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HIV Flashcards

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1
Q

What is the infectious agent for HIV?

A

human immunodeficiency virus (HIV-1 and HIV-2)

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2
Q

What are the 2 main subtypes of HIV?

A

HIV-1 and HIV-2

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3
Q

Describe the HIV infectious agent

A

enveloped, single-stranded RNA retrovirus

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4
Q

What is meant by a retrovirus?

A

have an enzyme (reverse transcriptase) which uses the viral RNA to make a complimentary DNA copy which can be incorporated into the host cell’s DNA and used to produce viral components

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5
Q

What are the components of the HIV infectious agent?

A

HIV glycoproteins, HIV envelope, HIV capsid, HIV RNA and HIV enzymes

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6
Q

Which cells does HIV infect?

A

CD4+ T lymphocytes, macrophages, dendritic cells

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7
Q

How does HIV infect / gain entry to CD4+ T lymphocytes, macrophages and dendritic cells?

A

via CD4, CCR5 or CXCR4 co-receptors

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8
Q

What is the effect of an infection with HIV?

A

progressive immunosuppression

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9
Q

What can HIV result in if untreated?

A

AIDS

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10
Q

Outline the HIV life cycle

A
  1. binding
  2. fusion (with plasma membrane of CD4+ T cell for example)
  3. reverse transcription
  4. integration
  5. replication
  6. assembly
  7. budding
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11
Q

Which component of HIV enables host-cell entry?

A

envelope proteins (gp120 / gp41)

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12
Q

How is the viral RNA integrated into the host genome?

A

via reverse transcriptase

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13
Q

What is the action and aim of anti-HIV drugs?

A

target specific stages of HIV life cycle to obstruct / block multiplication to prevent damage to CD4 cells

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14
Q

What is the effect of anti-HIV drugs?

A

number of CD4+ cells remain high and person with HIV maintains normal immune function

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15
Q

What is antiretroviral therapy (ART)?

A

typically is a combination of HIV medicines from different drug classes (at least 2) to treat HIV infection

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16
Q

Why does antiretroviral therapy consist of at least 2 different drug classes of HIV medication?

A

virus may overcome / develop resistance against a single antiretroviral drug but this is very unlikely against 2

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17
Q

How do HIV medicines from different drug classes protect the immune system?

A

block HIV at different stages of the HIV life cycle

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18
Q

Example of a drug class of HIV medication

A

Nucleoside reverse transcriptase inhibitors (NRTIs)

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19
Q

Examples of nucleoside reverse transcriptase inhibitors (NRTIs)

A

lamivudine, emtricitabine

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20
Q

What is the mechanism of action of nucleoside reverse transcriptase inhibitors (NRTIs)?

A

prevents HIV converting its RNA into DNA which is necessary for viral replication

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21
Q

Which stage of the HIV life cycle is targeted by nucleoside reverse transcriptase inhibitors (NRTIs)?

A

reverse transcription

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22
Q

Outline the course of an HIV infection

A
  1. acute infection
  2. chronic lymphadenopathy
  3. sub-clinical immune dysfunction
  4. skin and mucous membrane immune defects
  5. systemic immune deficiency
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23
Q

How can acute infection with HIV be detected?

A

viremia - detected serologically via p24 antigen on virus

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24
Q

What happens during chronic lymphadenopathy?

