AIDS
ETIOLOGY & VIROLOGY
Q: What virus causes AIDS?
A: Human Immunodeficiency Virus (HIV)
Q: What was HIV initially called?
A: Lymphadenopathy-associated virus (LAV)
Q: Who discovered HTLV-III and where?
A: Dr. Robert Gallo; Pasteur Institute in Paris
Q: LAV and HTLV-III are both names for what?
A: HIV
Q: What virus family and subfamily does HIV belong to?
A: Family: Retroviridae; Subfamily: Lentiviridae
Q: What are the two types of HIV?
A: HIV-1 and HIV-2
Q: Which HIV type has subtypes M (A-H), N, O?
A: HIV-1
Q: Which HIV type is endemic in West Africa?
A: HIV-2
HIV-1 STRUCTURE
Q: What are the three main genes in HIV-1?
A: env, gag, pol
Q: What does the env gene code for?
A: gp41 and gp120
Q: What does the gag gene code for?
A: p24, p17, p9, p7
Q: What does the pol gene code for?
A: p66, p51 (reverse transcriptase), p31 (integrase), p10 (protease)
HIV-1 REPLICATION
Q: What receptor does HIV attach to?
A: CD4 receptor
Q: What enzyme converts viral RNA into proviral DNA?
A: Reverse transcriptase
Q: What happens after the proviral DNA is formed?
A: It’s integrated into the host genome
Q: What results from viral genome integration?
A: Continuous potential for new virus production
Q: How do new virus particles leave the host cell?
A: Bud from the cell membrane
TARGET CELLS & IMMUNITY
Q: What viral protein binds CD4 receptors?
A: gp120
Q: Primary cell target of HIV-1?
A: CD4+ T-helper cells
Q: Other affected cells besides CD4+?
A: Macrophages, monocytes, lymph node cells, B-cells expressing CD4
Q: What type of immunity is impaired by HIV?
A: Cell-mediated immunity
EPIDEMIOLOGY & TRANSMISSION
Q: Where is HIV-1 most common?
A: North America, Sub-Saharan Africa
Q: Where is HIV-2 most common?
A: West Africa
Q: Modes of HIV transmission?
A: Sexual intercourse, blood transfusion
Q: What is infectious pattern 1?
A: Homosexual disease and IV drug abuse (e.g., Americas, W. Europe)
Q: What is infectious pattern 2?
A: Heterosexual disease (e.g., Africa, Caribbean)
Q: What is infectious pattern 3?
A: Both homo- and heterosexual (e.g., Asia, Middle East)
DIAGNOSIS & CLASSIFICATION
Q: What is the lab criteria for adults with HIV?
A: Positive HIV screening and confirmatory tests, or positive virologic test
Q: What defines HIV in a child <18 mos (definitive)?
A: Two positive virologic tests from separate specimens
Q: What defines HIV in a child <18 mos (presumptive)?
A: One positive test, no negative follow-up results
Q: Criteria for “not infected” (definitive)?
A: 2 negative antibody tests (>6 mos), or 2 negative virologic tests (>1mo & >4mos)
Q: Criteria for “not infected” (presumptive)?
A: One negative antibody test (>6mos) and no positive tests
Q: What is “perinatal exposure” to HIV?
A: Does not meet infection or “not infected” criteria
SIGNS & SYMPTOMS
Q: What are early HIV symptoms?
A: Asymptomatic or mild chronic lymphadenopathy
Q: What happens during widespread dissemination?
A: CD4+ drop, viremia, flu-like symptoms
Q: What characterizes the clinical latency period?
A: Asymptomatic with potential virus transmission
TREATMENT
Q: Name a reverse transcriptase inhibitor.
A: Zidovudine (Retrovir)
Q: Prophylaxis in HIV is used against what?
A: Pneumocystis carinii pneumonia
Q: Is there a cure for HIV?
A: No; treatment only prolongs AIDS-free time
PROGRESSION TO AIDS
Q: When does HIV become AIDS?
A: When CD4+ cell count falls below 200/μL
LABORATORY ASSESSMENT
Q: How often should HIV serology be repeated?
A: Every 3–6 months
Q: How often should CBC be repeated for HIV patients?
A: Every 3–6 months or more frequently if values are low
SEROLOGIC & MOLECULAR TESTS
Q: What is the “window period” in HIV?
A: 6–12 weeks post-infection before detectable antibodies
Q: Core antigens produced during replication?
A: Anti-gp41, anti-p24
Q: What test detects HIV nucleic acid early?
A: PCR (Polymerase Chain Reaction)
Q: What is the detection limit of PCR?
A: <100 viral nucleic acid molecules/mL
CONFIRMATORY & IMMUNO TESTS
Q: Standard confirmatory test for HIV-1?
A: Western Blot
Q: Major HIV proteins detected in Western Blot?
A: p24, gp41, gp120, gp160
Q: Advantage of Line Immunoassay (LIA)?
A: Better quality control than WB
Q: What does IHC detect?
A: HIV-1 in infected cells using enzyme-labeled antibodies
RAPID TESTING
Q: What kits are used for rapid HIV detection?
A: POCT kits
OPPORTUNISTIC INFECTIONS
Q: Name an HIV-related skin cancer.
A: Kaposi’s Sarcoma
Q: Parasitic infection common in HIV?
A: Cryptosporidiosis (by Cryptosporidium parvum)
Q: How is Cryptosporidiosis transmitted?
A: Contaminated water ingestion
Q: Other HIV-associated infections?
A: CMV, TB, Mycobacterium avium, Toxoplasma, Legionella, Herpes simplex, Histoplasma