Podcast
Questions and Answers
Which of the following tests is primarily used for the initial screening of HIV?
Which of the following tests is primarily used for the initial screening of HIV?
What is the primary purpose of ELISA in HIV testing?
What is the primary purpose of ELISA in HIV testing?
Which class of antiretroviral drugs includes Zidovudine and Tenofovir?
Which class of antiretroviral drugs includes Zidovudine and Tenofovir?
What is the key prevention target defined by WHO for HIV?
What is the key prevention target defined by WHO for HIV?
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Which HIV testing method is appropriate for detecting the HIV viral genome in infants under 18 months?
Which HIV testing method is appropriate for detecting the HIV viral genome in infants under 18 months?
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What is a unique feature of retroviruses?
What is a unique feature of retroviruses?
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Which genera does the HIV virus belong to?
Which genera does the HIV virus belong to?
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What is the primary distribution area of HIV-2?
What is the primary distribution area of HIV-2?
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Which HIV subtype group is known for faster progression of the disease?
Which HIV subtype group is known for faster progression of the disease?
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Which component is crucial for HIV's entry into the host cell?
Which component is crucial for HIV's entry into the host cell?
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Which of the following best describes the transmission of HIV-2 compared to HIV-1?
Which of the following best describes the transmission of HIV-2 compared to HIV-1?
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Which gene is not one of the common genes found in all retroviruses?
Which gene is not one of the common genes found in all retroviruses?
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Which type of HIV primarily responds to NNRTIs?
Which type of HIV primarily responds to NNRTIs?
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Which region had the highest estimated number of people living with HIV in 2021?
Which region had the highest estimated number of people living with HIV in 2021?
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What was the total number of people globally who became newly infected with HIV in 2021?
What was the total number of people globally who became newly infected with HIV in 2021?
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What percentage of the population do key populations at risk for HIV infection represent?
What percentage of the population do key populations at risk for HIV infection represent?
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How many deaths from AIDS-related illnesses occurred globally in 2021?
How many deaths from AIDS-related illnesses occurred globally in 2021?
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Which HIV strain is believed to have originated from chimpanzees?
Which HIV strain is believed to have originated from chimpanzees?
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What was the prevalence rate of HIV in Kenya mentioned in the content?
What was the prevalence rate of HIV in Kenya mentioned in the content?
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Which key population at risk for HIV infection has the highest percentage of new infections?
Which key population at risk for HIV infection has the highest percentage of new infections?
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How many people globally were receiving antiretroviral therapy in 2021?
How many people globally were receiving antiretroviral therapy in 2021?
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Which route of transmission of HIV has the highest risk?
Which route of transmission of HIV has the highest risk?
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What is the main type of cell that HIV infects?
What is the main type of cell that HIV infects?
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Which statement about the asymptomatic stage of HIV infection is true?
Which statement about the asymptomatic stage of HIV infection is true?
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What is not considered an opportunistic infection associated with HIV?
What is not considered an opportunistic infection associated with HIV?
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Which opportunistic infection affects the central nervous system?
Which opportunistic infection affects the central nervous system?
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What percentage of individuals may experience acute retroviral syndrome shortly after HIV exposure?
What percentage of individuals may experience acute retroviral syndrome shortly after HIV exposure?
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Which of the following is a type of opportunistic tumor associated with HIV?
Which of the following is a type of opportunistic tumor associated with HIV?
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What factor does not contribute to the risk of acquiring HIV infection?
What factor does not contribute to the risk of acquiring HIV infection?
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Study Notes
Global HIV Statistics
- 38.4 million people globally were living with HIV in 2021.
- 1.5 million people became newly infected with HIV in 2021.
- 650,000 people died from AIDS-related illnesses in 2021.
- 28.7 million people were accessing antiretroviral therapy in 2021.
- 84.2 million people have become infected with HIV since the start of the epidemic.
- 40.1 million people have died from AIDS-related illnesses since the start of the epidemic.
Global Distribution
- North America and western and central Europe: 2.3 million people living with HIV.
- Caribbean: 330,000 people living with HIV.
- Latin America: 2.2 million people living with HIV.
- Middle East and North Africa: 180,000 people living with HIV.
- Western and central Africa: 5.0 million people living with HIV.
- Eastern and southern Africa: 20.6 million people living with HIV.
- Eastern Europe and central Asia: 1.8 million people living with HIV.
