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16 Cards in this Set

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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
What is a ZOONOTIC PATHOGEN?
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.