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3. Mondays > 302 How viruses cause disease > Flashcards

302 How viruses cause disease Flashcards

1
Q

How many people were living with HIV in 2021?

A

38.4 million

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2
Q

What type of virus is HIV?

A

A retrovirus

Family: Retrovirdae
Subfamily: Orthoretroirnae
Genus: Lentivirus

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3
Q

What is the zoonic origin of HIV-1?

A

Chimpanzees and gorillas

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4
Q

What is the zoonic origin of HIV-2?

A

Sooty mangabeys (a monkey)

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5
Q

What are SIV’s?

A

Simian immunodeficiency viruses

They naturally infect a wide range of African nonhuman primates and are the souse of HIV-1 and HIV-2

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6
Q

What are the 4 genetically distinct groups HIV-1 is subdivided into?

A

M, N, O, and P

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7
Q

What are the 9 distinct groups that HIV-2 is subdivided into?

A

A-I

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8
Q

What is the global distribution of HIV subtypes?

A

M has a global distribution

N, O, and P and HIV-2 are confined to West central Africa

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9
Q

What are the 9 distinct genotypes of HIV-1 group M?

A

A-D, F-H , J, K

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10
Q

What are the different sub-subtypes of HIV-1 group M?

A

A1-A4, F1, F2

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11
Q

What are CRF’s?

A

Circulating recombinant forms

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12
Q

What are URF’s?

A

Unique recombinant forms

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13
Q

How do CRF’s and URF’s form?

A

Through recombination of different subtypes

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14
Q

Which area in the world has the highest HIV-1 genetic diversity?

A

Central Africa

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15
Q

Describe the structure of the HIV-1 virus

A

100nm in diameter
gp120 and gp41 membrane proteins

Has an envelope (outer membrane), matrix, viral capsid, 2 identical molecules of ssRNA, RT, and IN

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16
Q

What is RT in viruses?

A

Reverse transcriptase

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17
Q

What is IN in viruses?

A

Integrase

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18
Q

What is integrase in viruses?

A

It’s the viral enzyme that catalyses the integration of virally derived DNA into the host cell DNA in the nucleus

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19
Q

Describe the HIV life cycle

A
  1. Attachment and fusion into the host cell and uncoating once inside the host cell
  2. Reverse transcription
  3. Integration
  4. Transcription
  5. Translation into proteins that assemble into a virus
  6. Budding and maturation of the virus
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20
Q

At which part of the HIV life cycle do attachment inhibitors work on?

A

On the attachment part

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21
Q

At which part of the HIV life cycle do fusion inhibitors work on?

A

The fusion and uncoating part

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22
Q

What is the risk of transmission of HIV through different methods?

A

Blood transfusion 90%
Mother to child 23%
Drug injection equipment 0.63%
Percutaneous needle stick injections 1.4%
Insertive anal intercourse 011%
Receptive penile-vaginal intercourse 0.08%
Insertive penile-vaginal intercourse 0.04%

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23
Q

What are risks that increase HIV transmission?

A

-Other STI’s because there a higher number of target cells
-High viral load

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24
Q

Why can’t antiretroviral treatment (ART) eliminate infection?

A

Because it can’t eliminate the integrated viral DNA from infected cells

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25
Q

What role does the adaptive immune system play in the initial host response of HIV infection?

A

HIV declines after acute infection because of HIV-specific CD8+ cytotoxic T-cells

Overtime, they fail to durably control the virus because HIV is able to create cytotoxic T-lymphocyte (CTL) escape mutants

26
Q

What does CTL stand for?

A

Cytotoxic T-lymphocyte

27
Q

How does HIV evade the immune response?

A

-Increasing glycosylation of envelope as a shielding mechanism
-Evasion from cellular restriction factors (APOBEC3)
-Generating cytotoxic T-lymphocyte escape mutants

28
Q

What is pathogenesis of HIV?

A

-Slow depletion of circulating tissue-based CD4+ T-cells
-Cause a constant state of immune-activation, activation of the endothelium and of the coagulation system
-Profound alteration of lymphoid tissues
-Increases plasmatic circulation of polysaccharides
-Causes a proinflammatory state

29
Q

What is the effect of slow depletion of circulating tissue-based CD4+ T-cells?

A

They’re essential for regulating the immune response, depletion leads to immunosuppression with development of opportunistic infections and AIDS-related malignancies

30
Q

What are AIDS-related malignancies?

A

Cancers that are more likely to develop with a HIV infection
Eg. Kaposi sarcoma, non-Hodgkin lymphoma, cervical cancer, Hodgkin lymphoma, and cancers of the mouth, throat, liver, lung, and anus

31
Q

What is the effect of a constant state of immune-activation, activation of the endothelium and of the coagulation system?

A

-There are increased proinflammatory cytokines
- Low CD4/CD8 ratio
-Exhaustion and senescence of T-cells and monotypes

32
Q

What is the effect of alteration of lymphoid tissues by HIV infection?

A

It causes an increase in microbial translocation due to the disruption of the physiological gut barrier

33
Q

What is the effect of Increased plasmatic circulation of polysaccharides?

A

It’s a component of the bacterial cell wall

It enhances persistent immune activation

34
Q

What is the effect of a constant proinflammatory state on the body?

A

-Premature ageing observed in people living with HIV
-Multiorgan disease:
Premature onset of atherosclerosis and MI
Neurocognitive decline
Liver disease (non-fatty liver disease)
Metabolic syndrome
Osteoporosis
Onset non-AIDS related cancers
Overall increased mortality

35
Q

What is the pathogenesis of HIV in other sites beyond the immune system?

