chapter 17 Flashcards
What does a virus consist of?
nucleic acid genome packed in a protein coat
How can antibodies neutralize viruses?
-Binding to cell surface receptor
-Block viral penetration
-Facilitate opsonziation
What are some ways that viruses can evade host defense mechansims?
- Some viruses inhibit type I interferon expression (HCV non-structural protein)
- Some viruses inhibit MHC I presentation (HSV ICP47)
- Escape complement-mediated destruction
- Mutant to change their antigens
results from the accumulation of point mutations within regions of the
envelope glycoprotein genes that code for the antigenic domains of these proteins–RNA polymerases doesn’t have the proofreading mechanisms
antigenic drift
results from reassortment of influenza virus genes during mixed
infections with two or more virus subtypes. Cells infected simultaneously with two virus strains– could produce viruses can infect animal and human
antigenic shift
What are the four primary steps in bacterial infection?
- Attachment to host cells
- Proliferation
- Invasion of host tissue
- Toxin-induced damage
The humoral immune response is the main protective response against
_______________ bacteria.
extracellular
The cell-mediated immune response is the main protective response
against ________________ bacteria.
intracellular
Why is the host response to plasmodium infection poor?
plasmodium keeps changing its surface molecules during maturation
Pros of live, attenuated vaccines:
-weakened pathogens
-Retain their ability to replicate, promoting both humoral and cell-mediated responses
-Often do NOT need boosters
Cons of live, attenuated vaccines:
-May mutate back (revert) to pathogenic form
-May have more side-effect complications
-May also require a “cold chain” for stability during transport
Pros of inactivated or “killed” vaccines:
-Heated or chemically treated to inactivate
-No reversion to pathogenic form
-Often more stable/easy to store and transport
Cons of inactivated or “killed” vaccines:
-Often require booster shots
-Don’t replicate in host, so often don’t induce cell-mediated immunity (humoral only)
-Manufacturing risk to personnel
-Possible chemical exposures/adjuvants often required
-Potentially dangerous if not all pathogen is killed/inactivated
Describe subunit vaccines:
-Use purified macromolecules derived from pathogen
-Inactivated exotoxins/toxoids
– Inactivated capsular polysaccharides
– Inactivated surface glycoproteins (or recombinant protein Ag)
Recombinant vector vaccines:
- Use an attenuated pathogen
– Genetically engineer it to carry another pathogen’s genes and express
them
What are the pros and cons of recombinant vector vaccines?
pros: All the benefits of attenuated vaccines
Fewer risks―not using the actual pathogen, but something else
entirely!
cons: Some of the attenuated vaccine problems are still present
(especially stability issues)
describe the basis of DNA vaccines:
-plasmids carrying pathogen genes injected into muscle tissue
– Host cells take up DNA and express it internally
-Provides Ag presentation via MHC class I, stimulating CTL production
pros of DNA vaccines?
-Induces humoral and cell-mediated immunity
-Prolongs expression, enhancing memory
-VERY stable and customizable
What is the basis of mRNA vaccines?
Pathogen gene mRNA coated with lipid nanoparticles
injected into muscle tissue.
why are conjugate or multivalent vaccines beneficial?
Some molecules aren’t strong enough Ag on their own
to stimulate a good response
How do you induce CTL responses?
-You have to deliver Ag into cells for presentation in MHC class I
molecules
-Creation of lipid carriers known as immunostimulating complexes
(ISCOMs) for delivery
How can adjuvants enhance the immune response to vaccines?
-Promoting inflammation can recruit more immune cells to the area, enhancing effectiveness
-Slowing down Ag release can promote longer interactions, enhancing effectiveness
