Freeze-dried equine-derived redback spider antivenom: a local irritation study by intramuscular injection in rabbits and a repeated-dose toxicity study in rats.

The redback spider (Latrodectus hasseltii) is nonindigenous to Japan but has now spread throughout the country. Bites to humans are rare but can be fatal. We prepared freeze-dried redback spider antivenom for therapeutic use against bites in Japan by immunization of horse plasma. This study included two nonclinical tests of the antivenom: a local irritation study involving a single intramuscular administration to rabbits (with injections of physiological saline and an existing freeze-dried diphtheria antitoxin as control and comparison substances, respectively) and a 2-week repeated intermittent intravenous-dose toxicity study in rats. The irritation study showed the antivenom's irritancy to be comparable with that of the saline and the existing antitoxin preparations under the test conditions. In a repeated-dose toxicity study, no toxicity change was found in male or female rats, and the no-observed-adverse-effect level (NOAEL) was judged to be a dose volume of 20 mL/kg (1082 units/kg antivenom activity) in both male and female rats. In addition, there was no toxicological difference between proteinaceous diphtheria antitoxin and redback spider antivenom prepared to have the same protein content and the same additive composition. Based on these findings, we will further advance our research towards clinical application of the redback spider antivenom. This research was supported by the Research Program on Emerging and Re-emerging Infectious Disease of the Japan Agency for Medical Research and Development.

[Enhancement of regulatory T cell induction by intravenous S-sulfonated Immunoglobulin during the treatment of experimental autoimmune encephalomyelitis].

Intravenous immunoglobulin (IVIg) has been shown to be effective for a variety of autoimmune diseases. Despite its widespread use and therapeutic success, the precise mechanisms for the anti-inflammatory therapeutic effects of IVIg are not well understood. In particular, few reports have examined the mechanism of IVIg on regulatory T cells (Treg: CD4(+)CD25(+)FoxP3(+) T cells). In the present study, to clarify the effect of intravenous S-sulfonated immunoglobulin (S-IVIg) on Treg, we investigated experimental autoimmune encephalomyelitis (EAE), the representative animal model of autoimmune disease. First, when we evaluated the effect of S-IVIg in an acute EAE model, the prophylactic treatment of S-IVIg dose-dependently controlled the symptoms of EAE. Next, we measured Treg in EAE mice spleen by flow cytometry. The percentage of Treg in S-IVIg-treated mice was significantly increased compared with Saline-treated mice. Finally, in reinduced EAE, S-IVIg not only prevented EAE progression, but also increased the percentage of Treg in the spleen. The increase in percentage of Treg in S-IVIg-treated EAE might be associated with protection against EAE. These observations provide important evidence that IVIg is effective in T-cell-mediated control of autoimmunity.

Pharmacokinetics, distribution, and excretion of 125I-labeled human plasma-derived-FVIIa and -FX with MC710 (FVIIa/FX mixture) in rats.

INTRODUCTION: MC710 is a mixture agent consisting of plasma-derived activated factor VII (FVIIa) and factor X (FX) at a weight ratio of 1:10 developed as a novel bypassing agent for the management of the bleeding of hemophilia patients with inhibitors. The pharmacokinetics, distribution, and excretion of (125)I-labeled-FVIIa ((125)I-FVIIa) and -FX ((125)I-FX) were studied in male rats after a single intravenous administration of (125)I-FVIIa or (125)I-FX combined with MC710. METHODS: (125)I-FVIIa or (125)I-FX was administered intravenously with MC710 to male rats in a single dosage (FVIIa 0.4 mg and FX 4 mg/kg body weight) and radioactivity and antigen levels in plasma were quantified for 24h. Urine and feces were sampled to study the excretion of radioactivity during 168 h after dosing. Whole-body autoradiography was performed to evaluate the qualitative distribution of radioactivity 168 h after dosing. RESULTS AND CONCLUSIONS: The half-life (t(1/2)α and t(1/2)ß) of radioactivity and FVIIa antigen were 0.704 and 6.27 h, and 0.496 and 1.66 h, respectively and the area under the plasma concentration-time curve (AUC(0-∞)) of radioactivity and FVIIa antigen were 17,932 and 8671 ng·h/mL, respectively. The t(1/2) of radioactivity and FX antigen were 4.06 and 3.05 h, respectively, and the AUC(0-∞) of radioactivity and FX antigen were 320,143 and 395,794 ng·h/mL, respectively. About 80% of the administered dose of radioactivity was excreted in urine and feces by 168 h after administration. Tissue distribution experiments showed that FVIIa- and FX-related (125)I accumulated in bone and bone marrow, and disappeared slowly.