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Drug Action IV > Overview of Viruses (Patho) - Block 3 > Flashcards

Overview of Viruses (Patho) - Block 3 Flashcards

1
Q

Describe the extracellular state of a virus?

A
  1. Virus particle (virion)
  2. Nucleic acid is surrounded by protein and macromolecules
  3. Metabolically inert
  4. Transports viral genome from host cell to a new cell
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2
Q

Describe the intracellular state of a virus?

A
  1. Viral genome is introduced to new susceptible cell
  2. Viral replication occurs
  3. Virus utilizes the host cells machinery to replicate and assemble new virions
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3
Q

Describe the structural components of a virion?

A
  1. Capid protein coat composed of capsomeres (identical protein subunits)
  2. Nucleocapid (necliec acid and viral proteins packaged into a capsid)
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3
Q

What are the capsid shapes?

A

Helical, icosahedral, complex

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4
Q

Describe the structure of a naked virion?

A

Spikes used for viral adherence

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5
Q

Naked virions can withstand what kind of environments?

A
  1. Temperture
  2. Acidic conditions
  3. Proteases
  4. Drying
  5. Detergents
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6
Q

How does enveloped virions differ from naked?

A
  1. Nucleocapsid encased in an envelope
  2. Spikes
  3. Matrix proteins that mediates the interaction between the capsid proetins and envelope

More sensitive to heat, detergents, and lipid solvents

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7
Q

Describe the structure of helical symmetry?

A
  1. Rod or filamentous shaped virus
  2. Capid of single repeating polypeptide with nucliec acid
  3. Self-assembles into coils
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8
Q

Describe the structure of icosahedral symmetry?

A
  1. More complex spherical shaped with symmetrical units (capsomeres)
  2. Capid proteins held by hydrogen bond
  3. Tegument protein layer between capsid and envelope
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9
Q

What are examples of complex, larger viruses?

A
  1. Bacteriophage
  2. Poxvirus
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10
Q

Surface gylcoproteins serve as antigens to induce ____ response in the host?

A

HUmoral response

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11
Q

What is used to determine the serotype of a virus?

A

Surface antigens

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12
Q

What are the medical implications of multiple serotypes in viruses?

A
  1. Person immune to 1 serotypes can be infected by another of the same virus
  2. Vaccines contains all serotypes to provide complete coverage
  3. Difficult to produce an effective vaccine against a virus that is constantly changing from antigenic determinants
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13
Q

Cells must be both ___ and ___ for a successful infection?

A

Susceptible: surface receptors allowing the virus to recognize and attach to host
Permissive: intracellular components need to make more virions

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14
Q

What is the difference between virulent and moderate viruses?

A

Virulent: replication may lead to death of host cell
Moderate: replication may occur without damage to host cell

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15
Q

What are the steps of viral replication?

A
  1. Recognition of the target cell
  2. Attachment
  3. Penetration
  4. uncoating
  5. Macromolecular synthesis
  6. Assembly of virus
  7. Budding of enveloped viruses
  8. Release of virus
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16
Q

What is the basis for host and tissue specificity?

A

Tissue trophism

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17
Q

How does a virus undergo recognition and attachment to a host?

A

Surface proteins or glycoproteins on virion attach to surface receptors on the susceptible host cell

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18
Q

Describe binding of influenza?

A

Binds to sialic acid

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19
Q

Describe the binding of HIV?

A

Binds to CD4 on immune cells and CXCR4 or CC5 co-receptors

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20
Q

Describe the binding of SARS-CoV2?

A

Binds to ACE2

21
Q

Virus that can attach to host w/o a spike protein?

A

Rhinovirus

22
Q

Describe the penetration of a virus?

A

Nonenveloped: enter through receptor mediated endocytosis
Enveloped: Fuse their membrane with cellular membrane to deliver nucleocapsid directly

23
Q

What are the locations of uncoating?

A
  1. Plama membrane
  2. Nuclear membrane
  3. Cytoplasm
24
Q

Describe the replication and protein production ot the virus?

A

The viral genome must direct the synthesis of viral mRNA and protein translation

25
Q

What are the characterisitcs of Class I viruses?

A

dsDNA viruses replicate in the nucleus:
* uses host’s DNA-dependent DNA polymerase to replicate and DNA-dependent RNA polymerase to synthesize mRNA

26
Q

What are the characteristics of Class II viruses?

