Microbiology - Chapter 16: Innate Immunity PDF

CH 16: Innate Immunity 16-1 Differentiate innate and adaptive immunity. 16-2 Define Toll-like receptors. 16-3 Describe the role of the skin and mucous membranes in innate immunity. 16-4 Differentiate physical from chemical factors, and list five examples of each. 16-6 Classify leukocytes, and descri...

CH 16: Innate Immunity 16-1 Differentiate innate and adaptive immunity. 16-2 Define Toll-like receptors. 16-3 Describe the role of the skin and mucous membranes in innate immunity. 16-4 Differentiate physical from chemical factors, and list five examples of each. 16-6 Classify leukocytes, and describe the roles of granulocytes and monocytes. 16-7 Describe the eight different types of white blood cells, and name a function for each 16-8 Differentiate the lymphatic and blood circulatory systems. 16-9 Define phagocyte and phagocytosis. 16-10 Describe the process of phagocytosis, and include the stages of adherence and ingestion. 16-12 List the stages of inflammation. 16-13 Describe the roles of vasodilation, kinins, prostaglandins, and leukotrienes in inflammation. 16-14 Describe phagocyte migration. 16-15 Describe the cause and effects of fever. 16-16 List the major components of the complement system. 16-17 Describe three pathways of activating complement. 16-18 Describe three consequences of complement activation. 16-19 Define interferons. 16-20 Compare and contrast the actions of IFN-α and IFN-β with IFN-. 16-21 Describe the role of iron-binding proteins in innate immunity. Figure 16.1 An overview of the body’s defenses. like having system a security ForaSpecific First line of Second line of defense Third line of defense defense Intact skin Mucous membranes and their secretions Loading… Phagocytes, such as neutrophils, eosinophils, dendritic cells, and macrophages Specialized lymphocytes: T cells and B cells Antibodies Normal microbiota Inflammation Fever Antimicrobial substances First Line of Defense: Skin and Mucous Membranes Skin Mucous membranes and secretions Normal microbiota Physical Factors Chemical Factors  Physical Factors Skin Epidermis consists of tightly packed cells with Keratin, a protective protein  Physical Factors Mucous membranes ↓ Mucus: traps microbes Ciliary escalator: transports microbes trapped in mucus away from the lungs ↳ Bordatella pertussis (Whooping cough) paralyzes cilia with toxin Figure 16.4 The ciliary escalator. Trapped particles in mucus Cili a Goblet Insert Fig 16.4 cells Ciliated cells Computer-enhanced Physical Factors Secretions (wash away invaders) Lacrimal apparatus > - tear ducts Saliva Urine Vaginal secretions Chemical Factors Fungistatic fatty acid in sebum (sebaceous glands) Low pH (3–5) of skin (fatty acids, lactic acid) Lysozyme in perspiration, tears, saliva, and urine Low pH (1.2–3.0) of gastric juice (HCl, enzymes) Loading… Low pH (3–5) of vaginal secretions (lactic acid bacteria) Second Line of Defense Phagocytes neutrophils, eosinophils, dendritic cells, and macrophages Inflammation Fever Antimicrobial substances Fig 16.4 Hematopoiesis Figure 16.5a The lymphatic system. Thoracic Right (left lymphatic lymphatic) duct duct Left Right subclavia subclavian n Transports fluid back to vein vein bloodstream, recycles plasma proteins, delivers Tonsil leukocytes, filters out invaders Thymus Hear t Lymph fluid Thoracic duct Splee Lymphatic vessels Lymphatic vessel n Small intestine Lymphatic tissue (nodes and Large intestine Peyer’s organs) Red patch Lymph node Red bone marrow bone marrow (a) Components of lymphatic system Figure 16.5b-c The lymphatic system. Lymphatic capillaries between cells collect interstitial fluid from plasma (lymph) One way flow to lymphatic ducts, back to heart (plasma) Venule Interstitial fluid Blood capillary Tissue cell Bloo Arteriole One-way opening d Bloo d Interstitial Lymphatic capillary fluid (between cells) Lymp Tissue cell h Lymphatic capillary Lymp h Relationship of lymphatic capillaries to Details of a lymphatic capillary tissue cells and blood capillaries  