History repeats itself: horse originated hyperimmune sera production against SARS CoV-2

Background/aim: SARS-CoV-2 disease was announced as a pandemic by The World Health Organization in early 2020. It is still threatening the world population. Here, we aimed to produce hyperimmune sera that contain immunoglobulin G and F(ab')(2) fragments sourced from horse antibodies as an urgent response to the pandemic. Materials and methods: SARS-CoV-2 was produced and inactivated with three different methods [formaldehyde (FA), formaldehyde, and binary ethylene amine (FA + BEI), and heat treatment]. After in vitro inactivation control, immunogens were mixed with Freund's adjuvant, thereafter horses (n: 2 for FA, 4 for FA + BEI, 2 for heat inactivation) and New Zealand rabbits (n: 6 for FA, 6 for FA + BEI, 6 for heat inactivation) were immunized four times. Neutralizing antibody levels of the sera were measured at the 4th, 6th, and 8th weeks. When the antibodies were detected at the peak level, plasma was collected from horses and hyperimmune sera procured after the purification process. Results: Horses and rabbits produced highly neutralizing antibodies against the SARS-CoV-2 in FA and FA + BEI inactivation groups, foreign proteins were removed effectively after purification. Conclusion: This study presents a profitable practice to develop specific antisera in horses against SARS-CoV-2 for emergency and low-cost response. In further studies, new purification methods can be used to increase the efficiency of the final product.