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Hugh's MD1 Respiratory > Virology > Flashcards

Virology Flashcards

1
Q

What is the attachment receptor for most Rhinoviruses?

A

ICAM-1

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1
Q

Where do DNA viruses replicate generally?

A

The nucleus except Poxviruses that rep in the cytoplasm

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1
Q

Which viral proteins are synthesized first?

A

Non-structural - eg DNA and RNA polymerases

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1
Q

What is the difference between +sense and -sense RNA genome viruses in terms of their amplication?

A
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1
Q

What does Protein kinase R do?

A

Inhibits protein translation

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2
Q

What is an example of a virus that fuses in order to penetrate?

A

HIV

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2
Q

What are some viral strategies for blocking CD8 T cell recognition of infected cells?

A

Endocytose MHC I

Alter MHC I peptide

Block TAP on both sides

Bind to and retain MHC I in the ER

Inhibit the proteosome

Decrease MHC I gene transcription

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3
Q

What are the 4 mechanism of systemic spread in the body?

A

Local epithelial spread

Haematogenous

Via lymphatics

Neural

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5
Q

What is autocleavage?

A

The process by which long peptides cleave themselves into smaller active proteins

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5
Q

What are koplik spots?

A

Areas in the mouth where measles virus initially replicates, they are red due to lymphocytes

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5
Q

True or false, LN enlargement is due to direct viral action

A

False, it is due to immunopathology

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5
Q

What is an example of a disease where CD8 T cell cause pathology?

A

CD8 T cell kill liver cells and recruit neutrophils and monocytes in Hep B infection

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6
Q

What are some strategies viruses use to evade interferon immune response?

A

Interference with the PKR (protein kinase R) pathway

  • dsRNA-binding protein
  • PKR binding protein (vaccinia)
  • Abundant small RNAs (adenovirus)
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7
Q

What type of viruses carry their own polymerase?

A

-sense RNA viruses

retroviruses

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7
Q

What is the function of M cells?

A

Ingest and deliever Ag to APCs beneath them

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7
Q

What is an example of virally induced autoimmunity?

A

Myelin basic proteins are cross reactive with influenza proteins = demyelination and transient paralysis

or

Polyclonal B cell activation by EBV

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8
Q

What type of cell layer do most viruses enter through?

A

Serous epithelium

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9
Q

What does type II interferon do?

A

Activate macrophages

Inhibit viral replication

Enhances MHC I and II expression

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10
Q

What are two strategies enveloped viruses use to get out of the cell?

A

Budding

Release via the vesicle secretory pathway

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10
Q

What are common viral causes of URTI?

A

Adenoviruses

Rhinovirus

Coronavirus

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10
Q

What receptors does measles virus use?

A

CD150 and CD46

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10
Q

What cell types produce type I interferon?

A

virally infected:

DCs

Tissue cells

dsRNA

Macrophages

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11
Q

What is an example of a virus that will kill a developing foetus?

A

Smallpox

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12
Q

Which inteferons are considered type II interferon?

A

Interferon gamma

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13
Q

What is the ecilpse period?

A

The period between a virus infecting cells and mature virions assembling in the infected cells

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14
Q

T/F measles virus is breathed out not coughed out

A

True

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15
Q

What don’t viruses that infect the alimentary tract have?

A

Envelopes

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16
Q

What are some examples of viruses that enter via the resp tract and cause disease locally?

A

Rhinovirus

Influenza virus

RSV

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17
Q

What is secondary viraemia?

A

When virus is released after replicating in tissue after an initial infection

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19
Q

What are two ways viruses penetrate a cell?

A

Fuse with membrane or are endocytosed

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19
Q

How are non-enveloped viruses released from the cell?

A

They accumulate in the cytoplasm or nucleus into the cell lyses

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20
Q

What types of viruses does the PKR system work against?

A

Mainly RNA viruses as they are the main producers of dsRNA

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21
Q

What are some examples of viruses that enter via the resp tract but cause systemic disease?

A

Measles and mumps

Rubella

varicella-zoster

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22
Q

What are some viruses that enter via conjunctiva?

A

Adenovirus, HSV, enterovirus

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23
Q

How are viruses classified using the baltimore system?

A

I. dsDNA

II. ssDNA

III. dsRNA

IV. +sense RNA

V. -sense RNA

VI. +sense RNA (retroviruses)

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23
Q

Direct viral damage to infected tissue can include 4 things, list them.