Phagocytosis Eat cell Phago: from Greek, meaning eat Cyte: from Greek, meaning cell Ingestion of microbes or particles by a cell, performed by phagocytes The Phases of Phagocytosis Host Toll-like receptors (TLRs) attach to pathogen-associated molecular patterns (PAMPs) (e.g., LPS, peptidoglycan, flagellin, dsRNA) TLRs induce cytokines that regulate the intensity and duration of immune responses (inflammation and also T and B-cell response) https://www.youtube.com/watch?v=iZYLeIJwe4w Inflammation Redness, Swelling (edema), Pain, Heat Triggered by damage to tissues Cytokines (like TNF-α) activate acute-phase proteins (cause local and systemic responses, more cytokines, can amplify response) 3 general stages: Vasodilation (and increased permeability of blood vessels) Phagocyte migration/phagocytosis - Tissue repair Figure 16.9 The process of inflammation. Bacteria entering on knife Bacteria Epidermis Blood vessel Dermis Nerve Subcutaneous tissue (a) Tissue damage 1 Chemicals such as histamine, kinins, prostaglandins, leukotrienes, and enet cytokines (represented as blue basicallysating dots) are released by damaged cells. 2 Blood clot forms. 3 Abscess starts to form (orange area). (b) Vasodilation and increased permeability of blood vessels  Substances that lead to vasodilation ⑭ Histamine Vasodilation, increased permeability of blood vessels Kinins Vasodilation, increased permeability of blood vessels Prostaglandins Intensify histamine and kinin effect Leukotrienes Increased permeability of blood vessels, phagocytic attachment Figure 16.9b The process of inflammation. Blood vessel endothelium Monocyte 4 Margination— phagocytes stick to endothelium. 5 Diapedesis— phagocytes Insert Fig 16.8c squeeze between endothelial cells. 6 Phagocytosis of invading bacteria occurs. Red Macrophage blood cell (c) Phagocyte migration and phagocytosis Bacteriu m Neutrophil Figure 16.9c The process of inflammation. Sca b Blood clot Regenerated epidermis (parenchyma) Insert Fig 16.8d Regenerated dermis (stroma) (d) Tissue repair Fever Systemic reaction to infection Hypothalamus is normally set at 37°C Phagocytes release cytokines (interleukin-1 (IL-1, “pyrogen”), TNF) Cytokines cause hypothalamus to release prostaglandins, reset hypothalamus to a higher temperature Body increases rate of metabolism, vasoconstriction and shivering (chills) raise temperature Vasodilation and sweating: body temperature falls (“crisis”) Fever Advantages Disadvantages Increases transferrin Tachycardia production Acidosis stimulates T cells (CD8+ Dehydration cytotoxic) 44–46oC (112-114oF) Increases effectiveness fatal of interferon Increased rates of tissue repair May inhibit growth of some bacteria Antimicrobial Substances Complement Interferons Iron-binding proteins Antimicrobial peptides The Complement System Part of the innate immune, complements other immune responses Serum proteins (>30 types) activated in a cascade Activated directly by pathogen or by antibody-antigen reaction Antigen–antibody reaction (Classical) Proteins C3, B, D, P and a pathogen (Alternative) Macrophages produce cytokines, induces Lectin production by liver (binds to carbohydrates on pathogens) Leads to inflammation, cytolysis and opsonization Outcomes of Complement Activation 1 Inactivated C3 splits into activated C3a and C3b. C3 2 C3b binds to microbe, resulting in opsonization. C3 C3 C3b causes opsonization C3b b a (aids in phagocytosis) protein s C3a + C5a cause 3 C3b also splits C5 into C5a and C5b 5 C3a and C5a cause inflammation (attracts mast cells to release histamine, resulting in inflammation; phagocytes) C5a also attracts phagocytes. C5b + C6 + C7 + C8 + C9 opsonization cause cell lysis (cytolysis) C Enhancement of phagocytosis 5 C5a receptor C5 by coating with C3b Histamin a e C5 C5 b a 4 C5b, C6, C7, and C8 bind Insert Fig 16.9 Mast cell together sequentially and C6 C3a receptor C3 insert into the microbial plasma membrane, where they function as a receptor C7 a inflammation to attract a C9 fragment; C8 Increase of blood vessel additional C9 fragments