Vaccines, Antimicrobial Drugs, and Diagnostic Tests

Immunity Types

• Naturally Acquired Immunity:

  • The body produces antibodies.

  • Long-term immunity.

  • No technological help.

  • Examples:

    • Recovering from the flu.

    • Getting antibodies through breast milk.

• Artificially Acquired Immunity:

  • Antibodies are ready-made.

  • Short-term immunity.

  • Technological help is involved.

  • Examples:

    • Tetanus shot.

    • Receiving antibodies for rabies.

• Active Immunity: Takes time to work.

• Passive Immunity: Works immediately.

Smallpox Vaccine History

1. Edward Jenner's Observation:

   • Noticed milkmaids who worked with cows and had cowpox did not get smallpox.

   • Hypothesized they received immunity from cowpox.

2. Variolation Experiment:

   • Took cow pus and scratched it onto a boy’s skin.

   • Introduced the boy to people dying of smallpox.

   • The boy did not get sick.

3. Jenner's Conclusion:

   • Vaccinia virus (from cowpox) protects against Variola virus (smallpox).

Variolation vs. Vaccination

• Variolation:

  • Initial method for treating smallpox.

  • People, especially children, are slowly introduced to smallpox material to prepare their immune system.

  • Not ideal because the smallpox material is alive and could cause worse symptoms.

• Vaccination:

  • A preparation of antigens injected to stimulate the adaptive system to produce antibodies against the actual pathogen.

Types of Vaccines

1. Attenuated Vaccine:

   • Alive but weakened, resulting in low virulence.

   • Types:

     • Attenuated Bacteria: Example: Typhoid Fever

     • Attenuated Virus: Example: OPV

   • Not recommended for immunocompromised individuals.

2. Inactivated Vaccine:

   • No live materials, almost zero virulence.

   • Types:

     • Inactivated Whole Agent: Has the entire pathogen composition but is inactivated; Example: Flu shot containing whole influenza virus.

     • Toxoid: Inactivated toxin (exotoxin), not against bacteria but against its toxin; Example: Tetanus shot in dTaP.

     • Subunit: Only a part of the pathogen; Example: Hepatitis B shot has capsids, Gardasil for HPV.

     • Conjugated: Attaches capsule (sugar) to an inactivated toxin (toxoid) since sugar alone won't trigger the immune system. The immune system will then produce antibodies for both; Example: Prevnar 13 or Pneumovax 23 (The # means strains protected).

     • DNA: Injection or gene gun.

     • mRNA: Packaged in lipid nanoparticle delivery (fat bubble); Example: COVID-19.

Disease Eradication

• Only smallpox has been eradicated.

• Polio will hopefully be next.

• Disease requirements for eradication:

  1. Pathogen does not mutate.

  2. Low on resistance list.

  3. Only infects humans.

  4. Can be grown in a lab.

  5. Inexpensive.

  6. Oral instead of needles.

  7. Life-long immunity.

  8. Stable shelf-life without need for refrigeration for poor countries.

Diagnostic Test - ELISA

• ELISA: Enzyme-Linked Immunosorbent Assay

  1. Direct ELISA: Detects patient’s antigen

     • Patient Antigen → Manufactured Enzyme-Linked Antibody → Substrate → Color Change

  2. Indirect ELISA: Detects patient’s antibodies

     • Manufactured Antigen → Patient’s Antibodies → Manufactured Enzyme-Linked Antibody → Substrate → Color Change

  3. Sandwich ELISA: Detects Antigen by sandwiching

     • Manufactured Antibodies → Patient’s Antigen → Manufactured Enzyme-Linked Antibodies → Substrate → Color Change

• Enzyme-Linked Antibody:

  • Binds to patient’s antigen/antibodies.

  • Gives color.

• Example:

  • HIV Virus Antigen (from virus) to Antibody (from John) via Direct ELISA.

  • HIV Virus Antigen (from virus) to Antibody (from John) via Indirect ELISA.

Antimicrobial Drugs

Cell Wall Inhibitors

• Beta-Lactam (Natural): Penicillin

  • Mode of Action: Block enzymes PBP (needed to build peptidoglycan)

    • Contains a 3-Carbon and 1-Nitrogen Ring that resembles a component required to make the cell wall, so bacteria incorporate it, leading to a cidal effect.

