S2 I&i Exam 5: Virology Structure, Replication, Genetics

Front 1

Viruses are classified based on what?

Back 1

-Genome structure (DNA/RNA, single/double)
-Viral envelope (absence/presence)
-Virus particle shape (capsomere morphologic unit of capsid & protomer structural subunit of capsomere)

(virus= nucleid acid + capsid protein)*

Front 2

Viral shape is determined by symmetrical _________ arrangement. What are the possible shapes?

Back 2

capside (w/ capsomere units)

-isometrical (spherical)
-helical (cylindrical)
-complex (may have spherical head & cylindrical body)

(most medically sig. viruses are isometric (w/ icosahedral (5 protomer subunits) or helical)

Front 3

ALL viral envelopes are produced from host cytoplasmic membrane, EXCEPT ___________

What is this viral envelope made from?

Back 3

Herpes
-made from host nuclear membrane

(envelope = lipid bilayer= host membrane protein + viral glycolipid)
(virus may also lack envelope= 'naked' virus)

Front 4

Viruses may also have ____________ on envelope or on capsid (if "naked"), for host attachment.

If the virus doesn't have these, how does it act on host?

Back 4

spike protein


may fuse to host instead & insert viral DNA
(cell-membrane-fusion)

Front 5

Viruses usually have species-specific or even tissue-specific (lung, etc) host ranges. Some however may have a wider host range.

Give an example of this

Back 5

H1N1 (influenze virus)

swine, bird, & human flu
(^mosaic virus bc it has parts from each organism)

Front 6

3 possible outcomes of viral infection

Back 6

1. acute/lytic infection= host manifests disease (virion release & cell lysis) & dies
2. chronic/persistent infection= host manifests disease (viron release w/o lysis) & host survives (may be asymptomatic or relapse later)
3. latent/nonproductive infection= host does not manifest upon infection (virus becomes part of host DNA, may reactivate later or remain asymptomatic) (ex:herpes simplex)

Front 7

Differentiate btwn virulent & temperate virus

Back 7

virulent (lytic) virus- enter host, cause acute productive infection (reproduce) (then go to another host & repeat)

temperate virus- enter host, may become lytic/produce infection (at any point) OR may establish non-productive relationship (latent do not infect)

Front 8

Why can't viruses be eliminated by filtration?


How can they be eliminated?

Back 8

too small


eliminated by; 1. chemicals (destroy envelope), 2. UV (kills), 3. heat (denature capsid/nucleic acid, >90 C)

Front 9

Viral genomes may be arranged in _ or _ form

Back 9

linear or circular


(either RNA or DNA, not both)

Front 10

Retroviruses, such as HIV carry what type of genome?

Back 10

Diploid genome

2 identical copies of its genome

Front 11

DNA viruses are usually double stranded with the exception of _

Back 11

parvoviruses

Front 12

RNA viruses are usually single stranded with the exception of _

Back 12

REOviridae family

Front 13

Reoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some human relevant examples?

Back 13

dsRNA (10-12 segments)
Naked

ROTAvirus (#1 cause of infantile water diarhea), Colorado tick fever virus, & reovirus

Front 14

Viruses w/ single stranded RNA genomes may have (+) sense/polarity or (-) polarity nucleic acid. What is the difference?

Back 14

(+) sense: can use viral RNA directly as mRNA for translation (reproduction)

(-) sense: must transfer RNA to complementary (+) sense, then to mRNA

(DNA viruses usually a combination of +/-)

Front 15

The Coding Strand (+) is always read in the _' to _' direction.
The non coding strand (-) is always read in the _' to _' direction.

Back 15

5' to 3'

3' to 5'

Front 16

List the 7 (+) sense ssRNA families

Back 16

Call Henry Pico-Flow To Come Right away-->
Call= Calicivirdae
Henry= Hepevirdae
Pico= Picornaevirdae
Flow= Flaviviridae
To= Togaviradae
Come= Coronaviridae
Right Away= RETROviridae

Front 17

4 Common Characteristics of (+) sense ssRNA

Back 17

1. replicate in cytoplasm
2. do not have enzymes
3. icosahedral shape
4. enveloped
(some exceptions)

Front 18

Exception-
Which (+) ssRNA families are naked ?


*MOST are enveloped

Back 18

(Call Henry Pico-)
Caliciviridae
Hepeviridae
Picornaeviridae

Front 19

Exception-
Which (+) ssRNA are NOT icosahedral?

What shape?

Back 19

(come)
Coronaviridae

helical
(all (-) sense ssRNA are helical)

Front 20

Exception-
Which (+) ssRNA does NOT replicate in the cytoplasm?

