DNA vaccination against Entamoeba histolytica

• Main Author: Gaucher, Denis
• Format: Others
• Language: en
• Published: McGill University 2002
• Subjects: DNA vaccines.; Entamoeba histolytica.; Amebiasis > Vaccination.
• Online Access: http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82877

Invasive amebiasis, caused by the protozoan parasite Entamoeba histolytica, is one of the leading parasitic causes of mortality worldwide, and there are no vaccines available to control the disease. The heavy subunit of the E. histolytica Gal-lectin is regarded as a potential subunit vaccine candidate. A Th1 (cell-mediated) immune response is protective against invasive amebiasis, and DNA vaccination is a strategy to induce such a response against specific antigens. The objective of this study was to construct and test a Gal-lectin-based DNA vaccine against E. histolytica. DNA encoding as 894--1081 of the Gal-lectin heavy subunit was resynthesized using a gerbil codon frequency bias and inserted in a mammalian expression vector to generate the DNA vaccine pCISToGL6. Balb/c mice vaccinated intradermally developed a Gal-lectin-specific cellular immune response, as well as an anti-Gal-lectin humoral immune response. Serum antibodies recognized a recombinant portion of the Gal-lectin heavy subunit by immunoblot and ELISA, and bound to native Gal-lectin on the surface of live trophozoites, inhibiting adherence to target cells. The Gal-lectin-specific serum antibodies were of the IgG2a isotype, indicating that a Th1 response was stimulated by the vaccine. We were also interested in using DNA encoding IL-12, IL-18 or GM-CSF as genetic adjuvants co-injected with pCISToGL6 to potentiate the immune response. Since the DNA vaccine was destined to confer protection in the gerbil model of invasive amebiasis, we cloned gerbil IL-12 (p35 and p40), IL-18 and its convertase caspase-1, and GM-CSF. The proteins were expressed in mammalian cells and showed bioactivity in vitro. Taken together, these results have laid the foundation to optimize and test a working Gal-lectin with co-stimulatory molecules to elicit a Th1 immune response for protective immunity against invasive amebiasis.