What is the significance of mucosal antibodies in OPV?

• A. They help limit poliovirus multiplication in the gut.
• B. They prevent systemic viremia.
• C. They have no effect on infection.
• D. They cause immunity to spread to others.

Answer: (A)

Mucosal antibodies in OPV are important because they act right at the entry point of poliovirus—the gut. OPV is a live, gut‑replicating vaccine, so it stimulates strong mucosal immunity, especially IgA in the intestinal lining. This local immune response neutralizes the virus as it starts to replicate in the gut, limiting how much the virus multiplies there and how much is shed in the feces.

By reducing gut replication and fecal shedding, mucosal antibodies cut down the amount of virus that others are exposed to, helping interrupt transmission in a community. Systemic antibodies (from a different layer of immunity) help prevent disease in the individual, but the mucosal response is the main driver of preventing intestinal infection and onward spread with OPV.

The other options don’t fit as well because mucosal antibodies are not primarily about preventing systemic viremia, they do have a real effect on infection in the gut, and they don’t “cause immunity to spread”—they reduce spread by lowering shedding, rather than driving it.