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By: Karen Crawford, PhD.
President, List Labs
Staphylococcal enterotoxin type B (SEB) is a powerful player in the family of toxins; in scientific terms, a superantigen. This enterotoxin binds to major histocompatibility complex (MHC) class II molecules on antigen-presenting cells and specific V-β chains of the T-cell receptors. This interaction between the three molecules leads to up-regulation of markers and proliferation of T-cells; additionally, it causes a massive release of proinflammatory cytokines including tumor necrosis factor (TNF), interleukins IL-1, IL-6 and interferon-gamma (INF-gamma) (1,2). SEB can form a complex with and activate T cell receptors even in the absence of MHC Class II antigens, making it a useful tool in stimulating T cells (3).
SEB Toxin’s Associations with Human Diseases
SEB is associated with staphylococcal food poisoning, along with TSST-1, is part of the toxic shock syndrome (4) and very likely has a role in human diseases such as atopic dermatitis (5) allergy and rhinitis (6) and the development of autoimmune diseases (7). A mouse model to simulate Toxic Shock Syndrome has been created by exposing mice to both SEB and lipopolysaccharide (8).
Staphylococcal enterotoxin B is on the Centers for Disease Control and Prevention Select Agents & Toxins list, because of high toxicity and the potential to be aerosolized for wide dissemination; however, the quantity which a principal investigator can possess without registration is sufficient for research. Despite the toxicity and potential danger, SEB is a useful tool in research.
Some papers utilizing SEB toxin are described below:
Busbee et al (9) cultured splenocytes in 96-well plates in the presence and absence of SEB. Supernatants were collected and analyzed for cytokine levels using ELISA kits purchased from Biolegend (San Diego, CA) for determining interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), interleukin-2 (IL-2), and IL-6.
Herter et al (10) investigated T cell movement between lymph nodes and sites of inflammation. In this study, SEB is used extensively as a positive control, stimulating an immune response in the mouse kidney and in various cultured cells.
Janik and Lee (11) has used SEB in mice to develop an understanding of the inhibitory effect SEB may have on pre-existing immunity to pathogens unrelated to the superantigen. These studies demonstrated that SEB in BALB/c mice selectively targets memory CD4 T cells.
By: Grace Ayabe, Technical Support
Would you like a positive control for production of cytokines in human peripheral blood mononuclear cells (PBMC’s)? If your laboratory is testing for cytokine production, List Labs can provide you with SEB (Staphylococcus aureus, Enterotoxin Type B) to stimulate a positive response to assure that your cells are functional.
SEB is described as a ‘superantigen’ for its ability to bind to Major Histocompatibility Complex (MHC) class II molecules on antigen presenting cells and specific vβ regions of T-cell receptors stimulating a large population of T-cells; which in turn, produce an inappropriate flood of cytokines or a ‘cytokine storm’. Following SEB exposure, human peripheral blood cells release large quantities of IL-2, IL-4, IL-6, TNF-A and INF-c. SEB has also been found to bind to another regulator of the T-cell immune response, CD28. You can read more about T-cell proliferation with List Labs SEB here: https://thatsnice-testing6.com/blog/staphylococcus-enterotoxin-b-stimulates-t-cell-proliferation/
If your research utilizes an Enzyme-linked immunospot (ELISPOT) or cytokine flow cytometry (CFC)/intracellular cytokine staining (ICS) assay(s) for cytokine detection, List Labs provides a premium quality SEB (Staphylococcus aureus, Enterotoxin Type B; Product #122) for your use as a positive control.
Each vial of List Labs SEB (Staphylococcus aureus, Enterotoxin Type B; Product #122) contains 0.5 mg of SEB in 0.07 M Sodium Phosphate; pH 6.8 (lyophilized). For more information, visit: https://thatsnice-testing6.com/products/buy-enterotoxin-type-b-from-staphylococcus-aureus
SEB is a ‘Select Agent’. To order SEB from List Labs for the first time, please review the following link: https://thatsnice-testing6.com/controlled-substances/
By: Suzanne Canada, Ph.D.
Tanager Medical Writing
While you go about your day, you are surrounded by micro-organisms. Although most of us spend a lot of time washing up and trying not to think about the propensity of creatures that share our personal space, scientists have been studying them. Due to their great progress, we are reaching an understanding of how these bacteria and fungi affect our bodies’ functions . The evidence indicates that this inner-ecosystem can not only cause disease if perturbed, but also influence our overall health! Organisms including Escherichia coli, Helicobacter pylori, Streptococcus thermophilus, and species of Clostridia, Lactobacillus, and Bacterioides inhabit our gut. Corynebacterium jeikeium as well as Staphylococcus species live on our skin, and other Streptococci as well as Neisseria and Candida albicans inhabit our mouth and upper respiratory system . The makeup and diversity of organisms has been found to be strongly influenced, not only by what you eat , but also by who you live with [4, 5]. With greater understanding of this rich soup of life that we carry with us, the microbiome has become the new frontier in cutting-edge drug development .
In the last three years, research into the molecular basis of microbial influence has blossomed. The first and most obvious application for this information was in treating C. difficile infections; which result from overgrowth of the opportunistic pathogen after an antibiotic regimen or hospital stay. Researchers found that fecal transplants from a healthy individual were an effective way to treat this potentially fatal infection [7, 8]. The role of intestinal microbes in Inflammatory Bowel Disease (IBD) has been established  in the last year or two. Based on this knowledge, possible treatments for IBD, such as ulcerative colitis and Crohn’s disease, are in development. Other publications point to microbes’ role in inflammation of the skin and respiratory tract, including acne and asthma. More excitement has been generated as investigators have found links to other chronic diseases including diabetes [12, 13], hypertension [14, 15], and chronic liver disease . Preliminary investigations suggest a connection between overall gut microbial composition and obesity . Some studies in mouse models have even linked the microbiome to the neurological conditions of Alzheimer’s  and autism [19, 20].
With all this research going on, you need a great resource like LIST Biological Laboratories, with experience and expertise with microbial products spanning over 25 years. LIST has several products available that can serve as positive controls for your microbial research. Potent toxins from C. difficile are available (LIST products #157, #158), as well as antibodies that aid in their detection (LIST products #753, #754). Lipopolysaccharides are also available, which cause inflammation and activation of immune signaling cascades, and are extracted from bacterial cell walls of E. coli O111:B4, O55:B5, O157:H7, J5 and K12; Salmonella typhimurium, Salmonella minnesota and Bordetella pertussis. Other acute immune system activators such as Staphylococcal toxins (LIST products #120, #122) and Shiga toxins (LIST products #161 & #162) are also available.
In case the assortment of purified bacterial products on hand are insufficient for your research needs, LIST also provides contract manufacturing for biotherapeutics, as well as microbial purification services.
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).