Abstract
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 (dpi). At post mortem examination, samples of lymph nodes and spleen were collected from both dam and foetus for immunological analysis. Subcutaneous (sc) inoculation over the left prefemoral (LPF) lymph node of pregnant cattle at day 210 of gestation, led to the vertical transmission of parasites by 14 dpi, however no foetal deaths were observed in the infected animals. Foetuses from infected dams mounted Neospora-specific humoral and cell-mediated immune (CMI) responses by 14 dpi. These responses involved anti-Neospora IgG, antigen-specific lymphocyte proliferation, and the production of the cytokines IFN–γ, interleukin (IL)-4 and IL-10. There was also evidence of innate immunity during the response against Neospora from infected dams, with statistically significant (p < 0.05) increases in mean expression of toll like receptors (TLR)-2 on 56 dpi in maternal spleen, LPF, right prefemoral (RPF), left uterine (LUL) and right uterine (RUL) lymph nodes and TLR-9 in retropharyngeal (RLN), LPF and RPF lymph nodes from 28 dpi. Statistically significant (p < 0.05) increases in mean TLR-9 were detected in spleen samples from foetuses of infected dams, compared to the foetuses from control animals. Our results show that vertical transmission of the parasite occurred in all infected dams, with their foetuses showing effective Neospora-specific cell mediated, humoral and innate immune responses.
Highlights
Neospora caninum is recognised worldwide as a major cause of abortion and foetal death in farmed ruminants, mainly affecting cattle [1]; though sporadic cases have been reported leading to foetal deaths in sheep [2] and goats [3]
SYBR green quantitative polymerase chain reaction (qPCR) for glyceraldehyde-3-phosphate dehydrogenase (GAPDH), toll like receptor-2 (TLR) and toll like receptors (TLR)-9 To determine whether TLR-2 and TLR-9 expression is being up or down regulated during N. caninum infections we examined the expression of the TLRs in both maternal and foetal tissues at different stages following challenge, using the SYBR green qPCR primers and basic protocol described by Menzies and Ingham [36]
At the same time point, significantly lower (p = 0.023) mean levels of proliferation were observed in the right prefemoral (RPF) of infected animals compared to control animals
Summary
Neospora caninum is recognised worldwide as a major cause of abortion and foetal death in farmed ruminants, mainly affecting cattle [1]; though sporadic cases have been reported leading to foetal deaths in sheep [2] and goats [3]. Current control strategies for bovine neosporosis mainly It has become clear from natural and experimental data that primary Neospora infections in cattle can lead to abortions and reproductive losses, with cattle infected with Neospora for the first time during pregnancy being 3–7 times more likely to abort than uninfected animals [6,7]. In naturally infected cows that were experimentally challenged on day 70 of gestation, the animals showed protection against foetopathy, but vertical transmission of the parasite still occurred [11]. These results suggest that a protective immune response may be induced that can protect against abortion, it may be more difficult to prevent endogenous vertical transmission of the parasite
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