Monoclonal Antibodies to the Recombinant Protein VP7 of Bluetongue Virus

Abstract

Bluetongue, or catarrhal fever of sheep, is a viral vector-borne infection of ruminants, which is one of the economically significant arbovirus infections of animals. It is transmitted by blood-sucking insects of the Culicoides genus. Viral protein VP7 is a group-specific core protein of the virus, conservative for all known serotypes, and therefore represents the most suitable target for creation of diagnostic tests. To develop an immunochemical method for detecting viral infection, a panel of high-affinity monoclonal antibodies to VP7 has been obtained. The N-terminal fragment of VP7 expressed in E. coli and inactivated viral particles were used as immunogens. The resulting monoclonal antibodies are useful for detecting the virus in infected cells. As a species-specific antigen, a recombinant TrxA‑VP7_a protein has been created that contains spatial epitopes similar to those of the native viral antigen. With its help, promising antibodies were selected for diagnostics of the disease by competitive enzyme-linked immunosorbent assay, which allows the detection of specific antibodies to bluetongue virus in the sera of infected animals. Using competitive solid-phase ELISA, it has been shown that antibodies that interact most effectively with the TrxA-VP7_a protein (Bt14, Bt15, Bt18, Bt26, Bt33, Bt34, and Bt35) recognize close or overlapping VP7 epitopes. The interaction with the antigen of almost all the antibodies obtained was inhibited by reference specific sera against the bluetongue virus of 24 serotypes. The monoclonal antibody Bt14 showed maximum ability to block the interaction of VP7 with specific sera against 24 bluetongue virus serotypes. Thus, the resulting panel of monoclonal antibodies to VP7 of the bluetongue virus can be used to detect viral infection, as well as a component of kits for serological diagnosis of the disease.