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Virology Test 4 > Retroviruses > Flashcards

Retroviruses Flashcards

1
Q

All retrovirus are enveloped T/F

A

T

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2
Q

What does oncovirus mean?

A

it causes cancer. EX: HTLV causes adult T-cell leukemia (ATL)

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3
Q

What is the incubation period of Adult T cell Leukemia from HTLV? What does HTLV stand for? How does it spread?

A

20-50 years; Human T-lymphotropic virus; Infected CD4+ T-cells are spread via blood, semen, and breast milk

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4
Q

What binds to the CD4 receptor on T cells from HIV?

A

GP 120

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5
Q

What is the hallmark of HIV?

A

Succumbing to opportunistic microbial and viral infections (due to reduced t helper cells)

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6
Q

What are the phases of HIV?

A

Acute phase is Flu-like, followed by clinical latency for about 10 years to reach AIDS

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7
Q

What is the definition of aids? How is it diagnosed?

A

200 T cells /microliter (normal is 800-1200) serology and RT PCR to quantitate viral load

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8
Q

What is haart?

A

high active anti-retroviral therapy; it’s a cocktail of drugs, there is no vaccine for HIV

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9
Q

What type of virus is a retrovirus?

A

enveloped + strand RNA virus

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10
Q

What is it called when DNA is integrated into the host DNA?

A

provirus

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11
Q

What do all retroviruses encode?

A

RNA Dep. DNA pol (reverse transcriptase)

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12
Q

Rous sarcoma virus was first retrovirus to be isolated, what did it do?

A

produced solid tumors in chickens

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13
Q

What are other names for cancer causing retroviruses? How do they do this?

A

RNA tumor viruses or oncornaviruses; they express analogues for cellular growth controlling genes (oncogenes)

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14
Q

HTLV was the first retrovirus to be found associated with____ _____. From whom was it first isolated? 4 H’s of people dying from benign opportunistic infections? These symptoms defined a disease known as ____

A

human disease; Robert Gallo, who had T-Cell Leukemia; homosexual men, haitians, heroin addicts, and hemophiliacs; AIDS

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15
Q

How many people are suffering from AIDS worldwide?

A

34 million people

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16
Q

AIDS stands for

A

Acquired immunodeficiency syndrome

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17
Q

Oncoviruses (HTLV) include only retroviruses that can immortalize or transform target tissue T/F. What is the name of the subfamily?

A

T; Oncovirinae

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18
Q

What are lentiviruses (HIV) associated with ______. What is the name of their subfamily?

A

neurologic and immunosuppressive diseases; Lentivirinae

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19
Q

What size and shape are retroviruses? What is on the membrane and where is it acquired from?

A

spherical enveloped 80-120 nm; glycoproteins; plasma membrane

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20
Q

What does the virion contain? What is the purpose of the tRNA? What does the genome represent? Is it infectious?

A

10-50 copies of RT, integrase, and two cellular tRNAs (primers) as well as two identical copies of the + strand genome;
The tRNA is used as a primer for RT;
mRNA; no because does not encode a polymerase that can directly generate more mRNA

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21
Q

What are the three major polyproteins encoded by retroviruses? At the end of the genome are ___ ____ ___ ___ that contain promoters and enhancers to bind cellular transcription factors.

Complex retroviruses also encode several ____-_____ proteins that require ____ by cellular mechanisms

A

GAG (structural proteins), Pol (RT, protease, integrase), env (glycoprotein 120 and 41); long terminal repeat sequences

virulence-enhancing; splicing

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22
Q

What is produced by cleavage of the env gene? GP160 is cleaved into what? What are their functions?

A

viral glycoproteins; GP41 and GP 120; GP 41 promotes cell fusion, GP 120 binds to cell surface receptors, determines tissue tropism

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23
Q

GP120 is extensively ______ and its specificity can ____ over the course of an infection.
GP 41 is used to promote ___ ____.

A

glycosylated; drift; cell fusion

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24
Q

What is the coreceptor for HIV? what does binding to it do?

A

CCR5 (macrophages, other T cells); binding brings the viral envelope and cell plasma membrane close to allow gp41 to promote membrane fusion

25
Q

RT is very error prone. What is the mutation rate? What does this cause?

A

1/2000 base pairs; evolution of new strains.

26
Q

How is HIV DNA integrated into the genome? What is the name of the virus after integration? LTRs are ______ at each end of the genome. what does this allow for?

A

Viral cDNA is delivered into the nucleus and is integrated into host chromosome by integrase; provirus;

Duplicated; integration

27
Q

Provirus acts as a cellular gene, and its expression depends on cellular recognition of _____ encoded by regions of the ___. What are the two most important of these? What are the others?

A

promoters and enhancers; LTR; Tat (transactivation of viral and cellular genes) and Nef (downregulates cell surface CD4, activates T Cells, contributes in progression to aids); rev, vpr, vif, vpu (study these on slide 18 if you have time!)

28
Q

Viral glycoproteins are translated where? Having two copies of the genome and tRNA arrive at PM with Gag and Gag-Pol promotes what?

A

ON the rough ER, they then move to the PM via secretory pathway; budding of the virion

29
Q

What is the function of tat?

