HIV, AIDS And Opportunistic Infections Flashcards
Learning Objectives
- What is HIV?
- How is it transmitted?
- What does HIV do to your body?
- Opportunistic infections
- Prevention & Treatment
How has HIV evolved over the years?
- Between 1883 and 2025, HIV has caused 40.4 million deaths
- 1881: First cases of ‘rare lung infection’ reported in LA
- 1883: Discovery of a retrovirus that could cause AIDS
- 1996: ART established as effective treatment
- 1999: WHO reports HIV/AIDS leading cause of death in Africa
- 2004: First ART programmes in Africa
- 2011: Early ART reduces transmission
- 2012: Pre-exposure prophylaxis (PREP) approved
- 2015: WHO launches ‘test and treat’
- 2022: Injectable ART
What is HIV?
A type of Retrovirus: A very little package of RNA
Describe the HIV transmission
- It’s like a building block
- There’s a substrate and a binding site
- The molecule binds to the binding site to form an active binding site
What does HIV do?
- Infects immune ‘white’ cells (CD4+ T lymphocytes - predominantly)
- Turns them into HIV “factories”
- Stimulates an inflammatory immune response
- Provokes the progressive loss of CD4+ T (and other) cells
- Creates a “CD4+ T-cell-shaped hole” in immune system
- Allows for ‘opportunistic infections’ and related cancers = Acquired immunodeficiency syndrome (AIDS)
Describe the HIV life cycle
- CD4 cell - Binding
- Fusion
- Reverse Transcription
- Integration
- Replication
- Assembly
- Budding
What is the immune system response to infection?
- Innate immunity: Produces Monocytes, macrophages, M1/M2 macrophages, Neutrophil, Mast cell, Basophil, Natural killer cell, Eosinophil, Dentritic cell
- Adaptive immunity: Produces CD8+ T cell, Cytotoxic T cell, Granzymes, B cell, Plasma cell, Helper T cell, Memory B cell
Describe the natural history of untreated HIV infection
- Primary infection (HIV seroconversion): First few weeks, accompanied with flu like symptoms or asymptomatic
- Chronic infection (Clinical latency): Prolonged period (App 10 years), person remains asymptomatic or mild symptoms. CD4 count gradually declines
- Advanced HIV disease: CD4 count falls below 200 cells/uL, severe immunodeficiency and opportunistic infections
Describe Primary infection - HIV seroconversion
- 10 - 60% Asymptomatic
- Incubation: 2 - 4 weeks
- Symptoms: Acute retroviral syndrome, Flu like illness, Fever, fatigue, headache, muscle ache, sore throat
- Lumphadenopathy, Rash, Oral and genital ulcers, rarely meningitis
What does this mean clinically?
- Increased incidence/severity of some common infections
- Pneumonia, TB, Oral candida, Zoster (Shingles)
What is Oral candidiasis?
- Oral candidiasis (thrush)
- Fungal (yeast) infection
- Oral discomfort
- Altered taste
What is Pneumococcal lobal pneumonia?
- Pneumococcal lobar pneumonia
- Common bacterial cause of pneumonia
- High fevers
- Cough productive of sputum
- Sepsis
What is Zoster (shingles)?
- Zoster (shingles) (Varicella Zoster Virus)
- Reactivation Varicella Zoster Virus (VZV – cause of chickenpox)
- Painful vesicular rash in one dermatome
Describe pulmonary tuberculosis
- Mycobacterial infection
- Weight loss, night sweats, cough (+/- haemoptysis)
- ‘Classic’ appearance with infection of upper lobe of the lungs and cavitation more common if CD4>200
Describe opportunistic infections with some examples
E.g. PCP, CMV, Cryptosporidiosis
Describe PCP
- Pneumocystis jirovecii pneumonia (PCP)
- Fungal infection of lungs
- Shortness of breath on exertion
- ‘Ground glass’ shadowing on CXR
Describe CMV
- Cytomegalovirus (CMV)
- Reactivation of commonly acquired virus
- Retinitis – loss of vision, ‘pizza pie’ eye
- Colitis – diarrhoea
- Hepatitis - liver inflammation
Describe Cryptosporidiosis
- Cryptosporidiosis
- Parasitic infection- contaminated water
- Chronic watery diarrhoea
- Other causes of diarrhoea: Isospora beli (parasite); Microsporidia (parasite/fungi); CMV; HIV itself
How does tuberculosis affect an immunocompetent patient?
Immunocompetent Patient
- After exposure to Mycobacterium tuberculosis, 3% develop primary TB within 2 years.
- The remaining 97% develop latent TB, where the bacteria remain dormant.
- Of those with latent TB, 7% may experience reactivation over their lifetime, leading to active TB disease.
What effect does tuberculosis have in a HIV patient?
- Effect of HIV Infection
- HIV significantly increases TB risk. 30% of exposed individuals develop primary TB, compared to 3% in immunocompetent patients.
- Latent TB reactivates at a much higher rate of 10% per year (instead of 7% over a lifetime).
- TB dissemination (spread beyond the lungs) is more common in HIV-positive individuals due to immune suppression.
Describe malignancy in HIV infection
- HIV assosicsted malignancies: KS, Lymphoma
- High grade pathogens above 50 uL
- Low grade pathogens below 50 uL
- Very Low grade Pathogens below 10 uL
Describe Kaposi sarcoma
- Kaposi Sarcoma
- Malignancy related to HHV-8 infection (Herpes virus)
- Purplish/brown/black nodules, patches or plaques
- Visceral (e.g. gut, other organ) involvement possible
Describe advanced HIV disease
CD4 count <200 cells/mm3 in adults, or WHO stage 3 or 4 event, and all children under age 5
