Toxocara canis larvae reinfecting BALB/c mice exhibit accelerated speed of migration to the host CNS

Abstract

Using a small animal imaging system, migratory activity of Toxocara canis larvae stained by carboxyfluorescein succinimidyl ester (CFSE) was observed post primary infection (PPI) and post reinfection (PR) of BALB/c mice. Each infection was performed with 1,000 larvae per mouse. Primary infections were performed with labeled larvae, while for challenge infections the reinfecting larvae were stained by CFSE. The worm burden in mouse organs was determined during a period from 6 h to 21 days and 4 months PPI and PR. In comparison with primary infections that led to the first larvae appearance in the brain after 60 h, greatly accelerated migration of the parasites administered 3 weeks PPI to the CNS and eyes of challenged mice was noted-in both organs the larvae appeared 6 h PR. In all challenged mice, reinfecting larvae prevailed in the resident parasite population. Preliminary experiments with Toxocara cati larvae also revealed early brain involvement in primarily infected mice. Staining of T. canis larvae by CFSE had no effect on the development of a humoral antibody response against T. canis excretory-secretory antigens. In ELISA, elevated levels of specific IgG and IgG1 were noted on day 14 PPI and the levels of antibodies increased till the end of experiment. Reinfection induced an increase in the levels of both antibodies. In terms of optical density, IgG1 antibodies gave higher values in all sera examined. In ELISA for IgG antibodies, an increase in the avidity index of around 50% was detected 1 month PPI; higher-avidity antibodies were also detected in sera of reinfected animals.

Signal Transducer and Activator of Transcription Factor 6 Signaling Contributes to Control Host Lung Pathology but Favors Susceptibility againstToxocara canisInfection

“…Here it is noteworthy that in spite of a higher Th2-associated antibody response in WT mice, these displayed greater susceptibility to T. canis . These data agree with those recently reported by [18], who found that after T. canis reinfection in BALB/c mice, reinfected mice displayed significantly higher titers of T. canis -specific IgG1; moreover, those antibodies showed a greater avidity for T. canis antigens. However, re-infected mice displayed a major number of larvae in different tissues [18].…”

“…While widely accepted, Th2-type response in clearing helminth infections has limitations [11, 13–17], its role in mediating protection against toxocariasis in paratenic hosts is not clear, mainly because reinfection in toxocariasis favors parasite survival [18]. Recent advances in the immunobiology of T. canis indicate that regulatory mechanisms are raised after infection; mainly T regulatory cells have been involved in limiting pathologic damage by the inflammatory response [19]; however, there are few data regarding on mechanism of protection or susceptibility against such parasite.…”

Neurotoxocarosis alters myelin protein gene transcription and expression

“…These events might be multifocal trauma, hypoxia and accumulation of macrophages. After oral infection, Toxocara larvae reach the brain as early as 60 h later by perforating vessel walls (Kolbeková et al 2011). Subsequent haemorrhages and tissue migration lead to parenchymal damage (Cardillo et al 2009;Janecek et al 2014).…”

Determination of IgG avidity in BALB/c mice experimentally infected with Toxocara canis

“…The result of the present study are according to Fenoy et al (2008) that found high-avidity of IgG antibodies (over 50%) 60 days post-infection of BALB/c with 1000 T. canis eggs. However, another study using BALB/c mice reported high-avidity of IgG antibodies at only 30 days post-infection of 1000 larvae (KOLBEKOVÁ et al, 2011).…”

“…Studies using the ELISA immunoassay with urea, a denaturant agent that can dissociate the antigen-antibody interaction when the avidity is low (BERTOZZI et al, 1999), have been conducted to measure the IgG avidity percentage in human toxocariasis (HUBNER et al, 2001;ELEFANT et al, 2006). In experimental model, only two studies on avidity of specific IgG against TES were done (FENOY et al, 2008;KOLBEKOVÁ et al, 2011). The aim of this study is to investigate the applicability of indirect ELISA, associated with urea, to discriminate between the stages of toxocariasis infection in experimentally infected BALB/c mice.…”