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microbiology > HIV- Exam IV > Flashcards

HIV- Exam IV Flashcards

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1
Q

Describe genomic structure of HIV:

A

positive strand RNA virus

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2
Q

HIV is considered a ____ virus

A

retrovirus

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3
Q

Why is HIV considered a retrovirus?

A

because it contains reverse transcriptase enzyme that copies RNA into DNA

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4
Q

HIV causes chronic disease long after infection due to:

A

integration of viral DNA into host chromosome

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5
Q

Describe the structure of the retrovirus HIV: (4)

A
  1. enveloped virus
  2. HIV matrix proteins surround nucleocapsid
  3. core conical nucleocapsid
  4. envelope glycoproteins
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6
Q

HIV has ____ on the surface of the virus

A

adhesin

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7
Q

The adhesin on the surface of HIV engages with:

A

a CD4 receptor and a coreceptor (either CCR5 or CXCR4)

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8
Q

In HIV adsorption and penetration, the use of a coreceptor will:

A

dictate the types of cells that will become infected

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9
Q

Initial HIV infection =

A

M tropic

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10
Q

HIV infection infecting cells of macrophage lineage with coreceptor CCR5:

A

M tropic (initial infection)

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11
Q

HIV infection infecting T-cells with use of coreceptor CXCR4:

A

T tropic (later during infection)

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12
Q

Later HIV infection =

A

T tropic

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13
Q

What is the adhesin on the surface of HIV that binds to CD4 receptor?

A

viral ENV protein gp120

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14
Q

In HIV infection, when the coreceptor is engaged, what does this allow for?

A

The virus to become more closely positioned to the cell surface/membrane

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15
Q

After the coreceptor is engaged in HIV infection, allowing for close proximity of virus to cell surface/membrane, what occurs?

A

a second viral protein gp41 comes into contact with host cell membrane to promote viral fusion

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16
Q

What would occur in the absence of coreceptor binding by gp120?

A

low infectivity of HIV

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17
Q

How was it discovered that a coreceptor is necessary for infectivity of HIV?

A

a small number of individuals in the population are resistant to HIV infection

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18
Q

In HIV infection, coreceptor interactions is essential for:

A

GP41 contact and viral fusion with host cell

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19
Q

The individuals in the population who are resistant to HIV infection lack:

A

coreceptors

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20
Q

HIV penetration is due to:

A

membrane fusion promoted by gp41

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21
Q

retroviruses like HIV do not undergo:

A

an initial phase of translation

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22
Q

The penetration of the nucleocapsids into the cytoplasm of the host cell has to do with the interaction of:

A

viral gp41 protein with host cell membrane

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23
Q

Once the gp120 binds to the CD4 & to the coreceptor this allows the gp41protein to be close enough to the host cell membrane to undergo a ____ that causes part of the gp41 protein to engage both the _____ but also the ____.

A

conformational change; viral envelope; host cell membrane

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24
Q

Following Gp41 engagement with both viral envelope and host cell membrane, a subsequent conformational change pulls the viral envelope and host cell membrane together to ____ and allows the delivery of ____.

A

fuse; the viral nucleocapsid into host cell cytoplasm

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25
Q

In HIV infection, once the nucleocapsid is present with the host cell cytoplasm the first major step of viral replication involves the use of:

A

reverse transcriptase enzyme

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26
Q

What is the first step of completed by reverse transcriptase in HIV infection?

A

takes positive stranded RNA and copies it into a DNA strand

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27
Q

What is the second step of action completed by reverse transcriptase in HIV infection?

A

takes the DNA strand and copies it into a second complimentary strand to create a double stranded DNA complex

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28
Q

what is the first part of HIV genome replication?

A

synthesis of viral DNA copy

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29
Q

Reverse transcriptase synthesizes ___ using viral RNA as the template

A

one strand of DNA

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30
Q

Reverse transcriptase synthesizes ___ using the newly created viral single DNA strand as the template

A

the other strand of DNA

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31
Q

What is the major target for anti-HIV drugs?

A

RT enzyme

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32
Q

RT enzyme is very ___

A

error prone

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33
Q

Because RT enzyme is extremely error prone, this results in:

A

many HIV variants

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34
Q

When synthesizing the viral DNA copy, cellular tRNA is used as a ____ by reverse transcriptase

A

primer

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35
Q

Ultimately part 1 of HIV genome replication results in:

A

A copy of the viral RNA now in the double stranded DNA

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36
Q

Part 2 of HIV genome replication is:

A

integration of viral DNA copy into host cell genome

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37
Q

In part 2 of HIV genome replication: integration of viral DNA copy into host cell genome, this step is promoted by:

A

integrase

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38
Q

Part 3 of HIV genome replication is:

A

transcription of integrated viral DNA copy to create more viral RNA

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39
Q

In part 3 of HIV genome replication: transcription of integrated viral DNA copy to create more viral RNA, the viral DNA is transcribed into RNA by:

A

host cell RNA polymerase II

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40
Q

HIV protein expression and viral assembly:

____ serves as mRNA for translation

___ serves as the viral genome that is packaged into virions

A

viral RNA

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41
Q

HIV protein expression and viral assembly:

Viral assembly occurs at the ___.