are added to form a channel. permeability and chemotactic Together, C5b through C8 attraction of phagocytes and the multiple C9 fragments form the membrane attack complex, C9 resulting in cytolysis. Microbial plasma membrane Channe l Membrane attack C 6 C C5 C C6 C5 Cb Cb complex (MAC) 7 7 C C 8 8 Formation of 9 membrane Cytolysi 9 attack complex (MAC) s cytolysis Bursting of microbe due to inflow of extracellular fluid through transmembrane channel formed by membrane attack complex Some Bacteria Evade Complement Capsules prevent C activation Surface lipid–carbohydrate complexes prevent formation of membrane attack complex (MAC) Enzymatic digestion of C5a Loading… Interferons (IFNs) SARS-CoV2 silences interferon response IFN- and IFN- : cause cells to produce antiviral proteins that inhibit viral replication IFN- : causes neutrophils and macrophages to phagocytize bacteria Other Antimicrobial substances Iron binding proteins Antimicrobial peptides transferrin, ferritin, Activated by TLR’s lactoferrin, hemoglobin Dermicidin (sweat glands) Pathogens produce Defensins (immune cells) siderophores to access Lyse bacterial cells, degrade tightly bound Fe DNA/RNA, Sequester LPS, signal to immune cells… The Adaptive Immune System (Ch 17) LEARNING OBJECTIVES 17-1 Compare and contrast adaptive and innate immunity. 17-2 Differentiate humoral from cellular immunity 17-4 Define antigen, epitope, and hapten. 17-5 Explain the function of antibodies, and describe their structural and chemical characteristics. 17-6 Name one function for each of the five classes of antibodies 17-7 Compare and contrast T-dependent and T-independent antigens. 17-8 Differentiate plasma cell from memory cell. 17-9 Describe clonal selection. 17-10 Describe how a human can produce different antibodies. 17-11 Describe four outcomes of an antigen–antibody reaction. 17-12 Describe at least one function of each of the following: M cells, TH cells, TC cells, Treg cells, CTLs, NK cells. 17-13 Differentiate T helper, T cytotoxic, and T regulatory cells. 17-15 Define apoptosis. 17-16 Define antigen-presenting cell. 17-17 Describe the function of natural killer cells. 17-18 Describe the role of antibodies and natural killer cells in antibody-dependent cell-mediated cytotoxicity. 17-19 Distinguish a primary from a secondary immune response. 17-20 Contrast the four types of adaptive immunity. Immunity Innate immunity: defenses against any pathogen Adaptive immunity: induced resistance to a specific pathogen Dual Nature of Adaptive Immunity T and B cells develop from stem cells in red bone marrow Humoral immunity Due to antibodies B cells mature in the bone marrow Cellular immunity Due to T cells Loading… T cells mature in the thymus Figure 17.1 T and B cell development Figure 17.19 The dual nature of the adaptive immune system. Humoral (antibody-mediated) immune system Cellular (cell-mediated) immune system Control of freely circulating pathogens Control of intracellular pathogens Intracellular antigens are expressed on the surface of an Extracellular antigens APC, a cell infected by a virus, a bacterium, or a parasite. A B cell binds to the antigen for which it is specific. A T-dependent B A T cell binds to T cell cell requires cooperation MHC–antigen Cytokines activate T Cytokines activate complexes on the with a T helper (TH) cell. helper (TH) cell. macrophage. surface of the Cytokines Cytokines infected cell, activating the T cell (with its cytokine B cell receptors). Cytokines from the TH Activation of The B cell, often with cell transform B cells into TH cell macrophage stimulation by cytokines antibody-producing (enhanced plasma cells. from a TH cell, differentiates phagocytic activity). into a plasma cell. Some B cells become memory cells. The CD8+T cell Plasma cell Cytotoxic T becomes a cytotoxic T lymphocyte (CTL) craccines) lymphocyte able to induce Plasma cells Memory cell apoptosis of the target cell. proliferate and produce antibodies Some T and B cells differentiate against the antigen. into memory cells that respond rapidly