Evasion Of Host Immune Response

Front 1

What is a pathogen?

Back 1

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

Front 2

What is a OPPORTUNISTIC pathogen?

Back 2

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

Front 3

What is a ZOONOTIC PATHOGEN?

Back 3

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]

Front 4

What must extracellular pathogens evade in the immune system and how do they do it?

Back 4

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

Front 5

Explain how a pathogen, such as Streptoccus pneumoniae can evade the immune system

Back 5

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

Front 6

Explain how trypanosome [ie african sleeping sickness] can evade the immune system and why you see recurrent fever spikes

Back 6

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

Front 7

How does an intracellular pathogen evade the immune system?
and how do they do this?

Back 7

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]

Front 8

What is the concept of EVOLUTION and CO-EVOLUTION?

give an example

Back 8

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

Front 9

Give an example of how events triggered by pressure from 1 pathogen can produce advantages in unrelated pathogens

Back 9

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

Front 10

What is an EPIDEMIC disease and how is it caused?

Back 10

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]

Front 11

How are new influenza vaccines created?

Back 11

by looking at the antigentic drift from the season before

Front 12

What is a PANDEMIC disease and what causes it?

Back 12

PANDEMIC disease: global outbreak and is caused by ANTIGENTIC SHIFT

Front 13

Explain the difference in the antigenic drift and the antigenic shift in regards to the influenza virus

Back 13

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!

Front 14

What is LATENCY?
When does a pathogen attack?

Back 14

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

Front 15

Name two examples of pathogens w/ a latent component
and name where the pathogen resides

Back 15

Herpes virus: virus resides in neurons
Mycobacterium tuberculosis: bacterial pathogen resides in macs contained in granulomas

Front 16

How is CLINICAL LATENCY different that classic latency and what does it apply to?

Back 16

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.