Lecture Review
Chapter 18 - Application of Immune Responses
1. [18-01] Compare attenuated vaccine versus inactivated vaccine. Give examples of each – Lecture 8, Slides 3 and 4. –
Attenuated vaccine –Weakened, but still alive pathogen. Can still grow and cause disease in immune-compromised individuals. Usually, one injection is sufficient.
Ex: Polio (Sabin), Measles, Mumps, Rubella (MMR), Chickenpox (Varicella-Zoster), Smallpox (Vaccinia virus)
Inactivated vaccine –Killed pathogen/parts of the pathogen. Cannot cause disease in immune-compromised individuals. Usually, need multiple injections to develop strong immunity.
Ex: Polio (Stalk), Hepatitis, Rabies, Diphtheria, Tetanus, Pertussis (DTap), Meningitis (MCN-4, MPSV-4, Hib), Pneumonia (PCV-7, PCV-13).
Attenuated vaccine –Weakened, but still alive pathogen. Can still grow and cause disease in immune-compromised individuals. Usually, one injection is sufficient.
Ex: Polio (Sabin), Measles, Mumps, Rubella (MMR), Chickenpox (Varicella-Zoster), Smallpox (Vaccinia virus)
Inactivated vaccine –Killed pathogen/parts of the pathogen. Cannot cause disease in immune-compromised individuals. Usually, need multiple injections to develop strong immunity.
Ex: Polio (Stalk), Hepatitis, Rabies, Diphtheria, Tetanus, Pertussis (DTap), Meningitis (MCN-4, MPSV-4, Hib), Pneumonia (PCV-7, PCV-13).
2. [18-02] Describe the differences between subunit vaccine, toxoid and conjugated vaccines. Give example of each – Lecture 8, Slide 4 (notes). –
Subunit vaccine: Contain purified pathogen’s key protein antigens OR antigenic fragments. Ex: Acellular pertussis (part of DTap vaccine)
Toxoid: Toxins from a pathogen that is inactivated. Ex: Diphtheria and Tetanus toxoids (part of DTap vaccine)
Conjugated vaccine: Contains polysaccharides linked to carrier proteins à Turns polysaccharides into T-cell dependent antigens. Ex: Hib vaccine, PCV-7, PCV-13 (against S.pneumoniae)
Subunit vaccine: Contain purified pathogen’s key protein antigens OR antigenic fragments. Ex: Acellular pertussis (part of DTap vaccine)
Toxoid: Toxins from a pathogen that is inactivated. Ex: Diphtheria and Tetanus toxoids (part of DTap vaccine)
Conjugated vaccine: Contains polysaccharides linked to carrier proteins à Turns polysaccharides into T-cell dependent antigens. Ex: Hib vaccine, PCV-7, PCV-13 (against S.pneumoniae)
3. [18-03] Using poliomyelitis as examples, explain the importance of immunization in prevention of infectious diseases – Lecture 8, Slides 5, 6 –
Poliomyelitis – Viral disease transferred via fecal-oral route (mainly via contaminated water). 99% of infected NO signs & symptoms or mild ones. 1% develops paralytic polio.
Before vaccine ~ 50,000 cases every year in US.
After the introduction of Salk and Sabin vaccines, the number of cases fell dramatically. Leading to last indigenous case was in 1980. NO cases reported in US since 1998.
Poliomyelitis – Viral disease transferred via fecal-oral route (mainly via contaminated water). 99% of infected NO signs & symptoms or mild ones. 1% develops paralytic polio.
Before vaccine ~ 50,000 cases every year in US.
After the introduction of Salk and Sabin vaccines, the number of cases fell dramatically. Leading to last indigenous case was in 1980. NO cases reported in US since 1998.
4. [18-04] Describe DTaP and MMR vaccines used in the USA in the prevention of infectious diseases. – Lecture 8, Slide 8 –
DTap – Contains diphtheria toxoid, tetanus toxoid, and acellular portion of Bordetella pertussis cell wall.
MMR – Three attenuated viruses: measles, mumps, rubella.
*Both are part of the immunization schedule.
DTap – Contains diphtheria toxoid, tetanus toxoid, and acellular portion of Bordetella pertussis cell wall.
MMR – Three attenuated viruses: measles, mumps, rubella.
*Both are part of the immunization schedule.
