Induction of mucosal immunoglobulin A immune response by preparations of Neisseria gonorrhoeae porin proteins.

The aim of this study was to develop an immunization scheme appropriate for the induction of an immunoglobulin A (IgA) response against Neisseria gonorrhoeae at the mucosae. For several reasons, the major outer membrane protein of N. gonorrhoeae (gonococcal PI) is attractive as a component of a gonococcal vaccine. Purified PI obtained from strain B2 was used in Zwittergent 3-14 for immunization. Rats received the antigen subcutaneously, intraintestinally, or directly in Peyer's patches with or without the adjuvant N-acetylmuramyl dipeptide (MDP) or AlPO4. The immune response was studied in situ by a newly developed antigen-specific three-step immunoperoxidase method, whereas specific antibodies in the serum were measured by an enzyme-linked immunosorbent assay procedure. Subcutaneous immunizations triggered peripheral lymphoid organs, whereas intraintestinal and intra-Peyer's patch immunizations triggered mucosa-associated lymphoid organs. This was reflected not only in the lymph nodes involved, popliteal versus mandibular and mesenteric lymph nodes, but also in the isotypes of the produced anti-PI antibodies, IgG versus IgA. The adjuvants AlPO4 and MDP appeared to act differently during subcutaneous and intraintestinal immunizations. AlPO4 augmented subcutaneous immune responses, whereas MDP had no effects. In contrast, intraintestinal immune responses increased most with the adjuvant MDP. In summary, we concluded that PI is capable of inducing a mucosa-associated IgA response when administered intraintestinally and that this response can be augmented by the adjuvant MDP.