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List Labs currently has over 3300 citations with more being added every month! Within our citations page, we provide the ability to search and sort from over 100 cataloged items that are offered here.
We are honored to supply researchers worldwide with highly purified bacterial toxins that can potentially be instrumental in helping to change the world!
In this post, we’ve gathered all of our current citations for our Diphtheria product group. Please use these citations as a reference and resource for your potentially life-changing work!
Diphtheria Toxin & CRM
Corynebacterium diphtheriae is a Gram-positive, bacterium that infects epithelial cells of the upper respiratory tract and produces diphtheria toxin. Diphtheria toxin is proteolytically cleaved forming a two-part toxin, held together by a disulfide bridge. The amino-terminal carries the toxin’s enzymatic activity, capable of ADP-ribosylation and inactivation of translation elongation factor 2 (EF-2). The carboxy-terminal domain binds to specific host receptors, the heparin-binding EGF-like growth factor (HB-EGF) on human epithelial cells, and translocates the catalytic domain into the cell. After binding to the cell receptor, the diphtheria toxin is taken up by endocytosis, the pH of the endocytic vesicle drops, and the translocation region of the toxin helps guide the catalytic domain into the host cytoplasm where it is released. Within the cytoplasm, the diphtheria toxin catalytic domain ADP ribosylates EF-2, terminating protein synthesis and causing the death of the cell. Diphtheria toxin is highly potent, and as little as one catalytic domain is thought to cause cell death. In cell culture, diphtheria toxin inhibits protein synthesis and causes death in cells carrying the HB-EGF receptor. This toxin has been used to specifically eliminate receptor-expressing cells in transgenic mice.
View List Labs Diphtheria toxins for sale.
View some of List Labs Diphtheria related blogs:
Toxoids, Toxins and Vaccine Related Terminology
List Labs Reagents Used in Research – January ’18
Carrier Protein Used in Life-Changing Research
Cell Ablation Using Diphtheria Toxin (DT) is an Important Technique for Studying Regeneration in Living Animals
By: Mary N. Wessling, Ph.D. ELS
List Biological Laboratories’ (List Labs) catalog of products is related to furthering research in human health and preventing disease, most commonly as the starting materials for vaccine research & development or production around the world. Vaccines are mainly identified for their capacity to prevent diseases that the body’s innate defensive mechanisms (the skin and specialized cells in the blood, for example) can’t resist unaided. However, there are many other uses for these purified materials in medical research, and you will likely encounter wording on our website that is not part of everyday vocabulary for non-scientists. This article is intended to provide a basic understanding of some of the more frequently used terms and aid you in selecting the products most essential to your projects.
Toxin vs. Toxoid
For starters, what is the difference between “toxin” and “toxoid”. Broadly defined, anything that can cause harm to an organism is a toxin. However, for List Labs’ products and in biological usage, a toxin refers to a bacterial or viral product that has harmful effects when it enters the body (List Labs’ toxins are in a highly purified form). A toxoid is a chemically altered toxin that has reduced or no toxicity and is used for its remaining antigenic activity, which can stimulate an immune response.
Take, for example, cholera, a disease produced by Vibrio cholerae bacteria, possibly through contact with body fluids from a person ill with cholera or through contaminated water supply. Cholera causes severe diarrhea, and untreated, it can be fatal. However, the purified List Labs’ cholera toxin by chemical modification becomes a toxoid that lacks toxic activity but retains structures that make it useful for immunization of research animals or stimulation of immune cells in vitro.
How do Toxoids Impact the Immune Process?
To understand how some List Labs products work, an overview of the immune process is helpful. During the course of a day, we frequently touch, ingest, or breathe in something that has potential to harm the body. Our cells react to this invader: is this a threat, or not, and if so, how serious is the threat?
What is the Innate Immune Response?
The innate immune response is the first order of defense in the immune process. There are many different cell types in our body. Some of these cells are equipped by their structural and biochemical components to destroy dangerous microbial invaders–pathogens–quickly. The inflammation that we experience from minor infections is often a sign of this process as cells from the blood destroy the pathogen. This happens quickly, within hours.
What is the Adaptive Immune Response?
