The early intestinal immune response in experimental neonatal ovine cryptosporidiosis is characterized by an increased frequency of perforin expressing NCR1+ NK cells and by NCR1− CD8+ cell recruitment

Abstract

Cryptosporidium parvum, a zoonotic protozoan parasite, causes important losses in neonatal ruminants. Innate immunity plays a key role in controlling the acute phase of this infection. The participation of NCR1+ Natural Killer (NK) cells in the early intestinal innate immune response to the parasite was investigated in neonatal lambs inoculated at birth. The observed increase in the lymphocyte infiltration was further studied by immunohistology and flow cytometry with focus on distribution, density, cellular phenotype related to cytotoxic function and activation status. The frequency of NCR1+ cells did not change with infection, while their absolute number slightly increased in the jejunum and the CD8+/NCR1- T cell density increased markedly. The frequency of perforin+ cells increased significantly with infection in the NCR1+ population (in both NCR1+/CD16+ and NCR1+/CD16- populations) but not in the NCR1-/CD8+ population. The proportion of NCR1+ cells co-expressing CD16+ also increased. The fraction of cells expressing IL2 receptor (CD25), higher in the NCR1+/CD8+ population than among the CD8+/NCR1- cells in jejunal Peyer’s patches, remained unchanged during infection. However, contrary to CD8+/NCR1- lymphocytes, the intensity of CD25 expressed by NCR1+ lymphocytes increased in infected lambs. Altogether, the data demonstrating that NK cells are highly activated and possess a high cytotoxic potential very early during infection, concomitant with an up-regulation of the interferon gamma gene in the gut segments, support the hypothesis that they are involved in the innate immune response against C. parvum. The early significant recruitment of CD8+/NCR1- T cells in the small intestine suggests that they could rapidly drive the establishment of the acquired immune response.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-014-0136-1) contains supplementary material, which is available to authorized users.

Bovine cryptosporidiosis: impact, host-parasite interaction and control strategies

“…The role of NK cells during C. parvum infection has been studied in ovine, murine and human models of cryptosporidiosis. Within the first few days following infection of 1 day old lambs with C. parvum , the abundance of NKp46+ NK cells expressing CD16, CD25 and perforin was increased in the gut [ 114 ]. In mice, it was demonstrated that oocyst shedding was higher in C. parvum -infected Rag 2 −/− γ c −/− mice (mice lacking B, T and NK cells) compared with C. parvum -infected Rag2 −/− mice (mice lacking B and T cells).…”

“…CD8+ T cells, alongside CD4+ T cells and γδ T cells, are present at an increased frequency within the ileum of C. parvum -infected calves at day 3 post-infection, compared with tissues from uninfected calves [ 118 ]. Furthermore, following infection of 1 day old lambs with C. parvum , CD8+/NKp46− lymphocytes (which the authors concluded were most likely to be CD8+ T cells) were significantly increased in the small intestine at day 3 and day 6 post infection, reflecting their recruitment following infection [ 114 ]. Therefore, CD8+ T cells appear to be involved in the immune response after infection of calves and lambs with C. parvum.…”

An Immediate Innate Immune Response Occurred In the Early Stage of E.granulosus Eggs Infection in Sheep: Evidence from Microarray Analysis

“…As a major component of the innate immune system, natural killer cells are responsible for activating the cytolytic killing of foreign pathogen infection, primarily in defenses against virus, bacteria and parasite during early infection [ 30 ]. Here, we have shown that genes encoding the activator of NK cells (KIR2DS1, KLRJ1) were markedly up-regulated in the intestine tissue of CE infection sheep at 4-hour post infection, suggesting that NK cells might be strongly activated, and thus pose a high cytotoxic potential very early during infection, which is supported by the high expression of MPTX gene encoding mucosal pentraxin.…”

“…Our results are in partial agreement with reports on sheep C . parvum infection, showing the highly activation of NK cells in the intestine tissue during the very early stage [ 30 ]. Although E .…”

Systemic and Mucosal Immune Responses to Cryptosporidium—Vaccine Development

“…Both studies found that NK cell-dependent protection was primarily mediated through IFN-γ. Drouet and colleagues recently found an increase in early recruitment of activated, perforin+ NK cells to areas of infection in neonatal lambs infected with C. parvum (66)*. These studies suggest that the role of NK cells during Cryptosporidium infection may involve both IFN-γ-mediated protection and direct cytolysis.…”