Systemic and local immune responses in sheep after Neospora caninum experimental infection at early, mid and late gestation

Abstract

Besides its importance in cattle, Neospora caninum may also pose a high risk as abortifacient for small ruminants. We have recently demonstrated that the outcome of experimental infection of pregnant sheep with 106 Nc-Spain7 tachyzoites is strongly dependent on the time of gestation. In the current study, we assessed peripheral and local immune response in those animals. Serological analysis revealed earlier and higher IFN-γ and IgG responses in ewes infected at early (G1) and mid (G2) gestation, when abortion occurred. IL-4 was not detected in sera from any sheep. Inflammatory infiltrates in the placenta mainly consisted of CD8+ and, to a lesser extent, CD4+ T cells and macrophages (CD163+). The infiltrate was more intense in sheep infected at mid-gestation. In the foetal mesenchyme, mostly free tachyzoites were found in animals infected at G1, while those infected in G2 displayed predominantly particulate antigen, and parasitophorous vacuoles were detected in sheep infected at G3. A similar pattern of placental cytokine mRNA expression was found in all groups, displaying a strengthened upregulation of IFN-γ and IL-4 and milder increases of TNF-α and IL-10, reminiscent of a mixed Th1 and Th2 response. IL-12 and IL-6 were only slightly upregulated in G2, and TGF-β was downregulated in G1 and G2, suggestive of limited T regulatory (Treg) cell activity. No significant expression of TLR2 or TLR4 could be detected. In summary, this study confirms the pivotal role of systemic and local immune responses at different times of gestation during N. caninum infection in sheep.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-015-0290-0) contains supplementary material, which is available to authorized users.

Influence of dose and route of administration on the outcome of infection with the virulent Neospora caninum isolate Nc-Spain7 in pregnant sheep at mid-gestation

“…Very short-lived IFNγ levels were produced in antigen-specific stimulation analyses at the end of the first and during the second week following infection with N. caninum and prior to mounting a specific IgG response. Similar IFNγ kinetics have been described in previous reports carried out in cattle upon stimulation of peripheral blood mononuclear cells (PBMCs) [ 18 ] or in sheep serum [ 41 ]. In G1 (10 5 , IV), IFNγ released upon stimulation increased on day 7 pi in the same way that intravenous infection with 10 6 tachyzoites of the Nc-Spain7 isolate [ 23 ].…”

“…After intravenous infection of pregnant sheep at mid-gestation with 10 6 tachyzoites of the Nc-Spain7 isolate, IgG levels increased from day 12–14 pi [ 23 , 41 ], whereas IgG levels increased from day 21 pi in G1 (10 5 , IV). Furthermore, G1 (10 5 , IV) exhibited higher IgG levels than those found with lower doses, possibly due to exposure to more abundant antigen and increased lymphoid stimulation similar to that reported by [ 9 , 30 , 32 , 48 ].…”

Early feed restriction of lambs modifies ileal epimural microbiota and affects immunity parameters during the fattening period

“…Immunohistochemical analysis was performed according to the procedure described by Arranz-Solís et al (2016). Briefly, cross sections were cut from the ileum wall samples and placed onto poly-L-Lysine coated slides for immunohistochemical labelling of T (CD3 antigen), B (CD20 antigen) and M-cells (cytokeratin 18 antigen).…”

A model for chronic bovine besnoitiosis: Parasite stage and inoculation route are key factors

“…IFN‐γ levels were measured in serum samples from 5 days prior to infection (−5 days pi) until the end of the collection period, with a Bovine IFN‐γ ELISA development kit (Mabtech AB, Sweden) according to the manufacturer´s instructions (Arranz‐Solís et al, ).…”