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16 Cards in this Set

  • Front
  • Back
What is a pathogen?
any bacteria, virus, fungi, protozoa, or hemilinth worm] that causes sign. disease in otherwise healthy indiv.

ususally not part of normal flora, but if it is, it is in the wrong compartment
What is a OPPORTUNISTIC pathogen?
pathogen that does not cause disease in healthy individuals but capable of causing disease when given the advantage ie. suppressed immune system or has AIDS
microbes that generally infect animals other than humans, but human are the incidental host and disease in humans is more severe than in host [ie. lyme disease, salmonella, plague, etc]
What must extracellular pathogens evade in the immune system and how do they do it?
They must avoid antibodies, complement and phagocytes

Do so by: varying their composition as they will not be seen by immune system.
2 ways: a pathogen has different capsular polysaccharides or pathogen can constantly change it's polysaccharide coat
Explain how a pathogen, such as Streptoccus pneumoniae can evade the immune system
Different sterotypes of the pathogen have different capsular polysaccharides. Thus when infected w/ one type, the person must make antibodies for that specific sterotype, but if infected again w/ a second sterotype of same pathogen, must make new antibodies to that steroytpe
Explain how trypanosome [ie african sleeping sickness] can evade the immune system and why you see recurrent fever spikes
Trypanosomes constantly change their polysaccharide coat [have infinite number of choices] to evade the immune system. A person begins to feel better when they make antibodies to a particular coat, but fever spikes when pathogen changes coat
How does an intracellular pathogen evade the immune system?
and how do they do this?
By avoiding antibodies, Natural kiler, Cytoxic T cells and certain chemokine responses

do it by evolving strategies to survive in phagocytes [ie. inhibit phagolysosome fusion or neutralizing pH vacuoles or adapting to live in acidic vacuoles]
What is the concept of EVOLUTION and CO-EVOLUTION?

give an example
that all living creatures and pathogens are continuously adapting to pressures that effect their ability to reproduce

examples: TB and Retroviruses like HIV can evolve to selective pressures by drugs in days
Give an example of how events triggered by pressure from 1 pathogen can produce advantages in unrelated pathogens
subpop. of caucasions carry mutation in CCR5 which evolved in response to plague pandemic of middle ages. The same mutation also encodes for a co-receptor for macrophage tropic HIV to makes them resistant to HIV infection
What is an EPIDEMIC disease and how is it caused?
EPIDEMIC: disease that spreads through a population then subsides.

Caused by ANTIGENTIC DRIFT which is the continuous process of genetic change via mutations [occurs over time]
How are new influenza vaccines created?
by looking at the antigentic drift from the season before
What is a PANDEMIC disease and what causes it?
PANDEMIC disease: global outbreak and is caused by ANTIGENTIC SHIFT
Explain the difference in the antigenic drift and the antigenic shift in regards to the influenza virus
Antigentic drift-->point mutations in flu virus genes cause differences in structure of viral surface antigens.
--Person "P"--Ab's against hemagglutinin of Virus V
--Person "Q"--Point mutation of Virus V-->Virus V*--no ab's-->virus binds

Antigenic shift-->flu viruses reassort genomes and change surface antigens rapidly (rather than gradually). (pandemics)
--Person infected w/human and avian virus-->produces virus w/different hemagglutins-->no immunity in humans!
What is LATENCY?
When does a pathogen attack?
the abiility of a pathogen to live in a host w/o attracting the immune system by low metabolic activity. Pathogen attacks when the immune system is weak and enters a period of active replication and disease
Name two examples of pathogens w/ a latent component
and name where the pathogen resides
Herpes virus: virus resides in neurons
Mycobacterium tuberculosis: bacterial pathogen resides in macs contained in granulomas
How is CLINICAL LATENCY different that classic latency and what does it apply to?
in clinical latency, the virus and T cells production is very active and has repeated rounds of replication and re-infection until the virus exhausts all T cells.

applies to HIV and exhaustion allows disease to progress to AIDS

This confused me--here's a definition from Dr. Wikipedia: Clinical latency is the state, or time period, in which an infectious agent produces no clinical symptoms in a host. Latency is not equivalent to dormancy. Although HIV-positive patients usually exhibit little evidence of illness early in the disease, HIV is active in the lymphatic system accumulating a large viral load.