New model for analysis of mucosal immunity: intestinal secretion of specific monoclonal immunoglobulin A from hybridoma tumors protects against Vibrio cholerae infection.

Secretory immunoglobulin A (sIgA) plays a role in defense against Vibrio cholerae and other microorganisms that infect mucosal surfaces, but it is not established whether sIgA alone can prevent disease. We report here a strategy for identifying the antigen specificities of monoclonal sIgA antibodies that are capable of providing such protection. IgA hybridomas were generated from Peyer's patch lymphocytes after oral immunization with V. cholerae Ogawa 395. A clone was selected that produced dimeric monoclonal IgA antibodies directed against an Ogawa-specific lipopolysaccharide carbohydrate antigen exposed on the bacterial surface. Hybridoma cells were used to produce subcutaneous "backpack" tumors in syngeneic mice, resulting in secretion of monoclonal sIgA onto mucosal surfaces. Neonatal mice bearing anti-lipopolysaccharide hybridoma backpack tumors were specifically protected against oral challenge with 100 50% lethal doses of virulent Ogawa 395 organisms. Thus, the IgA hybridoma backpack tumor method identifies protective epitopes in the mucosal system and demonstrates that a single monoclonal sIgA can be sufficient to protect against intestinal disease.