[Construction and detection the bioactivity of human anti-rabies virus scdsFv]

The purpose of this study is to produce new antibody molecules to neutralize the rabies virus specifically by the way of constructing and expressing the human anti-rabies virus scdsFv (disulfide stabilized single chain antibody) gene, and characterizing its bioactivity.

We obtained the sequence of variable region of heavy chain (VH) and variable region of light chain (VL) of RV monoclonal antibody SO57 from GenBank, and it respectively mutated into cysteine in the gene loci VH44 and VL100. The scdsFv gene was synthesized and inserted into a prokaryotic expression vector pET22b(+). Purified inclusion body scdsFv proteins were obtained by Ni-NTA His Bind Resin affinity chromatography and identified by SDS-PAGE gel and Western blot assay. The binding activity of scdsFv was identified by ELISA and mouse brain tissues infected with rabies virus CVS strain. The relative affinity of scdsFv was measured by ELISA using thiocyanate elution. The capacity of the scdsFv to neutralize the rabies virus CVS strains was determined by fluorescent antibody virus neutralisation test (FAVN). The fusion proteins neutralized the CVS strain in a standard in vivo neutralized assay where the virus was incubated with the scdsFv molecules before intracranial inoculation in mice.

The fragment genes of scdsFv to rabies virus were constructed successfully. ScdsFv protein was expressed in E. coli with approximate molecular weight of 30.0 kDa, which could be recognized by anti-His mAb. ELISA results demonstrated that scdsFv could bind antigen specificity. It was found that the strong reactivity of scdsFv to the smear of RV infected mouse-brain was demonstrated by IFA. As determined by FAVN with a reference serum, the titer of scdsFv was 41 IU/mL. In addition, scdsFv could be 55.6% protection of mice against lethal challenge with rabies virus CVS.

The scdsFv can bind antigen specificity and has neutralization capacity to the virus in vitro and in vivo. The anti-rabies scdsFv is potential for application in rabies post-exposure prophylaxis.