Larval Taenia crassiceps secretes a protein with characteristics of murine interferon-gamma.

Previous studies have shown that excretory/secretory products of larval Taenia crassiceps have immunomodulatory activities. We report here that one of these products, termed p66, possesses activities that mimic some characteristics of murine interferon-gamma (IFN-gamma). Purified p66 cross-reacts with anti-murine IFN-gamma on immunoblots and increases concanavalin-A-induced splenic T-cell proliferative responses of normal and chronically infected mice. It has also been shown that p66 induces enhanced IFN-gamma and interleukin-10 (IL-10) production in cells from infected or normal mice. Adherent and non-adherent peritoneal exudates cells were stimulated with p66 and showed that the adherent cells were induced to produce IL-10 and that the non-adherent cells were induced to produce IFN-gamma. p66 was shown as well to upregulate nitric oxide production in macrophages and two T-cell lines, IEL and YAC-1, were shown to be stimulated to produce IFN-gamma and IL-10, respectively, by p66. Although the significance of p66 in immunoregulation is not known, we show here that this molecule mimics characteristics of IFN-gamma.

Immune destruction of larval taenia crassiceps in mice.

Immune destruction of larval Taenia crassiceps was examined by first injecting BALB/cJ mice subcutaneously with larval buds and 30 to 60 days later challenging the mice with larvae injected into the peritoneal cavity. The larvae injected intraperitoneally (i.p.) secondarily are killed by host cells that completely encase the larvae in a thick sheath. The peritoneal exudate cells and the cytokines they produced were characterized by flow cytometry, enzyme-linked immunosorbent assays (ELISAs), and reverse transcription PCR (RT-PCR). No changes in percentage of CD4(+) T cells, CD8(+) T cells, B1 cells, or macrophages were detected in the peritoneal cavities of mice that were killing larvae compared to mice with a primary 7-day infection i.p. Both RT-PCR and ELISA demonstrated a decrease in cytokines including gamma interferon (IFN-gamma), interleukin-4 (IL-4), and IL-10 in mice that were killing the larvae compared to control mice infected for 30 to 60 days i.p. alone, although there was little difference compared to mice infected for 7 days i.p. alone. Serum cytokine levels in mice that were killing the larvae showed a decrease in IFN-gamma and IL-4, an increase in IL-10 when compared to mice infected for 30 to 60 days i.p. alone, and increases in all cytokines compared to mice infected for 7 days i.p. alone. Inhibition of nitric oxide production did not significantly affect the number or the viability of larvae in the peritoneal cavity of mice that were killing larvae during secondary infection.