- Asia and the Pacific: 6.0 million people living with HIV.
Kenya
- HIV prevalence = 6%.
- 1.6 million People Living With HIV (PLHIV).
- 192,000 infected children.
- 102,000 new infections per year.
- 58,000 deaths per year.
Key Populations
- Key populations represent 2% of the global population and account for a third of all new HIV infections.
- Sex workers: 29% of new HIV infections.
- People who inject drugs (PWIDs): 18% of new HIV infections.
- Men who have sex with men (MSM): 18% of new HIV infections.
Origin of HIV
- HIV-1 Group M originated from chimpanzees (Pan troglodytes troglodytes) in the early 1900s.
- HIV-2 originated from sooty mangabeys (Cercocebus atys) in the early 1920s.
Retroviridae Family Classification
-
Subfamily: Orthoretrovirinae
- Genera: Alpharetrovirus, Betaretrovirus, Deltaretrovirus, Epsilonretrovirus, Gammaretrovirus, Lentivirus
- Species: Rous sarcoma virus, Mouse mammary tumor virus, Human T-Lymphotropic virus (HTLV), Walleye dermal sarcoma virus, Viper retrovirus, Porcine type C oncovirus, HIV-1, HIV-2, SIV, BIV, FIV, EIAV.
-
Subfamily: Spumaretrovirinae
- Genera: Spumavirus
- Species: Equine foamy virus
Retroviruses
- Undergo reverse transcription.
- Have three common genes (gag, pol, env) in all retroviruses.
- Contain two copies of ss (+)sense RNA.
HIV
- Baltimore Classification: Group 6 (ssRNA + Reverse Transcriptase).
- International Committee on Taxonomy of Viruses (ICTV) Classification:
- Family: Retroviridae
- Genus: Lentiviruses
- Species: HIV-1 & HIV-2
- Groups: HIV-1 – M, N, O, & P
- Clades: HIV-1 (A-K, CRFs); HIV-2 (A-H).
HIV Subtypes (Clades)
- HIV-1:
- Group M: A, B, C, D, F, G, H, J, K, CRFS
- Group N
- Group O
- Group P
- HIV-2: A-H
HIV-1 vs HIV-2
| Feature | HIV-1 | HIV-2 |
|---|---|---|
| Distribution | Worldwide | West Africa, Europe & USA |
| Transmission | Easier transmission | Less easily transmitted |
| Progression | Faster progression | Slower progression |
| Origin | Related to SIV_cpz_ (Chimpanzee SIV) | Related to SIV_sm_ (Sooty Mangabey SIV) |
| Treatment | Responds to NNRTIS* | No response to NNRTIS: e.g. EFV, NVP |
- NNRTIS = Non-nucleoside Reverse Transcriptase Inhibitors
HIV Particle Structure
- Nucleocapsid
- Protease
- Vif, Vpr
- Nef & p7
- Reverse Transcriptase
- Integrase
- RNA
- gp120
- gp41
- gag p17
- Lipid Membrane
- gag p24
HIV Ligand-Cell Receptor Interaction
- Ligand: HIV glycoprotein gp120.
- Cellular Receptor: CD4.
- Co-receptors: CCR-5 or CXCR4.
- HIV requires CD4 Receptor & a co-receptor for entry.
- The receptors/co-receptors are expressed by immune cells (T-Cells and Antigen Presenting Cells).
Retrovirus Replication Cycle
- Entry: The virus binds to the CD4 receptor and a co-receptor on the surface of the target cell and enters the cell.
- Reverse Transcription: The viral RNA genome is converted into DNA by the viral reverse transcriptase enzyme.
- Integration: The viral DNA is integrated into the host cell's genome.
- Transcription: Viral DNA is transcribed back into RNA.
- Translation: The viral RNA is translated into viral proteins.
- Maturation: Viral proteins assemble into new virus particles.
- Budding: New virus particles bud from the host cell, ready to infect other cells.
Transmission of HIV
- Sexual contact: oral, anal, vaginal
- Sharps – needles, blades
- Blood transfusion
- Mother to child transmission (MTCT): during pregnancy, delivery, or breastfeeding
Risk Factors: Acquisition of HIV Infection
- Nature of the exposure: the dose of HIV inoculum.
- Host susceptibility to infection: host genetics e.g. delta 32 mutation.
- Routes of transmission: intravenous > rectal > vaginal.