to any secondary Antigenfor encounter with an antigen. Lysed target cell Antigens Antigen (Ag): a substance that causes the body to produce specific antibodies or sensitized T cells Antibodies (Ab) interact with epitopes, or antigenic determinants Loading… Figure 17.2 Epitopes (antigenic determinants). Figure 17.3 Haptens. Hapten: small antigens must be combined with carrier molecules to start immune response Example: penicillin allergy (combines with host proteins) Hapten Carrier Hapten-carrier molecules molecule conjugate The Nature of Antibodies Globular proteins called immunoglobulins The number of antigen-binding sites determines valence Figure 17.4 The structure of a typical antibody molecule. V(D)J recombination: generation of antigen-binding diversity V(D)J recombination during B and T cell development Plus more diversity from randomly adding bases during joining, point mutations during immune response, mixing and matching of heavy and light chains >1013 possible types of antibodies/T-cell receptors some are self-reactive and will be deleted Evolved from transposon found in Amphioxus (earliest vertebrate)? Carmona & Schatz 2016 https://febs.onlinelibrary.wiley.com /doi/full/10.1111/febs.13990 heavy chain light chain Heavy chains have V, D and J Light chains only V and J 17.2  Antigen–Antibody Binding Agglutination Opsonization Activation of complement Antibody-dependent cell-mediated cytotoxicity Neutralization Figure 17.8 B Cells and Humoral Immunity B cell activation T cell-dependent T cell-independent Clonal selection B cell differentiation Loading… Antibody-producing plasma cells Memory cells Clonal deletion See MM animation (Study Area/ Microanimations/Host Defenses: Humoral Immunity: Clonal Selection and Expansion Activation of B Cells Major histocompatibility complex (MHC) expressed on mammalian cells Involved in organ transplant compatibility Type I: presented by infected cells Animation: Antigen Type II: presented by phagocytes Processing and Presentation: MHC T-dependent antigens Ag presented with (self) MHC to TH cell TH cell produces cytokines that activate the B cell T-independent antigens Stimulate the B cell to make Abs Figure 17.7 T-independent antigens. Polysaccharide (T-independent antigen) Epitopes B cell receptors Figure 17.5 Activation of B cells to produce antibodies. Extracellular antigens MHC class II with Ag fragment MHC class II with displayed on Antibodies Ag fragment Ag fragment surface B cell B cell Immunoglobulin Plasma cell receptors TH coating cell B cell B cell surface Cytokines Immunoglobulin receptors MHC class II–antigen- Receptor on the T helper cell B cell is activated by on B cell surface recognize fragment complex is (TH) recognizes complex of cytokines and begins and attach to antigen, displayed on B cell MHC class II and antigen clonal expansion. Some which is then internalized surface. fragment and is activated— of the progeny become and processed. Within the producing cytokines, which antibody-producing B cell a fragment of the activate the B cell. The TH cell plasma cells. antigen combines with has been previously activated by MHC class II. an antigen displayed on a dendritic cell (see Figure 17.10). Figure 17.6 Clonal selection and differentiation of B cells. Clonal deletion Clonal deletion eliminates harmful B cells During maturation in the bone marrow, self-reactive B cell lines are deleted (apoptosis)  T Cells and Cellular Immunity T cells mature in the thymus Thymic selection eliminates many immature T cells Positive selection (MHC), negative selection (self) T cells respond to antigen by T-cell receptors (TCRs) TCR related to Ig proteins, have variable and constant regions T cells require antigen-presenting cells (APCs) 17.3 T Helper Cells CD4+ or TH cells TCRs recognize antigens and MHC II on APC TLRs are a costimulatory signal on APC and TH TH cells produce cytokines and differentiate into: TH1cells TH2 cells Make different types of cytokines, stimulate TH17 cells different cells Memory cells Activation of CD4+ T Helper Cells Figure 