A

ssDNA must make a complementary DNA strand then:
* host’s DNA-dependent RNA polymerase can make mRNA
* Used for viral genome replication

27
Q

What are the characterisitcs of Class IV viruses?

A

+ssRNA viruses replicate and form mRNA in the cytoplasm:
* Directly translated into viral proteins
* Host cells do not possess RNA-dependent RNA polymerases (RdRp) and must be carried by the virus
* For replication, + strand is copied into a – sense template to make more + sense RNA strands by RdRp

28
Q

What are the characteristics of Class V viruses?

A

-ssRNA Viruses can’t be used as mRNA and must be copied into a + template strand:
* Uses a viral RNA-dependent RNA polymerase (RdRp) packaged within the nucleocapsid to produce a + sense strand
* + sense strand is used for translation into viral proteins
* + sense strand is used to produce –sense ssRNA strand for progeny virions

29
Q

What are the characteristics of Class III viruses?

A

dsRNA viral genomes contain both a + and – sense RNA strand:
* +RNA strand serves as mRNA and RNA template for – sense RNA strand by RNA-dependent RNA polymerase (RdRp)

30
Q

What is unique about Class VI?

A

Retrovirus: + ssRNA virus that replicates through a dsDNA intermediate
* Requires a viral encoded RNA-dependent DNA polymerase (reverse transcriptase)
* The dsDNA can integrate into the host DNA (provirus) using the viral enzyme integrase

31
Q

What is the difference between early and late proteins?

A

Early: synthesized after infection prior to viral replication
Late: synthesized later in infection after replication has begun

32
Q

What occurs during viral translation?

A

Viral mRNA is translated by the host cell’s ribosomes:
* Regulation of virion synthesis is controlled by virus not host
* Virus hijacks the hosts machinery

33
Q

What is a provirus?

A

Remains latent until host cell is activated to replicate

34
Q

Where are most RNA viruses assembled?

A

Cytoplasm

35
Q

Where are most DNA viruses assembled?

A

nucleus

36
Q

How are nonenveloped and enveloped viruses packaged?

A

Non: complete after the formation of the nucleocapsid
Envelop: enclosed in lipid envelope

37
Q

How are virions released?

A

Cell lysis (naked and enveloped) or budding process (enveloped)

38
Q

What is the infection cycle of a virus?

A
  1. Viral genome combines with host gene -> provirus
  2. Provirus can replicate and transfer to daughter cells during cell division
  3. Provirus can be excised from host and enter lytic phase
39
Q

Describe the process of budding?

A
  1. Viral specific proteins enter the host cell membrane
  2. Viral particles are inserted in the external plasma membrane of host cell
  3. Viral nucleocapsid then interacts with specific membrane site mediated by matrix protein
  4. Cell membrane invaginates and the enveloped particles buds off from the membrane
40
Q

What are the mechanisms of viral cytopathologies?

A
  1. Host cell death
  2. Fusion of virus infected cells to form multinucleated cells (syncytia)
  3. Can causes morphologic or functional change
  4. Inclusion bodies
41
Q

What is an oncogene?

A

Proto-oncogenes activated by cancer

42
Q

What is acute infection?

A

Burst of virions are released quickly causing death of host and immune systems

43
Q

What are rare complications caused by acute infection?

A

Subacute sclerosing panecephalitis (SSPE) due to proteins remaining from defective cirus replication after initial infection

44
Q

What is latent infection?

A

Virus replications in cells in a non-infectious state

45
Q

What is chronic infection?

A

after the initial infection with or without disease symptoms, low levels of infections virus are released from host with no symptoms

46
Q

Methods of transmission and entry into the host?

A
  1. Portals of entry
  2. Vertical transmission
  3. Horizontal transmission
  4. Direct and indirect transmission
  5. Animal/vecotr to human transmission
  6. Local or systemic infection
47
Q

What is direct transmission?

A

disease is passed directly from one infected person to another

48
Q

What is indirect transmission?

A

disease is passed from infected person to another person without direct contact

49
Q

What is vector transmission?

A

disease that requires another organism to transmit disease to another person

50
Q

How are non-enveloped viruses commonly transmitted?

A

fecal-oral route or from fomites

51
Q

Methods viruses can infect a patient?

A
  1. Transmission of the virus and entry into the host
  2. Replication of the virus and damage to cells
  3. Spread of virus to other cells and organs
  4. Immune response for host defense and as a contributing cause of disease
  5. Persistance of virus

Drug Action IV (21 decks)

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