Oral Immunization of BALB/c Mice with Giardia duodenalis Recombinant Cyst Wall Protein Inhibits Shedding of Cysts

Abstract

The process of encystation is a key step in the Giardia duodenalis life cycle that allows this intestinal protozoan to survive between hosts during person-to-person, animal-to-person, waterborne, or food-borne transmission. The release of cysts from infected persons and animals is the main contributing factor to contamination of the environment. Genes coding for cyst wall proteins (CWPs), which could be used for developing a transmission-blocking vaccine, have been cloned. Since the immunogenicity of recombinant Giardia CWP is unknown, we have investigated the immunogenicity of recombinant CWP2 (rCWP2) and its efficacy in interfering with the phenomenon of encystation taking place in the small bowels of BALB/c mice vaccinated with the recombinant protein. Here we report that the immunization of BALB/c mice with rCWP2 stimulated the immune system in a manner comparable to that for a live infection with Giardia muris cysts. Fecal and serum anti-rCWP2 immunoglobulin A (IgA) antibodies were detected in the immunized mice. In addition, anti-rCWP2 IgG1 and IgG2a antibodies were detected in the serum. mRNAs coding for Th1 and Th2 types of cytokines were detected in spleen and Peyer's patch cells from immunized mice. When the vaccinated mice were challenged with live cysts, the animals shed fewer cysts. We conclude that rCWP2 is a possible candidate antigen for the development of a transmission-blocking vaccine.

Expression of the Giardia lamblia cyst wall protein 2 in Lactococcus lactis

“…Our observed reduction level compares quite well with the 75 % reduction level demonstrated from a previous study where mice were orally immunized with the full-length 39 kDa form of recombinant CWP2 produced by E. coli (Larocque et al, 2003). Since both stages of the Giardia life cycle occur simultaneously in the intestine (Campbell & Faubert, 1994b), the immune clearance of the cysts from the intestinal lumen may be due to antibodies directed at the trophozoite stage.…”

“…The intestinal mucosal immune system of mice infected with Giardia muris recognizes CWP2 as a foreign antigen since specific antibodies are produced locally (Larocque et al, 2003). In addition, we have reported that immunization of BALB/c mice with the 39 kDa form of CWP2 reduces cyst shedding in the murine model of giardiasis when it is delivered orally with cholera toxin (Larocque et al, 2003). CWP2 has two forms.…”

“…Flat-bottom microtitre ELISA plates (Falcon) were coated with 100 ml G. lamblia encysting cell antigen at a concentration of 1 mg ml 21 in PBS and blocked with PBS/1 % albumin. Encysting cell antigen was prepared as described by Larocque et al (2003) and contains native CWP2 expressed by G. lamblia. Intestinal lavage samples were diluted 1 : 2 followed by twofold dilutions.…”

A New Family of Giardial Cysteine-Rich Non-VSP Protein Genes and a Novel Cyst Protein

“…The Giardia ' cyst wall is biologically important as a simple model extracellular matrix, with both structural and signal transduction functions [21], [22]. Encystation contributes to immune evasion [23] by two distinct pathways: first, the cyst wall covers the trophozoite surface during encystation and sequesters it from host defenses and second, encystation leads to switching of VSPs [18], [24], [25]. Despite its importance, the composition, architecture, and formation of the cyst wall are poorly understood.…”

Mucosal Vaccination and Therapy with Genetically Modified Lactic Acid Bacteria

“…Both LAB were engineered to express recombinant G. lamblia cyst wall protein 2 (CWP2) on the bacterial cell surface as a fusion to the C terminal half of the M6 molecule. CWP2 was previously shown to reduce cyst excretion in infected animals following mucosal immunization with cholera toxin as an adjuvant (Larocque et al 2003). Interruption of encystations is an attractive control measure against Giardia transmission, as the cysts allow parasite survival in the environment and thus transmission between susceptible hosts.…”