore the molecular hallmarks of very ancient DNA and belonged to the bacterial genus Chlorobium, a group of green sulfur bacteria capable of photosynthesis.

We inserted a synthetic version of this gene cluster into a “modern” bacterium called Pseudomona protegens so it could produce the chemical compounds encoded in the ancient genes. Using this method, we were able to isolate two previously unknown compounds we named paleofuran A and B and determine their chemical structure. Resynthesizing these molecules in the lab from scratch confirmed their structure and allowed us to produce larger quantities for further analysis.

By reconstructing these ancient compounds, our findings highlight how archaeological samples could serve as new sources of natural products.

Microbes are constantly evolving and adapting to their surrounding environment. Because the environments they inhabit today differ from those of their ancestors, microbes today likely produce different natural products than ancient microbes from tens of thousands of years ago.

As recently as 25,000 to 10,000 years ago, the Earth underwent a major climate shift as it transitioned from the colder and more volatile Pleistocene Epoch to the warmer and more temperate Holocene Epoch. Human lifestyles also dramatically changed over this transition as people began living outside of caves and increasingly experimented with food production. These changes brought them into contact with different microbes through agriculture, animal husbandry and their new built environments. Studying Pleistocene-era bacteria may yield insights into bacterial species and biosynthetic genes no longer associated with humans today, and perhaps even microbes that have gone extinct.

While the amount of data collected by scientists on biological organisms has exponentially increased over the past few decades, the number of new antibiotics has stagnated. This is particularly problematic when bacteria are able to evade existing antibiotic treatments faster than researchers can develop new ones.

By reconstructing microbial genomes from archaeological samples, scientists can tap into the hidden diversity of natural products that would have otherwise been lost over time, increasing the number of potential sources from which they can discover new drugs.

Our study has shown that it is possible to access natural products from the past. To tap into the vast diversity of chemical compounds encoded in ancient DNA, we now need to streamline our methodology to be less labor-intensive.

We are currently optimizing and automating our process to identify biosynthetic genes in ancient DNA more quickly and reliably. We are also implementing robotic liquid handling systems to complete the time-consuming pipetting and bacterial cultivation steps in our methods. Our goal is to scale up the process to be able to translate a vast amount of data on ancient microbes into the discovery of new therapeutic agents.

Although we can recreate ancient molecules, their biological and ecological roles are difficult to decipher. Since the bacteria that originally produced these compounds no longer exist, we cannot culture or genetically manipulate them. Further study will need to rely on similar bacteria that can be found today. Whether or not the functions of these compounds have remained the same in the modern relatives of ancient microbes remains to be tested. Although the original functions of these compounds for ancient microbes may be unknown, they still have the potential to be repurposed to treat modern diseases.

Ultimately, we aim to shed new light on microbial evolution and fight the current antibiotic crisis by providing a new time axis for antibiotic discovery.

Christina Warinner

Alexander Hübner

Pierre Stallforth

The Conversation

New biologic effective against major infection in early tests

Researchers at NYU Grossman School of Medicine and Janssen Biotech, Inc. have shown in early tests that a bioengineered drug candidate can counter infection with Staphylococcus aureus — a bacterial species widely resistant to antibiotics and a major cause of death in hospitalized patients.

Experiments demonstrated that SM1B74, an antibacterial biologic agent, was superior to a standard antibiotic drug at treating mice infected with S. aureus, including its treatment-resistant form known as MRSA.

Published online April 24 in Cell Host & Microbe,the new paper describes the early testing of mAbtyrins, a combination molecule based on an engineered version of a human monoclonal antibody (mAb), a protein that clings to and marks S. aureus for uptake and destruction by immune cells. Attached to the mAb are centyrins, small proteins that prevent these bacteria from boring holes into the human immune cells in which they hide. As the invaders multiply, these cells die and burst, eliminating their threat to the bacteria.

Together, the experimental treatment targets ten disease-causing mechanisms employed by S. aureus, but without killing it, say the study authors. This approach promises to address antibiotic resistance, say the researchers, where antibiotics kill vulnerable strains first, only to make more space for others that happen to be less vulnerable until the drugs no longer work.

“To our knowledge, this is the first report showing that mAbtyrins can drastically reduce the populations of this pathogen in cell studies, and in live mice infected with drug-resistant strains so common in hospitals,” said lead study author Victor Torres, PhD, the C.V. Starr Professor of Microbiology and director of the NYU Langone Health Antimicrobial-Resistant Pathogen Program.”Our goal was to design a biologic that works against S. aureus inside and outside of cells, while also taking away the weapons it uses to evade the immune system.”

