Drug & Device Development

Experimental vaccine effective in animal model of amebiasis

Last Updated: 2004-12-15 15:58:31 -0400 (Reuters Health)

NEW YORK (Reuters Health) - An experimental vaccine protects gerbils from liver abscess caused by infection with the intestinal protozoan Entamoeba histolytica, scientists from Germany report in the December issue of the journal Infection and Immunity.

Entamoeba histolytica, the causative agent of amebiasis in humans, is endemic in large areas of the world and is thought responsible for "tens of millions of cases of dysentery and liver abscess each year," the investigators note in their report.

Despite the availability of effective therapy, illness and death associated with amebic infection have persisted, suggesting that interventions are needed to reduce or eliminate disease, Dr. Hannelore Lotter from the Bernard Nocht Institute for Tropical Medicine in Hamburg and colleagues also note.

"Since humans are the only relevant host for E. histolytica, sufficient vaccine could potentially eradicate amebiasis," they write.

To that end, Dr. Lotter's team developed an oral vaccine consisting of live attenuated Yersinia enterocolitica expressing the E. histolytica galactose-inhibitable lectin fused to the Yersinia outer protein E (YopE).

With this vaccine, "protection against invasive amebiasis was achieved in the gerbil model for amebic liver abscess," they report. "Protection was dependent on the presence of the YopE translocation domain but was independent from the antibody response to the ameba lectin," they explain.

Dr. Lotter's team speculates that the vaccine induces production of gamma interferon and tumor necrosis factor alpha via stimulated CD4 T cells, leading to activation of macrophages and finally host defense against invading E. histolytica.

Infect Immun 2004;72:7318-7321.