Intranasal Delivery of Whole Cells of Neisseria Species: Study of Cross – Reactive Antigens in Rabbits

Neisseria lactamica, a commensal bacterium that is non-pathogenic to human beings and that is usually found in the upper respiratory tract of children, is closely related to the pathogenic species Neisseria meningitidis. A protocol was proposed to study the immunogenicity of killed whole cells of N. lactamica, N. meningitidis, N. sicca or N. meningitidis c (carrier-isolated) by i.n. immunization in rabbits,considering the natural pathogen entry route. Adult rabbits were inoculated i.n with oropharynx-isolated N. lactamica, N. meningitidis, N. sicca or N. meningitidis carrier strain (c), at a concentration of 1.0 optical density unit at 650nm in a volume of 500??L. The rabbits were immunized four times at sevendays intervals. The rabbits developed levels of specific IgG antibodies in serum, as determined by ELISA using whole cells of homologous and heterologous strains. Serum from rabbits immunized with N. lactamica, N. meningitidis, and N. sicca or N. meningitidis c strain, showed IgG antibodies reactive to 5 to 190kDa antigens on immunoblotting with high avidity.