A

transactivation of viral and cellular genes

30
Q

Proteins translated from gag, gag-pol, and env mRNA are synthesized as _______

A

polyproteins

31
Q

Two copies of genome and cellular tRNA molecules promotes _____ of the virion

A

budding

32
Q

GP120 is a

A

trimer

33
Q

Host RNA Pol II transcribes the genome into ___ ____ ____, which is then ____ into the ____.

A

full length RNA; processed; mRNA

34
Q

HIV infects ____ ____ during sex

A

mucosal surfaces

35
Q

People who have a genetic CCR5 deficiency are less susceptible to ___

A

HIV

36
Q

HIV exists persistently by infection of which cells. These cells serve as the ___ ____

A

macrophages, Dendritic cells, memory T cells, and hematopoietic T cells; major reservoirs

37
Q

Reduction in CD4 T Cell count during HIV infection occurs due to which two processes?

A

HIV- induced cytolysis of CD4 and by cytotoxic T cell induced cytolysis

38
Q

Increased AIDS symptoms correlates with ? Which protein promotes this? If this protein is mutated what happens? What are the infected people called?

A

Increased viral cell counts and decreased Th cell count; Nef; HIV doesn’t develop into AIDS; nonprogressors

39
Q

What is the concentration of retrovirus in the acute phase? T-cell proliferation and response produced symptoms similar to _____

A

1E7/mL; mononucleosis

40
Q

In the HIV clinical latent period where is the virus replicating? What happens to viral blood levels?

A

the lymph nodes; they decrease

41
Q

in HIV patients, late stage, why do CD8 cell levels decrease?

A

Lymph nodes are destroyed, and CD4 cells aren’t releasing activating cytokines

42
Q

Incapacitation of the adaptive response leads to _____ infections in AIDS patients. What are some other effects of HIV?

A

opportunistic; neurologic abnormalities due to microglial and macrophage infection and release of neurotoxic substances or chemotactic factors that promote inflammatory response. also patient is at risk for opportunistic nervous system infections

43
Q

At what concentration of CD4 T cells is onset of AIDS correlated? Full blown AIDS? What is the viral load?

A

less than 350 cells/microliter and increased viral load; 75,000 copies/mL

44
Q

What is HIV wasting syndrome?

A

Weight loss, diarrhea, for more than one month

45
Q

What else develops during HIV

A

lymphadenopathy, fever, malaise,opportunistic infections, malignancies, dementia

46
Q

What does infection of microglia and neural macrophages result in?

A

AIDS-related dementia; slow deterioration of intellectual abilities and other neurologic disorders; similar to symptoms of Alzheimers disease

47
Q

HIV Epidemiology: Is HIV easy or difficult to inactivate outside the body? The virus has a long prodromal period and people can shed virions before showing signs of infection T/F

A

easy; true

48
Q

Who commonly gets HIV? Who is at risk for transmission before 1985?

A

IV drug abusers, sexually active people with many partners, newborns; hemophiliacs and organ transplant recipients

49
Q

What are some modes of controlling HIV?

A

Drug therapy (HAART); Sterile needles; large-scale screening programs

50
Q

In 2009: How many people in the world had HIV? How many people were getting infected a day? How many deaths per year?

A

33.5 million; 7,000 infections per day; 1.8 million deaths per year

51
Q

What are the four reasons for testing for HIV?

A

Identify those infected so that drug therapy can be initiated; monitoring progression of HIV to AIDS; Identifying carriers who could transmit the disease to others; evaluation of the efficacy of treatment

52
Q

The chronic nature of HIV allows for the use of ____ tests. These tests’ limitations are the inability to:

A

serologic; identify recently infected people

53
Q

Recent HIV infection or late stage infection is determined by:

A

viral RNA levels in blood; p24 capsid antigen; or detection of RT

54
Q

The ratio of CD4:CD8 lymphocytes is ____ in HIV patients

A

low

55
Q

What are the two types of HIV?

A

HIV-1 and HIV-2

56
Q

Anti-HIV therapy is currently given as a cocktail of several drugs termed: This use of multiple drugs with different mechanisms of action has less potential to ___ ___ ____

This treatment is able to reduce blood levels of virus to ____ and reduce _____ in AIDS patients

A

HAART highly active anti retroviral treatment; select for resistance

almost zero; mortality

57
Q

When is HAART given? What clinical circumstance is it given for?

A

CD4 levelss shown to be highly beneficial. Also it can be given if viral load is high.
post-exposure prophylaxis

58
Q

What are some of the mechanisms of HAART?

A

nucleoside analog: inhibits viral polymerases by incorporating a terminal nucleoside
RT inhibitor: disrupts enzyme’s catalytic site
protease inhibitor: inhibits protease necessary for late stage of viral cycle
fusion inhibitor: blocks cellular and viral membrane fusion

59
Q

What are some holdups to an HIV vaccine? What are some methods being attempted?

A

Protein subunit vaccines for gp 120/160 only work for 1 strain; most recent vaccines prime T-cells via a viral vector; A GP160 DNA vaccine; A vaccine that generates an antibody against the GP120 CD4 binding site is in the works that would elicit a neutralizing antibody to most HIV strains

Virology Test 4 (4 decks)

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