Where does it replicate?

Back 20

RETROviridae

replicates in nucleus

Front 21

Exception-
Which (+) ssRNA DOES carry enzyme?

Why?

Back 21

RETROviridae

retroviruses do reverse transcription (RNA->DNA), need reverse transcriptase to do this

(all other (+) ssRNA do NOT need enzymes bc they can be used directly as mRNA w/o conversion/rxn)

Front 22

(call) Caliciviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 22

(+) ssRNA genome
No envelope (Naked)

Human relevant viruses:
-Norwalk agent/Noroviruses (causes 2/3 nonbacterial watery diarrhea in adults)
-Hepatitis E virus (fatal in preg)

Front 23

(Pico-) Picornaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 23

(+) ssRNA genome
No envelope (Naked)

Human relevant viruses:
-Hepatitis A
-Rhinovirus (common cold)
-Enteric viruses: Poliovirus (paralysis), Coxsackievirus, & Echovirus
(enter through GI, but effect other systems)
-Enterovirus

Front 24

(-Flow) Flaviviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 24

(+) ssRNA genome
Enveloped

Human relevant viruses:
Hepatitis C

Front 25

(To) Togaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 25

(+) ssRNA genome
Enveloped

Human relevant viruses:
Rubella virus (german measles, can cross placenta)

Front 26

(Come) Coronaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

Back 26

(+) ssRNA genome
Enveloped
*also Helical (w/ crown shaped surface proteins)

Human relevant viruses:
SARS coronavirus (flu-like symptoms)

Front 27

(Right away) RETROviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 27

(+) ssRNA genome, diploid*
Enveloped
*also replicates in nucleus & carries enzyme

Human relevant viruses:
-HIV-I, HIV-II (from Lentivirus genus, non-oncogenic)
-HTLV-I, HTLV-II (oncogenic, cause I-T cell, 2- B-cell leukemia)

Front 28

List the 6 (-) sense ssRNA families

Back 28

Pain Results From Our Bunion Always
Pain= Paramyxoviridae
Results= Rhabdoviridae
From= Filoviridae
Our= Orthomyxoviridae
Bunion= Bunyaviridae
Always= Arenaviridae

Front 29

4 Common Characteristics of (-) sense ssRNA

Back 29

1. Replicate in cytoplasm
2. Carry Enzymes
3. Helical shape
4. Enveloped

Front 30

Exception-
Which (-) ssRNA replicates in BOTH the cytoplasm & the cell nucleus?

Back 30

Orthomyxoviridae (influenze virus)

Front 31

(Pain) Paramyxoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

Back 31

(-) ssRNA genome
Enveloped

Human relevant viruses:
Parainfluenza virus
Respiratory syncytial virus (Croop)
Newcastle disease virus
Mumps virus
Rubeola (measles) virus

Front 32

(Results) Rhabdoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

Back 32

(-) ssRNA genome
Enveloped

Human relevant viruses:
Rabies virus (life-threatening)

Front 33

(From) Filoviredae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 33

(-) ssRNA
Enveloped

Human relevant viruses:
-Ebola virus (causes high fever, encephalitis, fatal)
-Marburg Virus

Front 34

(Our) Orthomyxoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 34

(-) ssRNA genome
8 segments
Enveloped
*replicates in BOTH cytoplasm & nucleus

Human relevant viruses:
Influenza A (multi-species, H1N1), B (human), and C (non-virulent) viruses

Front 35

(Bunion) Bunyaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 35

(-) ssRNA genome
3 circular (?) segments
Enveloped

Human relevant viruses: (most zoonotic)
Hantavirus (causes Hantavirus pulmonary syndrome)

Front 36

(Always) Arenaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 36

(-) ssRNA genome
2 segments
Enveloped

Human relevant viruses:
-Lymphocytic choriomeningitis virus
-Lassa fever virus
(both cause encephalitis)

Front 37

List the 6 DNA viral families

Back 37

Parden Papa As He Has Pox
Parden= Parvoviridae
Papa= Papoviridae
As= Adenoviridae
He= Hepadnaviridae
Has= Herpesviridae
Pox= Poxviridae

Front 38

What are the 4 common characteristics for DNA viruses

Back 38

1. double stranded
2. replicate in nucleus
3. Enveloped
4. Do NOT carry enzymes

Front 39

Exception-
Which DNA viral families are "naked"

Back 39

(Parden Papa As)
Parvoviridae, Papoviridae (papilloma), Adenoviridae

Front 40

Exception-
Which DNA viral family does NOT replicate in the nucleus?

