Intranasal immunization with Gal-inhibitable lectin plus an adjuvant of CpG oligodeoxynucleotides protects against Entamoeba histolytica challenge.

The development of an effective amebiasis vaccine could improve child health in the developing world, reducing cases of amebic colitis and liver abscess. An ideal vaccine would be comprised of a well-characterized parasite antigen and an adjuvant, which would have high potency while driving the immune response in a Th1 direction. This study describes a mucosal vaccine composed of the Entamoeba histolytica galactose/N-acetyl-D-galactosamine-inhibitable lectin (Gal-lectin) and CpG oligodeoxynucleotides (CpG-ODN). The Gal-lectin is a protein involved in parasite virulence and adherence and is known to activate immune cells, while CpG-ODN are known to be potent inducers of type 1-like immune responses. We demonstrated that intranasal administration of the vaccine resulted in strong Gal-lectin-specific Th1 responses and humoral responses. Vaccination induced the production of Gal-lectin-specific T cells and the production of the proinflammatory cytokine gamma interferon. Vaccinated animals had detectable serum anti-Gal-lectin immunoglobulin G (IgG) and stool anti-Gal-lectin IgA capable of blocking parasite adherence to target cells in vitro. One week after immunization, gerbils were challenged intrahepatically with live trophozoites. Vaccinated gerbils had no detectable abscesses after day 5, whereas control gerbils developed larger abscesses. These results show that mucosal vaccination with Gal-lectin and CpG-ODN can induce both systemic and humoral immune responses.