An isolated and purified
lactoferrin receptor protein is isolated and purified from bacterial pathogens, including Moraxella and
Neisseria, and has a molecular weight of between about 70,000 and about 90,000, as determined by SDS-PAGE. Such
lactoferrin receptor protein may be provided in combination with a
lactoferrin receptor protein from the bacterial
pathogen of a molecular weight of about 100,000 to about 105,000 daltons. The lactoferrin receptor protein may be produced by providing a solubilized membrane preparation from the bacterial
pathogen containing lactoferrin receptor proteins, non-lactoferrin receptor proteins and other contaminants, complexing the lactoferrin receptor proteins with lactoferrin and purifying the resulting complexes substantially free from the non-lactoferrin receptor proteins and the other contaminants, and separating the novel lactoferrin receptor protein from the complexes. The lactoferrin receptor protein is useful in diagnostic applications and immunogenic compositions, particularly for
in vivo administration to a host to confer protection against
disease caused by a bacterial
pathogen that produces the lactoferrin receptor protein or produces a protein capable of inducing antibodies in a host specifically reactive with the lactoferrin receptor protein.