Microbiology Exam 3 - Viruses

Front 1

Describe what happened when the Spaniards conquered America

Back 1

600 Spaniards conquered 8 million native Americans. They brought with them small pox and the native americans had no immunity to the virus. They did not have the right genes to fight small pox. They got conjunctivitis and died from it. The pink eye became meningitis.

Front 2

What happened during the Spanish flu virus?

Back 2

from 1918 to 1920

3% of the world population died/up to 100 million people.

Front 3

What took place during the 1930's in regard to viruses?

Back 3

The study of viruses took place with the invention of the microscope. Could actually see them and document them

Front 4

What are the main features of Viruses, Viroids and Prions?

Back 4

Not living agents

they require a host intracellular environment

they are much smaller than bacteria (nanometer scale)

For viruses:

carrier or normal host-harbor the virus without symptoms

Accidental host-not usual carrier, may develop disease.

Example - Ebola virus. Bats are the carriers and we have accidental exposure to them, we become the accidental host...

Front 5

What is the structure of Viruses, viroids and prions?

Back 5

Capsid - protein coat, made up of sub units called capsomers

nucleocapsid - protein coat + genetic material,

naked viruses - nucleocapsid is the virus

enveloped viruses - nucleocapsid is covered by a lipid membrane called an envelope ( very susceptible to environmental factors) Ex. HIV virus. after a few moments of exposure to the environment it will loose effectiveness.

Front 6

What is the taxonomic criteria based on for viruses?

Back 6

The genomic structure (the nucleic acid)

whether it has RNA or DNA

and if it is single stranded (SS) or double stranded (DS).

either linear or circular

Front 7

What are the virus particle structures?

Back 7

Isometric - spherical shaped (circular)

pleomorphic - ability of some bacteria to alter their shape or size in response to environmental conditions

Helical or rod shaped (linear)

can also be segmented

icosahedral (20 triangles)

Front 8

The presence of an envelope is called what

Back 8

enveloped, a lipid layer

Front 9

The absence of an envelope is called what

Back 9

naked, absence of a lipid layer

Front 10

What do viral proteins (coat) accomplish?

Back 10

provide protection

mediate adhesion

give host and organ specificity

some are enzymes

some can act like toxins

Front 11

what is the matrix protein

Back 11

located in the inner side of envelope and mediates between the capsid protein and envelope

Front 12

What is the viral envelope constructed of?

Back 12

Lipids and proteins

it has a hybrid structure, which contains host and viral molecules

the envelope gives instability to the virus. it is susceptible to soaps and lipid solvents (alcohol), environmental factors, such as heat and drying

Front 13

Enveloped viruses rely on what?

Back 13

direct transmission

examples, HIV, Herpes, Hepatitis B and C

Front 14

How do non enveloped viruses survive?

Back 14

They can only survive for a short period of time. They are more exposed to the environment.

Examples, Hepititis A, Norovirus and rotavirus

Front 15

Viral Growth Curve

Back 15

Attachment phase, number of virus acquired.

falls into eclipse phase, where the virus lays dormant for a period of time (3 to 4 hours).

then the log phase, where fast replication takes place.

During the burst or release phase, this is when you are the most contagious. at the peak of the curve. you don't necessarily have to have a fever.

Front 16

During the replication phase what happens to the host

Back 16

the host does not survive. replication happens fast, once the host has been used, it dies and the virus finds a new host.

Front 17

What happens during genome replication and expression?

Back 17

the first step for replication is the production of viral mRNA.

DNA viruses replicate in the nucleus.

RNA viruses replicate in the cytoplasm.

Front 18

How can RNA viruses be divided up?

Back 18

The positive RNA strand virus has the genome with the mRNA. (SSRNA)

The negative RNA strand virus needs RNA ploymerase to make mRNA. (SSRNA)

Ambisense - Double Stranded RNA

Reverse transcription - where RNA produces DNA

Front 19

How does protein production happen during genome replication and expression?

Back 19

The positive strand of RNA is translated into a polyprotein, which is more than one protein translated together.

The virus proteins are separated by Virus Protease.

Front 20

What are the steps of the Lytic cycle?

Back 20

1. The virus enters the cell

2. Hijacks the cells machinery

3. immediately initiates replication

4. the host cell ruptures after a few cycles of replication.

5. viral particles are released to infect new cells.

Front 21

What happens during the Lysogenic cycle?

Back 21

1. The virus enters the cell

2. intregrates into the host's genome and stays latent, sometimes for years

3. latency is broken when the virus switches to Lytic phase.

