BIO244-Lec22

Definition: A vaccine is a suspension of pathogens or portions of pathogens aimed at inducing artificially acquired active immunity.
Historical Example: Edward Jenner pioneered the use of cowpox to immunize against smallpox, leading to the eventual eradication of the disease.
Objective of Vaccination: To stimulate the normal immune response without causing disease through the formation of memory cells.

Inactivated Vaccines: Consist of killed bacteria or inactivated viruses; they only stimulate antibody-mediated immunity. Examples include flu shots and rabies vaccines.
Attenuated (Live) Vaccines: Contain weakened pathogens, triggering both antibody and cell-mediated immunity. Examples include MMR (measles, mumps, rubella) and chickenpox vaccines.
Toxoids: Inactivated toxins used in vaccines for diseases caused by toxins (e.g., Tetanus).

Composition: Contains a portion of the virus's genetic material enclosed in a liposome (e.g., spike protein sequence for Covid-19).
Mechanism: The mRNA is absorbed by cells and translated to express a viral spike protein, triggering an immune response.
Safety: The virus cannot replicate in this context, but the expressed spike protein stimulates a cell-mediated immune response.

Protection: Vaccination helps protect individuals from diseases.
Public Health: Mass vaccination can lead to herd immunity, reducing pathogen reservoirs and infection rates, thereby protecting even unvaccinated individuals.
Eradication Efforts: Successful vaccination programs can eradicate diseases, like smallpox, from populations.

HepB: Administered at birth to prevent hepatitis B.
DTaP: Diphtheria, tetanus, pertussis vaccine, given at 2 months.
Hib: Given at 2 months to prevent meningitis caused by Haemophilus influenzae.
IPV: Inactivated poliovirus vaccine given at 2 months.
MMR: Measles, mumps, rubella vaccine (attenuated virus), given at 1 year.
Chickenpox (Varicella): Attenuated virus vaccine, given at 1 year.
PCV: Pneumococcal conjugate vaccine given at 2 months to prevent meningitis and pneumonia.

Definition: Antimicrobial drugs are intended for internal use to eliminate or inhibit the growth of pathogens in infectious diseases.
Effectiveness: The ideal drugs have high toxicity to pathogens but low toxicity and minimal side effects for humans.
Challenge: Microbial drug resistance is a significant concern in modern medicine.

Antibiotics: Naturally occurring chemicals produced by fungi or bacteria.
Synthetic Drugs: Created in laboratories.
Semisynthetic Drugs: Laboratory-modified versions of antibiotics, starting from the natural antibiotic.

Categories Based on Action:
- Inhibition of cell wall synthesis or destruction.
- Inhibition of nucleic acid function or synthesis.
- Inhibition of protein synthesis.
- Interference with plasma membrane function.

Penicillin: Refers to over 50 antibiotics sharing a beta-lactam ring in their structure.
Origin: Various species of the mold Penicillium produce different versions of penicillin.
Spectrum: Generally effective against gram-positive cocci and spirochetes by inhibiting peptidoglycan cross-linking.

Structures: Illustrative structures of Penicillin G and Penicillin V highlight the beta-lactam ring common to natural penicillins.

Penicillinases: Enzymes produced by certain bacteria that confer resistance to penicillins, particularly in Staphylococcus species.
Semisynthetic Penicillins: Laboratory modifications lead to broader spectrum availability, examples include ampicillin and methicillin.

Structures Illustrated: Structures of ampicillin, methicillin, carbenicillin, and oxacillin showcasing their variations in side chains.

Cephalosporins: Derived from a related fungal genus; effective against penicillin-resistant strains (e.g., Cephalexin).
Bacitracin: A polypeptide targeting cell wall synthesis, effective against gram-positive bacteria.
Vancomycin: Used to treat infections resistant to penicillin and often reserved for severe infections.

Aminoglycosides: Include Streptomycin and Neomycin; they are broad-spectrum antibiotics, usually derived from Streptomyces.
Examples: Amikacin, Gentamicin, Tobramycin.

Tetracyclines: Known for adverse effects on microbiota and can cause side effects such as stomach upset and yeast infections.
Macrolides: Includes erythromycin, an alternative to penicillin with similar activity, also includes azithromycin.

Polymyxin B: Effective primarily against gram-negative bacteria; often used as a topical agent.
Usage: Treats infections from drug-resistant bacteria; associated with serious risks of toxicity to human membranes.

Rifamycins: Such as rifampin, useful against tuberculosis and leprosy via inhibition of mRNA synthesis.
Fluoroquinolones: Includes ciprofloxacin, which inhibits DNA replication; these are broad-spectrum synthetic drugs.

Resistance Mechanisms:
- Destruction or inactivation of antibiotics (e.g., via penicillinases).
- Prevention of drug penetration (e.g., MAR mutations in Gram-negative bacteria).
- Alteration of drug target sites, impacting efficacy (e.g., changes in rRNA).

Nucleoside Analogs: Drugs that resemble normal nucleosides leading to chain termination during replication. Example: Acyclovir for herpes infections.
Treatment for AIDS: Includes AZT and other nucleoside analogs.
Protease Inhibitors: Used in HIV treatment, inhibiting viral replication processes.
Tamiflu: Works by preventing the release of viral particles from host cells.

Eukaryotic Nature: Fungi are eukaryotes, and drugs that target them also have toxicity to humans.
Targeting Ergosterol: Many antifungal drugs inhibit ergosterol biosynthesis, differing from human cholesterol.
Cell Wall Target: Fungi's chitin-based cell walls are another target for various antifungal drugs.