Echinostoma caproni: Kinetics of IgM, IgA and IgG subclasses in the serum and intestine of experimentally infected rats and mice

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Abstract

The kinetics of specific immunoglobulin M, A and IgG subclasses against Echinostoma caproni (Trematoda: Echinostomatidae) were analyzed in serum and intestinal fluid of two host species (Wistar rats and ICR mice) in which the course of the infection markedly differs. In rats, the worms were rapidly expelled, whereas E. caproni evokes in mice long-lasting infection. The pattern of antibody responses in both serum and intestinal samples was different in each host species. Serum responses in mice were characterized by significant increases of IgM, IgA, total IgG, IgG1 and IgG3, but not IgG2a. In contrast, serum responses in rats showed elevated levels of IgM, probably in relation to thymus-independent antigens, and slight increases of total IgG, IgG1 and IgG2a. At the intestinal level, increases of IgM and IgA levels were observed in mice. In regard to IgG subclasses, increases in both IgG1 and IgG2a were detected. Later decreases to normal values in IgG2a were also detected. In rats, only increases in total IgG and IgG2a were found. According to our results the development of long-lasting E. caproni infections in mice appears to be associated with a dominance of Th2 responses at the systemic level and balanced Th1/Th2 responses at the local level, characterized by initial increases in IgG1 and IgG2a levels. In contrast, the worm expulsion appears to be related to increases in local IgG2a levels.

Introduction

Echinostoma caproni (Trematoda: Echinostomatidae) is an intestinal trematode with no tissue phases in the definitive host (Fried and Huffman, 1996). After infection, metacercariae excyst in the duodenum of the definitive host, and the juvenile worms migrate to the posterior third of the small intestine where they attach to the mucosa by the ventral sucker (Fried and Huffman, 1996, Fried and Graczyk, 2004).

E. caproni has a wide range of definitive hosts, though the worm survival greatly differs between hosts. In hamsters and mice, the infections are long-lasting, while in rats the infection is expelled at 7−8 week post-infection (wpi) (Odaibo et al., 1988, Odaibo et al., 1989, Christensen et al., 1990, Hansen et al., 1991, Mahler et al., 1995, Toledo et al., 2004a). The different compatibilities to E. caproni observed in different rodent species allows these host–parasite systems to be highly suitable for elucidating aspects of the host-specific components that determine the course of infections with intestinal trematodes (Toledo and Fried, 2005).

The existing literature provides little information on the host- and parasite-related factors leading to the development of chronic E. caproni infections or, in contrast the rapid expulsion of the parasite. Earlier studies have shown that hosts in which chronic infections are developed are characterized by high inflammatory local response, high levels of seroantigens and elevated IgG levels in the serum. In contrast, the infection in rats is characterized by low levels of local inflammation, seroantigens and systemic IgG (Graczyk and Fried, 1994, Toledo et al., 2004b, Toledo et al., 2005, Toledo et al., 2006a, Toledo et al., 2006b). However, there are several aspects of the immunological response against E. caproni that remain to be studied in detail, i.e., the intestinal antibody responses, the kinetics of IgG subclasses and the potential effect of the antibodies on the course of the infection (Toledo et al., 2006b). In this sense, the only data available are those reported by Agger et al. (1993) and Brunet et al. (2000). Agger et al. (1993) analyzed the kinetics of IgM, IgA and IgG in the serum and intestinal wall of E. caproni-infected mice, during the first 70 days post-infection (dpi) and in the intestinal luminal content at 28 dpi. Elevated levels of IgM, IgA and IgG were detected in the serum and intestinal wall and only and increased level of IgA was detected in the intestinal luminal content. Regarding the IgG subclasses, Brunet et al. (2000) analyzed the profiles of IgG1 and IgG2a in the serum of mice experimentally infected with E. caproni during the first 23 dpi and a weak increasing of IgG2a was detected.

The aim of the present study was to investigate the isotype specific immune responses both at the systemic and mucosal levels in two host species of E. caproni (rats and mice) in which parasite survival differs markedly. The results obtained may be of interest to gain further insight into the host–parasite relationships in intestinal trematode infections and into the factors determining worm rejection or the development of long-lasting infections.

Section snippets

Parasite and experimental infections

The strain of E. caproni has been previously described by Hosier and Fried (1991). Encysted metacercariae of E. caproni were removed from the kidneys and pericardial cavities of experimentally infected Biomphalaria glabrata snails and used to infect mice (ICR) and albino rats (Wistar). Each of 28 male mice, weighing 32−40 g, and 28 rats, weighing 100−120 g, was infected by stomach tube with metacercariae of E. caproni. The infective doses were 75 and 100 metacercariae/animal for mice and rats,

Infection

All mice and rats experimentally exposed to metacercariae of E. caproni were infected as determined by egg examination. The duration of the pre-patent period was uniform. Egg release began 9−12 (10.1 ± 0.4) dpi in mice and 10−12 (11.34 ± 0.44) dpi in rats. All the rats reverted had reverted to negative values at the 8 wpi.

Serum antibody responses

Immunoglobulin M: The experimentally infected mice and rats developed significant IgM responses in serum against E. caproni (Fig. 1). In mice, the IgM levels rapidly increased to

Discussion

To examine the potential role of antibody responses in host-protective immunity on primary E. caproni infections, we studied the serum and intestinal antibody kinetics in two host species exhibiting different patterns of E. caproni infection. Rats develop a marked capacity to expel primary infections of E. caproni and the worms are rapidly expelled (Hansen et al., 1991, Toledo et al., 2004a). In contrast, this species of echinostome evokes long-lasting infections in mice. In this context, the

Acknowledgements

The study was supported by the projects CGL2005-02321/BOS from the Ministerio de Educación y Ciencia (Spain), GV04B/107 and GV05/039 from the Conselleria d’Empresa, Universitat I Ciència de la Generalitat Valenciana (Spain) and the Project UV-AE-20050201 de la Universitat de València (Spain). This work has been carried out while the first author (J.S.) was recipient of a pre-doctoral fellowship from the Ministerio de Educación y Ciencia, Madrid (Spain). This research complies with the current

References (30)

  • R. Toledo et al.

    Immunology and pathology of intestinal trematodes in their definitive hosts

    Advances in Parasitology

    (2006)
  • M.K. Agger et al.

    The antibody response in serum, intestinal wall and intestinal lumen of NMRI mice infected with Echinostoma caproni

    Journal of Helminthology

    (1993)
  • A. Ben-Smith et al.

    The relationships between circulating and intestinal Heligmosomoides polygyrus-specific IgG1 and IgA and resistance to primary infection

    Parasite Immunology

    (1999)
  • L.R. Brunet et al.

    Immune responses during the acute stages of infection with the intestinal trematode Echinostoma caproni

    Parasitology

    (2000)
  • N.Ø. Christensen et al.

    Establishment, survival and fecundity in Echinostoma caproni (Trematoda) infections in hamsters and jirds

    Journal of the Helminthological Society of Washington

    (1990)
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