Which of the following combinations of bands would represent a positive Western blot for HIV antibody?

• A. P24 and P55
• B. P24 and P31
• C. Gp41 and Gp120
• D. P31 and P55

Answer: (C)

HIV Western blot detects antibodies to specific viral proteins, and a positive result comes from antibodies recognizing multiple HIV proteins, not just one. The envelope glycoproteins gp120 (often seen as gp160 on the blot) and gp41 are highly immunogenic and their antibodies are strongly indicative of infection. When both gp41 and gp120 bands are present, it provides solid evidence of HIV antibodies, making the blot positive. In contrast, a combination that includes core or matrix proteins like p24 or p31 with a non-envelope protein is less definitive and could be non-specific or less reliable early in infection. So, antibodies to both envelope proteins together best define a positive Western blot pattern.