One-third of the human population are carriers of S. aureus without symptoms, but those with weakened immune systems may develop life-threatening lung, heart, bone, or bloodstream infections, especially among hospitalized patients.

Inside Out

The new study is the culmination of a five-year research partnership between scientists at NYU Grossman School of Medicine and Janssen to address the unique nature of S. aureus.

The NYU Langone team together with Janssen researchers, published in 2019 a study that found that centyrins interfere with the action of potent toxins used by S. aureus to bore into immune cells. They used a molecular biology technique to make changes in a single parental centyrin, instantly creating a trillion slightly different versions of it via automation. Out of this “library,” careful screening revealed a small set of centyrins that cling more tightly to the toxins blocking their function.

Building on this work, the team fused the centyrins to a mAb originally taken from a patient recovering from S. aureus infection. Already primed by its encounter with the bacteria, the mAb could label the bacterial cells such that they are pulled into bacteria-destroying pockets inside of roving immune cells called phagocytes. That is unless the same toxins that enable S. aureus to drill into immune cells from the outside let it drill out of the pockets to invade from the inside.

In a “marvel of bioengineering,” part of the team’s mAbtyrin serves as the passport recognized by immune cells, which then engulf the entire, attached mAbtyrin, along with its centyrins, and fold it into the pockets along with bacteria. Once inside, the centyrins block the bacterial toxins there. This, say the authors, sets their effort apart from antibody combinations that target the toxins only outside of cells.

The team made several additional changes to their mAbtyrin that defeat S. aureus by, for instance, activating chain reactions that amplify the immune response, as well by preventing certain bacterial enzymes from cutting up antibodies and others from gumming up their action.

In terms of experiments, the researchers tracked the growth of S. aureus strains commonly occurring in US communities in the presence of primary human immune cells (phagocytes). Bacterial populations grew almost normally in the presence of the parental antibody, slightly less well in the presence of the team’s engineered mAb, and half as fast when the mAbtyrin was used.

In another test, 98% of mice treated with a control mAb (no centyrins) developed bacteria-filled sores on their kidneys when infected with a deadly strain of S. aureus, while only 38% of mice did so when treated with the mAbtyrin. Further, when these tissues were removed and colonies of bacteria in them counted, the mice treated with the mAbtyrin had one hundred times (two logs) fewer bacterial cells than those treated with a control mAb.

Finally, the combination of small doses of the antibiotic vancomycin with the mAbtyrin in mice significantly improved the efficacy of the mAbtyrin, resulting in maximum reduction of bacterial loads in the kidneys and greater than 70% protection from kidney lesions.

“It is incredibly important,” said Torres, “that we find new ways to boost the action of vancomycin, a last line of defense against MRSA.”

Along with Torres, authors from the Department of Microbiology at NYU Langone were Rita Chan, Ashley DuMont, Keenan Lacey, Aidan O’Malley, and Anna O’keeffe. The study authors included 13 scientists from Janssen Research & Development (for details see the study manuscript).

This work was supported by Janssen Biotech, Inc., one of the Janssen Pharmaceutical Companies of Johnson & Johnson, under the auspices of an exclusive license and research collaboration agreement with NYU. Torres has recently received royalties and consulting compensation from Janssen and related entities. These interests are being managed in accordance with NYU Langone policies and procedures.

  • Peter T. Buckley, Rita Chan, Jeffrey Fernandez, Jinquan Luo, Keenan A. Lacey, Ashley L. DuMont, Aidan O’Malley, Randall J. Brezski, Songmao Zheng, Thomas Malia, Brian Whitaker, Adam Zwolak, Angela Payne, Desmond Clark, Martin Sigg, Eilyn R. Lacy, Anna Kornilova, Debra Kwok, Steve McCarthy, Bingyuan Wu, Brian Morrow, Jennifer Nemeth-Seay, Ted Petley, Sam Wu, William R. Strohl, Anthony Simon Lynch, Victor J. Torres. Multivalent human antibody-centyrin fusion protein to prevent and treat Staphylococcus aureus infections. Cell Host & Microbe, 2023; DOI: 10.1016/j.chom.2023.04.004
  • NYU Langone Health / NYU Grossman School of Medicine

    Humans vs. Bacteria: Differences in ribosome decoding revealed

    Scientists at St. Jude Children’s Research Hospital revealed that human ribosomes decode messenger RNA (mRNA) 10 times slower than bacterial ribosomes, but do so more accurately. The study, published today in Nature, used a combination of field-leading structural biology approaches to better understand how ribosomes work. The scientists pinpointed where the process slows down in humans, which will be useful information for developing new therapeutics for cancer and infections.