5. [18-05] Describe the properties of polyclonal and monoclonal antibodies. Which antibody (polyclonal or monoclonal) is more likely to be suited for medical use? Explain why. – Lecture 8, Slides 10, 11. –
Properties of polyclonal antibody. They are called polyclonal as they are mixture of antibodies produced by different clones of plasma cells descended from various naïve B-cells. These antibodies can recognize various epitopes. Therefore, are more likely cross-react with other antigens.
Properties of monoclonal antibody. They are called monoclonal as they contain the antibody produced by single clone of plasma cells descended from single naïve B-cell. Produced by specific cell cultures called hybridomas. These antibodies can recognize only single epitope. Therefore, they are less likely to cross-react with other antigens, including human cells and tissues.
Medical use of antibodies. Monoclonal antibodies are better suited for medical use as they have higher specificity than polyclonal antibodies and they are less likely to cross-react with human antigens. Out of all monoclonal antibodies, humanized antibodies are the best for medical use, as they do not trigger an immune response in patients and can be used multiple times in the same patient.
Properties of polyclonal antibody. They are called polyclonal as they are mixture of antibodies produced by different clones of plasma cells descended from various naïve B-cells. These antibodies can recognize various epitopes. Therefore, are more likely cross-react with other antigens.
Properties of monoclonal antibody. They are called monoclonal as they contain the antibody produced by single clone of plasma cells descended from single naïve B-cell. Produced by specific cell cultures called hybridomas. These antibodies can recognize only single epitope. Therefore, they are less likely to cross-react with other antigens, including human cells and tissues.
Medical use of antibodies. Monoclonal antibodies are better suited for medical use as they have higher specificity than polyclonal antibodies and they are less likely to cross-react with human antigens. Out of all monoclonal antibodies, humanized antibodies are the best for medical use, as they do not trigger an immune response in patients and can be used multiple times in the same patient.
6. [18-06] Compare chimerical and humanized monoclonal antibodies. Which one is better suited for medical use in humans and why? – Lecture 8, Slide 12. –
Chimerical antibody is monoclonal antibody produced in hybridomas derived from genetically modified mice, when constant region of mouse antibody is replaced with constant region of human antibody. Chimeric antibody has reduced antigenic activity in humans (immune response against them is muted) and it can be injected into patient more than once.
Humanized antibody is monoclonal antibody produced in hybridomas derived from genetically modified mice, when constant and some of variable regions of mouse antibody are replaced with the human ones. If the humanized antibody is injected, it will not trigger the immune response in humans.
Both chimerical and humanized monoclonal antibodies can be used as immunotoxins, as they both can deliver the toxin specifically to targeted cell and kill it. Humanized antibodies are better suited for use in humans than chimerical antibody as they as less likely to case immune response in humans. Nine monoclonal antibodies have been approved for cancer therapy.
Chimerical antibody is monoclonal antibody produced in hybridomas derived from genetically modified mice, when constant region of mouse antibody is replaced with constant region of human antibody. Chimeric antibody has reduced antigenic activity in humans (immune response against them is muted) and it can be injected into patient more than once.
Humanized antibody is monoclonal antibody produced in hybridomas derived from genetically modified mice, when constant and some of variable regions of mouse antibody are replaced with the human ones. If the humanized antibody is injected, it will not trigger the immune response in humans.
Both chimerical and humanized monoclonal antibodies can be used as immunotoxins, as they both can deliver the toxin specifically to targeted cell and kill it. Humanized antibodies are better suited for use in humans than chimerical antibody as they as less likely to case immune response in humans. Nine monoclonal antibodies have been approved for cancer therapy.
7. [18-07] Describe fluorescent antibody test – Lecture 8, Slide 13 –
Two pathways: Direct labeling of antibody OR Indirect labeling of antibody
Direct labeling = Fluorescent dye is attached to antibody directed against microbe.
Indirect labeling = Involved secondary antibody that binds to antibody directed against microbe. (Better labeling b/c same-tagged secondary antibody can be used to label any antibody produced in the same biological species).
Two pathways: Direct labeling of antibody OR Indirect labeling of antibody
Direct labeling = Fluorescent dye is attached to antibody directed against microbe.
Indirect labeling = Involved secondary antibody that binds to antibody directed against microbe. (Better labeling b/c same-tagged secondary antibody can be used to label any antibody produced in the same biological species).
