- Unique modifications with phosphocholine and phosphoethanolamine define alternate antigenic forms of Neisseria gonorrhoeae type IV pili. Hegge, F.T., Hitchen, P.G., Aas, F.E., Kristiansen, H., Løvold, C., Egge-Jacobsen, W., Panico, M., Leong, W.Y., Bull, V., Virji, M., Morris, H.R., Dell, A., Koomey, M. Proc. Natl. Acad. Sci. U.S.A. (2004)