    Ribosomes are molecular machines within cells, responsible for synthesizing proteins by decoding mRNA. By conducting mechanistic studies on bacterial and human ribosomes, researchers can understand their similarities and differences to develop drugs and understand disease. Many antibiotics, the drugs we use to treat bacterial infections, work by targeting bacterial ribosomes. In humans, changes in how accurately ribosomes decode mRNA have been linked to aging and disease, representing a potential point of therapeutic intervention. This gives the work implications for the treatment of infections and cancer.

    “Bacteria have been very well studied for many decades, but the kind of studies that we do, careful mechanistic studies, have been missing on human ribosomes,” said corresponding author Scott Blanchard, Ph.D., St. Jude Department of Structural Biology. “We’re very interested in human ribosomes because those are what need to be targeted to find new treatments for cancer and viral infections such as COVID.”

    Resolution revolution

    Ribosomes decode mRNA using a molecule called aminoacyl-transfer RNA (tRNA) as substrate. The decoding process involves several different steps.

    The researchers deployed methods such as single-molecule fluorescence resonance energy transfer (smFRET) and cryo-electron microscopy (cryo-EM) to examine the human ribosome decoding mechanisms. The single-molecule imaging gives the researchers information on how quickly things occur. So, in this case, how quickly human ribosomes go through the different steps during the decoding process. Cryo-EM gives the researchers structural information. So, how the human ribosome looks or what conformations (shapes) it is in at each step. By combining these two methods, the scientists get information on how quickly these processes occur in humans compared to bacteria as well as about the underlying structural causes for any differences they observe.

    “We wanted to know how quickly a human ribosome can read the genetic code, how quickly it finds the tRNA that’s complementary to the mRNA,” said co-first author Mikael Holm, Ph.D., St. Jude Department of Structural Biology. “We found that the process is about 10 times slower for human ribosomes than it is in bacteria. But this slow down adds accuracy, because human ribosomes are known to be more accurate at translating the code than bacterial ribosomes.”

    Specifically, the researchers found that while humans and bacteria both decode mRNA, the reaction pathway of aminoacyl-tRNA movement during the decoding process is different on human ribosomes and is significantly slower. These differences arise from structural elements in the human ribosome and in the human elongation factor, eEF1A, that together are responsible for faithfully incorporating the right tRNA for each mRNA codon (piece of the sequence). The distinct nature and timing of conformational changes within the ribosome and eEF1A may explain how human ribosomes achieve greater decoding accuracy.

    “With our cryo-EM structural studies, we were able to resolve human ribosome structures to atomic resolution, which revealed unprecedented features such as rRNA and protein modifications, ions and solvent molecules present in the human ribosome,” said co-first author Kundhavai Natchiar, Ph.D., St. Jude Department of Structural Biology. “These features finely characterize the molecular basis of interactions of the drug molecules with the human ribosome, which is indispensable for human ribosome-based drug design and discovery.”

    Caught in the act

    The researchers also pinpointed exactly which step of the decoding process slowed down in human ribosomes. There are two steps in the process of the ribosome selecting the right tRNA: initial selection and proofreading selection. The second step, proofreading selection, is where the ribosome checks for a second time that it chose the right molecule. That is the step that is 10 times slower in humans than in bacteria.

    Think of a gymnast, contorting themselves into different shapes on the mat as they work through their routine. This is similar to how ribosomes transition into various conformations to achieve different results. The research showed that a lot of conformational gymnastics that human ribosomes undergo are not present in bacterial ribosomes and are thus likely tied to the slowdown of the proofreading selection process.

    The researchers also found that several drugs target the proofreading selection process, not initial selection. So, instead of hitting the step that is similar between humans and bacteria, these drugs focus on the most different, slowest step.