17.12 Activation of CD4+T helper cells. Figure 17.14 Lineage of effector T helper cell classes and pathogens targeted. Antigen-presenting cell TH cells of various classes TH17 cells secrete cytokines that TH1 cells are an important element of cellular promote inflammatory responses; immunity. Their cytokines (such as IFN-γ and IL-2) recruit neutrophils for protection activate CD8+ T cells and NK cells, which control against extracellular bacteria intracellular pathogens by killing infected host and fungi. IL-17 IIFN N- cells. They also enhance phagocytosis by antigen- γ presenting cells such as macrophages. IL-4 TH2 cells Fungi Extracellular bacteria Neutrophil Intracellular Macrophage bacteria and protozoa Important in allergic responses, especially by production of IgE. Mast cell Activate eosinophils to control Basophil extracellular parasites such as Eosinophil helminths (see ADCC discussion). Helminth T Cytotoxic Cells CD8+ or TC cells Target cells are self-cells carrying endogenous antigens Activated into cytotoxic T lymphocytes (CTLs) CTLs recognize Ag + MHC I Induce apoptosis in target cell CTL releases perforin and granzymes Figure 17.12 Killing of virus-infected target cell by cytotoxic T lymphocyte. Processed antigen presented with T cell MHC class I receptors Infected MHC target cell Processed is lysed antigen class I CTL Virus-infected cell (example of endogenous antigen) Virus-infected cell Cytotoxic T lymphocyte (CTL) A normal cell will not trigger a The abnormal antigen is The CTL induces destruction response by a cytotoxic T presented on the cell surface in of the virus-infected cell by lymphocyte (CTL), but a virus- association with MHC class I apoptosis. infected cell (shown here) or a molecules. CD8+T cells with cancer cell produces abnormal receptors for the antigen are endogenous antigens. transformed into CTLs. ANIMATION Cell-Mediated Immunity: Cytotoxic T Cells  T Regulatory Cells Treg cells CD4 and CD25 on surface Suppress T cells against self “Self” can include natural microbiome, developing fetus Natural Killer (NK) Cells Granular leukocytes destroy cells that don’t express MHC I Kill virus-infected and tumor cells Attack parasites ADCC Antibody-dependent cell-mediated cytotoxicity Figure 17.16 Antibody-dependent cell-mediated cytotoxicity (ADCC). Immunological Memory Primary response occurs after initial contact with Ag # Secondary (memory or anamnestic) response occurs after second exposure · Types of Adaptive Immunity Naturally acquired active immunity Resulting from infection T Naturally acquired passive immunity Transplacental or via colostrum Artificially acquired active immunity ga Injection of Ag (vaccination)· Artificially acquired passive immunity Injection of Ab · “convalescent plasma” Types of Adaptive Immunity Naturally acquired active immunity Resulting from infection Naturally acquired passive immunity Transplacental or via colostrum Artificially acquired active immunity Injection of Ag (vaccination) Artificially acquired passive immunity Injection of Ab “convalescent plasma” Learning Objectives Antimicrobial drugs (Ch 20-2 20-3 20) Name the microbes that produce most antibiotics. Describe the problems of chemotherapy for viral, fungal, protozoan, and helminthic infections. 20-4 Define the following terms: spectrum of activity, broad-spectrum antibiotic, superinfection. 20-5 Identify five modes of action of antimicrobial drugs. 20-6 Explain why the drugs described in this section are specific for bacteria. 20-7 List the advantages of each of the following over penicillin: semisynthetic penicillins, cephalosporins, and vancomycin. 20-8 Explain why isoniazid (INH) and ethambutol are antimycobacterial agents. 20-9 Describe how each of the following inhibits protein synthesis: aminoglycosides (streptomycin), tetracyclines, chloramphenicol, macrolides. 20-11 Describe how rifamycins and quinolones kill bacteria. 20-12 Describe how sulfa drugs inhibit microbial growth. 20-13 Explain the modes of action of currently used antifungal drugs. 