Gaétan Faubert

Immune Response to Giardia duodenalis

The intestinal protozoan Giardia duodenalis is a widespread opportunistic parasite of humans and animals. This parasite inhabits the upper part of the small intestine and has a direct life cycle. After ingestion of cysts, which are the infective stage, the trophozoites emerge from the cysts in the duodenum and attach to the small intestinal mucosa of the host. Since the migration of trophozoites from the lumen of the intestine into surrounding tissues is an unusual occurrence, the immune response to Giardia remains localized. The identification of antigens that play a role in acquired immunity has been difficult because of the occurrence of antigenic variation and because, Giardia being an ubiquitous organism, it is possible that the antigenic profiles of isolates from different geographic areas will vary. Innate-immunity mechanisms play a role in the control and/or severity of the infection. Both humoral and cell-mediated immune responses play a role in acquired immunity, but the mechanisms involved are unknown. A variety of serological assays have been used to detect circulating antibodies in serum. Because of the biological characteristics of the parasite and the lack of suitable antigens, the sensitivity of serological assays remains poor. On the other hand, detection of antigens in feces of infected patients has met with success. Commercial kits are available, and they are reported to be more sensitive than microscopic examination for the detection of giardiasis on a single specimen.

Trichinella spiralis: inhibition of sheep hemagglutinins in mice.

Abstract One hundred and twenty-four mice were injected intraperitoneally with sheep red blood cells. The mice had been previously either orally inoculated with T. spiralis (16 mice), or injected intraperitoneally during 7 consecutive days with normal saline (12 mice), normal mouse serum (6 mice), or infected mouse serum (6 mice), normal rabbit serum (6 mice), sera from lightly (36 mice) or heavily infected rabbits (36 mice), and rabbit anti-lymphocyte serum (6 mice). The homologous serum clearly demonstrated an immunosuppressive effect on the production of sheep hemagglutinins; however, it was impossible to conclude that heterologous serum has such an activity since the normal rabbit serum used as control demonstrated the same activity. The inhibition of hemagglutinin production has also been observed in mice infected with T. spiralis . The presence of a suppressive agent released by the parasite or antigenic competition is discussed as the possible mediator of immunological unresponsiveness.

Anti-giardial activity of gastrointestinal remedies of the Luo of East Africa

Activity in an in vitro assay with Giardia lamblia provided a test of the validity of a quantitative methodology used in an ethnobotanical survey of the Luo people of the Lake Victoria basin of Kenya and Tanzania. Forty-five taxa of remedies for gastrointestinal problems were reported by four or more independent informants and a log-linear model was used to calculate a statistical measure of informant consensus. Methanolic extracts of 21 of 36 taxa assayed were lethal or inhibited growth of Giardia trophozoites at 1000 ppm; 7 species were lethal at 500 ppm. Non-cathartic species are more likely to be active than cathartics. Lethal species of non-cathartics are reported by informants more frequently than non-lethal species although the lack of statistical significance did not provide satisfactory support for the validity of the quantitative methodology as a predictor of efficacious remedies.

Giardia muris: correlation between oral dosage, course of infection, and trophozoite distribution in the mouse small intestine.

Oral inoculations of Giardia muris cysts to CD-1 Swiss mice resulted in a reproducible pattern of infection measured by cyst excretion and the number of trophozoites in the small intestine. Housing of animals together or individually did not alter the pattern of cyst release for the first 30 days of infection. Administration of 10 to 10(5) cysts/mouse resulted in a similar rate of cyst excretion from Day 10 to the end of the infection period. There was a direct correlation between the size of inoculum and the length of the latent period. Mice which received larger doses (10(3), 10(4), 10(5] had significantly higher numbers of cysts in feces during the first week of infection, compared to those which received lower doses (10 or 100). The extent of trophozoite colonization and their distribution in the small intestine was not related to the size of inoculum. The location of trophozoites in the small intestine varied during the infection. In the first 3 to 8 days of infection the trophozoites were situated in the upper 25% of the small intestine, but moved posteriorly (upper 40%) during the period of peak cyst output. The number of trophozoites in the small intestine and cyst excretion were found to be proportional at all stages of infection.

Morphological changes in the jejunum of calves naturally infected with Giardia spp. and Cryptosporidium spp.

Abstract Giardiosis and cryptosporidiosis are frequently diagnosed in calves at the large animal clinic of the veterinary school. Few studies have been reported in the literature regarding pathogenesis of these two intestinal protozoa. The aims of this study were to follow the histological changes in the villi and crypts and the changes in the number of intraepithelial lymphocytes in the jejunum of naturally infected calves during the acute phase of infection. For this purpose, 29 calves aged between 7 and 10 days were bought at a local auction. The animals were housed in individual pens to avoid cross-contamination. Fecal samples were examined microscopically for the presence of Giardia cysts and Cryptosporidium oocysts, three times per week for a period of 45 days. Six calves did not pass any cysts or oocysts and were used as controls. Fifteen calves passed Giardia cysts only, five passed both cysts and oocysts, and three passed oocysts only. The villus to crypt ratio index was 1.76 in the control group and 1.08 in the Giardia-infected group. In the Cryptosporidium-infected calves, the ratio was 1.18 and calves infected with both parasites had an index of 1.37. The number of intraepithelial lymphocytes per millimeter of jejunum tissue was 21 in the control group. This number was doubled in the calves infected with Giardia, but was slightly lower in the other infected groups. All of the infected calves had intermittent diarrhea and mucus was seen in many fecal samples.

