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House Microbiology > Viral Reolication > Flashcards

Viral Reolication Flashcards

1
Q

When a virus infects a cell, ______ must be uncoated and must gain access to __________

A

nucleic acid

metabolic machinery of cell.

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2
Q

Attachment of a virus

specific binding of a ___ protein (the ________) to a constituent of the cell surface (the ______)

e.g.__________ of influenza virus

A

virion
anti-receptor

receptor

hemagglutinin

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3
Q

some complex viruses (HSV) may have more than one species of anti-receptor molecule

T/F

A

T

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4
Q

Penetration of a virus into a cell is not an energy-dependent step

T/F

A

F

It is

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5
Q

Penetration of a virus into a cell occurs ________ after _________

A

almost instantaneously after attachment

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6
Q

After the virus attaches to the host cell, it can enter the cell by several mechanisms:

(1) Transfer of ________ across the cell membrane by ______

(2) Transfer of _________ through the cell membrane

(3) ______________ with the host cell membrane

A

the entire viral particle ; endocytosis

only the viral genome

Fusion of the viral envelope

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7
Q

Uncoating of a virus

Can occur at ________ or ———

A

same time as penetration

shortly after

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8
Q

Uncoating of a virus

Is the _________ of ________ from _______

Released as:

________(_____)

as ________ (______)

A

separation of viral nucleic acid (n.a.)

outer structural components

free n.a.; picornaviruses

nucleocapsid; reoviruses

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9
Q

After uncoating of the virus

There should be _________ and ___________

A

Expression of viral genome

synthesis of viral components

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10
Q

After the viral nucleic acid is released inside the host cell:
The ________ and ———- processes of the host cell are redirected for the production of ______ and _______

A

transcription and translation

viral proteins and nucleic acids

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11
Q

The different types of nucleic acid genomes are expressed and replicated in several ways:

DNA genomes undergo replication-using ________________

RNA genomes may be +ssRNA; Can be ____________ or _________

RNA genomes may also be -ssRNA; The RNA must ____________________

A

processes similar to cellular replication

read directly as an mRNA or reverse transcribed by reverse transcriptase into DNA

first be used as a template to form +mRNAs

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12
Q

Assembly and Release of virus

Components of _____ synthesis directed by _________

______ stage of infection

A

capsid; late genes

Final

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13
Q

Assembly of enveloped viruses needs interaction with ________ which has been ________

A

plasma membrane

modified

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14
Q

Assembly and Release of virus

Enveloped viruses released _______ by __________ or _____

Naked viruses _______ in _______ and released during ______

A

gradually

budding or exocytosis

accumulate in cytoplasm ; lysis

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15
Q

Factors in Viral Pathogenesis

______ of the infecting virus

Effects of viral infection on ____ (Cellular ______)

Entry into the Host

A

Virulence

Cells; Pathogenesis

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16
Q

Factors in Viral Pathogenesis

_______ of Infection

Cell/Tissue ______

Cell/Tissue _______

______-____ Response

Virus _________ or ______

A

Course

Tropism

Damage

Host Immune

Clearance or Persistence

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17
Q

Course of Viral Infection

________

_______

_______

A

Primary Replication

Systemic Spread

Secondary Replication

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18
Q

Course of Viral Infection
Primary Replication
The place of primary replication is where the virus replicates after ____________

A

gaining initial entry into the host.

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19
Q

Course of Viral Infection

This frequently determines whether the infection will be __________ or _____________

A

localized at the site of entry

spread to become a systemic infection.

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20
Q

Course of Viral Infection

Systemic Spread
Apart from direct cell-to-cell contact, the virus may _____________ and ______

A

spread via the blood stream and the CNS.

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21
Q

Course of Viral Infection

Secondary Replication
Secondary replication takes place at ______________ following ________

A

susceptible organs/tissues following systemic spread.

22
Q

Viral Virulence

The ability of a virus to ______ in an infected host

A

cause disease

23
Q

A ______ strain causes significant disease

While

_________________ strain causes no or
reduced disease

A

virulent

An avirulent or attenuated

24
Q

Virulence depends on

_____

Virus _____ (genetics)

___________________

_______ factors -

A

Dose

strain

Inoculation route - portal of entry

Host

25
Q

Cell Tropism

Viral _____ for ____________

A

affinity

specific body tissues

26
Q

Cell Tropism

is determined by

Cell _______ for virus.

Cell ________ that recognize viral promoters and enhancer sequences.

Ability of the cell to __________.