20-14 Explain the modes of action of currently used antiviral drugs. 20-17 Describe the mechanisms of drug resistance 20-18 Compare and contrast synergism and antagonism (combination of drugs) 20-19 Identify three areas of research on new chemotherapeutic agents. Figure 20.1 Laboratory observation of antibiosis. Loading… Table 20.1 Representative Sources of Antibiotics Insert Table 20.1 The Spectrum of Antimicrobial Activity Broad vs narrow spectrum Why are Eukaryotic infections harder to treat? Euk microbes similar to human cells Low selectivity, high toxicity Viruses use host cells for growth, same issue The Action of Antimicrobial Drugs Bactericidal Kill microbes directly Bacteriostatic Prevent microbes from growing Synergistic drug interactions: more effective in combination (e.g., penicillin damages cell wall, helps streptomycin enter cell) Antagonistic drug interactions: tetracycline stops bacterial growth, preventing penicillin from being effective Disk-diffusion assay Figure 20.2 Major Action Modes of Antimicrobial Drugs. 1. Inhibition of cell wall synthesis: penicillins, 2. Inhibition of protein synthesis: chloramphenicol, cephalosporins, bacitracin, vancomycin erythryomycin, tetracyclines, streptomycin DNA mRNA Protein Transcription Translation Replication Enzyme 4. Injury to plasma membrane: polymyxin B 5. Inhibition of essential 3. Inhibition of nucleic acid replication metabolite synthesis: sulfanimide, trimethoprim and transcription: quinolones, rifampin Figure 4.13a Bacterial cell walls. N-acetylglucosamine (NAG) Tetrapeptide side chain N-acetylmuramic acid (NAM) Peptide cross-bridge Side-chain amino acid Cross-bridge amino acid NAM Peptide Carbohydrat bond e NA “backbone” G Structure of peptidoglycan in gram-positive bacteria. Inhibitors of Cell Wall Synthesis Penicillin Natural penicillins Semisynthetic penicillins Extended-spectrum penicillins Loading… Figure 20.6a The structure of penicillins, antibacterial antibiotics. Natural penicillins Common nucleus Penicillin G (requires injection) –lactam ring Penicillin V (can be taken orally) Semisynthetic penicillins Common nucleus Oxacillin: Narrow spectrum, only gram-positives, but resistant to penicillinase –lactam ring Ampicillin: Extended spectrum, many gram-negatives. Figure 20.8 The effect of penicillinase on penicillins. –lactam ring Penicillinase Penicillin Penicilloic acid Penicillinase (beta-lactamase) enzymes inhibited by clavulanic acid Useful in combination with antibiotics Inhibitors of Cell Wall Synthesis Cephalosporins First-generation: narrow spectrum; act against gram-positive bacteria Second-generation: extended spectrum includes gram-negative bacteria Third-generation: includes pseudomonads; injected Fourth-generation: oral Inhibitors of Cell Wall Synthesis Polypeptide antibiotics Bacitracin Topical application Against gram-positives Vancomycin Glycopeptide (made by Streptomyces orientalis) Important “last line” against antibiotic-resistant S. aureus Inhibitors of Cell Wall Synthesis Antimycobacterial antibiotics Isoniazid (INH) Inhibits mycolic acid synthesis Ethambutol Inhibits incorporation of mycolic acid Figure 20.4 The inhibition of protein synthesis by antibiotics. Protein Growing synthesis polypeptide site Tunnel Growing polypeptide 50S 5′ Chloramphenicol Binds to 50S portion and inhibits formation of peptide bond 30S 50S 3′ mRNA portion Three-dimensional detail of the protein synthesis site showing the 30S and 50S Protein synthesis site subunit portions of the 70S prokaryotic ribosome tRNA Messenger RNA 30S portion Direction of ribosome movement (Aminoglycosides) Streptomycin Tetracyclines 70S prokaryotic Changes shape of 30S portion, Interfere with attachment of ribosome causing code on mRNA to be tRNA to mRNA–ribosome read incorrectly Translation complex Diagram indicating the different points at which chloramphenicol, the tetracyclines, and streptomycin exert their activities Injury to the Plasma Membrane Lipopeptides Membrane depolarization (destroys proton gradient) Daptomycin used for MRSA Polymyxin B Topical