In Western blot (immunoblot) confirmation of HIV-1 infection, which band patterns are required by WHO/CDC criteria for a confirmed positive result?

• A At least two of three bands: p24 (gag), gp41 (env), gp120/gp160 (env) — CDC criteria ✓
• B Presence of any single band on the blot
• C Only presence of gp120 band alone
• D Presence of all 10 HIV-1 bands simultaneously

Explanation

CDC criteria for HIV-1 Western blot positivity require reactivity to at least 2 of 3 key bands: p24 (core antigen, gag-encoded), gp41 (transmembrane glycoprotein, env-encoded), and gp120 or gp160 (envelope glycoproteins, env-encoded). WHO criteria require reactivity with gag (p17, p24, p55) + pol bands + env bands. An indeterminate result (some bands present but criteria not met) is reported; retesting in 4–6 weeks is recommended. Currently, fourth-generation combination antigen-antibody immunoassays followed by HIV-1/HIV-2 differentiation immunoassay replace Western blot in many algorithms.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

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