Phase variation of lipopolysaccharide in Haemophilus influenzae.

Lipopolysaccharide (LPS) structures on Haemophilus influenzae, defined by monoclonal antibodies, can show phase variation from generation to generation. Several genetic loci are involved in LPS biosynthesis by H. influenzae. In this paper, we describe three loci which play a role in LPS phase variation: the lic loci; lic1 and lic3 have been sequenced and lic2 has been partially sequenced. Each locus consists of multiple open reading frames (ORF), and each contains a repetitive sequence within the 5' end of the first ORF which may be involved in the phase variability. Genes within lic1 and lic2 are directly involved in the expression of phase-variable epitopes, but the role of genes within lic3 is at a more complex level.