- Mucosal inflammation: ulceration by STDs.
Sequence of Events in HIV Infection
- HIV infects CD4 cells (APC).
- Disseminated infection.
- Specific immune response (antibodies, cell-mediated immunity).
- Clearance of most virus.
- Some persistence:
- Gradual loss of CD4 cells.
- Destruction of lymphoid tissue.
Clinical Features
-
Primary stage/Acute retroviral syndrome:
- Seen in 10% of individuals a few weeks after exposure.
- Acute seroconversion.
- Presents with an ‘flu-like' illness and lymphadenopathy.
-
Asymptomatic stage:
- Months to >10 years.
- Incubation period is 8-10 years.
-
Symptomatic and AIDS Stage:
- Opportunistic infections.
- AIDS defining illnesses and cancers set in.
Opportunistic Infections
| Type | Examples |
|---|---|
| Protozoal | Toxoplasmosis, cryptosporidiosis, Isosporiasis |
| Fungal | Candidiasis, cryptococcosis, histoplasmosis, coccidiodomycosis, PCP pneumonia |
| Bacterial | TB, Salmonella septicaemia, Multiple or recurrent pyogenic bacterial infection (meningitis, pneumonia, pyomyositis, etc.) |
| Viral | CMV, HSV, VZV |
Opportunistic Infections/Cancers (by system)
| System | Examples |
|---|---|
| Skin | Varicella zoster, Herpes virus, Kaposi sarcoma (associated with HHV-8) |
| Respiratory | PCP (Pneumocystis jirovecci pneumonia), Tuberculosis, Severe Bacterial pneumonia, Kaposi sarcoma |
| GIT | Cryptosporidiosis, Candidiasis, Isosporiasis, Kaposi sarcoma, Cytomegalovirus |
| CNS | Cytomegalovirus (CMV) infection, Herpes simplex (HSV) encephalitis, Toxoplasmosis, Cryptococcosis, Severe bacterial meningitis, Non-Hodgkins Lymphoma (NHL) |
Opportunistic Tumours
- Kaposi's sarcoma.
- Lymphomas.
- Cervical Cancer
HIV Testing
- Purpose: Diagnosis, Surveillance, Blood and organ transfusion, Travel.
HIV Tests
- Antibody Tests
- Antigen Tests
- Nucleic Acid Tests
Serological Tests
- Rapid HIV testing: Initial screening
- ELISA: Confirmation test
- Western Blot Analysis: Confirmation Test (rarely used nowadays)
- p24 antigen: Detection of a recent infection
Nucleic Acid Detection
- Detection of HIV viral genome through PCR.
- HIV RNA PCR can be:
- Qualitative: HIV PCR to detect the presence of infection.
- Quantitative: HIV PCR to measure viral load.
- HIV PCR is appropriate for infants < 18 months.
Classes of ARVs
- Nucleoside Reverse Transcriptase Inhibitors (NRTIs): Zidovudine, Lamivudine, Abacavir, Tenofovir
- Non-Nucleoside RT Inhibitors: Nevirapine, Efavirenz, Etravirine, Delavirdine
- Protease Inhibitors: Lopinavir, Ritonavir, Atazanavir, etc.
- Integrase Inhibitors: Raltegravir, Dolutegravir, Elvitegravir
- Attachment inhibitor: Maraviroc
- Fusion Inhibitor: Enfurvirtide
Prevention Targets
- Global: 90-90-90 by 2020 (90% of people living with HIV know their status, 90% of those diagnosed are on treatment, and 90% of those treated are virally suppressed).
- WHO: Universal Testing & Treatment (UTT).
- Ultimate: Eradicate HIV.
Control & Prevention
- Safer Sex practices.
- Screening (blood & blood products, organ donors).
- Prevention of Mother to Child Transmission (MTCT).
- Early testing and linkage with care.
- Treatment for prevention.
- Voluntary Male Medical Circumcision (VMMC).
- Post-exposure prophylaxis (PEP).
- Pre-exposure prophylaxis (PreP).
- Vaccines (Research in progress).
Bone Marrow Transplant
- The Berlin Patient: Tim Brown
- London patient: Adam Castillejo
- Chicago patient
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Description
Explore the latest global statistics on HIV, including information on infection rates, demographics, and access to antiretroviral therapy. Understand the impact of HIV across various regions and the ongoing challenge of AIDS-related illnesses worldwide.