Another cellular response system requires a longer time to react to the threat. These cells react by changing from an inactive form to one that will start a more complex defensive process: this is the second step, the adaptive immune response. There are two different classes of cells that comprise the adaptive immune response; they differ by the structures that give them their ability to bind antigens– the invading bacteria and viruses. Both these cells are called lymphocytes; individually, they are the B-lymphocytes (B-cells) and T-lymphocytes (T-cells). Both originate from stem cells in the bone marrow; B and T refer to the place in the body where they mature. T-cells mature in the thymus into several subclasses of T-cells that circulate in the blood and lymph. “Killer” T-cells recognize foreign antigens on cell surfaces (e.g. from viral infection or malignancy). “Helper” T-cells induce B-cells to produce antibodies. “Suppressor” T-cells dampen or regulate the immune response to prevent over-reaction. B-cells mature in the bone marrow and migrate to secondary lymphoid tissues (e.g. spleen and lymph nodes). When they encounter foreign antigens and/or helper T-cells, they are stimulated to divide and expand clonally to produce antibodies and differentiate into plasma cells.
What is Immune Memory?
After the B and T-lymphocytes react to an antigen, two results are possible. The first, and desirable result, is that the invader is identified and defeated, leaving behind what might be called its criminal record: immune memory. When the antigen comes creeping back in the future, the adaptive immune system recognizes it and attacks. The second possibility is an over-reaction and lack of cessation of the adaptive immune process that is harmful to the body: an autoimmune condition.
Antigens, Epitopes and Vaccines
Where do vaccines come into this process? An antigen is a substance that causes the body to mount an immune response against it. Antigens include toxins, bacteria, viruses, or other substances that the body recognizes as foreign or not “self”. Vaccines have structural features similar to structures of the toxin or invading pathogen that can elicit adaptive immunity.
An epitope is a specific molecular region on the surface of an antigen, typically one of many on the antigen, that elicits an immune response and is capable of binding with the specific antibody produced by the response. A toxin has many epitopes that can be recognized by the immune response. The epitopes that are required for toxicity have been altered chemically in toxoids or by specific genetic mutations in inactive mutants; however, many epitopes are retained and can stimulate an adaptive or memory immune response that will be effective against the toxin.
Toxins and Toxoid Products for Research
Below is a list of toxin and toxoid or inactive mutant pairs of products available to support your research.
|Toxin and product numbers||Toxoid||Inactive Mutant|
|Botulinum Neurotoxin Type A from Clostridium botulinum – 130A, 130B, 9130A||133L|
|Botulinum Neurotoxin Type B, Nicked, from Clostridium botulinum – 136A, 136B||139|
|Toxin A from Clostridium difficile – 152C||153|
|Toxin B from Clostridium difficile – 155A, 155B, 155L||154A|
|Diphtheria Toxin, Unnicked, from Corynebacterium diphtheriae – 150||151||149|
|Enterotoxin Type B from Staphylococcus aureus – 122||123|
|Tetanus Toxin from Clostridium tetani – 190A, 190B||191A, 191B|
By: Rachel Berlin, Marketing Manager
The List Labs website hosts a library of scientific article abstracts related to the research performed using our products called the Citations Page. Visitors can search this library to learn how others have used List Labs’ reagents in their research. This valuable resource is updated monthly with new articles from a wide variety of publications. Check out a few recent articles below:
Don’t see the reagent you’re interested in? You can search the citations by product, year, publication, or by the type of cell, animal, assay, protein or research. Check it out today!
By: Suzanne Canada, Ph.D.
Diphtheria toxin is an important tool used for selective killing (ablation) of cells for research purposes. Using this technique, dubbed “toxin receptor–mediated cell knockout” when it was first used , researchers can selectively remove a specific type of cell in a live mouse without having to generate transgenic “knockout” animals, which can be more time-consuming. The animals are engineered to express a diphtheria toxin (DT) receptor on the surface of a specific cell type. These animals are normal until exposed to DT, which acts as a potent inhibitor of protein synthesis and kills only those cells that express the DT receptor. This technique is a powerful tool to explore the role of specific cell types in disease, and is being used to study both the recovery of pituitary cells and the role of T-cells in inflammatory colitis.