Combined with bacitracin and neomycin in over-the-counter preparation Inhibitors of Nucleic Acid Synthesis Rifamycin Inhibits RNA synthesis Antituberculosis and leprosy Penetrates tissues and abscesses Side effect: Orange-red body fluids Quinolones and fluoroquinolones (FQ) Nalidixic acid Ciprofloxacin (next gen, broader spectrum) Inhibit DNA gyrase Urinary tract infections  Competitive Inhibitors Sulfonamides (sulfa drugs) Inhibit folic acid synthesis Broad spectrum Inhibiting the Synthesis of Essential Metabolites Figure 20.13 Actions of the antibacterial synthetics trimethoprim and sulfamethoxazole. PABA PABA Sulfamethoxazole, a Sulfamethoxazole sulfonamide that is a structural analog of Sulfamethoxazole PABA, competitively inhibits the synthesis of dihydrofolic acid from PABA. Dihydrofolic acid Dihydrofolic acid Trimethoprim Trimethoprim, a structural analog of a portion of dihydrofolic acid, competitively Trimethoprim inhibits the synthesis Tetrahydrofolic acid of tetrahydrofolic acid. Precursors of proteins, DNA DNA, RNA RNA Antifungal Drugs: Inhibition of Ergosterol Synthesis/disruption of cell membranes Polyenes Azoles (imidazoles like clotrimazol) and Amphotericin B Allylamines inhibit ergosterol synthesis Disrupt membrane Figure 20.14 The structure of the antifungal drug amphotericin B, representative of the polyenes. Amphotericin B Antifungal Drugs: Inhibiting Cell Wall Synthesis Echinocandins Inhibit synthesis of -glucan Caspofungin (Candida, Aspergillus) Mammals don’t convert flucytosine to active form (nucleoside analog)  Antiviral treatments Inhibitors of: Entry/Fusion Nucleic acid synthesis, genome integration (retroviruses) Assembly and exit Interferon Fig. 19.19. Drugs that inhibit the HIV life cycle Highly Active Antiretroviral Therapy (HAART) against HIV Multi-drug therapy (to reduce resistant variants) Controls growth, but doesn’t eliminate latent proviruses integrated into host genome Possible future approach: CRISPR/Cas9 system to excise proviral DNA from host genome Antiviral Drugs: Entry/Exit Inhibitors Entry inhibitors Amantadine: influenza Fusion inhibitors Prevent membrane-envelope fusion (and/or budding) Zanamivir, Tamiflu: neuraminidase inhibitors (influenza) Enfuvirtide (HIV) Figure 20.16 The structure and function of the antiviral drug acyclovir Acyclovir structurally Interferes with viral resembles the nucleic acid synthesis nucleoside deoxyguanosine Antiviral Drugs: Interferons Prevent spread of viruses to new cells Alpha interferon: Viral hepatitis Imiquimod Promotes interferon production Treating COVID19 Future directions: natural polysaccharides to stimulate immune Research is ongoing, many contradictory results system? Computer screening of existing drugs to Several preexisting anti-malarial drugs have predict binding to SARS-CoV2 targets? been explored: chloroquine, hydroxychloroquine (HCQ), mefloquine, artemisinins, ivermectin, anti-inflammatory drugs nitazoxanide, niclosamide SARS-CoV2 causes cytokine storm in more Some have antiviral effects in vitro, but evidence severe cases, therefore anti-inflammatory in clinical trials and in vivo studies is weak drugs can be helpful HCQ has no proven antiviral effect in vivo However, SARS-CoV2 attacks multiple tissue types, including adrenal grand, which However, low doses at early stage can be helpful increases cortisol levels, reducing lymphocyte as anti-inflammatory activation But so is Ibuprofin! Inflammation in other areas may “deceitfully distract” lymphocytes away from lungs Glucocorticoids can make this worse Early use of non-steroidal anti-inflammatory drugs (NSAIDs) blocks the diffuse inflammation produced by SARS CoV-2, and might prevent COVID-19 complications Early use of glucocorticoids might increase chance of complications, beneficial only for patients with late acute respiratory distress syndrome (ARDS). Kelleni (2021) Biomedicine & Pharmacotherapy Volume 133, January 2021, 110982 Antibiotic Resistance “A post-antibiotic era—in which common infections and minor injuries can kill—far from being