ORIGINAL PAPER Stefan M. Geiger Æ Carlos Grae-Teixeira Peter T. Soboslay Æ Hartwig Schulz-Key Experimental Angiostrongylus costaricensis infection in mice: immunoglobulin isotype responses and parasite-specific antigen recognition after primary low-dose infection Received: 20 May 1998 / Accepted: 10 September 1998 Abstract Immunoglobulin isotype responses and para- site-specific antigen recognition were investigated in ex- perimental Angiostrongylus costaricensis infection in two dierent mouse strains. Even in a low-dose infection with third-stage larvae (L3), BALB/c mice showed high mortality until 28 days postinfection (p.i.) in association with a low patency rate in surviving animals. On the other hand, low mortality and a high rate of patent in- fection was observed in C57BL/10 mice. Parasite-specific IgM, total IgG, and IgG subclasses against crude adult- worm antigen (AcAg) rose in both groups of mice from day 14 onward, with IgG and IgG1 being significantly elevated in BALB/c mice at 21 and 28 days p.i., re- spectively. For total IgE, significantly elevated concen- trations were detected at 14 days p.i. in BALB/c mice as compared with C57BL/10 mice. A. costaricensis-specific antigen recognition by total IgG, IgG1, or IgG2a was similar in both mouse strains, intensifying from 3 to 4 weeks p.i., with recognition of immunodominant AcAg ranging between 80 and 210 kDa. This study provides evidence that in BALB/c and C57BL/10 mice, immu- noglobulins, with the possible exception of IgE and IgG1, do not decisively contribute to the outcome of a primary A. costaricensis infection with respect to immunopathogenesis or parasite permissiveness. Introduction The metastrongylid nematode Angiostrongylus costa- ricensis is the causal agent for human abdominal angiostrongyliasis and is of increasing importance for public health in Latin America (Morera 1985; WHO 1987; Grae-Teixera et al. 1991a; Pena et al. 1995). Even though the natural hosts for A. costaricensis are cotton rats and other wild rodents, immunoepidemiological studies have shown that human populations are at high risk of accidental infection, with seropositivity reaching up to 66% in rural areas (Grae-Teixera et al. 1997). Despite high local seropositivity and infection preva- lence in definitive (wild rodents) and intermediate (slugs) hosts (Duarte et al. 1992; Morera 1995), the low inci- dence of reported and confirmed clinical cases – e.g., Costa Rica has only 21.6 cases per 100,000 inhabitants (Morera 1995) – is attributed in part to the diculty of specifically diagnosing this zoonosis in humans. Fur- thermore, most human infections are thought to be subclinical, typified by minor abdominal problems and spontaneous cure, depending on the number of larvae ingested and/or the individual immune response to the parasite (Grae-Teixeira et al. 1987). Previous experimental infection of several mouse strains with 10–20 L3 revealed strain-dependent dier- ences in susceptibility to A. costaricensis, suggesting a genetic predetermination for the dierent outcome of infections (Ishii and Sano 1989; Ishih and Nishimura 1997). In the present study we investigated in detail the dynamics and specificity of Ig isotypes in two mouse strains with regard to their parasite-specific and unspe- cific antibody production during the acute phase of in- fection. Both strains – BALB/c (haplotype H-2 d ) and C57BL/10 (haplotype H-2 b ) – show a contrasting response to A. costaricensis marked by either lethal immunopathogenesis or susceptibility to infection. Materials and methods Animals BALB/c and C57BL/10 mice were purchased from Charles River Laboratories (Germany) and kept under standardized laboratory conditions. When infected animals were 4–6 months old, and Parasitol Res (1999) 85: 200–205 Ó Springer-Verlag 1999 S.M. Geiger (&) Æ P.T. Soboslay Æ H. Schulz-Key Institute of Tropical Medicine, University of Tu¨bingen, Wilhelmstrasse 27, D-72074 Tu¨bingen, Germany E-mail: hartwig.schulz-key@uni-tuebingen.de, Fax: +49-7071-29-3017 C. Grae-Teixeira Laboratory of Molecular Parasitology, PUCRS, Av. Ipiranga 6681, Porto Alegre-RS, Brazil