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MBBS IV - Junior Clerkship WCS > JC102 (Medicine) - HIV infection > Flashcards

JC102 (Medicine) - HIV infection Flashcards

1
Q

HIV

Genus, Family
Subtypes

A

Genus: lentivirus

Family: retroviridiae

Two subtypes including HIV-1 and HIV2
• HIV-1 is more virulent which is causing the global HIV pandemics

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2
Q

HIV

Routes of transmission

A

Transmission:

  • Sexual- semen, vaginal fluid, breast milk: Heterosexual or homosexual
  • Blood: IV drug use, contaminated bloods transfusion, contaminated organs, needles
  • Vertical: Mother to child
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3
Q

HIV

  • Screening and confirmation tests
  • Window period
A

HIV antibodies:

  • Screening with ELISA to detect anti-HIV-1 ***
  • Confirmation by Western blot *** of IFA or HIV RNA viral load (virological test) by RT=PCR
  • Indeterminate Western blot = repeat blot in 1 month

Window period: between contracting HIV and positive HIV antibody test
- 3 months to 6 months

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4
Q

Outline the HIV reporting system in HK

  • Major fields of information
  • Sources of reports
A

Info:

  • Gender, Age
  • Ethnicity
  • Source of reports
  • Progression to AIDS
  • Route of transmission
  • Suspected place of infection

Reporting:
- Voluntary, anonymous reports from physicians and confirmatory laboratories

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5
Q

Population group with highest HIV incidence rate in HK

  • gender, ethnicity, sexual orientation, age, source of infection, source of reporting
A

Male
Chinese
Homosexual > heterosexual
Age: 30-39 peak, followed by 20-29 and 40-49
Sexual contact (80%) - mostly male-to-male
Reporting: Most from public hospitals, clinic, labs

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6
Q

Reporting centers for HIV in HK

A

Public and private hospitals, clinic, laboratories

Drug rehab centers 
AIDS service organisations 
HK Red Cross Blood Transfusion Service
AIDS unit in Department of Health 
Social hygiene clinics in Department of Health
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7
Q

AIDS-defining illnesses/ Definition of AIDS

A

Definition of AIDS
o CD4+ T-cell count < 200/μL (OR)
o Presence of any AIDS-defining conditions

AIDS-defining Illnesses:

  1. Pneumocystis pneumonia** and recurrent bacterial pneumonia
  2. Esophageal candidiasis
  3. HIV wasting syndrome
  4. Kaposi’s sarcoma
  5. Tuberculosis and Non-MTB infections
  6. CMV infections
  7. HIV encephalopathy and CNS Toxoplasmosis

Others: lymphomas, recurrent bacterial and fungal infections, paracytic infections…etc

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8
Q

Examples of HIV testing services by community organisations

A
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9
Q

Selected population group that requires regular HIV testing every 12 months

A

MSM - men who have sex with men
Transgender
Female sex workers and their male clients
IVDU
Spouse/regular partner with HIV infection

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10
Q

Name one other virus that infects MSM patients at risk of HIV

A

HAV

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11
Q

Risk factors of HIV infection

A

High HIV viral load

Lack of circumcision

Unprotected sex (0.08% per act for male to female; 0.04% per act for female to male)

Anal sex (1.7% risk per act)

Presence of ulcerative STD: genital herpes, syphilis (10x - 300x)

HIV superinfection or co-infection

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12
Q

All HIV infected pt will develop AIDS eventually

True or False?

A
  • HIV + AIDS-defining conditions = AIDS
  • Half of infected people without treatment will progress to AIDS in 10 years
  • HIV treatment effectively prevents progression to AIDS
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13
Q

Factors influencing local HIV epidemiology

A

Individual behaviors
• Expanding local epidemic in MSM in HK
• IVDU in HK

Social environment
• International travelling/ sex networking increase risk to epidemic growth
• Fear of HIV-related stigma and discrimination reduces practice of preventive measures

Physical environment
• Availability of free condom

Health services
• Advances in antiretroviral therapy and HIV treatment services

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14
Q

Phases of HIV infection

A

Primary infection

Acute HIV syndrome - wide dissemination of virus, seeding into lymphoid organs

Long clinical latency phase: progressive depletion of CD4+ Th cells

AIDS-phase: Constitutional symptoms with AIDS-defining illnesses

Death

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15
Q

Mechanism of progressive immunodeficiency in HIV infection

A

Immunodeficiency resulting from progressive quantitative and qualitative deficiency of CD4+ helper T-cells in a setting of polyclonal immune activation

Mechanism of cellular depletion
• Direct infection and destruction of cells by HIV
• Immune clearance of infected cells
• Cell death associated with aberrant immune activation
• Immune exhaustion due to aberrant cellular activation

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16
Q

Pathogenesis of primary HIV infection

A

Primary infection and initial dissemination of virus
• Disruptions in mucosal barriers facilitate viral entry and efficiency of infection
• Virus infects resting and activated CD4+ T-cells and establish infection
• Replication in lymphoid tissue (NOT detectable in plasma)

Dissemination of virus to draining LNs and other lymphoid compartments with dense concentration of CD4+ T-cells
o Allow burst of high-level viremia

17
Q

Pathogenesis of chronic HIV infection

A

Once infection is established, HIV is Never eliminated completely despite mounted cellular and humoral immune response

Development of chronicity with persistent viral replication
o Establishment of a sustained level of replication&raquo_space;> generation of viral diversity via mutation and recombination against antibodies
o Clinical transition from acute primary infection to clinical latency

