Abstract: The invention relates to the isolation and cloning of the structural gene, hipP, for the NTHi pili serotype 5 and the LKP operon. The invention relates to DNA molecules capable of hybridizing to the DNA sequences of the Haemophilus influenzae genome related to the pili. The invention further relates to a DNA molecule which encodes a pili protein, particularly a tip adhesion protein. The DNA molecules of the invention can be used in a method for assaying a sample, such as a blood sample, for the presence of Haemophilus influenzae in the sample. Accordingly, the invention further relates to the use of the DNA molecules as a diagnostic. The invention also relates to a recombinant Haemophilus influenzae pili protein, such as a tip adhesion protein. The protein can be employed in a method for immunizing an animal, such as a human, as a therapeutic or diagnostic.