    “In structural biology, a single snapshot of a macromolecular machine is not always sufficient to explain how it functions,” said co-first author Emily Rundlet, Ph.D., St. Jude Department of Structural Biology. “Often, the snapshot that’s needed to answer your biological question is not the most stable form of the molecule, but instead it is short-lived and difficult to capture. Using smFRET and cryo-EM together brings the dimension of time to structural biology, which allows us to visualize important transient intermediate steps of human decoding and understand the different mechanisms on a new level.”

  • Mikael Holm, S. Kundhavai Natchiar, Emily J. Rundlet, Alexander G. Myasnikov, Zoe L. Watson, Roger B. Altman, Hao-Yuan Wang, Jack Taunton, Scott C. Blanchard. mRNA decoding in human is kinetically and structurally distinct from bacteria. Nature, 2023; DOI: 10.1038/s41586-023-05908-w
  • St. Jude Children’s Research Hospital

    Mosquito saliva can weaken body’s defenses against deadly dengue viruses, scientists discover

    The saliva of mosquitoes infected with dengue viruses contains a substance that thwarts the human immune system and makes it easier for people to become infected with these potentially deadly viruses, new research reveals.

    Dengue has spread in recent years to Europe and the Southern United States in addition to longstanding hotspots in tropical and subtropical areas such as Southeast Asia, Africa and Latin America. The new discovery, from a University of Virginia School of Medicine scientist and his collaborators, helps explain why the disease is so easily transmitted and could eventually lead to new ways to prevent infection.

    “It is remarkable how clever these viruses are — they subvert mosquito biology to tamp down our immune responses so that infection can take hold,” said Mariano A. Garcia-Blanco, MD, PhD, who recently joined UVA as chair of the Department of Microbiology, Immunology and Cancer Biology. “There is no doubt in my mind that better understanding of the fundamental biology of transmission will eventually lead to effective transmission-blocking measures.”

    Further, Garcia-Blanco suspects that researchers will find similar immune-dampening substances accompanying other mosquito-borne infections such as Zika, West Nile and yellow fever. “Our findings are almost certainly going to be applicable to infections with other flaviviruses,” Garcia-Blanco said. “The specific molecules here are unlikely to apply to malaria, but the concept is generalizable to viral infections.”

    Understanding Dengue

    Approximately half the world’s population is at risk for dengue, and roughly 400 million people are infected every year. Dengue’s symptoms, including fever, nausea and skin rash, are often mistaken for other diseases. Most people will have mild cases, but about 1 in 20 will develop severe illness that can lead to shock, internal bleeding and death. Unfortunately, it’s possible to contract dengue repeatedly, as it is caused by four related viruses transmitted primarily by the Aedes aegypti species of mosquito. There is no treatment, but the new discovery from Garcia-Blanco and his colleagues identifies an important contributor to the disease’s spread as researchers seek to find better ways to combat it.

    Garcia-Blanco and his team found that infected mosquitoes’ saliva contained not just the expected dengue virus but a powerful conspirator: molecules produced by the virus that can blunt the body’s immune response. The injection of these molecules, called sfRNAs, during the mosquito bite makes it more likely that the victim will become infected with dengue, the scientists conclude.

    “By introducing this RNA at the biting site, dengue-infected saliva prepares the terrain for an efficient infection and gives the virus an advantage in the first battle between it and our immune defenses,” the researchers write in a new scientific paper outlining their findings.

    Scientists who study mosquitoes previously had suspected that the insects’ saliva might contain some type of payload to enhance the potential for infection. Garcia-Blanco’s team’s new findings pinpoints one weapon in the viruses’ arsenal and opens the door to finding new ways to help reduce transmission and control the disease’s spread. For now, the best way to avoid getting seriously sick with dengue remains to avoid getting bitten.

    “It’s incredible that the virus can hijack these molecules so that their co-delivery at the mosquito bite site gives it an advantage in establishing an infection,” said researcher Tania Strilets, a graduate student with Garcia-Blanco and co-first author of the scientific paper. “These findings provide new perspectives on how we can counteract dengue virus infections from the very first bite of the mosquito.”

