Parâmetros biológicos de Amblyomma sculptum alimentados em diferentes linhagens de camundongos e desenvolvimento de resposta imune antissaliva

Abstract

Amblyomma sculptum, a tick of the family Ixodidae, has as main hosts equines, capybaras, and tapirs. These hosts do not develop effective immunity against the tick and may have high parasitic loads. Because of the need to develop new ways of combating ticks, the maintenance of A. sculptum colony in the laboratory with a sufficient number of specimens to carry out experiments is essential. However, the use of mice for the maintenance of A. sculptum colonies is still poorly described in the literature. In the present study, the main objective was to describe the biological parameters of the tick A. sculptum fed on different strains of mice and to evaluate the development of immune response by the hosts. For this, A. sculptum was fed on C57BL/6, Swiss, BALB/c, and BALB/c knockout mice for the ST2 (kST2) receptor. Star tick nymphs were also fed at different parasitic densities and successive infestations. Blood from infested mice was collected for antibody assessment. The results showed that BALB/c, C57BL/6, and Swiss mice can be used to maintain a colony of A. sculptum larvae and nymphs in the laboratory. However, nymphs fed on Swiss mice had lower weight after feeding, 13.1 ± 4.3 mg, and longer mean molting time, 17.1 ± 1.4 days. Nymphs fed on BALB/c knockout mice to the ST2 receptor (kST2) performed blood meal with efficiency similar to nymphs fed on BALB/c mice. However, they took longer to feed, 5.3 ± 1.4 days. A. sculptum nymphs were more efficient when fed at parasitic densities of 10 nymphs/mice. When five nymphs were fed at the same location in the mouse, the weight after feeding was significantly lower, 12.9 ± 5.3 mg in BALB/c mice and 12.9 ± 3.9 mg in kST2 mice. The nymphs successfully performed hematophagy on the three successive infestations in BALB/c, kST2, and Swiss mice demonstrating that these mice did not develop acquired resistance. Feeding time was longer when nymphs fed on mice of the BALB/c and kST2 strains previously infested with ticks, 7.5 ± 1.0 and 6.5 ± 1.3 days, respectively. In the Swiss line, the feeding time and the seedling time were shorter, 4.7 ± 1.2 and 14.3 ± 0.4 days, respectively. The serum of the parasitized Swiss mice showed increasing antisaliva antibodies after a third infestation. The antibodies present in the serum of Swiss mice recognized, through Western Blot, molecules of the gland extract and the saliva of the tick, the latter represented by two bands, which indicates that the saliva has few immunogenic proteins. Our work showed that mice are good hosts for the A. sculptum tick, which can be used for up to three infestations without developing effective immunity against the parasitism.