Back 40

Poxaviridae

Front 41

Exception-
Which viral DNA families carry enxymes?
(most DONT)

Back 41

Hepadnaviridae & Poxaviridae

Front 42

(Parden) Parvoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 42

(+ or -) ssDNA genome
No envelope (Naked)

Human relevant viruses:
Parvovirus B19 (anemia) (causes Slapcheck fever)

Front 43

(Papa) Papovaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 43

dsDNA genome
*circular
No envelope (Naked)

Human relevant viruses:
-Human papillomavirus (HPV) (cervial cancer)
-JC virus (PMI in AIDs pt)
-BK virus (kidney disease in AIDs pt)

Front 44

(As) Adenoviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 44

dsDNA genome
No envelope (Naked)

Human relevant viruses:
Human adenoviruses (common cold or malignancy)

Front 45

(He) Hepadnaviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 45

dsDNA genome
*Gapped circle (incomplete dsDNA)
Enveloped

Human relevant viruses:
Hepatitis B virus

Front 46

(Has) Herpesviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 46

dsDNA genome
Enveloped (from host nuclear membrane*)

Human relevant viruses:
-Herpes
-Epstein-Barr virus (mono & cancer)
-Cytomegalovirus
-Varicella-Zoster (chicken pox-->shingles)

Front 47

(Pox) Poxviridae has a (ds/ss) (RNA/DNA) genome and is (naked/enveloped).

What are some examples?

Back 47

dsDNA genome
*Dual Enveloped

Human relevant viruses:
Variola virus (smallpox- irradicated)

Front 48

Common Respiratory (transmitted) viruses

Back 48

Influenze (orthomyxoviridae), rhinoviruses

Front 49

Common Enteric (transmitted) viruses

Back 49

Enteroviruses (polio, coxsacki B), rotaviruses (diarhea)

Front 50

Epstein Bar uses _ & _ receptor for attachment

Back 50

CR2 & CD21 (on B cell)

causes B cell lymphoma)

Front 51

Rabies virus uses _ receptor for attachment

Back 51

Nicotinic acetocholine receptor (neuromuscular jxn)

Front 52

Rhinovirus uses ___ receptor for attachment

Back 52

ICAM1 (adhesion molecule)

(rhinovirus is #1 cause of common cold)

Front 53

HIV uses ____ receptor for attachment

Back 53

CD4

& CXCR$ & CCR5 coreceptors

Front 54

What are the 2 mechanisms of enveloped animal virus entry to host cell?

Back 54

1. Direct membrane fusion
2. Receptor-mediated endocytosis (viropexis)

(both begin w/ virus envelope spikes attaching to specific receptors on host cell)

Front 55

__________ involves viral envelope fusion w/ & incorporation into host cell membrane, nucleocapsid is released into host cell, nucleic acid separates from capsid (uncoating)

Back 55

Direct membrane Fusion

Front 56

_________ involves host plasma membrane surrounding virus & forming vesicle, vesicle endocytosed, viral envelope fuses w/ plasma membrane allowing nucleocapsid to be released from endosomal vesicle, uncoating occurs

Back 56

Receptor-mediated endocytosis (viropexis)

Front 57

What is the mechanism for naked animal virus entry into host cell?

Back 57

Receptor-mediated endocytosis (viropexis)

Front 58

How does viropexis differ for naked animal viruses?

Back 58

lack of envelop prevents nucleocapsid release from endosomal vesical using membrane fusion

(some naked animal viruses use other mechanisms besides fusion to release nucleic acid from endosome, lysis, etc)*

Front 59

Most RNA viruses use the _ as the site of replication and transcription

What is the exception?

Back 59

cytoplasm

Orthomyxoviruses and Retroviruses

Front 60

All DNA viruses, except Pox viruses use the _ as the site of replication and transcription

How do they get to the site of replication?

Back 60

nucleus
(Pox replicates in cytoplasm)

pilot proteins accompany & translocate (phage) viral genome to nucleus

Front 61

All viruses (RNA & DNA) need to _________ before replication (via polymerase) may occur

How does this differ for large & small viruses?

Back 61

uncoat (separate nuc. acid from capsid protein coat)

large- uncoat, then enter nucleus to replicate
(herpes, adeno)
small- enter nucleus, then uncoat
(parvo, papo)

Front 62

When in the cell cycle is cellular DNA polymerase expressed?

Back 62

S phase (in nucleus)

*The viruses that use cellular DNA polymerase have mechanisms to force the cell into its cell cycle, therefore expressing the DNA polymerase

Front 63

When in the cell cycle is RNA polymerase expressed?