A

steady depletion in CD4 T cells

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25
What happens during sub-clinical immune dysfunction?
increased risk of opportunistic infections
26
How is sub-clinical immune dysfunction detected?
via rising anti-HIV antibody (gp120)
27
Example of a skin and mucous membrane immune defect
Candidiasis (concentration of CD4+ T cells < 200)
28
What happens during systemic immune deficiency?
patient incredibly susceptible to opportunistic infections due to severely depleted CD4 T cells (usually end stage of HIV)
29
What type of infection is HIV an example of?
zoonotic infection
30
What is meant by a zoonotic infection?
an infectious disease transmitted from an animal host to humans
31
Which animal virus did HIV arise from?
Simian immunodeficiency virus (SIV)
32
When was Simian immunodeficiency virus (SIV) transmitted to humans?
around 1890-1920 in Central Africa
33
How many African non-human primate species do SIVs infect?
over 40 primate species
34
What has been learnt about the Simian reservoir in primate hosts?
most primate hosts show non-pathogenic, co-evolved infections, indicating long-term virus-host adaptation
35
Which subtype of HIV is responsible for >95% of global HIV cases?
HIV-1 group M
36
What did HIV-1 group M arise from?
SIVcpz in chimpanzees
37
How did HIV-2 originate?
from SIVsmm (sooty mangabeys) with at least 8 independent transmission
38
How does HIV-2 compare to HIV-1?
HIV-2 is less transmissible, largely West Africa-restricted, has slower disease progression
39
What mechanisms facilitated the transfer of SIV in chimps / sooty mangabeys into humans?
bushmeat hunting and butchering (blood exposure), bites / injuries from infected primates
40
What were early human infections with HIV like?
likely were rare and self-limiting until viral variants developed adaptations favouring efficient replication in humans (human-to-human transmission)
41
What country in Africa became a hub for HIV's diversification and spread in the mid-1900s?
Kinshasa - now Democratic Republic of Congo
42
What human factors amplified the rapid spread of HIV?
- urbanisation in central/W Africa - colonial-era medical practices including unsafe injections - sexual networks (commercial sex work, genital ulcer disease prevalence) - increased human mobility via river and rail transport
43
How did the HIV infectious agent move out of Africa?
social contact network between Kinshasa and Haiti as in early 1960s many Haitian professionals worked in DRC
44
Why was Haiti a key transitional hub for HIV?
- high connectivity with central Africa (1960s) - growing urban populations - transnational links with North America
45
What is the evidence of Haiti being a transitional hub for HIV?
genetic evidence - shows all early US HIV-1 subtype B viruses fall within Haitian lineage
46
What features of HIV were noted by physicians in 1980/1?
an infectious mononucleosis-like syndrome involving fever, weight loss, swollen lymph nodes as well as oral and anal thrush.
47
Why did HIV seem to be a very unusual infection?
1. all patients were young men and homosexual 2. suffered from pneumonia (pneumocystis carinii) and candidosis
48
How did pneumocystis carinii pneumonia present on a chest radiograph?
Ground-glass appearance (due to proliferation of pneumocystis infectious agent in alveoli)
49
What is Kaposi's sarcoma?
cancer caused by human herpes virus 8 (HHV-8) affecting people with advanced HIV (immunocompromised)
50
What does AIDS stand for?
acquired immune deficiency syndrome (AIDS)
51
What population groups is AIDS seen in?
homosexual men and people with haemophilia
52
What was learned from AIDS affecting people with haemophilia?
AIDS is spread via an infectious agent in contaminated blood
53
What is the difference between HIV and AIDS?
HIV is the infectious agent that causes HIV infection whereas AIDS is the last stage of HIV infection
54
What happens as the HIV infection advances to AIDS?
amount of HIV in the body increases (proportion of virus in bodily fluids increases) and number of CD4+ cells decreases
55
When and how was HIV discovered?
discovered independently by two parties by isolating a virus from the swollen lymph gland of an AIDS patient. The virus was named lymphadenopathy-associated virus (LAV) and AIDS-related virus (ARV) respectively.
56
When was the virus named human immunodeficiency virus (HIV)?
1986 (3 years after isolated as LAV and ARV)
57
What were the social impacts of HIV?
people afraid to touch person with AIDS - Princess Diana squashed this belief by shaking the hand of person with AIDS