an apocalyptic fantasy, is instead a very real possibility for the 21st century” - World Health Organization (2014) Loading… A variety of mutations can lead to antibiotic resistance Resistance genes are often on plasmids or transposons that can be transferred between bacteria Last new class of antibacterial drugs discovered in the 1980’s But new synthetic derivatives of natural products can be effective Chloramphenical derivatives against MRSA Polymixin derivatives against Gram negative superbugs LPC-069 against plague “One definition of insanity is repeating the same task over and over again while expecting a different outcome. This is especially applicable to antibiotic discovery research where much emphasis has been placed on finding new natural product antibiotics” - Paul Hoffman 2020 Antibiotic Resistance Misuse of antibiotics selects for resistance mutants Using outdated or weakened antibiotics Using antibiotics for the common cold and other inappropriate conditions Using antibiotics in animal feed Failing to complete the prescribed regimen Using someone else’s leftover prescription Overuse of triclosan selects for multidrug resistant bacteria? hand soap, toothpaste, deodorant, surgical scrubs, shower gel, hand lotion, hand cream, and mouthwash 1.1-4.2 × 105 kg/year discharged in waste water (US)  Carey and McNamara (2014) The impact of triclosan on the spread of antibiotic resistance in the environment. Front Microbiol. 5: 780. Minimum inhibitory concentrations of chloramphenicol and tetracycline for control strains (striped bars) and TCS adapted strains (solid bars) are shown from various studies and bacteria Figure 20.20 Bacterial Resistance to Antibiotics. 1. Blocking entry Antibiotic Antibiotic 2. Inactivation by enzymes Antibiotic Altered target molecule Enzymatic action Inactivated antibiotic 3. Alteration of target molecule 4. Efflux of antibiotic Clinical Focus Antibiotics in Animal Feed Linked to Human Disease, Figure A. S. Cephalosporin-resistance in E. ente coli transferred by conjugation rica S to Salmonella enterica in the afte. intestinal tracts of turkeys. E r e. conj n c uga t o tion e li ri c a Resistance plasmid  Clinical Focus Antibiotics in Animal Feed Linked to Human Disease, Figure B. Vancomycin-Resistant Enterococcus (VRE) declined sharply after vancomycin banned for veterinary use in Europe (1997) FQ-resistance emerged with use of FQ in humans and animals (textbook data is a little off, approved in US for animals in 1995) FQ-resistance still high, despite ban for poultry FQ still used in cattle and humans Poor sanitation in farms and slaughterhouse? Future of Chemotherapeutic Agents and synthetic analogs of Antimicrobial peptides peptides or lipopeptides, like Broad-spectrum antibiotics cyclam-based antibacterial molecules (CAMs) designed Nisin (lactic acid bacteria) based on natural polymixins Defensins (human) Magainin (frogs) Squalamine (sharks) Gene silencing (covered earlier) Phage therapy Fig. 1 Chemical structure of (A) Used in Paris in 1919 to treat dysentery last resort Gram-negative antibiotic, colistin and (B) cyclam- Currently used in Eastern Europe based antibacterial molecules FDA study in US: shown to be safe (CAMs). Konai et al. 2020  Bacteriophages from ExPEC* Reservoirs Kill Pandemic Multidrug-Resistant Strains of Clonal Group ST131 in Animal Models of Bacteremia (Green et al. 2016) Sepsis cases: >1 million/year in the US (many immunocompromised) ~50% die: more deaths than prostate cancer, breast cancer, and AIDS combined Pandemic antibiotic-resistant strains, e.g. E. coli 131 Phage hunting in local parks and bird refuges to collect avian and canine feces Found combination of phages that could kill 12 antibiotic-resistant strains *Extra-intestinal pathogenic Escherichia coli https://www.nature.com/articles/srep46151 http://www.genengnews.com/gen-news-highlights/resistant-superbugs-meet-natural-foe-in-phage-therapy/81254220? utm_medium=newsletter&utm_source=GEN+Daily+News+Highlights&utm_content=01&utm_campaign=GEN+Daily+News+Hig hlights_20170419