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Microbiology > HIV (Exam IV) > Flashcards

HIV (Exam IV) Flashcards

1
Q

Describe the 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 surrounding nucleocapsid
  3. Core conical nucleocapsid
  4. Envelope glycoproteins
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6
Q

HIV contains ____ 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 & 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 characteristic of cells of macrophage lineage with the use of co-receptor CCR5:

A

M tropic (initial)

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11
Q

HIV infection characteristic of T cell infection with use of co-recptor 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 co-receptor 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 co-receptor is engaged in an HIV infection, allowing for close proximity of virus to cell surface/membrane what occurs?

A

A second viral protein gp41 comes in to contact with host cell membrane to promote viral fusion

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16
Q

What would occur in the absence of co-receptor binding by gp120?

A

Low infectivity of HIV

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17
Q

How was it discovered that a co-receptor 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

Co-receptor interaction during HIV infection is essential for:

A

gp41 contact & viral fusion with host vell

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19
Q

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

A

The co-receptors

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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 nucleocapsid 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 CD4 and to the coreceptor this allows the gp41 protein to be close enough to the host cell membrane to undergo a _______ that causes part of the gp41 protein to engage with both:

A

Confirmational change; viral envelope & host cell membrane

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24
Q

Following gp41 engagement with both the viral envelope & host cell membrane, a subsequent conformational change pulls the viral envelope & host cell membrane together to _____ & 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 within 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 action completed by reverse transcriptase in HIV infection?

A

Takes + stranded RNA & 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 & copies it into a second complementary 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 (RT) synthesizes ____ using viral RNA as the template

A

One strand of DNA

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30
Q

Reverse transcriptase (RT) 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 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 one of HIV genome replication results in:

A

a copy of the viral RNA now in double-stranded DNA form

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36
Q

Part two of HIV genome replication is:

A

Integration of viral DNA copy into host cell genome

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37
Q

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

A

Viral integrase

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38
Q

Part three 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 three 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 & viral assembly:

_____ serves as mRNA for translation

____ serves as the viral genome that is packaged into virions

A

Viral RNA (both)

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41
Q

HIV protein expression & viral assembly:

Viral assembly occurs at the ______

A

Plasma membrane

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42
Q

HIV protein expression & viral assembly:

Virions acquire their membrane by _____ from the plasma membrane

A

Budding of nucleocapsids

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43
Q

HIV protein expression & viral assembly:

Translation creates:

A

Viral polyproteins

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44
Q

HIV protein expression & viral assembly:

Viral polyproteins get cleaved to final mature sizes by:

A

Viral protease

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45
Q

During an HIV infection, can modulation the host cell & assist the virus in the 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 & enhances viral release:

A

VPU

49
Q

VPU ultimately acts to:

A
  1. Reduce cell surface CD4 expression
  2. Enhances viral release
50
Q

VPU & Nef are both important:

A

HIV accessory factors

51
Q

LTRs:

A

Long terminal repeats

52
Q

Acts as promoter element for RNA polymerase to begin transcription & also a terminator element to stop the RNA transcription:

A

Long terminal repeats (LTRs)

53
Q

The upstream LTR acts as the:

A

Transcriptional promoter

54
Q

The downstream LTR acts as the:

A

Transcriptional terminator

55
Q

Promoter responds to host 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. Microabrasions on mucosal surfaces (sexual contact)
  2. Needle punctures (IV drug users)
  3. Intact mucosal surfaces (sexual contact)
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

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 very slow rate)

61
Q

Greater than 99% of viral replication occurs during:

A

The initial phase

62
Q

What populations of cells are responsible for viral latency?

A
  1. long-lived cell populations (macrophages)
  2. infected resting CD4 lymphocytes
63
Q

What population 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 into contact with _____

A

Dendritic cells; lymph node; CD4 T cells

68
Q

DTH:

A

Delayed-type hypersensitivity (Type IV hypersensitivity)

69
Q

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

A

Delayed-type hypersensitivity (DTH)

70
Q

DTH is mediated by:

A

CD4 T cells

71
Q

HIV causes ____ & _____ infection of CD4 T cells

A

Lytic & latent

72
Q

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

A

monocyte-macrophage family; neurons

73
Q

Loss of T cell function due to HIV infection leads to:

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

Although not fully understood, what is thought 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 by other cells that promote inflammation in 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

They display AIDs indicator conditions

78
Q

What follows 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 in HIV disease are defined by:

A
  1. CD4 T cell level
  2. Occurrence of opportunistic diseases
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 sarcoma
  3. Mycobacterium infections
  4. Pneumocystis
82
Q

Transmission of HIV occurs by:

A

Direct exposure of person’s bloodstream to body fluid contain 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 health care 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 specific 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 in AIDs treatment:

A

gp41

92
Q

The study included a recombinant virus sassy 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 responses mounted towards early viruses (0-39 months)?

A

Plasma virus continually & rapidly evolved to escape neutralization

95
Q

In the study:

The neutralizing antibodies exert a level of _____ that has been underappreciated, 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 following primary HIV infection

A

Neutralizing antibody responses

97
Q

Artificial virions containing altered envelope proteins:

A

Psuedovirions

98
Q

In the study, the envelope 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 has been replaced with _____

A

envelope gene (env); luciferase

100
Q

In the study, the replacement of env gene with luciferase allows 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 & because the virions contain separately supplied env proteins they are considered:

A

Pseudovirions

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 viral samples were challenged from various months with plasma samples containing antibodies from the various months after infect what they found was:

  • for month zero
A

Month zero plasma did NOT neutralize month zero virus

107
Q

When the viral samples were challenged from various months with plasma samples containing antibodies from the various months after infect what they found was:

-Comparing month 12 plasma to month zero virus

A

The month 12 plasma (once diluted) was able to neutralize virus by 50% inhibition

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 & lymphoma?

A

HTLV-I

111
Q

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

A

HTLV-II, -III, -IV

Microbiology (22 decks)

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