Host Cytokine Production, Lymphoproliferation, and Antibody Responses during the Course of Ancylostoma ceylanicum Infection in the Golden Syrian Hamster

Abstract

The Syrian Golden hamster (Mesocricetus auratus) has been used to model infections with the hookworm Ancylostoma ceylanicum. New molecular immunological reagents to measure cellular immune responses in hamsters were developed and used to determine the impact of A. ceylanicum hookworm infection on host cytokine responses and lymphoproliferation. Initial larval infection with 100 third-stage A. ceylanicum larvae resulted in predominant Th1 responses (upregulation of proinflammatory cytokines) that lasted for the duration of larval migration and continued up to 14 days postinfection (prepatency). Subsequently, development of larvae into egg-laying adult hookworms (patency) coincided with a switch to Th2 predominant responses (interleukin-4 [IL-4]) as well as a marked increase in IL-10 production. This switch also concurred with reduced host lymphoproliferative responses to hookworm antigens. The findings demonstrate a similarity in immune responses between hamsters and humans infected with hookworms, suggesting that hamsters will be a useful animal model species for examining host immunity to human hookworm infections.Hookworm infection is one of the most prevalent parasitic diseases infecting over 700 million people in tropical and subtropical regions of the world (16). Clinical symptoms of human hookworm infection include iron-deficiency anemia (18) and protein-losing enteropathy (14) that may lead to physical, mental and cognitive growth retardation effects (25,42,43). Although chemotherapy is effective at eliminating existing adult parasites, reinfection can occur rapidly after treatment (1, 38). This observation, together with the unique epidemiology of hookworm infection, in which the worm burdens increase with age in endemic regions (6), have led to the suggestion that hookworms can either evade or suppress host immune responses (28, 35). Therefore, characterization of the immune response to hookworm in animal models would constitute a valuable tool to understand the underlying immunological mechanisms of human hookworm infections.The Syrian Golden hamster (Mesocricetus auratus) has been developed as a model to study hookworm infection caused by the dog and cat hookworm, Ancylostoma ceylanicum. A. ceylanicum is also a minor cause of human hookworm infection in parts of Asia (11). Unlike mice, which do not permit the development of adult hookworms (12, 41), hamsters are permissive hosts for the hookworm A. ceylanicum (19,24,32,40,46). In most studies to date, hamsters have been infected with A. ceylanicum third-stage infective larvae (L3) via oral gavage. As the human hookworm A. duodenale is both orally infective as well as infective through the percutaneous route, this approximates a natural route of infection. More importantly, this model reproduces weight and blood loss that result from human infection with A. duodenale.In addition to modeling the host-parasite relationship for human hookworm infection, the hamsters have been used with some success for investigating protective immunity from a new generati...

Role for Nitric Oxide in Hookworm-Associated Immune Suppression

“…The results presented here confirm previous observations that A. ceylanicum infection is associated with impaired lymphocyte proliferation (23,45), a phenomenon that has also been observed in filarial nematode infections (25,26,54). By day 70 p.i., there were very few adult worms remaining in the intestine (Fig.…”

“…However, few studies have attempted to probe the mechanisms underlying this phenomenon in human and/or laboratory animal hosts (23,45,46). In the present study, we utilized the hamster model of A. ceylanicum to characterize the modulation of host cellular immune responses and potential mechanisms underlying such immunosuppression.…”

“…Spleens and MLN were harvested from naïve and infected hamsters (six animals/group). Splenocytes were depleted of red blood cells by lysis and washed with RPMI medium with 10% fetal bovine serum, 2-mercaptoethanol, antibiotics, and L-glutamine (RPMI-10) (45). Single-cell preparations made in RPMI-10 were plated in triplicate (10 5 per well) in 96-well plates (Becton Dickinson) and stimulated with concanavalin A (ConA; 1 g/ml) (Sigma) or kept unstimulated for 24 h at 37°C with 5% CO 2 .…”

“…Although the nature of this response has yet to be elucidated fully, infection appears to be associated with a mixed Th1/Th2 host cytokine profile (22,49). It has also been reported that hookworm infection is associated with suppression of host cellular responses to hookworm-specific and heterologous antigens (22,45,49). These studies suggest that hookworms, like other parasites, effectively downregulate host cell-mediated responses, blunting development of protective immunity (1,41,51).…”

Molecular Cloning, Biochemical Characterization, and Partial Protective Immunity of the Heme-Binding GlutathioneS-Transferases from the Human HookwormNecator americanus

“…An antibody titer reduction following larval challenge is a common phenomenon for hookworm vaccine trials (43,69), putatively because of antibody absorption by specific antigen produced by the challenged hookworms. No efforts were made to further characterize the cytokine responses, although some hamster reagents are beginning to become available (24,42). Only hamsters vaccinated with rNa-GST-1 achieved protection levels comparable to those reported previously with Ac-GST-1 (65,69).…”