58
What is the only natural reservoir for HIV?
humans
59
What parts of the body does HIV replicate in?
lymphoid tissues, blood, genital fluids, breast milk, CSF
60
What secretions contain the highest HIV viral concentrations?
blood, semen, rectal, vaginal secretions
61
What feature of HIV allows for asymptomatic transmission?
long clinical latency (virus replicates without causing symptoms)
62
What is the dental relevance of the long clinical latency of HIV?
treat every patient as a potential carrier (universal precaution)
63
How can patients with HIV achieve undetectable viral loads?
antiretroviral therapy (ART)
64
What is U=U?
undetectable = untransmissible (with ART)
65
How many people were living with HIV in 2024?
40.8 million
66
How many people acquired HIV in 2024?
1.3 million
67
How many HIV-related deaths occurred in 2024?
630 000
68
What is the most common HIV-related cause of death?
TB infection
69
Which region of the world has the highest distribution of people living with HIV (2024)?
African region (65%)
70
Which region of the world has the highest distribution of new infections (2024)?
African region (50%)
71
What is the trend of the number of people acquiring HIV and HIV-related deaths globally?
declining (number acquiring HIV peaked in 1995 and number of HIV-related deaths peaked in 2005)
72
Is there a cure for HIV infection?
no - but has become a manageable chronic health condition
73
Outline the exposure categories of people acquiring HIV diagnoses
- men who have sex with men - people who inject drugs - heterosexual sexual intercourse
74
How many HIV diagnoses were made in 2024 in Scotland?
375 (largely attributed to heterosexual sexual intercourses - homosexual male intercourse used to be main contributer)
75
What goals are in place for ending HIV transmission in Scotland by 2030?
- prevent people acquiring HIV - find people living with HIV in Scotland (some are undiagnosed) and support - reduce stigma
76
Which bodily fluids containing infectious virions can HIV exit the host via?
blood, semen, vaginal secretions, rectal secretions, breast milk
77
Which bodily fluids are not a portal of exit for HIV?
saliva, sweat, tears, urine
78
What is the main portal of exit of HIV in dental settings?
blood (bleeding during procedures or contaminated sharps / instruments injury)
79
What does HIV need to access in order to be transmitted?
direct access to bloodstream or mucosal surfaces with appropriate cell receptors
80
What are the major routes of HIV transmission?
sexual transmission, vertical transmission, bloodborne transmission
81
Via what methods can vertical transmission of HIV occur?
pregnancy, labour / delivery, breastfeeding
82
What is the environmental stability of HIV (outside body)?
poor environmental stability - rapidly inactivated by drying, heat, detergents, disinfectants
83
What are the implications of the poor environmental stability of HIV?
cannot be transmitted via fomites e.g. sharing cutlery, toilet seats
84
How can bloodborne transmission of HIV occur?
needlestick injury, blood transfusion (rare), shared needles (IVDU)
85
What is the risk of HIV transmission from a needlestick from an HIV-positive source?
~0.3%
86
What is the risk of HIV transmission via a mucous membrane exposure?
~0.1%
87
What is the risk of HIV transmission via an intact skin exposure (e.g. contacting blood)?
negligible
88
What is the highest sexual risk of HIV transmission?
condomless receptive anal intercourse
89
How can sexual acquisition of HIV be prevented?
using HIV PrEP
90
What is HIV PrEP?
HIV Pre-Exposure Prophylaxis - prescription medication that significantly reduces the risk of acquiring HIV
91
What does HIV PrEP contain?
combination of 2 antiretroviral drugs that block replication
92
How can oral manifestations of HIV be classified?
into 3 groups: - group 3 = lesions seen in HIV infection - group 2 = lesions less commonly associated with HIV infection - group 1 = lesions strongly associated with HIV infection
93
Examples of group 1 lesions (strongly associated with HIV)
oral candidiasis, oral hairy leukoplakia, Kaposi's sarcoma, necrotizing ulcerative periodontitis, non-Hodgkin lymphoma
94
Which case raised concerns about HIV transmission in the dental practice?
the Florida "Acer case"
95
What was the Florida "Acer case"?
six former patients of an HIV-positive Florida dentist (Dr Acer) were diagnosed with HIV - resulting in an investigation into whether transmission occurred during dental treatment
96
What did the disease control and prevention investigation into the Acer case involve?
