Conconavalin A-stimulated bovine T-cell supernatants inhibit growth of Cowdria ruminantium in bovine endothelial cells in vitro

Abstract

Conconavalin A-stimulated bovine T-cell supernatants inhibited the growth of Cowdria ruminantium in bovine endothelial cells in vitro but did not affect their entry. This finding represents one mechanism by which T cells may control C. ruminantium multiplication and hence affect the severity of disease.

Neutralization of bovine Concanavalin‐A T cell supernatant‐mediated anti‐Cowdria ruminantium activity with antibodies specific to Interferon gamma but not to tumor necrosis factor

“…The Con-A T cell supernatants used in this study were those that were used in the previous study (Mahan et al 1994), and were obtained on the third day of Con-A stimulation of peripheral blood leucocytes of an uninfected bovine animal (Mahan et al 1994). The concentration of IFN in the Con A-stimulated bovine T cell supernatant was 272 pg/ml determined by use of a commercially available ELISA (Commonwealth Serum Laboratories, Parkville, Victoria, Australia).…”

“…Four experimental groups were created each containing five 25 cm 2 flasks of BPA 593/1 endothelial cells. The isolation, propagation and maintenance of these cells has been described previously (Byrom & Yunker 1990, Mahan et al 1994. All endothelial cell cultures were infected with 1 ml supernatant of C. ruminantium Crystal Springs strain organisms from a terminally infected culture as described previously (Mahan et al 1994).…”

“…These T cell supernatants had to be added to the cultures immediately after inoculation with C. ruminantium to induce the growth inhibition, and had no effect if added after the cultures had an established infection. This inhibitory effect was neither C. ruminantium strain nor endothelial cell type specific (Mahan et al 1994). IFN has been recognized as an important factor in controlling rickettsial infections both in vivo and in vitro (Hanson 1991, Jerrels et al 1986Li et al 1987, Turco & Winkler 1983a,b, 1984, 1985, 1993, Wisseman & Waddell 1983, and therefore its role in inhibiting C. ruminantium growth was investigated.…”

“…Previously we demonstrated that growth but not entry of C. ruminantium, in bovine endothelial cells was inhibited by bovine T cell supernatants derived from Concanavalin-A (con-A) stimulated bovine peripheral blood leucocytes (Mahan, Smith & Byrom 1994). These T cell supernatants had to be added to the cultures immediately after inoculation with C. ruminantium to induce the growth inhibition, and had no effect if added after the cultures had an established infection.…”

A DNA vaccine protects mice against the rickettsial agent Cowdria ruminantium

“…Cell-mediated immunity can be mediated directly through cell cytotoxic effects and indirectly via the production of cytokines that enable the elimination of intracellular infection (Abbas et al 1994). Cytokines in general (Turco & Winkler 1983a, Wisseman & Waddel 1983, Mahan et al 1994 and interferon (IFN)-gamma in particular, have been shown to exert antirickettsial effects in in vitro (Turco & Winkler 1983a,b, 1989, 1994, Wisseman & Waddel 1983, Manor & Sarov 1990, Gao et al 1993, Feng et al 1994, Mahan et al 1994, 1996 and in vivo (Li et al 1987) studies. The inhibitory effects of IFN-gamma (Totte et al 1993, Mahan et al 1996 and IFN-alpha (Totte et al 1993(Totte et al , 1994 on the growth of C. ruminantium have been demonstrated.…”