What role do mucosal antibodies play in OPV effectiveness?

• A. They provide local immunity in the intestines, crucial for interrupting transmission
• B. They provide systemic immunity in the blood
• C. They have no role
• D. They enhance mucous production in the nose

Answer: (A)

Mucosal antibodies provide local immunity in the gut, which is where poliovirus first replicates after ingestion. In people vaccinated with OPV, secretory IgA in the intestinal mucosa neutralizes the virus and limits its replication in the gut. This reduces what they shed in stool, helping to interrupt fecal-oral transmission within a community. While some systemic antibodies can be formed, the crucial factor for OPV’s ability to prevent spread is this mucosal gut immunity. The other statements miss this key point: mucosal antibodies do not primarily drive nasal mucus production, and the main transmission-blocking effect of OPV comes from the intestinal, not systemic, immune response.