  • Examples:

    • Penicillin G (injectable) - for Syphilis

    • Penicillin V (oral) - for oropharyngeal infections

  • Specific Cellular Target: Peptidoglycan

• Beta-Lactam (Semi-synthetic)

  • Examples:

    • Amoxicillin: Resistant to stomach acid; used for Middle Ear Inflammation and Streptococcal pharyngitis; mostly Gram (+).

    • Methicillin: Discontinued due to beta-lactamase; used for Staphylococcus aureus. MRSA developed resistance.

• Beta-Lactam (Cephalosporins)

  • Mode of Action: Block enzymes PBP (needed to build peptidoglycan)

  • Medications begin with prefix: ceph-, kef-, cef-

  • Its beta-lactam ring is more resistant to beta-lactimase compared to penicillin.

  • Only 5th Gen is effective against MRSA.

  • Examples:

    • Cephalothin

    • Cefaclor

    • Cefixime

    • Cefepime

  • 5th Gen: Ceftaroline

• Non-Beta Lactam Cell Wall Inhibitor: Vancomycin

  • Mode of Action: Interferes with Alanine amino acids in cross-bridge of cell wall.

  • Targets the Cross-Bridge (peptide part) of the Cell Wall, which is great for Gram-positive due to exposed cell wall.

  • Clinical Use:

    1. Treat MRSA, given before surgery.

    2. Ineffective against Gram (-) because the outer membrane blocks it from reaching peptidoglycan because the drug is too big.

• Non-Beta Lactam Cell Wall Inhibitor: Isoniazid

  • Mode of Action: Blocks the production of enzymes for mycolic acid production to form the cell wall.

  • Targets Mycolic Acid.

  • Clinical Use: Treatment of Tuberculosis.

• Non-Beta Lactam Cell Wall Inhibitor: Ethambutol

  • Mode of Action: Interferes with the integration of mycolic acid into the cell wall.

  • Targets Mycolic Acid.

  • Clinical Use: Treatment of Tuberculosis.

  • Synergy with Isoniazid.

  • Issues with patient compliance since treatment is too long, requiring DOT (Directly Observed Therapy).

Cell Wall Inhibitors target:

• PBP

• TB.

Cell Membrane Inhibitors

• Disrupts the cell membrane.

• Not common since humans have cell membranes too.

• Used topically, otherwise toxic.

• Small range, only Gram (-).

• Example: Polymixin in Polysporin and Neosporin (A, B, C, D, E) (B most common).

Protein Synthesis Inhibitors - 30s

• Aminoglycosides

  • Mode of Action: Changes shape of 30s Ribosome.

  • Examples:

    • Streptomycin (old): Toxic, so used for TB only.

    • Tobramycin (inhaler) and Amikacin (newer, good penetration).

  • Clinical Use:

    • Streptomycin: Tuberculosis.

    • Pseudomonas.

    • Gram (-).

    • Bone infections.

  • Synergistic with beta-lactam.

  • Cons: Ear damage, broad range.

• Tetracyclines

  • Mode of Action: Block docking site of tRNA on 30s Ribosome.

  • Broad range.

  • Examples:

    • Natural: Tetracycline.

    • Semi-Synthetic: Doxycycline, Minocycline, Tigecycline.

  • Clinical Use:

    • Intracellular parasitic bacteria (Chlamydia, Rickettsia - Rocky Mountain fever).

    • Pneumonia.

    • Tigecycline for MRSA.

    • Doxycycline for Lyme Disease.

  • Cons: Calcium ions disable it (e.g., with milk).

Protein Synthesis Inhibitors - 50s

• Chloramphenicol

  • Mode of Action: Blocks 50s Ribosome so peptide bonds cannot form in amino acids.

  • Broad range.

  • Toxic, so given as a last resort.

  • Cannot breastfeed while on it.

  • Causes reversible and aplastic anemia.

  • Backup drug for Salmonella and Pink Eye.

• Macrolides

  • Mode of Action: Blocks movement of 50s Ribosome along mRNA.

  • Examples:

    • Erythromycin

    • Azithromycin (Z-PAK)

    • Clarithromycin

  • Clinical Use:

    • For Penicillin-allergic patients.

    • Gram (+) infections (Staph and Strep).