4. the host cell ruptures after a few cycles of replication

5. viral particles are released and infect new cells

Front 22

At what age does Herpes simplex 1 become viable? and what are the stages of this virus?

Back 22

age 3 usually. you will see blistering around mouth and nose. once out of lytic phase, the virus will hide in the cranial nerve, neuronal cell. This is the lysogenic cycle. It will periodically resurface and go back into lytic phase.

Front 23

what viral cycle causes disease?

Back 23

the lytic cycle, when you are most contageous

Front 24

What triggers disease?

Back 24

cell death by the virus

Front 25

How are animal viruses classified?

Back 25

Disease causing viruses often grouped by route of transmission.

Example would be respiratory viruses

Front 26

How are viruses grouped or classified by route of transmission?

Back 26

enteric viruses: generally transmitted via fecal oral route, often cause gastroenteritis and some can cause systemic disease.

respiratory viruses: usually inhaled via infected respiratory droplets and generally remain localized in respiratory tract.

Zoonotic viruses: transmitted from animal to human vial animal vector ( a vector is any agent (person, animal or microorganism) that carries and transmits an infectious pathogen into another living organism.)

Sexually transmitted viruses: can cause lesions on genitalia or cause systemic infection.

Front 27

How do animal viruses interact with accidental hosts?

Back 27

the outcome of infection of eukaryotic cells depends on factors independent of the cell and the defense mechanisms of the host.

the relationships are divided into two categories:

1. acute: only lytic cycles. an example would be measles. once you've had the disease you won't get it again.

2. persistent: only lysogenic cycles.

Front 28

How do animal viruses interact with their normal hosts?

Back 28

Normal host: no obvious disease or damage is caused to host.

there is a state of balanced pathogenicity.

example: lassa fever carried by rodents

Front 29

Explain the interactions of animal viruses with their hosts in regard to an acute infection.

Back 29

acute infections are usually short in duration.

the host may develop long lasting immunity.

results in productive infections, which means it produces large number of viruses during replication.

The disease symptoms result from tissue damage and infection of new cells.

Front 30

list the process of animal virus replication

Back 30

1. attachment

2. entry

3. targeting

4. uncoating, which exposes the nucleic acid

5. replication and synthesis

6. maturation

7. cell lysis

8. spreading within the host

9. shedding and transmission

Front 31

Explain the interactions of animal viruses with their hosts in regard to a persistent latent infection.

Back 31

after initial infection, virus replicates in neurons in non-infectious state. Then virus is activated to produce new symptoms.

Example: Chicken pox to zoster or shingles

Front 32

Explain the interactions of animal viruses with their hosts in regard to a persistent chronic infection.

Back 32

after initial infection with or without disease symptoms, infectious virus is release from host with no symptoms. you are always contagious with a chronic infection.

Example: Hep B and C

With a chronic infection you have both lytic and lysogenic cycles happening simultaneously.

Front 33

Explain the interactions of animal viruses with their hosts in regard to a persistent slow infection.

Back 33

slow developing disease. transmissible agents multiply without resulting in disease symptoms until they cause a fatal infection.

Example: HIV becoming the aids virus after many years.

Front 34

Where does the virus stay during the latent or dormant phase.

Back 34

it migrates and resides in the ganglia of the neck area. will show up in certain areas depending on which ganglia it resides in.

Stress levels can activate a virus to migrate to the skin

Front 35

protein can only be formed from

Back 35

RNA+ or messenger RNA

Front 36

Review diagram on page 076

Back 36

Single stand and double strand replication

Front 37

Acute infections (Animal viruses with their host)

Back 37

Usually short in duration.

host may develop long-lasting immunity.

result in productive infections (produce large number of viruses during replication).

disease symptoms result from tissue damage and infection of new cells.

Example: measles

Front 38

Persistent infections are categorized how?

Back 38

1. latent

2. chronic

3. slow

Front 39

Give the steps for animal virus replication

Lytic cycle

Back 39

1. attachment

2. entry

3. targeting

4. uncoating (exposing nucleic acid)

5. replication and synthesis

6. maturation

7. viral release

8. spreading- within the host

9. shedding and transmission

Front 40

Animal virus replication-latency

Back 40

1. attachment

2. entry

3. targeting

4. uncoating -->

5. latency established

6. reactivation

7. replication and synthesis

8. maturation

9. viral release

10. spreading - within host

11. shedding and transmission

Front 41

describe and give an example of a persistent latent infection

Back 41

the infection is followed by symptomless period, then reactivation.

infectious particles not detected until reactivation.

symptoms of reactivation and initial disease may differ.

Example: herpes simplex viruses 1 and 2. after latent period may develop into shingles.