The immune response to Giardia

The flagellate Giardia duodenalis has been considered for many years to be a commensal living in the lumen of the small intestine of its host. It is only 25 years ago that it was accepted that Giardia is a significant pathogen of humans. Knowledge that Giardia can elicit an immune response that would probably contribute to the onset or absence of symptoms is not much older. The use of animal models to study the disease in the laboratory, together with the production of the whole life cycle in a test tube, have contributed greatly to our present knowledge of the immune responses to Giardia and of antigens that are specific to the trophozoite or cyst stages. In this review, Gaétan Faubert focuses on studies published since the last review in Parasitology Today in 1988, and examines the roles played by the humoral and cell-mediated immune responses in the control of the infection. It also covers the immunodiagnostic assays that have been recently developed on the basis of advances in our knowledge of the antigens of Giardia.

Comparison of the local immune response against Giardia lamblia cyst wall protein 2 induced by recombinant Lactococcus lactis and Streptococcus gordonii

Lactococcus lactis and Streptococcus gordonii are lactic acid bacteria (LAB) currently being advocated for use as live antigen delivery vehicles to mucosal sites. Since both vehicles differ in their capability to persist within the small intestine and in their mode of antigen delivery, we sought to compare them to determine which one was superior. In this study, we compared the efficacy of recombinant L. lactis and S. gordonii to stimulate intestinal immune responses against Giardia lamblia cyst wall protein-2 in BALB/c mice. Oral administration of either vector significantly increased the number of CD4(+) T helper and B-cells in the mesenteric lymph nodes (MLN) and Peyers patches (PP) of immunized animals. Delivery of recombinant CWP2 (rCWP2) by L. lactis stimulated a balanced IFN-gamma/IL-4 response (MLN and PP cells) and a CWP2-specific intestinal IgA antibody response. Alternatively, delivery of rCWP2 by S. gordonii stimulated a higher frequency of IFN-gamma secreting MLN and PP cells, as well as doubling the amount of CWP2-specific intestinal IgA. In challenge studies, L. lactis and S. gordonii reduced cyst output by 71 and 90%, respectively. When compared to each other, S. gordonii-immunized animals shed 65% fewer cysts than their L. lactis-immunized counterparts. Based on these findings, we concluded that S. gordonii was superior to L. lactis as an intestinal vaccine delivery vehicle.

Inactivation of Giardia lamblia cysts by polychromatic UV.

Aims:  Giardia lamblia is one of the most important waterborne pathogens in the world. In this study, we determined the effectiveness of a promising alternative UV technology – a polychromatic emission from a medium‐pressure (MP) UV lamp – against G. lamblia cysts in phosphate buffered saline (PBS) and a filtered drinking water.

Characterization and biological activities of anti-Brugia pahangi tubulin monoclonal antibodies

Three monoclonal antibodies (mAb) specific to beta-tubulin were used to investigate the heterogeneity of tubulins from nematodes and mammals. Western blot analysis of one-dimensional SDS-PAGE showed that anti-Brugia pahangi tubulin mAb 1B6 and P3D react with epitope(s) specific to nematode beta-tubulin and recognize tubulin from adults and microfilariae of B. pahangi, adult B. malayi and Dirofilaria immitis, eggs of Haemonchus contortus and adult Ascaris suum. However, the same mAb did not recognize tubulin from trophozoites of Giardia lamblia, pig brain or 3T3 mouse fibroblast cells. In two-dimensional SDS-PAGE, mAb 1B6 recognized one isoform of beta-tubulin and mAb P3D recognized two beta-tubulin isoforms. Limited proteolysis showed that mAb 1B6 reacted with the amino-terminal fragments of beta-tubulin. In contrast, mAb P3D recognized the carboxy-terminal fragments of beta-tubulin. In ELISA, mAb P3D reacted with an 18 amino acid peptide corresponding to residues 430-448 of B. pahangi beta-tubulin. These observations confirm that the epitope of mAb P3D is located on the extreme carboxy-terminal region. Immunogold labelling of adult B. pahangi sections with mAb P3D revealed the presence of beta-tubulin isoforms in the cuticle, hypodermal layer and somatic muscle blocks of B. pahangi. Under in vitro conditions, mAb P3D caused 80% reduction in worm viability, during exposure over 48 h.

Identification of tubulin isoforms in different tissues of Ascaris suum using anti-tubulin monoclonal antibodies

Three monoclonal antibodies specific to alpha- and beta-tubulin were used to examine the expression of tubulin isoforms in the intestine, reproductive tract and body wall muscle of A. suum. The tubulins were found to be different in their isoelectric points, number of isoforms and peptide maps with Western blot analysis of one-dimensional polyacrylamide gel confirming the presence of alpha-, beta 1- and beta 2-tubulin. Commercial cross-reactive anti-alpha and anti-beta MAbs 356 and 357 recognized tubulin from A. suum tissues as well as from pig brain, whereas anti-A. suum beta-tubulin specific MAb P3D6 recognized tubulin from the A. suum tissues only. Two-dimensional gel analysis showed different isoform patterns in different A. suum tissues with anti-A. suum beta-tubulin MAb P3D6 and cross-reactive beta-tubulin MAb 357 recognizing 2-4 beta-tubulin isoforms and anti-alpha-tubulin MAb 356 recognizing 1-6 alpha-tubulin isoforms. Different peptide maps of tubulin were observed in the three tissues, when subjected to limited proteolysis followed by SDS-PAGE. The data indicate that different tubulins are found in different tissues of adult A. suum.