CONICET | Buscador de Institutos y Recursos Humanos

The aim of this study was to evaluate whether Neospora caninum tachyzoites (Nc-1) inoculated by the conjunctival route in pregnant cows were able to generate infection in theirfetuses. Group 1 contained 2 naturally infected cows; group 2 contained two cows inoculated intravenously with 2.5 × 108 tachyzoites, group 3 contained two cows inoculatedwith 2.5 × 108 tachyzoites by the conjunctival route, and group 4 contained two uninfectedcontrol cows. The four inoculated cows from groups 2 and 3 were challenged at 23 weeks ofgestation. An indirect fluorescent antibody test (IFAT), recombinant NcGRA7-based ELISA,ELISA for IgG subisotypes and Western blot analysis were assessed to characterize thehumoral immune response in dams. Sera from their fetuses were tested also using Westernblot analysis. Routine microscopic evaluation of H&E stained fetal tissues was madeand any fetal tissues and placentas with lesions compatible with Neospora-infection wereprocessed by immunohistochemistry (IHC). DNA extraction from fresh and formalin-fixed,paraffin-embedded fetal tissues were tested by nested PCR. All dams from groups 1, 2 and 3were seropositive by IFAT, rNcGRA7-based-ELISA and Western blot. IgG1/IgG2 ratios were ≤1 at weeks 27 and 29 of gestation. Only fetuses from groups 1 and 2 developed N. caninum specific antibodies by Western blot. Histopathological lesions compatible with those caused by N. caninum were observed in fetuses from groups 1 and 2. N. caninum cysts and tachyzoites were observed by IHC on fetal tissues from groups 1 and 2. Only fetal samples from group 2 were positive by PCR. Further work is needed not only to characterize the cellular immune response but also to clarify the consequences on the dam after conjunctival inoculation of N. caninum tachyzoites. This study shows that N. caninum tachyzoites inoculated by the conjunctival route were not vertically transmitted in pregnant cows.

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