Viruses

Question 1

viruses are obligate intracellular parasites because

Answer 1

• they cannot reproduce without a host
• not considered to be living
• virus genome more similar to host genome than other virus genomes
• almost identical to host genome in some groups

Question 2

Iwanoski

Answer 2

first to isolate virus in 1892

tobacco mosaic virus

Question 3

virus classifications

Answer 3

• host range
• size
• structure
• virus life cycle

Question 4

host range

Answer 4

• viruses infect all organisms

- usually adapted to one species or related species

Question 5

size

Answer 5

smaller than ribosomes

Question 6

structure

Answer 6

• nucleic acid
• capsid
• animal viruses have envelope outside capsid

Question 7

nucleic acid in viruses

Answer 7

can have DNA or RNA
single or double strand
1 piece or more than 1 piece

Question 8

capsid

Answer 8

protein container enclosing nucleic acid

• helical, rod, tobacco mosaic virus
• polyhedral, 20 sided, adenovirus, cold virus
• complex, tail, head, sheath, bacteriophage

Question 9

animal virus external envelope

Answer 9

-outside capsid
-derived from host membrane
HIV, flu
-envelope allows virus to merge with membrane when entering and leaving the host

Question 10

virus life cycle

Answer 10

1. virus binds host membrane
2. virus releases nucleic acid into host cell
3. new virus nucleic acids and virus proteins synthesized in host
4. new capsids assemble around nucleic acids
5. new viruses released from host cell
   - some kill host cell as new viruses are released
   - enveloped virus- leaves host cell without killing host
   cell

Question 11

3 virus groups

Answer 11

1. DNA viruses (bacteriophages)
2. RNA viruses
3. retroviruses (RNA)

Question 12

Bacteriophage

Answer 12

DNA virus
infects E. coli
viral DNA injected into host
lytic and lysogenic life cycles
more bacteriophages on body than all other cell types combined
ex: Corynebacterium, Vibrio, Clostridium botulinum

Question 13

lytic cycle

Answer 13

virulent

produces new viruses and kills host and then infects other cells

Question 14

lysogenic life cycle

Answer 14

viral DNA incorporated into host DNA and replicated with host DNA as host divides
all resulting cells contain viral DNA and express the viral toxin
the bacteriophage infection makes non-pathogenic bacterial disease causing toxins cause symptoms
more bacteriophages on body than all other cell types combined

Question 15

RNA virus

Answer 15

8 RNA strands

influenza

Question 16

RNA virus enzyme

Answer 16

RNA replicase (RNA dependent RNA polymerase)
copies virus RNA into more virus RNA
NO DNA and NO transcription- genetic information already in RNA form

Question 17

RNA virus presentation

Answer 17

respiratory infection often followed by secondary bacterial infections; pneumonia
spread by respiratory droplets and fomites (contaminated objects)

Question 18

influenza envelope

Answer 18

2 surface spike protein patterns (H and N)

spikes allow virus to bind, enter and exit host

Question 19

spike variation determines______

Answer 19

capsid antigen characteristics (A, B or C)

Question 20

antigenic shift

Answer 20

recombines RNA from human, pig or bird flu strains
RNA from different species combined into new influenza virus in host
preformed antibodies may still function
most severe

Question 21

antigenic drift

Answer 21

variation from random point mutations
only a few amino acids changed
preformed antibodies may still function
not as severe

Question 22

influenza A

Answer 22

most common, most severe form
cause of pandemics in 1918, 1957, 1968, 1977
Spanish flu

Question 23

avian flu

Answer 23

H7H9, H5N1, H7N7
infection in poultry in Asia and Africa
60% fatality rate

Question 24

H3N2

Answer 24

human flu

Question 25

H1N1, H2N2

Answer 25

swine flu

Question 26

Retrovirus

Answer 26

2 RNA strands

Question 27

Retrovirus enzyme

Answer 27

reverse transcriptase | copies RNA into DNA

Question 28

HIV

Answer 28

Human Immunodeficiency Virus 1. binds CD4 receptors on T4 helper cells and macrophages - structure changes to reduce antibody response 2. moves inside T4 cells - RNA converted to DNA by reverse transcriptase - virus DNA inserts into host DNA - may remain inactive but usually produces and releases new viruses that infect other cells 3. T4 count falls - body cannot produce enough new T4 cells - indicates onset of AIDS 4. HIV destroys immune system and death results from secondary infection

Question 29

secondary infection/ diseases related to HIV

Answer 29

Pneumocystis carinii Toxoplasma Mycobacterium tuberculosis Karposi's sarcoma

Question 30

HAART

Answer 30

Highly Active Antiretroviral Therapy | drug cocktails

Question 31

drug cocktail effects

Answer 31

reduce virus to low levels maintain T4 helper cell number reduce resistance of viruses to treatment

