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Objective: Ricin is a highly toxic ribosome-inactivating lectin derived from castor beans. To date, no antidote is available to treat ricin-poisoned patients, and the development of a safe and effective antidote is urgently needed. Methods: First, ricin was prepared and used to construct a mouse model and a rhesus monkey model of ricin intoxication. Second, pepsin-digested F(ab')2 fragments of serum IgG from horses injected with Freund's-adjuvanted purified ricin were prepared. Third, the protective efficacy was evaluated in mouse and rhesus monkey models of lethal ricin intoxication. Results: The purity quotient of the prepared ricin and F(ab')2 fragments exceeded 90% and 85% in the mouse and monkey models, respectively. The LD50 of ricin in mice and rhesus monkeys was 2.7 and 9 µg/kg, respectively. A quantity of 6.25 and 1.85 mg/kg F(ab')2 was sufficient to treat lethal ricin intoxication in the mice and rhesus monkeys, respectively. Finally, the effect of this therapeutic antibody on peripheral blood immune cells was examined by analysis of peripheral blood immune cells through single cell sequencing. The underlying mechanism was found to involve restraining neutrophil activation, proliferation, and differentiation. Conclusion: Purified F(ab')2 fragments administered with needle-free devices fully protect mice and rhesus monkeys against lethal doses of ricin intoxication. [ABSTRACT FROM AUTHOR]

Objective: Smallpox, a severe infectious disease caused by the smallpox virus, causes a death rate as high as 30% within 15-20 days after infection. Therefore, development of anti-Smallpox product as a strategic reserve is urgently needed. Methods: We prepared and tested pepsin-digested F(ab')2 fragments of serum IgG from horses. Results: Transmission electron microscopy indicated that the purified virus showed morphology consistent with VVTT. The titer was above 1.0 × 107 PFU/mL. The purity of the antigen exceeded 90%, according to HPLC. After purification and cleavage, the yield of the purified product F(ab')2 was approximately 1.3%, its purity exceeded 90%, and the neutralizing antibody titer exceeded 1:3200. F(ab')2 fragments had good preventive and therapeutic effects in mice at antibody doses of 5.2 mg/mL and 2.6 mg/mL. The viral loads of the drug-treated mice were suppressed to varying degrees, and the higher dose groups (5.2 and 2.6 mg/mL) showed a 2-3 fold lower viral load than that in the control group. Conclusion: A process for producing equine immunoglobulin F(ab')2 against VVTT was established. The prepared horse anti-smallpox immunoglobulin product had good neutralizing antibody effects on VVTT. The highly purified preparation may serve as a potential candidate for smallpox treatment. [ABSTRACT FROM AUTHOR]