patient interviews, review of infection-control practices and genetic sequencing of HIV viruses from Dr Acer and the affected patients
97
What did the investigation into the Acer case conclude?
unusually close relationship between the patient's HIV strains and Dr Acer was found, suggesting probable transmission during dental treatment
98
Why was the Florida Acer Case controversial?
1. scientific uncertainty (HIV transmission during dental procedures is extraordinarily rare - requires exposure to significant amounts of infected blood) 2. no mechanism of transmission was ever identified 3. Argument of genetic analysis being limited by the technology at the time
99
What was the impact of the intense media coverage of the Florida Acer case?
amplified fears of catching HIV from the dentist
100
What was the impact of the Florida Acer case on infection prevention in dentistry?
1. high speed handpieces should be cleaned and heat-treated between patients 2. adoption of universal / standard precautions 3. sharps and exposure prevention 4. HIV-positive clinician practice policies
101
What was the logic behind introducing sterilisation of dental handpieces in an autoclave?
investigations revealed dental handpieces could aspirate patient material and expel them during subsequent use
102
What does universal / standard precautions involve?
mandatory use of gloves, eye protection, masks, sterile single use devices, effective sterilisation of instruments
103
What should be assumed with regards to standard precautions?
all patients may carry infectious agents
104
What are modern policies (including UK) on HIV-positive clinician practice?
allow HIV-positive clinicians to practice if viral load is undetectable and occupational health supervision is followed
105
What are the portals of entry of HIV?
- mucous membranes (vaginal, rectal, oral, ocular) - non-intact skin - direct inoculation into bloodstream (needles, sharps, IVDU) - vertical transmission (placenta / breastfeeding)
106
What needs to be present in the tissues for HIV to enter?
access to susceptible immune cells
107
How can the risk of HIV entry be reduced?
effective PPE use (gloves, masks, visors) and sharps safety
108
Who are susceptible hosts for HIV?
anyone if: - exposed to contaminated blood via sharps / mucosal splash - not protected by PPE - not following appropriate instrument decontamination - not following appropriate sharps-handling protocols - cuts, dermatitis, broken skin exposed to blood
109
How can the risk of HIV transmission be reduced if a high-risk exposure occurs?
post-exposure prophylaxis (PEP)
110
What factors does susceptibility depend on?
- biological factors - mucosal integrity - co-existing STIs - behavioural factors - lack of preventative measures
111
Examples of biological factors that affect susceptibility
- presence of target cells (CD4+ T cells) - co-receptor availability (CCR5, CXCR4) - CCR5-32 mutation decreases susceptibility
112
What aspects of mucosal integrity increase susceptibility?
inflammation, ulcers - increase risk
113
Examples of co-existing STIs that increase susceptibility
syphilis, HSV-2, chlamydia (inflammation / ulcers of mucosal membrane)
114
What behavioural factors increase susceptibility?
sexual practices, IVDU, occupational exposures
115
What preventative measures if lacking can increase susceptibility?
PrEP, condom, ART in index case
116
What diseases are dental professionals obligated to declare to the GDC?
any infectious disease, blood-borne virus (HIV, Hep B, Hep C) or other transmissible disease
117
How can the chain of infection be broken at the infectious agent level?
ART (viral suppression reduces transmission by >96%)
118
How can the chain of infection be broken at the reservoir level?
- universal HIV testing - immediate ART initiation
119
How can the chain of infection be broken at the portal of exit level?
- condom use - viral suppression via ART
120
How can the chain of infection be broken at the transmission level?
- PrEP for high risk individuals - PEP for occupation exposures - harm-reduction services (clean needles)
121
When is the optimal time for PEP for occupation exposures?
best within 1-2hr, up to 72hrs
122
How can the chain of infection be broken at the portal of entry level?
- barrier methods - safe injection practices (IVDU) - PPE and sharps safety in healthcare
123
How can the chain of infection be broken at the susceptible host level?
- vaccination for coinfections (HBV, HPV) - reducing mucosal trauma - STI treatment
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