VIRUS · Enveloped ssRNA retrovirus (diploid)
Human Immunodeficiency Virus 1
HIV-1 — Transmission electron micrograph
Stain: Transmission electron microscopyMorphology: Spherical enveloped virion (~100 nm) with cone-shaped electron-dense core containing two copies of (+) ssRNAYield: HIGHDifficulty: HARD
Image: Wikimedia Commons · CDC/PHIL (Public Domain)
Key facts
**Pathogenesis**: gp120 binds CD4 with CXCR4 (T-cell tropic) or CCR5 (macrophage tropic) coreceptor → fusion via gp41 → reverse transcription of ssRNA to dsDNA → integration by integrase. Progressive CD4+ T-cell depletion. CCR5-Δ32 homozygotes are immune. **Diagnostic clue**: 4th-gen Ag/Ab (p24 + anti-HIV); confirm with HIV-1/HIV-2 differentiation; viral load by RT-PCR; CD4 count for staging (<200 = AIDS). **Virulence**: Reverse transcriptase has no proofreading → antigenic variation; integrates as provirus.
Boards buzzwords
- CD4 + CXCR4/CCR5
- reverse transcriptase
- p24 antigen
- gp120/gp41
- AIDS-defining illness < 200 CD4
- ART
Associated diseases
- Acute retroviral syndrome (mono-like)
- AIDS (PCP, Toxoplasma encephalitis, CMV retinitis, MAC, cryptococcal meningitis, Kaposi sarcoma, CNS lymphoma)
- HIV-associated nephropathy
- HIV dementia
Treatment
ART (2 NRTIs + INSTI preferred — e.g., bictegravir/tenofovir alafenamide/emtricitabine); PrEP; PEP within 72h; prophylaxis at CD4 thresholds (TMP-SMX <200 for PCP)
