Toxocara canis: Effect of inoculum size on pulmonary pathology and cytokine expression in BALB/c mice
Introduction
Toxocara canis is a roundworm of dogs and the causative agent of toxocariasis (Kayes, 1997). Humans and mice can also become infected with T. canis after ingestion of embryonated eggs present in soil contaminated with dog feces. In these paratenic hosts, the larvae do not develop to the adult stage but persist in tissues as the larval stage for many years (Schantz, 1989). Once the eggs are ingested, the larvae hatch, penetrate the small intestine and migrate to different tissues in the body inducing inflammatory responses. Migration of T. canis larvae can lead to a syndrome known as visceral larva migrans (VLM). Symptoms of VLM include fever, hepatosplenomegaly, and respiratory distress such as wheezing, coughing, and episodic airflow obstruction (Feldman and Parker, 1992, Taylor et al., 1988). Other symptoms include eosinophilic pneumonia (Loeffler’s pneumonia) that bears a clinical resemblance to the pulmonary inflammatory responses observed in asthmatic patients. Immunological features of toxocariasis include eosinophilia and increased serum IgE levels (Obwaller et al., 1998, Sugane and Ohshima, 1984).
Using murine models, several groups have shown that infection with T. canis results in pulmonary inflammation characterized by the infiltration of eosinophils, neutrophils, and lymphocytes (Buijs et al., 1994, Kayes et al., 1987, Pinelli et al., 2001). Recently, we reported on airway hyper-responsiveness, pulmonary inflammation, and increased levels of IgE that persist in BALB/c mice for months after a single T. canis infection (Pinelli et al., 2005).
Early studies have shown that inoculum size is a significant factor determining the proportional recovery of larvae from different organs (Kayes and Oaks, 1976). Studies on cerebral toxocariasis have shown that the infective dose influences not only the larval burden in brain but also the behavior of Toxocara-infected mice (Cox and Holland, 1998). Information regarding the effect of T. canis inoculum size on pulmonary inflammation and type of immune response induced is limited. In the present study, we monitored the effect of different T. canis inoculum size on antibody production, pulmonary pathology, and cytokine expression in lungs of BALB/c mice.
Section snippets
Parasites and experimental infection
Toxocara canis adult worms were recovered from naturally infected dogs, after routine deworming using antihelminthic treatment. Eggs were collected from the uteri of female worms and were allowed to embryonate in 0.1 M H2SO4 in the dark at room temperature for 4–6 weeks. Embryonated eggs were stored in 0.1 M H2SO4 at 4 °C until use.
Specified pathogen-free female BALB/c mice (5–6 weeks) were obtained from Harlan Netherlands BV (Horst, The Netherlands). Mice were housed in Macrolon III cages with
Histology
Infection of BALB/c mice with 100 embryonated eggs leads to moderate perivascular infiltration, mainly consisting of esosinophils and lymphocytes, slight peribronchiolitis with the same pattern of inflammatory cells, and minimal alveolitis containing large macrophages, eosinophils, and microhaemorrhages (Table 2). We also observed moderate hypertrophy of the bronchiolar goblet cells with PAS-positive staining indicating mucus production (data not shown). The observed changes persisted up to 60
Discussion
We have previously shown that infection of BALB/c mice with 1000 T. canis embryonated eggs results after 7 days in marked histological changes in the lungs and increased levels of total IgE in serum (Pinelli et al., 2001). The observed pulmonary inflammation has been shown by us and others to persist for months after infection (Buijs et al., 1995, Pinelli et al., 2005). In the present study, we aim at determining whether the T. canis inoculum size has an effect on the type of immune response
Acknowledgments
The authors thank H. Strootman, P.J. van Schaaik, and D. Elberts for their technical assistance.
References (26)
- et al.
Toxocara canis-induced airway eosinophilia and tracheal hyporeactivity in guinea pigs and mice
European Journal of Pharmacology
(1995) - et al.
Influence of murine Toxocara canis infection on plasma and bronchoalveolar lavage fluid eosinophil numbers and its correlation with cytokine levels
Veterinary Parasitology
(2005) - et al.
The expanded spectrum of Toxocaral disease
The Lancet
(1988) - et al.
Low-level infection with Trichuris muris significantly affects the polarization of the CD4 response
European Journal of Immunology
(1994) - et al.
Relationship between allergic manifestations and Toxocara seropositivity: a cross-sectional study among elementary school children
European Respiratory Journal
(1997) - et al.
Toxocara canis-induced murine pulmonary inflammation: analysis of cells and proteins in lung tissue and bronchoalveolar lavage fluid
Parasite Immunology
(1994) - et al.
