Chimeric Antibody 14D5 Protects Mice against the Far-Eastern, Siberian, and European Tick-borne Encephalitis Virus

Tick-borne encephalitis virus (TBEV), belonging to the Flaviviridae family, is the most significant pathogen transmitted by Ixodes ticks and causing one of the most severe human neuroinfections. In Russia, serum immunoglobulin produced from the donor blood is currently used for post-exposure prophylactic and therapy of tick-borne encephalitis virus. However, it is known that preparations obtained from donated blood have certain disadvantages, and therefore development of novel preparations for post exposure prophylaxis and therapy of tick-borne encephalitis is required. To develop an alternative preparation, which does not include donor blood, a chimeric antibody ch14D5 against glycoprotein E of TBEV was constructed. This study was aimed to investigate protective efficacy of the chimeric antibody ch14D5 against the Far-Eastern, Siberian, and European subtypes of TBEV in in vivo experiments. A peripheral mouse model of tick-borne encephalitis was used in this study: the chimeric antibody ch14D5 was administrated intravenously in mice one day after their intraperitoneal infection with TBEV strains Sofjin, Vasilchenko, and Absettarov. Anti-TBEV serum immunoglobulin was used as a control preparation, which was administered in the same way. Protective efficacy of the chimeric antibodies 14D5 was assessed using the log-rank test. In the study, the presence or absence of antibody-dependent enhancement of infection (ADE) was examined when mice, infected with different subtypes of the TBEV, got the antibody ch14d5. Obtained results demonstrated high efficacy of the ch14D5 antibody in post-exposure prophylaxis of the disease in mice infected with any of the used TBEV strains, as well as the absence of ADE. It was shown that protective efficacy of antibody ch14D5 is higher than that of the anti-TBEV serum immunoglobulin, and antibody ch14D5 could be used for development of a therapeutic preparation for post-exposure prophylaxis.