What would most likely cause resistance to ritonavir/lopinavir in a patient with HIV?

• A. Mutation affecting nucleic acid synthesis
• B. Mutation affecting protein processing
• C. Mutation affecting viral envelope formation
• D. Mutation affecting genome integration

Answer: (B)

Ritonavir/lopinavir is a combination antiretroviral medication used primarily for the treatment of HIV infection and belongs to a class of drugs known as protease inhibitors. Resistance to these drugs is frequently driven by mutations in the viral protease, which is critical for processing viral polyproteins into functional proteins necessary for viral replication and assembly.

When considering what could lead to resistance to ritonavir/lopinavir, mutations affecting protein processing are particularly relevant. These mutations can occur in the protease gene, resulting in changes to the protease enzyme that hinder the effectiveness of the drug. Such alterations can prevent ritonavir and lopinavir from binding effectively to the protease, allowing the virus to replicate despite the presence of these medications.

While mutations affecting nucleic acid synthesis, viral envelope formation, or genome integration can all have various implications in HIV pathogenesis and treatment, they are not directly involved in the mechanism of action or resistance related to protease inhibitors like ritonavir and lopinavir. Therefore, the specific effect of mutations on protein processing is the most likely cause of resistance in this context.