A

plasma membrane

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42
Q

HIV protein expression and viral assembly:

Virions acquire their membrane by ____ from the plasma membrane

A

budding of nucleocapsids

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43
Q

HIV protein expression and viral assembly:

Translation creates:

A

viral polyproteins

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44
Q

HIV protein expression and viral assembly:

Viral poly proteins get cleaved to final mature sizes by:

A

viral protease

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45
Q

during an HIV infection _____ can modulate the host cell and assist the virus in types of cells it can infect

A

HIV accessory factors

46
Q

during HIV infection, functions to decrease expression of MHC class I molecules on the surface of an infected cell, preventing killing by cytotoxic T-cells

A

nef

47
Q

What is the ultimate action of nef?

A

prevent killing by cytotoxic T-cells (by decreasing expression of MHC class I molecules on surface of infected cell)

48
Q

during HIV infection, functions to reduce cell surface CD4 expression and enhance viral release:

A

vpu

49
Q

vpu ultimately acts to:

A

reduce cell surface CD4 expression & enhances viral release

50
Q

vpu and nef are both important:

A

HIV accessory factors

51
Q

LTRs

A

Long terminal repeats

52
Q

acts as a promoter element for RNA polymerase to begin transcription and also as a terminator element for the stopping of transcription:

A

Long terminal repeats

53
Q

Upstream LTR acts as the:

A

transcriptional promotor

54
Q

Downstream LTR acts as the:

A

transcriptional terminator

55
Q

Promotor responds to host cell cell signals and can also be relatively dormant, creating the ___ that is an important characteristic of HIV

A

latent state

56
Q

What state is characteristic of HIV infection?

A

Latent state

57
Q

HIV can enter through: (3)

A
  1. microabrasians on mucosal surfaces
  2. needle punctures (IV drug users)
  3. intact mucosal surfaces
58
Q

HIV may enter as: (2)

A
  1. part of an infected cell (macrophage, lymphocyte & spermatozoa)
  2. free virus
59
Q

Describe the viral replication that occurs during initial infection:

A

The burst of viral replication

60
Q

During the chronic phase of HIV infection, following the burst of viral replication that occurs during the initial infection, what is continuing to occur?

A

HIV replication (at slow rate)

61
Q

What populations of cells are responsible for viral latency?

A
  1. long-lived cell populations (macrophages)
  2. infected resting CD4 lymphocytes
62
Q

Greater than 99% of viral replication occurs during:

A

the initial phase

63
Q

What populations of cells are responsible for greater than 99% of viral replication?

A
  1. uninfected activated CD4 lymphocytes
  2. productively infected CD4 lymphocytes
64
Q

Neurological dysfunction seen in the later stages of AIDS:

A

AIDS dementia

65
Q

How much viral replication is taking place during the latent stage of HIV infection?

A

Less than 1%

66
Q

The initial contact of HIV is with:

A

macrophage lineage cells

67
Q

After the initial contact of HIV with macrophage lineage cells, they infect/stick to ___ and then transport to the ____ where they will come in contact with ____.

A

dendritic cells; lymph node; CD4 T cells

68
Q

DTH:

A

Delayed-Type Hypersensitivity (Type 4 hypersensitivity)

69
Q

Important for controlling fungal an intracellular pathogens (bacterial & viral); mediated by CD4 T-cells:

A

DTH

70
Q

DTH is mediated by:

A

CD4 T cells

71
Q

HIV causes ___ & ___ infection of CD4 T cells

A

lytic and latent

72
Q

In addition to HIV causing lytic and latent infection of CD4 T cells, it causes persistent infection of cells of the ___ family and disrupts ____.

A

monocyte macrophage; neurons

73
Q

Loss of T-cell function results in:

A
  1. severe systemic opportunistic infections
  2. Kaposi’s sarcoma
  3. Lymphoma
74
Q

Although not fully understood, what is though to be the basis of the neurological symptoms caused by HIV?

A
  1. possibly due to viral infection of neurons
  2. possibly due to the release of substances of other cells that promote inflammation of the brain
75
Q

P24 is a :

A

viral capsid protein

76
Q

What is the criterion for AIDS?