  • Shih-Chia Yeh, Tania Strilets, Wei-Lian Tan, David Castillo, Hacène Medkour, Félix Rey-Cadilhac, Idalba M. Serrato-Pomar, Florian Rachenne, Avisha Chowdhury, Vanessa Chuo, Sasha R. Azar, Moirangthem Kiran Singh, Rodolphe Hamel, Dorothée Missé, R. Manjunatha Kini, Linda J. Kenney, Nikos Vasilakis, Marc A. Marti-Renom, Guy Nir, Julien Pompon, Mariano A. Garcia-Blanco. The anti-immune dengue subgenomic flaviviral RNA is present in vesicles in mosquito saliva and is associated with increased infectivity. PLOS Pathogens, 2023; 19 (3): e1011224 DOI: 10.1371/journal.ppat.1011224
  • University of Virginia Health System

    Fomepizole helps overcome antibiotic-resistant pneumonia in mice, study finds

    Pneumococcal disease leads to over three million hospitalizations and hundreds of thousands of deaths annually. A study publishing March 16 in the open access journal PLOS Biology by Carlos J. Orihuela at the University of Alabama at Birmingham, Alabama, United States, and colleagues suggests that the FDA-approved drug Fomepizole may reduce disease severity in the lungs of mice with some forms of bacterial pneumonia and enhance the efficacy of the antibiotic erythromycin as well.

    Streptococcus pneumoniae is the leading cause of community-acquired pneumonia. While vaccines to protect against the bacteria are available, these vaccines are not effective against all strains, with some versions being especially problematic as they are multidrug-resistant. Currently, there are very limited treatment options for combating multidrug-resistant S. pneumoniae infections.

    In order to test the effects of novel treatments for antibiotic-resistant S. pneumoniae, the researchers conducted a series of experiments with mice. Fomepizole is an FDA-approved drug normally used as an antidote for the ingestion of toxic alcohols (such as methanol or ethylene glycol), and works by inhibiting the enzyme alcohol dehydrogenase. Researchers inoculated mice with a multidrug-resistant S. pneumoniae and tested the effect of fomepizole in a combinatorial treatment with antibiotics. They quantified the bacterial burden in the organs of infected mice, comparing the experimental group with the control group.

    The researchers found that using Fomepizole blocked normal energy production by S. pneumoniae and enhanced the bacteria’s susceptibility to antibiotics and reduced bacterial burden in the lungs of mice with pneumonia. The combination treatment was effective in preventing the development of invasive disease. Future research is needed however, as this novel drug treatment has not been replicated in clinical studies on humans, who may present with complicating factors such as comorbidities, advanced age, or environmental variables that may play a role in disease outcomes.

    Orihuela adds, “Pharmacological targeting of fermentation pathways is a new way to enhance the susceptibility of some bacteriato antimicrobials. Combination treatment of erythromycin and fomepizole, an alcohol dehydrogenase inhibitor, prevented the in vivo dissemination of antibiotic-resistant Streptococcus pneumoniae.”

  • Hansol Im, Madison L. Pearson, Eriel Martinez, Kyle H. Cichos, Xiuhong Song, Katherine L. Kruckow, Rachel M. Andrews, Elie S. Ghanem, Carlos J. Orihuela. Targeting NAD+ regeneration enhances antibiotic susceptibility of Streptococcus pneumoniae during invasive disease. PLOS Biology, 2023; 21 (3): e3002020 DOI: 10.1371/journal.pbio.3002020
  • PLOS

    Researchers develop new technology to easily detect active TB

    A team of faculty from Wayne State University has discovered new technology that will quickly and easily detect active Mycobacterium tuberculosis (TB) infection antibodies. Their work, “Discovery of Novel Transketolase Epitopes and the Development of IgG-Based Tuberculosis Serodiagnostics,” was published in a recent edition of Microbiology Spectrum, a journal published by the American Society for Microbiology. The team is led by Lobelia Samavati, M.D., professor in the Center for Molecular Medicine and Genetics in the School of Medicine. Samavati was joined by Jaya Talreja, Ph.D, and Changya Peng, research scientists in Wayne State’s Department of Internal Medicine.

    TB remains a global health threat, with 10 million new cases and 1.7 million deaths annually. According to the latest World Health Organization report, TB is the 13th leading cause of death and the second leading infectious killer after COVID-19. Latent tuberculous infection (LTBI) is considered a reservoir for TB bacteria and subjects can progress to active TB. One-third of the world’s population is infected with TB and, on average, 5 to 10% of those infected with LTBI will develop active TB disease over the course of their lives, usually within the first five years after initial infection.

    The gold standard tests to determine whether an infection is active TB are the sputum smear and culture tests. However, these methods require collecting sputum, which is time consuming, expensive, requires trained personnel and lacks sensitivity. The current conventional tests differentiating LTBI from uninfected controls — such as tuberculin skin tests (TST) and/or interferongamma release assay (IGRA) — do not differentiate between active TB infection and latent TB. Despite advances in rapid molecular techniques for TB diagnostics, there is an unmet need for a simple inexpensive point-of-care (POC), rapid non-sputum-based test.