Chapter 20 - Antimicrobial Medications
8. [20-01] Define the terms “selective toxicity”, “bactericidal”, “bacteriostatic”, “narrow-spectrum”, “broad-spectrum” as they are applied to antibiotics. Give examples – Lecture 8, Slide 14 –
Selective toxicity –Ability to interfere with microbial growth without causing damage to patient. Therapeutic index = [lowest toxic to human] / [lowest toxic to microbe]
Bactericidal –Kills bacteria (Used against acid-fast bacteria). Ex: penicillin, streptomycin.
Minimal bactericidal concentration = [lowest] that kills 99.9% of microbes.
Bacteriostatic –Stops bacterial growth (Used against Gram-negative bacteria). Microbes resume growth after drug withdrawal. Ex: Tetracycline, erythromycin
Narrow-spectrum– Active against a specific group of microbes. Ex: penicillin, erythromycin (Gram positive bacteria only).
Broad-spectrum– Active against a wide range of various microbes. Ex: Tetracycline (Gram+/-), streptomycin (Gram+/-, acid-fast).
Selective toxicity –Ability to interfere with microbial growth without causing damage to patient. Therapeutic index = [lowest toxic to human] / [lowest toxic to microbe]
Bactericidal –Kills bacteria (Used against acid-fast bacteria). Ex: penicillin, streptomycin.
Minimal bactericidal concentration = [lowest] that kills 99.9% of microbes.
Bacteriostatic –Stops bacterial growth (Used against Gram-negative bacteria). Microbes resume growth after drug withdrawal. Ex: Tetracycline, erythromycin
Narrow-spectrum– Active against a specific group of microbes. Ex: penicillin, erythromycin (Gram positive bacteria only).
Broad-spectrum– Active against a wide range of various microbes. Ex: Tetracycline (Gram+/-), streptomycin (Gram+/-, acid-fast).
9. [20-02] Compare three groups of antibiotics that inhibit the cell wall synthesis – Lecture 8, Slide 18 –
ß-lactum drugs – Competing with side chain of peptidoglycan for binding to active site of penicillian-binding protein (PBP). Binds to PBP preventing cross-linking of NAM-NAG polymeric fibers. Ex: Pencillian, Cephalosporins.
Vancomycin – Competing with penicillin-binding protein for binding to peptide side chain. Binds to side chains of NAM in peptidoglycan, preventing NAM-NAG cross-linking. Ex: Vancomycin. CANNOT cross outer membrane of Gram-negative bacteria, only used against gram-positive bacteria. Poor absorption from GI tract, so much is given intravenously.
Bacitracin –Interferes with the delivery of peptidoglycan precursors across the membrane. The drug inhibits de-phosphorylation of bactoprenol-phosphate (carrier for precursors). Highly toxic so limited to topical applications. Ex: Bacitracin.
Vancomycin – Competing with penicillin-binding protein for binding to peptide side chain. Binds to side chains of NAM in peptidoglycan, preventing NAM-NAG cross-linking. Ex: Vancomycin. CANNOT cross outer membrane of Gram-negative bacteria, only used against gram-positive bacteria. Poor absorption from GI tract, so much is given intravenously.
Bacitracin –Interferes with the delivery of peptidoglycan precursors across the membrane. The drug inhibits de-phosphorylation of bactoprenol-phosphate (carrier for precursors). Highly toxic so limited to topical applications. Ex: Bacitracin.
10. [20-03] Mechanisms of bacterial resistance to b (beta) lactam drugs and vancomycin – Lecture 8, Slide 18 –
Bacterial resistance to ß lactam drugs:
1 – Mutation in penicillin-binding protein so it no longer binds penicillin, but still functions in cross-linking peptidoglycan fibers.
2 – Microbe produces enzyme (penicillases/ß-lactamases that break down ß-lactum ring of penicillins/cephahlosporins).
Bacterial resistance to vancomycin:
Genetic mutation that leads to replacement of terminal amino acid in pentapeptide side chain of peptidoglycan. NO longer binds vancomycin, but still can be cross-linked by penicillin binding protein.
Bacterial resistance to ß lactam drugs:
1 – Mutation in penicillin-binding protein so it no longer binds penicillin, but still functions in cross-linking peptidoglycan fibers.
