Preventive effect of Toxoplasma lysate antigen (TLA) on fatal infection with mouse piroplasma.

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Abstract
Toxoplasma lysate antigen (TLA), mouse Babesia lymphokines (B-LKs) and mouse Toxoplasma lymphokines (Tp-LKs), were used to examine the effect of immune adjuvant in reducing clinical symptoms of Babesia rodhaini infection in mice. Normal mice were treated twice at an interval of 2 wk with an emulsion of TLA in Freund''s incomplete adjuvant (TLA emulsion), or a combination of TLA emulsion and B-LKs or Tp-LKs. Two weeks after the 2nd treatment, these mice were infected with B. rodhaini (102 parasitized erythrocytes/mouse, i.p.); 35.7% (5/14, number of survivals/number examined) of mice treated with TLA emulsion, 53.3% (8/15) of mice treated with a combination of TLA emulsion and B-LKs, and 73.3% (11/15) of mice treated with a combination TLA emulsion and Tp-LKs, survived for > 20 days postinfection. The defence mechanisms possibly involved in the group treated with TLA emulsion and combination of TLA emulsion and Tp-LKs, were examined with respect to macrophage activation. Mice treated with TLA emulsion showed a slight increase of leukocyte count, and O2 release of macrophages. The activity of macrophage migration inhibitory factor (MIF) of spleen cell culture supernatant and serum was not increased in this group. The mice treated with a combination of TLA emulsion and TP-LKs showed increased MIF activity and greater macrophage phagocytosis. Apparently, treatment with TLA emulsion and a combination of TLA emulsion and B-LKs or Tp-LKs induces a degree of immunity in the host against Babesia infection, and macrophage activation is part of this defence mechanism.