Surface protein p104 is involved in adhesion of Listeria monocytogenes to human intestinal cell line, Caco-2

Adhesion of Listeria monocytogenes to intestinal endothelial cells is an im portant initial event in the pathogenesis of infection which is not well un derstood. The suggestion has been made that some proteins, including intern alin and actin polymerisation protein (ActA), and carbohydrate molecules me diate, at least in part, the adhesion of listeria to certain cultured mamma lian cells. This study investigated the role of a L, monocytogenes cell-sur face protein of 104 kDa (p104) in adhesion to human intestinal enterocyte-l ike Caco-2 cell lines by transposon (Tn916) mutagenesis and a p104-specific monoclonal antibody (MAb-H7), Genotypic and phenotypic characteristics of Tn916-transformed L, monocytogenes strains, AAMU530 and AAMU572, revealed t hat these strains did not express p104, and the transposon had been inserte d at a single locus in the structural gene. Strains AAMU530 and AAMU572 yie lded only 10 and 6.3% adhesion to Caco-2 cells. Coating of L. monocytogenes and L. innocua wild-type strains with MAb-H7 reduced adhesion to Caco-2 ce lls from 100% to 50 and 45%, respectively, whereas on isotype control MAb E M-7G1 had no effect. Western blot analysis with MAb-H7 indicated that p104 is present in all Listeria spp, except in L, grayi, Furthermore, p104 is al so present in internalin (BUGS) and ActA (LUT12) deficient strains, suggest ing that p104 is indeed different from internalin or ActA proteins, Cytotox icity analysis of strains AAMU530 and AAMU572 demonstrated that these strai ns, although haemolytic and phospholipase-positive, were avirulent when tes ted with a hybridoma B-lymphocyte cell line. Loss of virulence could be att ributed to the interruption of adhesion of mutant strains to the hybridoma cell line. These results strongly suggest that p104 is an adhesion factor i n L, monocytogenes and possibly in other Listeria species and is involved i n adhesion to intestinal cells.