Experimental toxocariasis in BALB/c mice: relationship between parasite inoculum and the IgG immune response

Abstract

BALB/c mice were inoculated with 5-500 Toxocara canis infective eggs, and bled at 15-120 days post infection (dpi) to evaluate the dynamics of IgG antibody response and larvae distribution. Positive results were observed in all occasions for every inoculum, and a direct proportional relationship between antibody detection and the parasitic load was observed. In samples collected at 60 dpi, detection of IgG was more intense, especially with the 50 and 500 egg doses; also, a correlation between antibody level and egg count was observed with these two inocula. At 120 dpi, a decrease in antibody titer was observed for all groups; and at the end of the experiment, larvae were recovered from carcass, liver and brain. In the liver, larvae were only found in mice inoculated with 500 T. canis eggs. In carcasses, these were recovered in all groups, and the group inoculated with 50 eggs showed the highest percentage of larvae in the brain.

Reactivity of recombinant Toxocara canis TES‐30/120 in experimentally infected mice

“…There was no significant difference between different infectious doses of T. canis ( P = 0.31) or protein sensitivity (rTES‐30 P = 0.26 and rTES‐120 P = 0.77). These results concur with Fonseca et al (2017), which did not find a significant influence of parasite inoculum nor humoral immune response …”

“…Different doses in each challenge were used according to Fonseca et al (2017) and Havasiová‐Reiterová et al (1995) . Experiment 1 used a dosage in accordance with experiment 2, validating rTES‐30 with T. cati infected mice; we decided to not infect mice with a higher dose of T. cati infectious eggs because maximum sensitivity had already been achieved with a lower dose.…”

Human Toxocariasis: 2010 to 2020 Contributions from Brazilian Researchers

“…Aspects of the immune response of nonhuman paratenic hosts, with possible benefits for surveys aimed at determining the frequency of infections by Toxocara larvae, have been studied in vivo, in mouse or rabbit models. [80][81][82][83][84][85][86][87][88][89][90] Serological surveys carried out on synanthropic animals that are paratenic hosts of T. canis revealed significant natural frequencies of infection, indicating that there is a risk involved in the human consumption of raw or undercooked meat from these animals. [91][92][93][94] Recombinant proteins used in ELISAs and Western blot assays for the diagnosis of Toxocara infections of cattle, horses, and sheep have obtained good results.…”

Toxocara canis 30-35 kDa excretory-secretory antigen is an important marker in mice challenged by inocula containing different parasite load levels

“…This fact might explain the recognition of smaller numbers or less intense antigenic fractions in group I. The immune response of mice infected with T. canis has been related to the inoculum 6 , 19 . We can infer that the remaining larvae from group I might not have stimulated the immune response as observed in animals from groups II and III that were challenged by higher parasite load levels.…”