The pituitary gland plays an important role in the endocrine system, which presides over growth and development, stress response (adrenal glands), and metabolism (thyroid gland). Willems and colleagues  have been studying the regeneration of the pituitary—research that could lead to methods or therapies to heal pituitary deficiencies. Transgenic mice that express a DT receptor on the membrane of the growth hormone (GH) cells were treated with DT, which selectively killed those cells. The researchers then monitored the ability of these ablated cells to regenerate. Using this technique, they found that stem cells in the pituitary participate in the regeneration process. Younger mice had a greater ability to recover from injury to the pituitary than older mice. However, if the injury was prolonged (11 days compared with 3 days) the ability for stem cells to react and aid in recovery could be delayed or even blocked. These researchers may find how stem cells could be activated to boost regeneration of a damaged pituitary gland.
Cell regeneration also plays an important role in the digestive system: researchers are studying how T-cells regulate inflammation in the gut. Increases in activated T-cells are associated with active flare-ups of ulcerative colitis and Crohn’s disease [Kappler, 2000]. To that end, Boschetti and colleagues  used DT to selectively deplete CD4+, CD25+, and Foxp3+ regulatory T-cells [T-regs] in the gut of transgenic mice. Using that process, the researchers were able to ablate >95% of the T-regs. The proliferation and recovery of the various T-cell subsets in the lymph nodes and colon was monitored using flow cytometry. By monitoring the recovery of the T-regs, the researchers found that inflammation causes regulatory T-cells to move to the colon lamina propria, and that those cells could suppress proliferation of CD4+ effector cells in vitro. Although the Foxp3+ T-regs could not completely prevent colitis in the mice, they did reduce the severity of inflammation in the gut.
This technique is a powerful approach to selectively remove certain cells in mice and other model systems where the animals do not naturally have a DT receptor. The DT from List Labs is recommended for this purpose because its high purity produces the best desired effect.
To read about even more uses of Diphtheria Toxin and other List Labs products, browse our Citations page.
By: Suzanne Canada, Ph.D.
Tanager Medical Writing
An exciting report was released in October about a new class of targeted anti-tumor drugs, in which genetically engineered stem cells were used to deliver cytotoxins to brain tumors.1 Brain cancers known as glioblastomas (GBM) are notoriously difficult to treat because the tumors often re-grow after surgery and because most standard cancer therapies cannot pass the blood-brain barrier. Those cancer therapies that can reach the tumors must be delivered at high doses which can be toxic to the entire body, without specifically targeting the GBM tumor. In this case, a research team at Massachusetts General Hospital (MGH) in Boston used stem cells, added to mouse brain tumors after surgery, to deliver Pseudomonas exotoxin directly at the site of the tumor itself. 2
Although this research is cutting-edge and an exciting development for GBM patients, the idea of using toxins attached to targeting molecules such as antibodies or specific ligands has long been explored as a way of fighting diseases, especially cancer. One popular approach has been to use antibodies linked to toxins to aid in targeting the therapy. (See Chari 2008 and Goldmacher 2011 for reviews).3, 4 An example is the approach taken by group of researchers looking for ways to increase the effectiveness of Herceptin®, a monoclonal antibody that is best known for targeting HER-overexpressing malignant breast cancer tumors. Antibody was coupled to both diphtheria toxin and multi-walled carbon nanotubes. They found that both conjugates were more effective in specifically killing HER-2 expressing cells than Herceptin® alone.5
An elegant approach to targeting toxins is to activate the toxin by cleavage at the site of therapy. This is precisely the approach used by Schafer and colleagues.6 Their model system exploited the fact that metalloproteinases are commonly overexpressed on the surface of squamous cell cancers. Anthrax toxin was engineered to be activated by cleavage by urokinase plasminogen activator (uPA) on the cell surface and metalloproteinases. This approach seemed to work on xenografted human head and neck squamous cell carcinoma (HNSCC) cell lines by inducing apoptotic and necrotic tumor cell death. However, cultured cancer cell lines were found to be insensitive to the engineered toxin, so the researchers concluded that the regulation of two-fold activation was not straightforward as anticipated.
Shiga toxin– produced by an organism responsible for bacterial dysentery – has properties that could be harnessed for cancer research7. A group of researchers took advantage of the binding of the Shiga toxin B pentamer to the glycosphingolipid globotriaosylceramide (Gb3) on the cell surface. After binding, the Shiga toxin complex is internalized by eukaryotic cells where the Shiga toxin A moiety can exert its toxic effect. Gb3 is reportedly over-expressed in throat, gastric, and ovarian cancers—and researchers hope that this overexpression pattern could be used to attain more targeted therapy. Specific binding of GB3 by the Shiga toxin B pentamer could also be exploited for imaging of these tumors and for delivering a genetically engineer Shiga toxin A chimera that would only be activated in cancer cells.