The relationship between numbers of larvae recovered from the brain of Toxocara canis-infected mice and social behaviour and anxiety in the host
Parasitology
(1998) - et al.
Cytokine response and outcome of infection depends on the infective dose of parasites in experimental infection by Echinococcus granulosus
Parasite Immunology
(2003) - et al.
Visceral larva migrans associated with the hypereosinophilic syndrome and the onset of severe asthma
Annals of Internal Medicine
(1992) - et al.
A seroepidemiological study of toxocariasis and risk factors for infection in children in Sri Lanka
Southeast Asian Journal of Tropical Medicine and Public Health.
(2003)
Human toxocariasis and the visceral larva migrans syndrome: correlative immunopathology
Chemical Immunology
Use of bronchoalveolar lavage to compare local pulmonary immunity with the systemic immune response of Toxocara canis-infected mice
Infection and Immunity
Effect of inoculum size and length of infection on the distribution of Toxocara canis larvae in the mouse
American Journal of Tropical Medicine and Hygiene
Cited by (45)
Proteomic analysis of soluble protein extract of adult Toxocara cati
2020, Comparative Immunology, Microbiology and Infectious DiseasesCitation Excerpt :Diagnosis of toxocariasis is primarily based on symptoms, clinical signs, and serodiagnosis [12]. The patient’s history, including contact with domestic animals, asthma and ingesting of raw meat or liver should also be checked [8,13,14] Furthermore, cross-reactivity is an issue in countries with prevalent soil-transmitted helminths. Therefore, the use of specific antigens of T. cati with high diagnostic sensitivity and specificity is preferable [15].
Humoral immune response of pigs infected with Toxocara cati
2020, Experimental ParasitologyCitation Excerpt :In the chronic stage of infection both isotypes persisted at high levels. These results are consistent with those reported in other animal models (Helwigh et al., 1999; Sommerfelt et al., 2001, 2006b; Pinelli et al., 2007; Fenoy et al., 2008; Bin et al., 2016; Novák et al., 2017), although they differ from the results reported by Rodríguez-Caballero et al. (2017) who found negative values for IgM at 98 and 112 d. p.i. in mice inoculated with 100 and 50 eggs, respectively. However, similar results were found with respect to IgG levels which persisted from day 28 or 42 d. p.i., depending on the number of infective eggs, until 140 d. p.i. (end of the experiment).
Short communication: Experimental toxocarosis in Chinese Kun Ming mice: Dose-dependent larval distribution and modulation of immune responses
2015, Research in Veterinary ScienceImmunodiagnostic approaches for the detection of human toxocarosis
2015, Experimental ParasitologyCitation Excerpt :The level of total IgE was further confirmatory marker for determination of current status of infection. Coffman et al. (1993) and Pinelli et al. (2007) showed that parasite-derived antigens stimulate Th0 cells to become Th2 cells, leading to the production of IL-4 and IL-5, which stimulate IgE production and eosinophil proliferation and maturation, respectively. In industrialised countries, high levels of total IgE and eosinophilia are frequently associated with allergy diseases; in developing countries, they are highly associated with parasitic infection (Cooper, 2008).
Detection and identification of Toxocara canis DNA in bronchoalveolar lavage of infected mice using a novel real-time PCR
2013, Veterinary ParasitologyCitation Excerpt :During Toxocara spp. infection larval invasion and migration through the lungs may result in respiratory distress characterized by wheezing, coughs and mucous production. Murine models for toxocarosis have been extensively used to study the immunological and pathological consequences of infection with this nematode (Buijs et al., 1994; Kayes et al., 1987; Pinelli et al., 2005, 2007). Experimental infection of mice with T. canis results in pulmonary inflammation that can persist up to 60 days post infection.
Factors affecting disease manifestation of toxocarosis in humans: Genetics and environment
2013, Veterinary ParasitologyCitation Excerpt :The immune response may include both humoral and tissue factors. Although mouse isotypes (IgG1, IgG2a, IgG2b and IgG3) are different from human (IgG1, IgG2, IgG3 and IgG4); in a study in mice using a TES ELISA, the time and inoculum-dependent increases in serum IgG1 were found to be greater than for IgG2a (Pinelli et al., 2007). Fan et al. (2003) found that although IgG1 antibody is the primary responder it did not seem to have a larvicidal effect with no correlation being observed between the level of IgG1 and the decrease in mean total larval recovery in mice; on the contrary, the murine IgG1 antibodies may cause pathogenesis related to immediate-type hypersensitivity thus leading to tissue damage instead of killing the T. canis larvae in the tissues.