The role of the secretory immune response in the infection by Entamoeba histolytica

Abstract

Intestinal infection with the protozoan parasite Entamoeba histolytica elicits a local immune response with rising of specific secretory IgA (sIgA) antibodies detectable in several compartments associated to mucosa. Anti-amoebic sIgA antibodies have been reported in faeces, saliva, bile and breast milk from dysenteric patients and research trying to elucidate their role in protection has recently intensified. IgA antibodies inhibit the in vitro adherence of E. histolytica trophozoites to epithelial cell monolayers by recognizing several membrane antigens, including the galactose-binding lectin (Gal-lectin), main surface molecule involved in adherence, and the serine and cystein-rich proteins, all of them potential vaccine candidates. In fact, the presence of sIgA anti-Gal lectin in faeces of patients recovered from amoebic liver abscess (ALA) was associated with immunity to E. dispar. Moreover, the combined nasal and intraperitoneal vaccination of C3H/HeJ mice with native and recombinant Gal-lectin protected mice against an intracecal challenge with virulent E. histolytica trophozoites, protection that seemed to be associated with the induction of specific intestinal sIgA antibodies. Therefore, the stimulation of intestinal secretory response by mucosal delivery of amoebic antigens has been positioned as a promising strategy for inducing protection against human amoebiasis.

Salivary Defense Proteins: Their Network and Role in Innate and Acquired Oral Immunity

“…The primary function of salivary (secretory and other) immunoglobulins is to inactivate parasites: bacteria, fungi and viruses (as well as certain microbial toxins) via binding and/or agglutination of such particles [18,29–31]. Such binding and/or agglutination may prevent mucosal adhesion of microbes and their toxins [30,31] and can lead to clearance toward the stomach, resulting in a consequent acidic digestion [30].…”

“…Such binding and/or agglutination may prevent mucosal adhesion of microbes and their toxins [30,31] and can lead to clearance toward the stomach, resulting in a consequent acidic digestion [30]. Surface immune exclusion (fixation to surfaces and immobilization until elimination) of the pathogens within the oral cavity via anchorage of secretory immunoglobulin-binding antigens to the superficial mucous layer lining the mucosal surface is another important mechanism to prevent invasion of the underlying tissues [25,32].…”

Entamoeba histolytica and E. dispar trophozoites in the liver of hamsters: in vivo binding of antibodies and complement

“…These antibodies may persist within the circulation even after eradication of the amoebiasis and may not prevent a new infection [12]. …”

Proteases fromEntamoebaspp. and Pathogenic Free-Living Amoebae as Virulence Factors

“…sIgA functions in vivo by reducing mucosal colonization by pathogens and neutralizing diverse toxins and enzymes [156]. E. histolytica elicits a local immune response, in which an increase in specific IgA is detectable in several compartments associated with the mucosa [157, 158]. IgA inhibits the in vitro adherence of amoebae to epithelial cell monolayers by recognizing several membrane antigens [157, 159], reduces proteolytic activity [160], and has amoebicidal action [161].…”