Front 42

describe what happens with herpes simplex 1 latent infection and the development of a cold sore.

Back 42

first, the initial infection occurs in 3 to 5 year old children. with fever, soar throat, fever blister. It then moves into the trigeminal nerve and becomes dormant or latent in the sensory ganglia of the nerve.

Front 43

describe what happens when the herpes virus is reactivated later in life.

Back 43

the virus becomes reactivated and travels back down the nerve and causes cold sores.

Front 44

describe a persistant chronic infection

Back 44

infectious virus can be detected at all times. the disease may be present or absent during extended times or may develop late.

example: hepatitis b (serum hepatitis)

Front 45

describe slow persistant infections

Back 45

infectious agent increases count slowly over long period of time and no significant symptoms apparent during this time.

two groups of infectious agents cause slow infections.

examples: retroviruses (HIV) and prions

Front 46

double stranded DNA viruses are responsible for most virus induced tumors in humans, how?

Back 46

20% of viral infections become cancer. cancers caused by DNA viruses result from integration of viral genome into host DNA, changing the make-up of the host DNA. you have uncontrolled growth results.

Examples: kaposi's sarcoma (HSV8 - cancer of the connective tissue)

EBV - burkitt's lymphoma, nasopharyngeal carcinoma (back of throat, nose), B cell lymphoma

HPV - cervical CA

Hep B and C - liver

HTLV-1 - T cell lymphoma (retrovirus)

Front 47

a culture prepared directly from an animal host is called

Back 47

primary culture

Front 48

How are viruses cultivated

Back 48

viruses only multiply inside host cell.

host cells are cultivated in the laboratory in cell culture or tissue culture.

Front 49

What are prions?

Back 49

proteinaceous infectious agent

they are linked to a number of fatal human diseases. They are always fatal. they always affect the central nervous system. It causes brain degeneration with sponge-like holes.

the disease is transmissible and called spongiform encephalopathies

symptoms include: dementia, comma and then death

Front 50

Examples of prion diseases

Back 50

scrapie agent - the host is sheep (scrapie spongiform encephalopathy)

kuru agent - the host is humans (kuru spongiform encephalopathy)

creutzfeidt-jacob agent - the host is humans (creutzfeidt-jacob disease)

mad cow agent - the host is humans and cows (mad cow spongiform encephalopathy)

chronic wasting disease agent - the host is deer and elk (chronic wasting disease)

transmissible mink agent - the host is ranched mink (transmissible mink encephalopathy)

Front 51

Do prions replicate?

Back 51

No. They convert normal proteins into prions. they affect the Tertiary structrue of a protein. mutation caused otherwise normal host protein to have different folding properties.

they are resistant to proteases.

they are resistant to UV & nucleases because of their lack of nucleic acid.

inactivated by chemicals that denature proteins.

very tough to kill. surgical equipment has to be discarded.

Front 52

describe viroids

Back 52

smaller than viruses.

replicate autonomously in susceptible cells.

single viroid capable of infecting a cell.

small circular ss RNA molecule and resistant to RNAses.

vary in length.

have no protein coat and resistant to proteases.

Front 53

What do viroids infect?

Back 53

all indentified viroids infect plants

examples: potato spindle tuber, chrysanthemum stunt, cadang-cadang (coconuts, do not produce coconut water)

when it affects agriculture, the land has to be free of plant with viroids for 25 years to clear it.

Front 54

How can viral vectors be used for therapeutic value

Back 54

adenoviruses for gene therapy which allows the replacement of mutated genes in humans promising results for cystic fibrosis. a good copy of the virus is inserted, which could rectify the disease entirely. the symptoms will revert

genetically engineered vaccines. viruses that can immunize against malaria.

Front 55

Some viruses contain regulatory proteins in a structure called the _____. Where is it located and what do they do or accomplish?

Back 55

Tegument

they are located between the nucleocapsid and the envelope. they include transcription and translation factors that control either viral or cellular processes.

Example: herpes simplex virus and cytomegalovirus

Front 56

The envelope is comprised of what type of protein?

Back 56

lipoprotein

lipid derived from the host cell membrane and protein that is viral specific.

Front 57

What are the spike like projections found on viruses comprised of?

Back 57

glycoproteins

Front 58

What does the matrix protein do?

Back 58

mediates the interaction between the capsid protein and the envelope.

Front 59

the capsid is composed of repeating subunits called:

Back 59

capsomers

Front 60

typically the envelope is acquired as the virus exits from the cell in a process called

Back 60

budding

Front 61

what is a virion?

Back 61

the complete, infective form of a virus outside a host cell, with a core of RNA or DNA and a capsid.