SummaryOne of the under-represented genes identi®ed by cDNA representational difference analysis (RDA) between avirulent Entamoeba histolytica strain Rahman and virulent strain HM-1:IMSS was the amoebic light (35 kDa) subunit of the Gal/GalNac lectin complex. This lectin complex, which mediates the adhesion of the parasite to the target cell, also contains a heavy (170 kDa) subunit, which has the carbohydrate-binding domain. Stable transfectants of the virulent strain in which the expression of the 35 kDa subunit was inhibited by antisense RNA were not signi®cantly affected in their adhesion activity to mammalian or bacterial cells but were strongly inhibited in their cytopathic activity, cytotoxic activity and in their ability to induce the formation of liver lesions in hamsters. These ®nd-ings suggest that the 35 kDa subunit may have a speci®c function in the pathogenic pathway and provides a new insight into the role of this component of the Gal/GalNac lectin complex in amoebic virulence.

Trophozoites of virulent Entamoeba histolyticatransfected with the antisense gene encoding cysteine proteinase 5 (CP5) have only 10% of the CP activity but retain their cytopathic activity on mammalian monolayers. In the present study we found that the transfected trophozoites with low levels of CP activity were incapable of inducing the formation of liver lesions in hamsters.

Argon surface plasma treatment (APT) of poly(propylene)/silver (PP/Ag) and poly(propylene)/ copper (PP/Cu) nanocomposite improves their antibacterial properties against pathogenic bacteria. Dispersions of PP/Ag and PP/Cu nanocomposites were prepared by sonication assisted melt mixing 0.05, 0.5, and 5 w/w% metal nanoparticle/polymer compositions, and then melt casted to form films that were surface treated with argon plasma. Scanning electron and atomic force microscopy showed that APT increase the surface roughness and the exposed nanoparticles. Also, APT produced implanted oxygen and nitrogen species as demonstrated by XPS analysis and enhanced the surface wettability. Antibacterial activity (AA) against S. aureus and P. aeruginosa of the plasma treated NC films was significantly increased in all conditions tested such as NP loading and interaction time; copper NCs were more effective than silver NCs. Surface activation of the PP/Ag and PP/Cu NC films by APT is a viable technique to increase the antibacterial activity of nanocomposites, an important issue in medical and health care applications.

Entamoeba histolytica virulence is related to a number of amebic components (lectins, cysteine proteinases, and amebapore) and host factors, such as intestinal bacterial flora. Trophozoites are selective in their interactions with bacteria, and the parasite recognition of glycoconjugates plays an important role in amebic virulence. Long-term monoxenic cultivation of pathogenic E. histolyticatrophozoites, strains HK-9 or HM-1:IMSS, with Escherichia coli serotype O55, which binds strongly to the Gal/GalNAc amebic lectin, markedly reduced the trophozoites’ adherence and cytopathic activity on cell monolayers of baby hamster kidney (BHK) cells. Specific probes prepared from E. histolytica lectin genes as well as antibodies directed against the light (35-kDa) and heavy (170-kDa) subunits of the Gal/GalNAc lectin revealed a decrease in the transcription and expression of the light subunit in trophozoites grown monoxenically with E. coli O55. This effect was not observed when E. histolyticawas grown with E. coli 346, a mannose-binding type I pilated bacteria. Our results suggest that the light subunit of the amebic lectin is involved in the modulation of parasite adherence and cytopathic activity.

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