A

Less than 200 CD4 T-cells/mm^3

77
Q

Patients with higher CD4 T cells than the criterion for AIDs may still be considered to have AIDS if:

A

If they display AIDS indicator conditions

78
Q

What follow the initial mononucleosis-like symptoms of HIV infection?

A

long clinical latency period

79
Q

The progressive decrease in the number of CD4 T cells, even during the latency period, allows:

A

opportunistic infections to occur

80
Q

The stages of HIV disease are defined by the:

A
  1. CD4 T cell levels
  2. Occurrence of opportunistic infections
81
Q

Due to the loss of CD4 T-cells resulting in AIDs, a patient will be at risk for opportunistic infections such as:

A
  1. candidiasis (bronchi, trachea, lungs, esophagus
  2. kaposi’s sarcoma
  3. mycobacterium infections
  4. pneumocystis
82
Q

HIV transmission occurs by:

A

direct exposure of person’s blood stream to body fluid containing virus

83
Q

HIV is found in the ____, ____, or ____ of someone who is infected with the virus

A

blood, semen, vaginal fluid

84
Q

HIV is NOT transmitted via:

A

casual contact

85
Q

There is a risk for healthcare workers to become infected with HIV via a needle stick however:

A

less than 1% of exposures show seroconversion

86
Q

Progressive destruction of CD4+ T cells leading to the collapse of immune system:

A

AIDS

87
Q

What type of disease is also associated with AIDS?

A

central nervous system disease (Specifically dementia)

88
Q

What cancer is related to AIDS and what is it caused by?

A

Kaposi’s sarcoma; caused by human herpesvirus 8

89
Q

Treatment of AIDS involves:

A

antiviral agents

90
Q

The antiviral agents that are used to treat AIDS include:

A
  1. nucleoside analogue reverse transcriptase inhibitors
  2. nucleoside RT inhibitors
  3. protease inhibitors
  4. fusion-penetration inhibitors
91
Q

The target of fusion-penetration inhibitors is:

A

gp41

92
Q

This study included a recombinant virus assay that was used to characterize ____ directed at circulating autologous HIV in plasma

A

neutralizing antibody responses

93
Q

In the study: most patients with primary HIV infection rapidly generated:

A

significant neutralizing antibody responses to early viruses (0-39 months)

94
Q

In the study: How does the virus overcome the significant neutralizing antibody response mounted toward early viruses (0-39 months)?

A

plasma virus continually and rapidly evolved to escape neutralization

95
Q

In the study: neutralizing antibody extra a level of ___that has been under appreciated based on earlier, less comprehensive characterizations

A

selective pressure

96
Q

In the study: the data argues that _____ account for the extensive variation in the envelope gene that is observed in early months after primary HIV infection

A

neutralizing antibody responses

97
Q

artificial virions containing altered envelope proteins:

A

psuedovirions

98
Q

In the study: the enveloped proteins (gp41 & gp120) come from viral envelope genes amplified from:

A

patient serum samples

99
Q

In the study: The HIV DNA on the plasmid created lacks the ___, which had been replaced with __.

A

envelope gene (env); luciferase

100
Q

In the study: The replacement of env with luciferase allowed for HIV env genes from patient samples to be used for creation of:

A

HIV virions

101
Q

In the study, the env genes are replaced with luciferase and instead expressed from:

A

a second plasmid in the cells

102
Q

In the study, the env genes are replaced with luciferase and instead expressed from a second plasmid in the cells and because the virions contain separately supplied env proteins they are considered:

A

psuedovirions

103
Q

In the study, the luciferase present within HIV is used to detect ___ by the pseudovirions produced

A

subsequent infection

104
Q

In the study, if cells become infected they will express ___, which is easily detected using ____.

A

luciferase; light-based assay

105
Q

defined as the reciprocal of the dilution of plasma that produces 50% inhibition of virus replication:

A

titer

106
Q

When the virals samples were challenged from various months with plasma samples containing antibodies from the various months after infection, what they found was: (For month zero)

A

Month zero plasma did NOT neutralize month zero virus

107
Q

When the virals samples were challenged from various months with plasma samples containing antibodies from the various months after infection, what they found was– comparing month 12 plasma to month 0 virus:

A

The month 12 plasma (once diluted) was able to neutralize the virus

108
Q

Why is the plasma antibodies always behind compared to the virus?

A

the virus that is not susceptible to the antibodies becomes the dominant viral population in the patient

109
Q

Other human retroviruses include:

A

Human T-cell lymphotropic viruses (HTLVs -I, -II, -III, - IV)

110
Q

What human T-cell lymphotropic virus causes adult T-cell leukemia and lymphoma?

A

HTLV-1

111
Q

What human T-cell lymphotropic viruses are associated with no known diseases?

A

HTLV-II, III, IV

microbiology (24 decks)

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