Passive immunization with Neisseria meningitidis PorA specific immune serareduces nasopharyngeal colonization of group B meningococcus in an infant rat nasal challenge model

To examine the protective efficacy of specific immune sera generated by men ingococcal vaccine candidates against nasopharyngeal colonization, we devel oped an infant rat nasal colonization model for group B meningococcus, In t his model, Sprague-Dawley infant rats were challenged intranasally (IN) wit h host adapted, piliated Neisseria meningitidis group B strains H355 or H44 /76 administered concurrently with iron dextran. Colonization was assessed by quantitative culture of nasal homogenates and expressed as log(10) colon y forming units (c.f.u.) per nose. Three to five log(10) c.f.u. of N. menin gitidis were routinely recovered from the nasal tissue up to 4 days post-ch allenge. Passive immunization (i.p.) of the infant rats with either PorA or whole cell antisera 24 h prior to homologous challenge resulted in a signi ficant reduction of N. meningitidis colonization in the nasal tissues of th ese animals. These results demonstrate that this model can be utilized to e valuate the role of antibody to prevent the initial nasopharyngeal coloniza tion by group B meningococcus. (C) 2001 Elsevier Science Ltd. All rights re served.