18
Q

Clinical presentation of Acute HIV infection

A 
General symptoms (non-specific, think general viral infection)
• Fever
• Pharyngitis
• Lymphadenopathy
• Headache/ Retro-orbital pain
• Arthralgia/ Myalgia
• Lethargy/ Malaise
• Anorexia/ Weight loss
• Nausea/ Vomiting/ Diarrhea

Neurological symptoms ***
• Meningitis/ Encephalitis
• Peripheral neuropathy
• Myelopathy

Dermatological symptoms *** (higher yield)
• Erythematous maculopapular rash
• Mucocutaneous ulceration

19
Q

Clinical presentation of HIV infection without AIDS

A

Asymptomatic infection

Persistent generalized lymphadenopathy (PGL)

Symptomatic infection: Non-AIDS-defining conditions
e.g. Vaginal candidiasis, Oral hairy leukoplakia, Peripheral neuropathy, Cervical dysplasia, Idiopathic thrombocytopenic purpura

20
Q

Outline history taking questions for HIV infection

A 
History taking (5Ps)
- Partners: number of partners in the last 12 months, sex of partners
  • Prevention of pregnancy: contraceptive methods
  • Past history of STDs, partner STDs
  • Protection from STDs: Contraceptive methods, condom use, correct condom use
  • Practice: Vaginal, anal, oral sex

Risks:

  • IVDU
  • Paid sex/ prostitution
21
Q

Monitoring methods for HIV infection

A

Monitor plasma HIV RNA viral load every 4 weeks after initiation of therapy

CD4+ T-cell count:

  • CD4+ T-cell count < 200/μL = Primary prophylaxis for P. jiroveci is indicated
  • CD4+ T-cell count < 50/μL = Primary prophylaxis for CMV, M. avium complex (MAC) and T. gondii is indicated
22
Q

Medical treatment options for HIV

  • Standard regimen, types of drugs
A

2 NRTI (backbone) + 1 NNRTI/ boosted PI / Integrase inhibitor/ CCR5-antagonist

NRTI: Nucleotide/ nucleoside reverse transcriptase inhibitors 
- Nucleoside analog
 Abacavir
 Zidovudine
 Lamivudine
- Nucleotide analog
 Tenofovir

NNRTI: Non- nucleoside reverse transcriptase inhibitors
 Efavirenz
 Nevirapine

Integrase inhibitor: Raltegravir

Protease inhibitor:
 Indinavir
 Ritonavir
 Lopinavir

CCR5/ Entry or fusion inhibitors
 Maraviroc
 Enfuvirtide

23
Q

Primary prevention against HIV in HIV negative patients

A

Avoid high-risk sexual behaviors

Avoid risk behavior by needle sharing

Voluntary male circumcision

Antiretroviral-based pre-exposure prophylaxis:
Tenofovir disoproxil fumarate-emtricitabine (TDF-FTC)
o TDF and FTC: 2 NRTIs
o Reduce risk of HIV transmission > 90%

24
Q

Secondary prevention in HIV +ve patients

A

Partner counselling and referral (PCRS)

  • Marital partner or regular sex partner: regular screening
  • Non-commercial or non-regular sex partner: regular screening
  • Regular or non-regular needle-sharing partner: stop IVDU, refer to rehab, methadone program
  • Offspring with HIV+ve mother

Prevention of sexual transmission: Intensive behavioral counselling, Referral to supportive services

Prevention of transmission through needle sharing

Routine Screening of STIs

25
Q

Prevention of vertical transmission of HIV

A

Antepartum + Intrapartum + Post-partum + Infant prophylaxis

combination ART:
Intrapartum = Zidovudine + Lamivudine + Nevirapine
Postpartum = Zidovudine + Lamivudine

Antiretroviral treatment for newborn prescribed by paediatrician

26
Q

NRTI

MoA
Examples

A

Inhibit DNA synthesis

 Structurally similar to nucleosides/ nucleotides
 Competitive inhibitors of reverse transcriptase
 Blocks the attachment of next nucleotide to the growing DNA chain
 Terminate DNA chain

Nucleoside analog
 Abacavir
 Zidovudine
 Lamivudine

Nucleotide analog
 Tenofovir

27
Q

NNRTI

MoA
Examples

A

Inhibit DNA synthesis

 Non-competitive inhibitors of reverse transcriptase
 Direct binds to reverse transcriptase and changes its structure
 Active site of enzyme is disrupted
 Unable to convert viral RNA to viral DNA

 Efavirenz
 Nevirapine

28
Q

Integrase inhibitor

MoA
Examples

A

Inhibit integration of viral genome
 Inhibit HIV enzyme called integrase
 Integrase facilitates the incorporation of HIV genome into host cell genome

 Raltegravir

29
Q

Protease inhibitor

MoA
Example

A

Inhibit the activation of proteins
 Block active site on HIV proteases
 Inhibit HIV proteases from cleaving proteins such as reverse transcriptase and integrase
 Prevent release of individual core proteins
 Viral particles cannot be matured

 Indinavir
 Ritonavir
 Lopinavir

30
Q

Entry/fusion inhibitors:

MoA
Examples

A

Reduces viral attachment to plasma membrane

Maraviroc:
 Block transmembrane chemokine receptor CCR5
 Decreases viral attachment

Enfuvirtide:
 Binds to glycoprotein 41 (gp41) subunit of the viral envelop
 Prevent conformational changes needed for the fusion of membranes
 Decreases viral attachment

MBBS IV - Junior Clerkship WCS (131 decks)

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