Which is most likely a positive Western blot result for infection with HIV?

The presence of bands at p24 and gp120 on a Western blot test is indicative of a positive result for HIV infection. The p24 protein is a core protein of the HIV virus and is one of the earliest markers to appear during infection, typically detectable about 2-3 weeks after exposure. The gp120 protein is an envelope glycoprotein that forms part of the surface structure of HIV and is critical for the virus's ability to enter host cells.

In a diagnostic context, both of these proteins being present strongly suggests an advanced stage of the viral infection. Additionally, the Western blot is considered a confirmatory test for HIV due to its specificity for HIV proteins, making the presence of these bands compelling evidence of infection.

Other bands listed, such as p31 or gp60, are not standard markers used to confirm HIV infection. While p31 is associated with HIV, it is not as definitive or widely recognized as part of the positive interpretation compared to p24 and gp120. Thus, the combination of p24 and gp120 provides a more robust confirmation of HIV presence.