The present invention relates to the use of mutant glycoproteins from pathogenic bacteria lacking one or more phosphorylcholine and/or glycosylation post-translational modifications as immunogens. These post-translational modifications act as masking structures that elicit an immune response which does not confer protection on an infected individual. The removal or modification of these masking structures alters the protein such that it elicits a stronger immune response to the protein and/or the bacterial pathogen. Particular examples are pilin proteins and nitrite reductase glycoproteins of Neisseria bacteria.
