Identification of Neospora antigens recognized by CD4⁺ T cells and immune sera from experimentally infected cattle

Abstract

Neospora caninum is recognized as a major cause of infectious abortion in cattle. Very little is known about immunity to Neospora. Cell mediated responses have previously been shown to be important in the development of protective immunity to the closely related parasite Toxoplasma gondii, and may therefore be an important component in the immune response to Neospora. In this paper we report that a group of low molecular weight NCI strain tachyzoite antigens (< or = 30 kDa) separated by SDS PAGE and bound to nitrocellulose membrane stimulated proliferation in vitro of CD4+ T cells from calves experimentally infected with N. caninum. Proliferation was accompanied by production of high concentrations of IFN-gamma. Several of these antigens were also recognized by antibody produced in these animals. As the most effective vaccines require the stimulation of both humoral and cell mediated immune responses, these antigens may be important in the development of a vaccine against neosporosis.

Upregulation of Cytokines Is Detected in the Placentas of Cattle Infected withNeospora caninumand Is More Marked Early in Gestation When Fetal Death Is Observed

“…Similarly, the immune response in cattle, as investigated by in vitro studies of peripheral blood cells, is characterized by expression of high levels of IFN-␥ (28,44) by CD4 ϩ T cells (1,28,44). Furthermore, IFN-␥ inhibited intracellular multiplication of N. caninum in culture (17), and Staska et al (39) showed killing of N. caninum-infected autologous targets by CD4 ϩ cytotoxic T cells, indicating that these are likely control mechanisms in vivo.…”

The ProtozoanNeospora caninumDirectly Triggers Bovine NK Cells To Produce Gamma Interferon and To Kill Infected Fibroblasts

“…The importance of gamma interferon (IFN-␥) for protection against N. caninum has been well documented in mouse models (1,22,28) and bovine tissue cultures (20,47). The source of this proinflammatory cytokine during bovine neosporosis has been attributed to CD4 ϩ T lymphocytes (26). Parasite-specific cytotoxic T lymphocytes, predominantly of the CD4 ϩ phenotype, have been demonstrated in N. caninum-infected cattle (38).…”

The inhibitory Effect of Interferon Gamma and Tumor Necrosis Factor Alpha on Intracellular Multiplication of Neospora caninum in Primary Bovine Brain Cells.

“…IFN-γ suppressed the parasite growth in brain cells, which agreed with the previous in vitro [13] and in vivo [9,14] studies. In addition, a high concentration of IFN-γ was produced by CD4 + T cells stimulated with Neospora antigen [18], and therefore, IFN-γ may be a critical component of the cell-mediated response to Neospora infection. In studies using T. gondii, murine astrocytes [11], murine microglia [5], human astrocytes [21], human microglia [6] and human endothelial cells [25] activated by IFN-γ inhibited tachyzoite growth.…”