Selection and characterization of highly specific recombinant antibodies against West Nile Virus E protein.

West Nile virus is a widespread mosquito-borne human and animal pathogenic virus of increasing importance. The E protein of the viral envelope is critical for attachment and entry into the host cell and has been the target for vaccine design and small molecule inhibitors. Furthermore, the detection of anti-E IgM and IgG antibodies is widely used in serology to diagnose these infections. Here we describe a strategy for the production of recombinant antibodies against the E protein of West Nile virus for research and immunodiagnostic purposes. Initially the fast and easy protocol previously developed for the similar Tick-borne encephalitis virus has been adapted to West Nile virus E antigen production and purification. A human naïve scFv phage library has been selected on the produced antigen, identifying a panel of highly specific anti-E protein antibodies. Once produced as scFv-Fc recombinant proteins, the selected antibodies have been characterized by mapping their binding sites and by defining their affinity for the target. The impact on neutralizing virus attachment and entry has been also evaluated. The obtained results demonstrate the potential of the produced reagents for research and diagnostic applications.

A method for rapid and high-yield production of the tick-borne encephalitis virus E and DIII recombinant proteins in E. coli with preservation of the antigenic properties.

Tick-borne encephalitis virus (TBEV) is a member of the Flavivirus genus and is the main pathogenic arbovirus circulating in Europe, Russia and China. The envelope (E) protein is exposed on the viral surface and is the main antigen that is employed in diagnostic tests based on the detection of protein-specific antibodies from serum samples of infected individuals. The high degree of similarity among the E proteins of flaviviruses can, in some cases, lead to cross-reactivity and false-positive results in serological tests. Increased specificity in the detection of positive sera for different Flavivirus infections is often obtained by using a portion of the E protein, namely, the DIII domain. Different strategies and expression systems have been described for E and DIII protein production. Here, we present the optimization of an easy and fast method for TBEV E and DIII antigen production and partial purification from E. coli inclusion bodies. The antigenic properties of the produced antigens are retained, as validated by ELISAs with anti-TBEV murine sera as well as sera from infected human patients. The potential applications of both proteins as diagnostic reagents were confirmed.