    • Intracellular and respiratory infections.

    • Chlamydia Trachomatis (mom to child).

  • Short regimen so patients complete it due to longer half-life.

  • Binds to GI Tract receptors, causing Diarrhea.

  • Erythrocytes: US mandates eye drops to newborns.

Antimetabolites

• Shut down metabolic pathways.

• Analog of PABA/Vitamin B.

• Broad range.

• 3% are allergic.

• Sulfonamides

  • Examples:

    • Sulfisoxazole

    • Sulfamethoxazole (SMX)

  • Clinical Use: Protozoan infections.

• Trimethoprim (TMP)

  • Analog of Dihydrofolic acid.

  • Broad range.

  • Synergism with sulfonamides (SMX-TMP).

  • Clinical Use:

    • Pneumonia

    • Gastrointestinal tract infections

    • UTIs

Nucleic Acid Inhibitors

• Shut down DNA/RNA.

• Fluoroquinolones

  • Mode of Action: Targets DNA Gyrase, which is needed for DNA replication during binary fission.

  • Examples:

    • Ciprofloxacin

    • Norfloxacin

    • Levofloxacin

    • Ofloxacin

  • Broad range.

  • Cidal effect.

  • Cannot be taken with multivitamins.

  • Ciprofloxacin: Use with caution due to tendon rupture and CNS toxicity, so can't be prescribed to anyone under 18

  • Clinical Use:

    • Gram (-)

    • MRSA

    • Urogenital & GI tract (diarrhea)

    • Drug-resistant pneumococci

• Rifampin

  • Mode of Action: Inhibits RNA polymerase to block synthesis of mRNA.

  • Targets RNA Polymerase (mRNA Synthesis).

  • Clinical Use: Tuberculosis.

  • Causes red-orange urine.

• All TB meds: R: Rifampin, I: Isoniazid, S: Streptomycin, E: Ethambutol

Playposit Questions & Answers

• Disrupting normal flora leads to vulnerability to yeast, etc.

• Ribosome subunits: upper is 30s, lower is 50s, total is 70s.

• Bacteria's barrier: cell wall or peptidoglycan.

• Bacteria creates Extracellular enzymes to digest or dissolve the Beta Lactam Ring, making them resistant to the Beta Lactam Ring medication.

• TB bacteria == mycobacterium tuberculosis

• Isoniazid blocks enzymes involved in mycolic acid synthesis of the cell wall, especially in Mycobacterium tuberculosis.

• Ethambutol interferes with the integration of mycolic acid into the cell wall, while Isoniazid blocks enzymes to inhibit the formation of mycolic acid, so both are combined to combat TB.

• Tetracyclines target the 30s ribosome by blocking the docking site of tRNA to inhibit proteins from being made

• Fluoroquinolones target DNA function by targeting DNA gyrase, which is an enzyme needed to replicate DNA for binary fission.

• All Tuberculosis medications (RISE): R = Rifampin, I = Isoniazid, S = Streptomycin, E = Ethambutol

• Normal flora competes against possible pathogens that would occupy the body, some produce acids and bacteriocins against competitors.

• Sign: high temperature; Symptom: fatigue.

Koch's Postulates

1. Same pathogen must be present in all disease cases.

2. Pathogen should be isolated and grown in pure culture.

3. Pathogen should be injected into a healthy susceptible animal.

4. The same pathogen should be present when re-isolating.

Problems with Koch's Postulates

1. Isolating the right cause of disease is challenging.

2. Finding a susceptible host is another challenge.

3. Problems growing the pathogen in the lab (e.g., H. Pylori).

4. There are challenges with each postulate.

Aerosols vs. Droplets

• Aerosols don't have weight and stay in the air.

• Droplets are heavier and fall down.

Summary Points

1. A pus sample from a cow infected with the vaccinia virus was inoculated into the skin of a boy.

2. The boy was placed around people with smallpox/Variola virus.

3. The boy did not get smallpox because the cowpox had protection against it.

4. Since it is not an injectable needle, volunteers can administer it without the need of nurses, or doctors, making the vaccine more available

5. Herd Immunity is when a given population reaches a high amount of vaccinated individuals that protect the ones that cannot get vaccinated. The herd refers to the people capable of vaccination. It protects the vulnerable people that cannot get the vaccination.