    Samavati’s research group has worked for more than 15 years to develop technology for detection of antibodies in various respiratory diseases. Her lab has developed a novel non-sputum based technology and has discovered several novel immune-epitopes that differentialy bind to specific immunoglobulin (IgG) in TB-infected subjects. The levels of epitope-specific IgG in seum can differentiate active TB from LTBI subjects, healthy contols and other respiratory diseases. This technology can be used as a simple serum assay non-sputum based serological POC- TB test, which is highly specific and sensitveto diffentiate active TB from LTBI.

    “Previously, we developed a T7 phage antigen display platform and after immunoscreening of large sets of serum samples, identified 10 clones that differentially bind to serum antibody (IgG) of active TB patients differentiating TB from other respiratory diseases,” said Samavati. “One of these high-performance clones had homology to the Transketolase (TKT) enzyme of TB bacteria that is an essential enzyme required for the intracellular growth of the bacteria in a host. We hypothesized that abundance of IgG in sera against the identified novel neoantigen that we named as TKTµ may differentiate between active TB, LTBI and other non-TB granulomatous lung diseases such as sarcoidosis. We developed a novel direct Peptide ELISA test to quantify the levels of IgG in serum samples against TKTµ. We designed two additional overlapping M.tb TKT-peptide homologs with potential antigenicity corresponding to M.tb-specifictransketolase (M.tb-TKT1 and M.tb-TKT3) and hence standardized three Peptide ELISA (TKTμ, M.tb TKT1 and M.tb TKT3) for the TB serodiagnosis.”

    After development and standardization of a direct peptide ELISA for three peptides, the research team tested 292 subjects, and their TKT-peptide ELISA results show that TB patients have significantly higher levels of TKT-specific antibodies compared to patients who were healthy controls and with LTBI. The increased levels of TKT-specific antibodies is presumably associated with growing M.tb bacteria in active TB patients. TKT plays a key role in the switch from the dormancy to proliferative phase and TKT specific IgG may uncover the differences between active TB and LTBI. Thus, IgG-based serodiagnosis of TB with TKT-peptide ELISA is promising.

    Currently, commercially available serological TB tests show poor sensitivity and specificity. The ELISA results obtained with the Wayne State team’s discovered TKT peptides yielded high specificity and sensitivity. Their results show that IgG antibodies against transketolase can discriminate active tuberculosis. 

    “Our TKT peptide ELISA test requires chemically synthesized TKT peptides to coat the wells in the ELISA plate, less than 100µl blood serum sample from patient, detection reagents and an ELISA plate reader,” said Samavati. “We are extremely enthusiastic about our technology and the fact that with a simple test we can differentiate active TB from LTBI and other respiratory diseases. We believe that our method and TKT peptide ELISA can fit the requirements of the World Health Organization and the Centers for Disease Control and Prevention as a POC screening method.”

    The research team has applied a patent application on its technology and is actively seeking companies interested in investing.

    This research was supported by the National Heart, Lung and Blood Institute of the National Institutes of Health, grant numbers 113508 and 148089. The Foundation for Innovative New Diagnostics (FIND, Geneva, Switzerland) provided TB and LTBI samples.

  • Jaya Talreja, Changya Peng, Tuan-Minh Nguyen, Sorin Draghici, Lobelia Samavati. Discovery of Novel Transketolase Epitopes and the Development of IgG-Based Tuberculosis Serodiagnostics. Microbiology Spectrum, 2023; 11 (1) DOI: 10.1128/spectrum.03377-22
  • Wayne State University – Office of the Vice President for Research

    Infections with many different types of bacteria including Streptococcus pneumonia, Listeria monocytogens, and Neisseria mengitidis can cause bacterial …

    Infections with many different types of bacteria including Streptococcus pneumonia, Listeria monocytogens, and Neisseria mengitidis can cause bacterial meningitis. It’s estimated that every year over 1.2 million cases of bacterial meningitis happen around the world, and without treatment, this deadly disease is fatal to seven of ten people who are sickened by it. Even with antibiotic treatments, three of ten patients die. Survivors are left with issues like chronic headaches, seizures, loss of vision or hearing, and other neurological consequences. New research reported in Nature has revealed how bacteria are able to penetrate the meninges that surround and protect the brain to cause bacterial meningitis. The findings have shown that bacteria use neurons to evade immunity and infect the brain, and the work may aid in the creation of new therapeutics.

