Intro to Microbial Pathogens (Feldman) Flashcards
Virus
Protein capsid surrounds either RNA or DNA
Some have lipid bilayer “envelope”
Viruses are not cells, they are obligate intracellular parasites. What does this mean?
Computer analogy: a computer virus must be in a computer in order to be destructive
Viruses can’t synthesize proteins, can’t generate energy, and can’t maintain ionic potential across membrane. They need OUR cells’ mitochondria, etc. to act
Enveloped Viruses
Lipid bilayer surrounding capsid contains viral attachment proteins
When alcohol, etc sprayed on virus, membrane dissolves and virus has no way of infecting cells
Less stable than non-enveloped
Transmission host-to-host
Ex: HIV (but HIV is resiliant! Conformational masking, etc)
Non-Enveloped Viruses
Tough protein capsid contains viral attachment proteins
Resistant to alcohol, low pH, etc.
More stable than enveloped viruses
Transmission is fecal-oral
Ex: Polio, HepA, HPV
Bacteria
No nucleus
One chromosome (usually circular)
70S Ribosomes
Cell wall
Gram positive cell wall
Plasma membrane
Thick peptidoglycan cell wall
Teichoic acid on peptidoglycan cell wall
Ex: Streptococcus, staphylococcus
(Two layers)
Gram negative cell wall
Plasma membrane
Thin peptidoglycan layer
Outer membrane
LPS on outer membrane
Ex: Neisseria
(Three layers)
Targets of anti-bacterial drugs
Cell wall (because humans don’t have one)
Protein synthesis (humans have 80S and bacteria have 70S)
DNA gyrase (humans don’t have it)
Viral infection
1) Viral glycoprotein binds specific receptor on cell
2) Virion uncoats
3) Virus replicates by synthesizing nucleic acid and empty capsids
4) Virus inserts viral glycoproteins into cell’s membrane
5) Viral egress: capsids full of nucleic acid emerge from cell, picking up envelope and inserted viral glycoproteins on the way out
CD8 T cells
Differentiate to cytotoxic T cells (IL-2 helps) that kill viral infected cells by secreting granzymes
CD4 Th2 cells
Activate B cells to become plasma cells that secrete antibodies to kill/neutralize/opsonize extracellular pathogens or toxins
CD4 Th1 cells
Activate macrophages (engulf) and NK cells (which can activate lysosomes) to kill intracellular pathogens replicating in phagosomes or lysosomes
Pattern Associated Molecular Pattern (PAMP)
Molecule on pathogen that is seen as foreign and activates the immune system
Ex: LPS on gram negative bacteria; Teichoic Acid on gram positive bacteria
Toll-Like Receptor (TLR)
On immune cells, recognize PAMPs on pathogen and trigger immune response
Complement pathways
MB-Lectin Pathway (Innate)
Alternative Pathway (Innate)
Classical Pathway (Adaptive)