Question 32

treatment targets on HIV

Answer 32

- interfere with reverse transcriptase - fusion inhibitors - integrase inhibitors - protease inhibitors - block virus assembly

Question 33

treatments that interfere with reverse transcriptase

Answer 33

inhibit DNA synthesis from RNA

Question 34

AZT

Answer 34

mimics thymine nucleotides | produces non-functional DNA

Question 35

fusion inhibitors

Answer 35

prevents virus entry into host membrane

Question 36

protease inhibitors

Answer 36

prevent modification of HIV proteins

Question 37

integrase inhibitors

Answer 37

prevent HIV DNA from inserting into host DNA

Question 38

HIV treatment drawbacks

Answer 38

high cost toxic side effects may not completely remove virus`

Question 39

why some HIV is a "long term non progress or"

Answer 39

weaker virus | abnormal receptors on T4 cells

Question 40

Hepatitis

Answer 40

targets liver fecal/oral transmission many strains, syndromes, outcomes

Question 41

Hepatitis A

Answer 41

``` infectious hepatitis RNA contagious before symptoms appear survives for days on surfaces resistant to bleach 1/3 Americans have antibodies form Hep A ```

Question 42

Hepatitis A passive vaccine

Answer 42

effective within 2 weeks of exposure | protection lasts six months

Question 43

Hepatitis A active vaccine

Answer 43

(developed in) 1995 (?)

Question 44

Hepatitis B

Answer 44

chronic hepatitis liver cancer DNA transmission similar to HIV- infected blood, blood products, IV drug use, unsafe sex

Question 45

Hepatitis B active vaccine

Answer 45

for newborns and children

Question 46

Hepatitis B passive vaccine

Answer 46

reduces severity of infection after exposure to hep B

Question 47

Hepatitis C

Answer 47

``` chronic RNA no vaccine similar transmission to HIV higher fatality rate than HIV main reason for liver transplant ```

Question 48

Rhabdovirus

Answer 48

rabies | ssRNA

Question 49

rhabdovirus reservoir

Answer 49

mammals (not rodents)

Question 50

rhabdovirus transmission

Answer 50

bites | travels along nerves to brain

Question 51

rhabdovirus infection

Answer 51

40 day incubation time causes encephalitis usually fatal within a few days of onset of symptoms

Question 52

hydrophobia

Answer 52

painful muscle spasms from swallowing water | contractions of jaw muscles

Question 53

furious rabies

Answer 53

biting maintains virus in animal populations

Question 54

polio virus

Answer 54

ssRNA poliomylelitis strains 1, 2, 3 human only host inhibits motor neurons in cord

Question 55

polio transmission

Answer 55

fecal/oral stable in swimming pools, lakes, drinking water, food only 1% becomes paralytic

Question 56

Salk vaccine

Answer 56

first active vaccine antigens for all 3 polio strains inactive virus so requires boosters used to vaccinate children

Question 57

Sabin vaccine

Answer 57

oral vaccine attentuated (living) providing long lasting immunity 80 polio cases in secondary contacts since 1980

Question 58

post polio syndrome

Answer 58

muscle weakness that occurs later in life as nerves become inhibited

Question 59

herpes simplex 1

Answer 59

oral herpes

Question 60

herpes simplex 2

Answer 60

genital herpes

Question 61

human papilloma virus

Answer 61

many strains | some cause cervical cancer

Question 62

Ebola

Answer 62

Africa fruit bat reservoir incurable 90% fatality rate

Question 63

west Nile virus

Answer 63

bird reservoir mosquito vector f

Question 64

Viroids

Answer 64

infectious RNA molecules only infect plants potato spindle tuber, cadang/cadang

Question 65

prions

Answer 65

infectious proteins that infect brain | no cure

Question 66

prion infection

Answer 66

eating meat contaminated with CNS tissue slow acting with long incubation time not destroyed by high heat

Question 67

prion effect

Answer 67

convert normal proteins in brain to prions | prions are a misfiled form of normal protein (beta sheet, prion PrP)

Question 68

scrapies

Answer 68

prion in sheep

Question 69

bovine spongiform encephalopathy

Answer 69

mad cow disease | sheep to cow, cow to cow, cow to human

Question 70

Creutzfeldt Jacob disease

Answer 70

human for of mad cow

Question 71

Kuru

Answer 71

related to cannabalism

Question 72

chronis wasting disease

Answer 72

deer and elk

Question 73

Viruses and cancer

Answer 73

cause 20-25% of cancers HIV- Karposi's sarcoma HPV- cervical cancer