Back 63

NEVER

RNA viruses must code for RNA polymerase (transcriptase) & RNA dependent RNA polymerase (replicase), host cells don't have these in cytoplasm

Front 64

What type of virus relies completely on host cell enzymes for mRNA synthesis?

(does NOT use viral enzymes to synth mRNA )

Back 64

DNA

Front 65

(+) RNA viruses can directly translate into a single polypeptide (w/o enzyme). Why?

What happens to this polypeptide/polyprotein?

Back 65

because (+) RNA can be used as mRNA & translated directly into proteins

Polypeptide cleaved into RNA polymerase (replicase), protease, & viral structural components

Front 66

RNA polymerase (replicase) (produced via cleavage) copies (+) sense RNA into ___________________

Then what?

Back 66

complementary (-) sense RNA


this (-) sense RNA serves as a template for new (+) sense strands

Front 67

What is the fate of the new (+) sense RNA?

Back 67

3 options;
1. used as template to make more (-) strands
2. package into new virions
3. translated into another polyprotein**

Front 68

New (-) sense RNA can be acted on by RNA polymerase (transcriptase) & translated into _____
OR
by RNA polymerase (replicase) & copied into _____

Back 68

(+) mRNA**

(+) sense RNA

(can also be packaged into virions)

Front 69

How is retrovirus (HIV) RNA virus replicated?

Back 69

-reverse transcriptase converts ssRNA to dsDNA
-host integrates viral nucleic acid into host genome
-creating provirus
-host cell replicates genomic & viral nucleic acid
-protease cleaves polyprotein into capsid, envelope spikes & reverse transcriptase enzyme
-components reassemble as new virus particle

Front 70

How are new viruses assembled?

Back 70

-scaffolding proteins reassemble proteins into capsid, proteins release after capsid formation
-concatemers thread nucleic acid into empty capsid

Front 71

How are new virus particles released from host?

Back 71

naked viruses- released via lysis, leads to host death

enveloped virus- released by budding, virus evaginates host & becomes enveloped during exocytosis, host lives
(except- Poxvirus, not released by budding)

Front 72

What is antigenic drift?

Back 72

genetic mutation of influenza virus changes antigenic structure on envelop protein

(host antibodies will no longer match virus antigen= new infection by mutated strain)

Front 73

What is antigenic shift?

Back 73

host infected w/ 2 diff viral strains, genetic reassortment of 2 segmented genomes occurs, recombinent progeny is an entirely diff virus (than 2 parent strains)

(only occurs in segmented virus, orthomyxo or reo)

Front 74

What is phenotypic mixing

Back 74

Host cell contains 2 diff viruses, during replication, protein coat nucleic acid is exchanged, new virus has protein coat w/ unique surface proteins, allowing it to act on different hosts
(viral surface proteins attach to specific host membrane receptors*)

Front 75

Some viruses (particularly retrovirus (HTLV), adenovirus, herpes) can cause malignant transformation in host cells. What does this mean?

Back 75

Host cell morphology is altered
grows indefinately due to lost regulation of cell replication

(transformation induced via viral oncogenes)

Front 76

What RNA retrovirus induces malignancy?

What kind of tumor does it cause?

Back 76

HTLV1- T cell leukemia

(HTLV2 induces B cell leukemia)

Front 77

Which 2 DNA viruses cause hepatocellular carcinoma?

Back 77

Heptatitis B & C

Front 78

What DNA virus leads to Burkit's or B cell lymphoma

Back 78

Epstein-Bar

Front 79

What DNA virus leads to Kaposi's sarcoma?

Back 79

Herpes 8



(HPV is a DNA virus, causes cervical cancer)

Front 80

What are three reasons a virus would shut down the host protein synthesis?

Back 80

More protein synthesis machinery available for production of viral proteins

Blocks cell presentation of viral proteins to immune system

Blocks production of anti-viral proteins

Front 81

Innate Immune response to virus:
Alpha & beta interferons are found in are released from virally infected cell, what is their mechanism of action?

Back 81

stimulate NK

NK leads to antiviral response in entire area, release IFN-gamma enhancing T cell response, & directly kill infected cells

Front 82

What is the humoral & cellular adaptive immune responses to viral infection?

Back 82

humoral- neutralize antiviral antibodies
cellular- virus specific CTL (kill infected cells)

Front 83

There are 2 lines of Anti-HIV drugs. How does the first line work?

Back 83

targets reverse transcriptase & protease enzymes in attempt to inhibit viral replication

Front 84

How does the second line work?

Back 84

targest integrase (enzyme) & CCR5 (receptor) prevent viral uptake into new host cells