Bartley, P.M., Katzer, F., Rocchi, M.S., Maley, S.W., Silvan, J.B., Purslow, C., Nath, M., Pang, Y.P., Chianini, F. and Innes, E.A.
||This study examined the immunological responses of pregnant cattle and their foetuses following an experimental challenge with live Neospora caninum tachyzoites at day 210 of gestation. Animals were bled prior to and weekly throughout the experiment and sacrificed at 14, 28, 42 and 56 days post inoculation (pi). At post mortem, samples of lymph nodes and spleen were collected from both dam and foetus for immunological analysis. Inoculation of pregnant cattle at day 210 of gestation, lead to the vertical transmission of parasites by day 14pi. However, no foetal deaths were observed in the challenged animals. Foetuses from infected dams mounted humoral and cell mediated immune (CMI) responses against the parasite by day 14pi. These responses involved anti-Neospora IgG, antigen-specific lymphocyte proliferation, the production of the cytokines IFN-γ, interleukin (IL)-4 and IL-10. There was also evidence of involvement of the innate immunity during the response against Neospora, with statistically significant (p<0.05) increase in mean expression of toll like receptors (TLR)-2 and TLR-9 from day 28pi in maternal samples from infected dams. Statistically significant (p<0.05) increases in mean TLR-9 were detected in spleen samples from foetuses of infected dams, compared to the control animals. Our results demonstrate that vertical transmission of the parasite occurred in all challenged dams, with their foetuses showing effective CMI, humoral and innate responses to Neospora. These results suggest that infection of naïve animals at day 210 of gestation may lead a high rate of vertical transmission of Neospora with little sign of disease in the foetuses.