A

receptors

transcription factors

support virus replication

27
Q

Cell Tropism

is determined by

_______ barriers.

Local ______,___,______

enzymes and non- specific factors in —————

_____ enzymes and ____ in the gastrointestinal tract that may inactivate some viruses.

A

Physical

temperature, pH, and oxygen tension

body secretions

Digestive; bile

28
Q

Viruses may replicate widely throughout the body without any disease symptoms if they do not cause _________

A

significant cell damage or death.

29
Q

Cell Damage

Picornaviruses cause ___________ the cells in which they replicate, leading to ____ and increased ____ secretion in the case of Rhinoviruses, then paralysis or death (usually due to ______ failure) for Poliovirus .

A

lysis and death of

fever.; mucus

respiratory

30
Q

Retroviruses do not generally cause cell death

T/F

With reason

A

T

Because they released from the cell by budding rather than by cell lysis, and cause persistent infections.

31
Q

The _______ to the virus probably has the greatest impact on the outcome of infection.

A

immune response

32
Q

Immune Response

In the most cases, the virus is ______ from the body and results in ______

In other infections, the immune response is unable to ____________ and the virus _____.

A

Cleared completely; complete recovery.

clear the virus completely; persists

33
Q

In general, ______ immunity plays the major role in clearing virus infection whereas ______ immunity protects against reinfection.

A

cellular

humoral

34
Q

Immune Pathological Response

Enhanced viral injury could be due to one or a mixture of the following mechanisms;-

Increased _________ to Tc cells e.g. HBV

Specific _________ or ___________

Binding of _______ virus

Immune _______ in organs such as the skin, brain or kidney e.g. ____ of rubella and measles.

A

secondary response

ADCC or complement mediated cell lysis

un-neutralized

complex deposition; rash

35
Q

Immune Pathological Response

Binding of un-neutralized virus- ____ complexes to cell surface ___ receptors, and thus _______________ e.g. ______ haemorrhagic fever, _____.

A

Antibody ; Fc

increasing the number of cells infected

Dengue; HIV

36
Q

Viral Clearance or Persistence

There are 2 types of chronic persistent infections.

_________

________

A

True Latency
Persistence

37
Q

The majority of viral infections are ______ but certain viruses may cause ________

A

cleared

persistent infections.

38
Q

Viral Clearance or Persistence

True Latency - the virus ____________________________ e.g. HSV, VZV. Its genome may be _______ or _________

A

remains completely latent following primary infection

integrated into the cellular genome or exists as episomes.

39
Q

Viral Clearance or Persistence

Persistence - the virus __________ in the body at a ________ level e.g. ___,_____,____ ____

A

replicates continuously

very low

HIV, HBV, CMV, EBV.

40
Q

Mechanisms of Viral Persistence

______ variation

_______ tolerance

restricted __________

A

antigenic

Immune

gene expression

41
Q

Mechanism of viral persistence

immune tolerance- causing ___________, may be due to _____ factors, _______ infection,_________

A

a reduced response to an antigen

genetic

pre-natal

molecular mimicry

42
Q

Mechanisms of Viral Persistence

down-regulation of _______________, resulting in ____________

e.g.

_____viruses

A

MHC class I expression

lack of recognition of infected cells

Adeno

43
Q

Mechanisms of Viral Persistence

down-regulation of accessory molecules involved in _________ e.g. _____ and _____ by ____.

infection of immunopriviliged sites within the body e.g. ____ in _______ in _____

direct infection of the cells of the ________ e.g. ______ viruses, _______ - often resulting in __________.

A

immune recognition

LFA-3 and ICAM-1 ; EBV

HSV ; sensory ganglia in the CNS

immune system itself

Herpes; Retroviruses (HIV) ; immunosuppression

44
Q

Matrix proteins connect _____ to ——-

A

envelope to capsid

45
Q

Vaccinia virus = _____ virus

B19 = ——-

A

pox

parvo

46
Q

Robo- ———
Arbo - __________

A

rodent

arthropods

47
Q

Baltimore classification

The division of the viruses into classes based on _______ and ________

Suggested by ______ – ____ Baltimore classes.

A

genome type

mode of replication and transcription

David Baltimore

Seven

48
Q

Baltimore classification

CLASS1-
CLASS2-
CLASS3-
CLASS4-
CLASS5-
CLASS6-
CLASS7-

A

Double stranded DNA
Single stranded DNA
Double stranded RNA
single stranded RNA plus sense
Single stranded RNA minus sense
Single stranded RNA that replicated with DNA intermediate
Double stranded DNA that replicated with RNA intermediate

49
Q

In the Baltimore classification, which classes have examples fo bacterial viruses

A

Class 1-4

50
Q

Early mRNA codes for ?

Late mRNA codes for ?

A

Proteins to ensure it’s infectivity . Eg proteins to shut off host cell, or replicate viral genome

Structural proteins . Eg capsid

House Microbiology (93 decks)

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