Immune Response toGiardia duodenalis

Abstract

SUMMARY 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 ubiquituous 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.

Validity of silver, chitosan, and curcumin nanoparticles as anti-Giardia agents

“…Giardia duodenalis, Giardia intestinalis) is a protozoan parasite which inhabits the lumen of the small intestine of a wide variety of mammalian hosts (Faubert 2000). Transmission of Giardia occurs by fecaloral route (Musher and Musher 2004), that is why it has been implicated in multiple outbreaks.…”

Goblet cells: are they an unspecific barrier against Giardia intestinalis or a gate?

“…All these stimuli modify the intestinal morphology and give rise to intestinal villi atrophy and a reduction in the enzymatic activity of isomaltase and other disacharidases, alcaline phosphatase, ATPases, and others (Belosevic et al 1989;Nain et al 1991). On the other hand, the host develops specific (Faubert 2000) and unspecific self-defense mechanisms against parasites (Eckmann 2003;Roskens and Erlandsen 2002). Among specific mechanisms are immune responses based on B-and T-cell-dependent mechanisms (Singer and Nash 2000).…”

Evaluation of an immunochromatographic assay: Giardia-Strip® (Coris BioConcept) for detection of Giardia intestinalis in human fecal specimens

“…As cysts are excreted intermittently and their numbers may vary from day to day, the sensitivity of microscopic examination is rather low [7]. Assays that detect the presence of small amounts of antigens in the feces have been proven to be useful [10].…”

“…Since excretion of Giardia intestinalis cysts may be intermittent, the sensitivity of this method is rather low [7]. In order to increase this sensitivity, tests that identify a soluble Giardia antigen have been developed.…”