A

Lysis of cell during replication (eg enterovirus)

Release of toxic viral produces

Apoptosis

Loss of cell function (eg rhinovirus and cilia stasis)

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24
Q

The cytokines responsible for fever are?

A

IL-1 and TNF

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25
Q

What are some strategies viruses use to interfere with cytokines immune response?

A

Inhibit receptor production

Inhibit interferon production

Interfere with interferon function

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27
Q

What are three mechanisms of genome modification

A

Random mutation - viruses don’t have proof reading

Reassortment - Swapping of genome segments for 2 viruses that have segmented genomes and infect the same cell

Recombination - exchange of stretches of genome for 2 viruses that infect the same cell

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29
Q

When endocytosed how do viruses get their material into the cytoplasm?

A

Low pH in the lysosome trigger conformational change in viral protein that allows fusion with endosomal membrane

Or endosome is lysed and virus is released

30
Q

How does ancyclovir work?

A

It is incorporated into the extending chain but does have the -OH group required continue extension

30
Q

What do type I interferons do?

A

Activate NK cells

Inhibit viral genome replication

Enhances MHCI presentation

30
Q

What cell types produce type II interferon?

A

NK cells (and T cells)

31
Q

What are the stages of viral replications

A

Attachment

Penetration

Uncoating

Genome replication

RNA synthesis

Protein translation

Assembling

Budding/Lysis

33
Q

4 viral induced consequences?

A
  1. Lysis
  2. Chronic infection - slow release of virion
  3. Latent infection - dormant then lysis
  4. Tumour transformation
34
Q

What is the latent period?

A

The period between viral penetration and appearance of virions outside the cell

35
Q

Over what size with droplet load in the nose?

A

>10 microns

36
Q

What is an example of a tumour forming virus?

A

Oncogenic retrovirus

38
Q

What are the barriers to infection in the ailmentary tract?

A

Constant movement of stomach contents

Stomach acidity

Intestinal alkalinity

Lipolytic bile

Proteolytic enzymes

Mucus

Macrophages

IgA

40
Q

What is an example of a chronic virus?

A

Hep C virus

41
Q

What is the viral cause of croup?

A

Parainfluenza

42
Q

Where does influenza cause disease in the resp tract?

A

Large airways mainly

rarely in the alveoli

44
Q

What are inclusion bodies?

A

Accumulations of viral protein near the site of viral exit from a cell

45
Q

What are some strategies viruses use to evade the NK cell immune response?

A

  1. Mutations in ligand for activating receptor-MCMV
  2. Virus-encoded MHC class I-like molecules - HCMV
  3. Upregulation of non-classical class I molecules- HCMV
46
Q

Which viruses are people without NK cells susceptible to?

A

CMV and varicella

48
Q

What type of drug is ancyclovir?

A

Nucleoside analogue

50
Q

What are some viruses that use the alimentary tract to gain entry but cause disease elsewhere?

A

Hepatitis A

Poliovirus

52
Q

What are the 2 mechanisms of viral infection leads to tissue damage?

A

Direct damage by virus

Immune respond mediated damage

53
Q

Name 4 mechanisms to stop viral replication?

A

Antibody neutralisation

NK cell killing of infected cells

Interferon

Anti-viral drugs

54
Q

What is an example of a latent virus?

A

Herpes

56
Q

How is diarrhea cause by virus infection?

A
  1. Decreased fluid absorption due to destruction of entercytes
  2. Viral secretion of NSP4 that causes fluid to be secreted by remaining enterocytes
57
Q

What is an example of a lytic virus?

A

Enterovirus

59
Q

What is the pathogenesis of rotavirus?

A

It infects and kills intestinal villi and M cells causing diarrhoea. It has a triple peptide capsid for protection

60
Q

What are the most common viral causes of bronchiolitis?

A

RSV and parainfluenza

61
Q

DNA viruses don’t usually carry their own polymerase but which do?

A

Poxvirus because it replicates its genome in the cytoplasm and Hepadna because it is very complex

62
Q

What is the consequence of glycosylation of viral proteins in the RER and golgi?

A

They are deposited on the host membrane

64
Q

What barriers against infection are present in the respiratory tract?

A

Cilia,

alveolar macrophages

Temperature 33C

secreted IgA

Mucus

65
Q

What are some strategies viruses use to evade the immune response?