2 – Microbe produces enzyme (penicillases/ß-lactamases that break down ß-lactum ring of penicillins/cephahlosporins).
Bacterial resistance to vancomycin:
Genetic mutation that leads to replacement of terminal amino acid in pentapeptide side chain of peptidoglycan. NO longer binds vancomycin, but still can be cross-linked by penicillin binding protein.
11. [20-04] Compare the properties of Streptomycin and Tetracycline – Lecture 8, Slide 19 –
Streptomycin
Class = Aminoglycosides
Broad-spectrum, Bactericidal
Binds irreversibly to 30S ribosomal subunit blocking initiation of translation.
Effective Gram+/-, acid-fast. NOT effective against Enterococcus and Streptococcus.
Side effects: Extended use may lead to nephrotoxicity.
Resistance: Enzymes to modify antibiotic.
Tetracyline
Class = Tetracyclines
Broad-spectrum, Bacteriostatic
Stops growth by reversible binding to 30S ribosomal subunit + blocking tRNA binding to ribosome.
Effective Gram+/-.
Side effects: Discoloration of teeth when used by young children.
Resistance: Reduce uptake/increase excretion.
Streptomycin
Class = Aminoglycosides
Broad-spectrum, Bactericidal
Binds irreversibly to 30S ribosomal subunit blocking initiation of translation.
Effective Gram+/-, acid-fast. NOT effective against Enterococcus and Streptococcus.
Side effects: Extended use may lead to nephrotoxicity.
Resistance: Enzymes to modify antibiotic.
Tetracyline
Class = Tetracyclines
Broad-spectrum, Bacteriostatic
Stops growth by reversible binding to 30S ribosomal subunit + blocking tRNA binding to ribosome.
Effective Gram+/-.
Side effects: Discoloration of teeth when used by young children.
Resistance: Reduce uptake/increase excretion.
12. [20-05] Compare the properties of Erythromycin and Chloramphenicol – Lecture 8, Slide 19 –
Erythromycin
Class = Macrolides
Narrow-spectrum, Bacteriostatic
Inhibits bacterial growth by reversible binding to 50S ribosomal subunit + blocking translocation of ribosome → blocks elongation of polypeptide chain during protein synthesis.
Effective Gram+.
Resistance: Enzyme that chemically modifies 23S ribosomal RNA via methylation.
Chloramphenicol
Class = Chloramphenicol
Broad-spectrum, Bacteriostatic
Inhibits bacterial growth through reversible binding to 50S ribosomal subunit + blocking peptide bond formation → blocks elongation of polypeptide chain during protein synthesis.
Effective Gram+/-.
Side effects: Toxic → last resort. Can cause fatal aplastic anemia, increase risk of leukemia.
Resistance: Enzyme that acetylates antibiotic.
Erythromycin
Class = Macrolides
Narrow-spectrum, Bacteriostatic
Inhibits bacterial growth by reversible binding to 50S ribosomal subunit + blocking translocation of ribosome → blocks elongation of polypeptide chain during protein synthesis.
Effective Gram+.
Resistance: Enzyme that chemically modifies 23S ribosomal RNA via methylation.
Chloramphenicol
Class = Chloramphenicol
Broad-spectrum, Bacteriostatic
Inhibits bacterial growth through reversible binding to 50S ribosomal subunit + blocking peptide bond formation → blocks elongation of polypeptide chain during protein synthesis.
Effective Gram+/-.
Side effects: Toxic → last resort. Can cause fatal aplastic anemia, increase risk of leukemia.
Resistance: Enzyme that acetylates antibiotic.
13. [20-06] Compare the properties of Ciprofloxacin and Rifampin (Rifampicin) – Lecture 8, Slide 20 –
Ciprofloxacin
Class = Fluoroquinolones
Broad-spectrum, Bactericidal
Irreversibly inhibits DNA gyrase and other enzymes involved in DNA synthesis.
Effective Gram+/-.
Side effects: Tendon, muscle, central nervous system issues.
Resistance: Genetic mutations changes targeted enzymes.
Broad-spectrum, Bactericidal
Irreversibly inhibits DNA gyrase and other enzymes involved in DNA synthesis.
Effective Gram+/-.
Side effects: Tendon, muscle, central nervous system issues.
Resistance: Genetic mutations changes targeted enzymes.