    A digitally-colorized SEM image depicts of Streptococcus pneumoniae bacteria (lavender), as they were being attacked by a white blood cell (pink).  / Credit: CDC/ Dr. Richard Facklam

    Right now, antibiotics can help eliminate the bacterial pathogens that cause this illness. But steroids are also needed to control the dangerous inflammation that can occur along with the infection. However, reducing inflammation also weakens the immune response, making it harder to get rid of the infection.

    In this research, the scientists used Streptococcus pneumoniae and Streptococcus agalactiae bacteria, which can both cause bacterial meningitis in humans. They determined that when these bacteria get to the meninges, they release a toxin, which activates neurons in the meninges that sense pain. This pain neuron activation could explain why bacterial meningitis patients get horrible headaches, noted the researchers.

    The activated pain neurons then release a signaling molecule called CGRP, which binds to a receptor called RAMP1 on the surface of immune cells called macrophages. Once CGRP binds to RAMP1 on macrophages, the immune cells are basically disabled, and they stop responding to bacterial infections like they normally would.

    The link between CGRP and RAMP1 on macrophages also stops them from signaling to other immune cells, which allows the bacterial infection to not only penetrate the meninges but to spread infection.

    This work was confirmed with the use of a mouse model that lacked the pain neurons that are activated by bacteria. Compared to mice with those neurons, the engineered mice had less severe brain infections when they were exposed to bacteria that cause meningitis. There were also lower levels of CGRP in the engineered mice compared to normal mice. The normal mice, however, had higher levels of bacteria in the meninges.

    Additional experiments also showed that when mice were treated with drugs that block RAMP1, the severity of the bacterial infection was reduced. Mice treated with RAMP1 blockers were able to clear their infections faster too.

    It may be possible to help the immune system clear cases of bacterial meningitis with medications that block either CGRP or RAMP1, potentially in conjunction with antibiotics. There are already drugs that can do this, and they are generally used to treat migraine.

    Sources: Harvard Medical School, Nature

    Carmen Leitch

    Mushrooms are part of the world of fungi, and while they are often thought of as plants, they …

    Mushrooms are part of the world of fungi, and while they are often thought of as plants, they are in a class by themselves. Some mushrooms have more in common with animals than plants, such as a cholesterol-like molecule called ergosterol, and mushrooms have been called a “third food kingdom.” Edible fungi have been eaten in many cultures throughout history, which valued mushrooms for various reasons. Many edible mushrooms contain valuable nutrients including vitamin B6, selenium, potassium, and zinc. Other ‘poisonous’ mushrooms have psychoactive effects. Some studies have suggested that mushrooms have health benefits, like lowering high blood pressure, boosting immunity, keeping the heart healthy, and protecting the brain.

    Researchers found lion's mane mushroom improved brain cell growth and memory in pre-clinical trials. Image credit: UQ

    Now a study reported in the Journal of Neuroscience has identified a compound in a type of fungi called lion’s mane mushrooms (Hericium erinaceus) that can promote nerve growth and may enhance memory.

    While traditional Asian medicine has relied on lion’s mane mushroom extracts for centuries, noted Professor Frederic Meunier of the Queensland Brain Institute, the study authors wanted to use a scientific approach to examine the potential impact these extracts have on brain cells.

    Pre-clinical tests have suggested that lion’s mane mushrooms can improve memory and brain cell growth significantly. This study used neurons growing in culture to assess the effects of compounds that were isolated from those mushrooms. Active compounds were found to promote the extension of neuronal projections, noted Meunier, the corresponding study author.

    “Using super-resolution microscopy, we found the mushroom extract and its active components largely increase the size of growth cones, which are particularly important for brain cells to sense their environment and establish new connections with other neurons in the brain,” said Meunier.

    The study authors were aiming to find bioactive compounds in nature that are able to reach the brain, a sensitive organ that is protected by the selective blood-brain barrier, and influence neuronal growth and memory formation. These findings potentially have applications for the prevention or treatment of neurodegenerative diseases that affect cognition and memory, like Alzheimer’s disease, added study co-author Dr. Ramon Martinez-Marmol of the University of Queensland.

    Sources: University of Queensland, Journal of Neuroscience

    Carmen Leitch