A

Lie dormant in cells - eg HSV in herpes

66
Q

When does Ab responses cause pathology or contribute to disease?

A

When Ab-virus complex mediated endocytosis of virus via FcR into cells

With Ab-Ag complexes are deposited - eg kidney failure in chronic Hep B carriers

67
Q

What is an example of a virus that requires two receptors?

A

HIV - it requires CD4 for initial attachment and conformational change of its gp120 protein so that it can bind to CCR-5 and form a stronger connection.

68
Q

How do non-enveloped viruses assemble?

A
  1. Spontaneous as the assembled state is the lowest energy
  2. Require proteolytic cleavage to induce the final state
69
Q

What virus does ancyclovir work against?

A

Herpes

70
Q

What is the attachment receptor for influenza?

A

Sialic acid

71
Q

What are some strategies viruses use to evade the T cell immune response?

A

Antigenic variation (shift and drift)

Downregulate MHCI expression

Inhibit processing of viral peptides

72
Q

T/F Only proteins can act as receptors for virus attachment

A

False, carbohydrates can too!

72
Q

What cytopathic effect is seen with RSV infection?

A

Giant cells

73
Q

Why does downregulating surface MHC I on virally infected cells leave them susceptible to NKs?

A

Surface MHC I is recognised by NKs are acts as a survival signal that overrides the killing signal it gets when it recognises viral produce on the surface of infected cells

74
Q

What are some viral strategies to inhibit the PKR system?

A

Produce small stretches of dsRNA only large enough for one monomer therefore PKR can’t activate

Produce it’s own protein to bind to its dsRNA to protect it from PKR binding

Produce homologue on eIF2 alpha that competes with actual eIF2 for PKR phosphorylation

75
Q

What are some routes of entry for viruses?

A

Conjunctiva

Respiratory tract

Alimentary tract

Urogenital tract

Skin

Parenteral inoculation

77
Q

T/F post translational cleavage of polyproteins is usually carried out by host enzymes?

A

False, they are usually by virally encoded enzymes

78
Q

What are some ways viruses inhibit T cell priming?

A

Vaccinina and HCV block cytokine production

HSV blocks signal transduction

Measles and CMV block T cell stimulation

79
Q

What are the six determinants of viral trophism?

A

Specific receptor availability

pH

Availability of macrophages and lymphocytes

Cell polarity

Optimal temperature

Presence of activating enzymes

80
Q

What are some genetic factor that alter susceptibility to virus infection?

A

Don’t produce a virus’ receptor eg CCR5 in HIV - good

Defect in Ig class eg IgG2 increased susceptibility to 2009 flu

MHC polymorphisms - some are good or bad

82
Q

Why doesancyclovir only work in virally infected cells?

A

It requires modification by herpesvirus thymidine kinase

83
Q

Where do RNA viruses replicate usually?

A

In the cytoplasm, except influenza that replicates in the nucleus

84
Q

What cells do measles virus infect?

A

Macrophages

Lymphocytes

DCs

85
Q

T/F Some virus encodes oncogenes?

A

True

86
Q

Why doesn’t Protein Kinase R act all the time?

A

It must be activated

87
Q

What size droplet will lodge in the alveoli?

A
89
Q

Which interferons are considered type I?

A

Interferon alpha and beta

90
Q

What is the clinical presentation of congenital rubella syndrome

A

Microcephaly

Congenital heart defects

Cataracts

91
Q

What do RNA viruses need that the host cell can’t provide?

A

RNA dependent RNA polymerase

92
Q

What is antigenic drift?

A

Random mutations in RNA genome that causes altered structured glycoprotein are selected for as they allow avoidance of Ab response - eg influenza and HIV

93
Q

What are some non-genetic factors that increase susceptibility to viral infection?

A

Age

Pregnancy

Multiple infections

Malnutrition

95
Q

What is an examples disease with CD4 T cell responses cause pathology

A

Rash in measles due to CD4 T cell recruiting eosinophils

96
Q

How is Protein Kinase R activated?

A

It is activated when it is recognises dsRNA (only viruses produce this)

Two Pkr monomers wrap around dsRNA bringing their KD domains closer therefore allowing phosphorylation and activation

97
Q

What are four outcomes of viral infection?

A

Death

Full recovery

Permanent damage - eg polio

Chronic infection - eg HSV

98
Q

What is an example of a virus that is endocytosed to penetrate?

A

Togavirus

Hugh's MD1 Respiratory (15 decks)

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