Digalactoside Expression in the Lipopolysaccharide of Haemophilus influenzaeand Its Role in Intravascular Survival

ABSTRACTDigalactoside (galα-1-4 galβ) structures of the lipopolysaccharide (LPS) of Haemophilus influenzaeare implicated in virulence. A confounding factor is that tetranucleotide repeats within the lic2A, lgtC, and lex2genes mediate phase-variable expression of the digalactosides. By deleting these repeats, we constructed recombinant strains of RM153 constitutively expressing either one or two LPS digalactosides. Expression of two digalactosides, rather than one, was associated with increased virulence of H. influenzaein vivo.