Delayed type hypersensitivity induced by intradermal inoculation of a Neospora caninum tachyzoite antigen in previously exposed cattle

Abstract

The aim of this study was to evaluate delayed type hypersensitivity (DTH) induced by the intradermal inoculationof a Neospora caninum tachyzoite soluble lysate in cattle previously exposed with the protozoa. Fourexperimental groups were selected according to the prior exposure to N. caninum antigen. All cows were intradermallyinjected with a N. caninum tachyzoite soluble lysate and skinfold thickness growth at the inoculationsites was measured at 0, 24, 48, 72 and 96 h post inoculation (hpi). Additionally, specific antibodies and IFN-γproduction were assessed. Cows experimentally infected with live N. caninum tachyzoites and cows naturallyexposed to N. caninum developed skin reactions compatible with DTH between 24 and 96 hpi (p < 0.05).Moreover, cows inoculated with an experimental N. caninum vaccine and cows without evidence of exposure toN. caninum did not show a significant increase in skin thickness (p > 0.05). Furthermore, serological status ofthe animals was not modified due to the intradermal inoculation. The highest IFN-γ production was observed at15 days after intradermal inoculation (p < 0.05). Therefore, these results suggest that cattle previously exposedto N. caninum develop a reaction compatible with DTH which could be useful as in vivo cell mediated immunityparameter for assessed bovine neosporosis.