In their quest for new and more effective therapies, researchers have noted that bacterial toxins are examples of highly toxic, but also targeted and regulated systems that have co-evolved with the eukaryotic hosts (humans).8, 9 In the words of Fabbri et al., “Knowledge of their properties could be used for medical purposes.” List Biological Laboratories, Inc. provides purified bacterial toxins for research purposes, including Anthrax toxins (Product # 169, 172, & 176), Shiga toxins (Product # 161 & 162), Diphtheria toxins (Product # 149, 150, & 151), and others.
By: Suzanne Canada, Ph.D.
Tanager Medical Writing
Vaccines have been used to help control diseases for more than 200 years and are the common practice for children and adults. Childhood vaccination has substantially reduced the morbidity and mortality from infectious diseases in much of the developed world, and influenza vaccinations have reduced the impact of seasonal influenza infections.1 However, medical researchers are constantly looking for ways to improve the vaccines that are already used, and develop new ones.
Opportunities for improvement of vaccines abound. For example, although much attention is given to child vaccinations, a reservoir of infection could be eliminated through promotion of adult booster shots such as pertussis booster shots for expectant mothers and close family members, to help protect susceptible newborns. In addition, some diseases that have vaccines currently available still flourish in areas of the world where infrastructures for vaccination are poor and are too costly or cannot be delivered in their current forms.1 Researchers are still trying to develop vaccines for other important diseases, such as HIV/AIDS, malaria and leishmaniasis. Vaccines are also being developed for bacterial pathogens, such as Vibrio cholerae O1 and enterotoxigenic Escherichia coli (ETEC) that are responsible for a high proportion of diarrheal disease and death in adults and children in many countries in Africa and Asia.2
By modifying the factors included in the vaccine, researchers balance the effectiveness of the immune response with the side effects. Previously, whole cell vaccines containing whole organisms that had been chemically inactivated were the norm, but the side effects of fever and discomfort following injections were much more common. Many of the vaccines used today, including those for measles and some influenza vaccines, use live, attenuated viruses. Others use killed forms of viruses, pieces of bacteria (lipopolysaccharides), or inactivated forms of bacterial toxins, known as “toxoids.” Killed viruses, lipopolysaccharides and toxoids can evoke an immune response that protects against future infection.3 Acellular vaccines were introduced in the late 1990’s that contain either three or five key bacterial proteins and have been quite effective in protecting infants and children under four with a much lower rate of side effects.
List Labs offers several virulence factors which are used in vaccine testing. For testing C. difficile vaccines; available reagents are C. difficile Toxin A (Product #152), C. difficile Toxin B (Product #155), C. difficile Toxoid A (Product #153), C. difficile Toxoid B (Product #154), and both subunits of the Binary Toxin (Products #157 and #158). Numerous Bordetella pertussis virulence factors are available for use in testing including: Products #179, #180 or #181 Pertussis Toxin, Product #170 FHA, Product #186 Fimbriae, Product #187 Pertactin, Product #188 and #189 Adenylate Cyclase and Product #400 Highly Purified B. pertussis LPS. Anthrax vaccine testing maybe carried out using Protective Antigen (Product #171) with Lethal Factor (Product #172) in a toxin neutralization assay. Although these factors are not suitable for testing on humans, they are excellent research tools.
Inactive toxins are quite useful in making antibodies or in capturing antibodies from a vaccinated population on ELISA plates. Three of our inactivated toxins, which carry mutations in the toxin active site, are B. pertussis Adenylate Cyclase Toxoid, Pertussis Toxin Mutant, Product #184 and CRM197, a non-toxic Mutant Diphtheria Toxin, Product #149. Toxoids made by formaldehyde treatment of toxins include versions of C difficile Toxins (Products #153 and #154), Diphtheria Toxoid (Product #151), Staphylococcus aureus Enterotoxoid B (Product #123), Tetanus Toxoid (Product #191) and Toxoids of Botulinum Neurotoxins A and B (Product #133 and #139, respectively).