Rifampin
Class = Rifamycins
Broad spectrum, Bactericidal
Irreversibly inhibits RNA polymerase and RNA synthesis.
Effective against Gram+/-. Used in TB treatment.
Side effects: Hepatotoxicity.
Resistance: Genetic mutations changes targeted enzymes.
14. [20-07] Describe the strategy used in antibiotic treatment of infections caused by acid-fast bacteria – Lecture 8, Slide 22 –
1 – Reduce hydrophobicity of cell wall
Ethambutol– Prevents attachment of mycolic acids to cell wall.
Isoniazid– Inhibits synthesis of mycolic acid.
Pyrazinamide– Action NOT clear, ≈ inhibits fatty acid synthesis.
2 – Bactericidal kill microbe
Streptomycin – Irreversibly binds to ribosomes + inhibits protein synthesis.
Rifampin– Irreversibly binds to RNA polymerase + inhibits RNA synthesis.
Ciprofloxacin– Irreversibly binds to DNA gyrase + inhibits DNA synthesis.
Directly Observed Therapy – Health care professional makes sure patient takes the right dose of medication (watches them swallow every pill).
Ethambutol– Prevents attachment of mycolic acids to cell wall.
Isoniazid– Inhibits synthesis of mycolic acid.
Pyrazinamide– Action NOT clear, ≈ inhibits fatty acid synthesis.
2 – Bactericidal kill microbe
Streptomycin – Irreversibly binds to ribosomes + inhibits protein synthesis.
Rifampin– Irreversibly binds to RNA polymerase + inhibits RNA synthesis.
Ciprofloxacin– Irreversibly binds to DNA gyrase + inhibits DNA synthesis.
Directly Observed Therapy – Health care professional makes sure patient takes the right dose of medication (watches them swallow every pill).
15. [20-08] Describe the mechanisms of microbial resistance to antibiotics. Give examples – Lecture 8, Slides 24 –
Microbes can become resistant to antibiotics either through mutations in existing genes or through acquisition of new genes.
Mutations in existing genes may lead to alteration of target molecule so that antibiotic no longer binds to it or alteration of the molecule responsible in the transport of antibiotic into the cell. Examples: Resistance to vancomycin is due to replacement of terminal D-Ala by lactic acid in peptidoglycan precursor’s side chain; Resistance to penicillin is due to modification of penicillin-binding protein – PBP type 2a in S. aureus; Resistance to tetracyclines may occur due to either reduced drug uptake or Increased excretion rate by microbial cell; Resistance to ciprofloxacin, rifampin, sulfa drugs, and trimethoprim occur due to mutations in the genes encoding corresponding bacterial enzymes targeted by these antibiotics.
Acquisition of new genes may lead to alteration of target molecule so that antibiotic no longer binds to it or alteration of antibiotic structure and antibiotic inactivation. Examples: Acetylation of chloramphenicol by newly acquired bacterial acetyltransferase; Breakdown of β-lactam ring of penicillins or cephalosporins by newly acquired bacterial penicillinase or β-lactamase; Resistance to erythromycin due to methylation of 23S rRNA by newly acquired methylase.
Microbes can become resistant to antibiotics either through mutations in existing genes or through acquisition of new genes.
Mutations in existing genes may lead to alteration of target molecule so that antibiotic no longer binds to it or alteration of the molecule responsible in the transport of antibiotic into the cell. Examples: Resistance to vancomycin is due to replacement of terminal D-Ala by lactic acid in peptidoglycan precursor’s side chain; Resistance to penicillin is due to modification of penicillin-binding protein – PBP type 2a in S. aureus; Resistance to tetracyclines may occur due to either reduced drug uptake or Increased excretion rate by microbial cell; Resistance to ciprofloxacin, rifampin, sulfa drugs, and trimethoprim occur due to mutations in the genes encoding corresponding bacterial enzymes targeted by these antibiotics.
Acquisition of new genes may lead to alteration of target molecule so that antibiotic no longer binds to it or alteration of antibiotic structure and antibiotic inactivation. Examples: Acetylation of chloramphenicol by newly acquired bacterial acetyltransferase; Breakdown of β-lactam ring of penicillins or cephalosporins by newly acquired bacterial penicillinase or β-lactamase; Resistance to erythromycin due to methylation of 23S rRNA by newly acquired methylase.
No comments:
Post a Comment