New Progress has been Made in the Preparation of

Horse Anti- COVID-19 Serum

Jilin University, the Academy of Military Medical Sciences and Inner Mongolia University for Nationalities, together with leading domestic biotechnology companies have made breakthrough in the development of horse anti-2019 new coronavirus disease (COVID-19) serum. At present, although the domestic COVID-19 epidemic has been effectively controlled, the world-wide epidemic situation is getting more and more severe, which brings a lot of uncertainty. In the absence of definite curative drugs, plasma therapy of recovered patients is not only included in my country's "New Coronavirus Pneumonia Diagnosis and Treatment Program" (trial version 6) due to its obvious curative effect, but also recommended as a clinical treatment program by the United States, Italy and other countries. However, the source of plasma of recovered patients is limited, and it is difficult to meet the medication needs of a large number of patients.

In the face of the urgency of the epidemic and the limitations of plasma collection of recovered patients, Jilin University quickly organized an emergency team. With the support of relevant national departments, relying on the Collaborative Innovation Center for Major Disease Prevention and Control Technology of Jilin Province, research on horse anti- COVID-19 serum was launched in early February. They used the receptor binding domain (RBD) of the new coronavirus spike protein (S protein) as the immunogen, and first completed the eukaryotic expression and purification of the protein fragment, and completed immunization injection of the first batch of horses on February 14. After the three immunizations, the ELISA kits used to detect the qualified plasma titer in the recovery period of covid-19 patients were used on the horses. The results showed that the antibody IgG titer of horse antiserum is as high as 10,240-fold dilution, which is 64 times the qualified plasma titer (160-fold dilution) of the current convalescent plasma. The vitro virus neutralization test showed that the neutralization blocking titer of horse antiserum to the virus reached 5,120 times dilution, which is 128 times higher than the neutralization titer of currently known convalescent sera (Note: according to the data published on page 270 of Nature Vol. 579 on the 12^th March 2020, the serum neutralization titer of recovered patients is between 40-80 times dilution). At present, the batches of serum collected after the three immunizations have been concentrated, purified and prepared by domestic biotechnology companies into IgG F(ab′)2 products that can be used for experimental treatment, and relevant quality identification has been completed. The human dose of IgG F(ab′)2 of 2.5 ml can reach the total potency of 500 ml of the maximum dose specified in the Clinical Treatment Plan for Convalescent Plasma for Patients Recovered from Covid-19 (Trial Version 2). At present, the total amount of antiserum obtained has reached more than 100,000 ml.

   According to Professor Liu Mingyuan from the Institute of Zoonoses of Jilin University/Key Laboratory of Zoonoses Research of the Ministry of Education, judging from the current rehabilitation process of the infected, the new coronary pneumonia is a self-limited infection. Most of the people can recover by gradually producing antibodies. At the same time, the infection test of rhesus monkeys also showed that the recovered animals will not be reinfected, and the lungs have no infection or pathological changes, indicating that the antibodies obtained from the first infection have good protection and safety function. These characteristics and experimental results show the unique antiviral effect of antibodies. Anti-serum antibody therapy belongs to passive immunotherapy, especially in the outbreak of severe infectious diseases, in the absence of effective drugs and vaccines, the use of serum or plasma from recovered patients for clinical treatment has always been one of the most effective and quick methods. It has been used for more than 100 years. However, due to the limited sources of serum or plasma of recovered patients, it cannot meet the massive clinical needs during the outbreak of the disease. Therefore, it can only be used as an emergency treatment and can only be used for a small number of patients. Using large animal horses to prepare antisera for related infectious diseases in batches is the most effective and quick way to solve the shortage of serum/plasma of recovered patients. It has been widely used in the preparation and production of antisera against many infectious diseases, especially viral diseases, by countries all over the world. The medical tetanus antitoxin, anti-rabies serum, anti-botulinum toxin serum and anti-diphtheria, anthrax measles, hepatitis A, polio and other anti-serums currently used in batches are prepared by horses without exception. The preparation and production of horse antiserum is not only mature in technology but also standardized in technology. Horse anti-COVID-19 serum is to a large extent a new use of old drugs, and the only difference from other horse antisera is the difference in immune antigens. The new use of old drugs can not only avoid the many uncertainties of new drugs, but also can be applied to clinical treatment as soon as possible. It is especially important that with the continuous strengthening of immunization, the antibody titer will be higher and higher, and the dosage will be less and less. Continuously meet the massive demand during the outbreak of severe infectious diseases.

Horse anti-coronavirus serum is not only expected to be used in the treatment of severe and critical illness, but also in the treatment and preventive treatment of mild patients, suspected patients and close contacts, thereby reducing the conversion rate of severe illness and the risk of virus transmission. It also can be strategic reserve of uncertain diseases. At present, foreign countries are also stepping up relevant research.

(Li Zhaohui, Science and Education Office, Institute of Zoonoses, Jilin University/Key Laboratory of Zoonoses Research, Ministry of Education) 2020-03-29