A

-In the CNS, the virus can affect astrocytes via a CD4-independent mechanism
-HIV can infect renal epithelial cells in the kidneys

These mechanisms are the basis of the onset of HIV-associated neurocognitive disorder (HAND) and HIV-associated nephropathy (HIVAN)

36
Q

What % of patients develop symptoms of HIV?

A

50-90%

They’re easy to miss, transient symptoms that overlap with common infections
Characterised by high viral load

High inflammatory response causes systemic symptoms

37
Q

What are some viral differential diagnoses of primary HIV infection?

A

Epstein-Barr virus
Cytomegalovirus
Primary herpes simplex virus
Influenza
Early-stage hepatitis
Parvovirus B19
Rubella

38
Q

What is Epstein-Barr virus?

A

EBV can cause infectious mononucleosis (mono)

39
Q

What is Parvovirus B19?

A

Most commonly causes fifth disease, a mild rash illness that usually affects children

40
Q

What is Rubella?

A

AKA German measles
It’s a rare illness that causes a spotty rash

41
Q

What are some bacterial differential diagnoses of HIV infection?

A

Streptococcal disease
Secondary syphilis
Lyme disease
Rickettsial disease
Disseminated gonococcal infection

42
Q

What is Lyme disease?

A

A bacterial infection that can be spread to humans by infected ticks

Rarely deadly, easily treated if diagnosed early

43
Q

What is Rickettsial disease?

A

A group of bacteria that spread by the bite of an infected tick or mite

Symptoms:
Fever.
Headache.
Rash (sparse maculopapular or papulovesicular eruptions on the trunk and extremities)
Muscle aches

44
Q

What is a disseminated gonococcal infection?

A

AKA DGI

It occurs when the sexually transmitted pathogen Neisseria gonorrhoeae invades the bloodstream and spreads to distant sites in the body

45
Q

What are some parasitic differential diagnoses of HIV infection?

A

Acute toxoplasmosis

46
Q

What is acute toxoplasmosis?

A

An infection with a parasite called Toxoplasma gondii

People often get the infection from eating undercooked meat, having contact with cat faeces, or it can be passed to a baby during pregnancy

Most people infected with the parasite do not have symptoms

47
Q

What are some non-infectious differential diagnoses of HIV infection?

A

Adult Still disease
Systemic lupus erythematosus
Systemic vasculitis
Drug reaction

48
Q

What is Adult Still disease?

A

A rare type of inflammatory arthritis that features fevers, rash and joint pain

49
Q

What is Systemic lupus erythematosus?

A

A chronic autoimmune disease that can cause severe fatigue and joint pain

50
Q

What are the Fiebig stages of HIV infection?

A

-Eclipse: No plasmatic markers because initial replication of virus happens at the inoculation site
-1 (5 days): HIV RNA becomes detectable in plasma
-2 (10days): Positive p24 antigen (Ag) in plasma
-3 (14 days): seroconversion (anti-HIV antibodies present)
-4 (19 days): Indeterminate Western blot
-5 (88 days): Reactive Western blot for p31 Ag
-6 (88+ days): Reactive Western blot with positive p31 Ag

51
Q

What is seroconversion?

A

When the body starts producing detectable levels of HIV antibodies

52
Q

What is the Indeterminate Western blot in HIV?

A

Banding pattern on a Western blot test that failed to meet the criteria for positivity

53
Q

What is the purpose of the Fiebig stages?

A

They describe the emergence of virologic and immunologic markers following infection with HIV

54
Q

What is the definition of the AIDS stage in HIV infection?

A

CD4 count <200 cells/mm3 (advanced HIV infection)

Onset of opportunistic infections and malignancies

55
Q

What are some AIDS stage opportunistic infections?

A

-Recurrent bacterial infections usually only found among <6 years olds
-Candiditis of bronchi, trachea, or lungs
-Cryptococcosis (extrapulmonary)
-Cytomegalovirus disease
-Herpes simples (chronic ulcers >months duration, or bronchitis, pneumonitis, or oesophagitis)
-Salmonella septicaemia
-Toxoplasmosis of the brain
-Recurrent pneumonia

56
Q

What is a cytopathic effect of viruses?

A

Morphological changes of the cells caused by the infecting virus

57
Q

Give examples of cytopathic effects of viruses

A

-Inhibition of cell transcription/translation
-Changes in membrane permeability
-Alterations of the cytoskeleton or trafficking pathways
-Cell-cell fusion
-Induction of apoptosis

58
Q

What is the cytopathic effect of Venezuelan equine encephalitis virus (VEE)?

A

It causes a direct cytopathic effect on neurones

59
Q

What are immune complexes?

A

Aggregates of viruses and antibodies that form within small blood vessels and lead to the development of inflammation (vasculitis)

60
Q

What diseases are immune complexes responsible for?

A

Glomerulonephritis

61
Q

How doe viruses promote the onset of cancer?

A

-Immunosuppression (Eg. HIV and Kaposi’s sarcoma)
-Chronic inflammation (HCV and HCC)
-Cellular transformation (HPV and cervical cancer)

62
Q

What is Kaposi’s sarcoma?

A

A cancer caused by viral infection that affects the mouth and skin

First appears as purple, red, or brown lesions on the skin

3. Mondays (126 decks)

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