Preparation and Optimization of Rift Valley Fever Antigen and Sheep Anti-RVF Antibody for Sero-Diagnosis of Rift Valley Fever

Abstract

Rift Valley fever (RVF) is a zoonotic, arthropod–borne RNA viral disease that may cause abortions in pregnant ruminants and haemorrhage in humans. RVF vaccination is currently unstable and shortlasting warranting need for safe, specific and sensitive diagnostic tools for veterinary and surveillance laboratories. The objectives were to culture RVF virus (antigen) in vitro using African monkey kidney (Vero) cells; to identify the extracted antigen using Immunofluoresce antibody (IFA) test and to optimize the antigen and RVF-positive serum sample (antibody) obtained from sheep (sample H2550) using Indirect ELISA for designing an ELISA-based diagnostic kit. The experimental study was done at KARI-Biotechnology Centre between August 2008 and December 2008. RVF virus was cultured and sub-cultured in vitro using Vero cells and identified. Indirect ELISA, modelled as a titration chequerboard, was done using the extracted antigen and antibody. The readings from the ELISA were done at an optical density (OD) of 405nm. An OD of approximately 1 was sought, this being a representation of the optimum concentrations of antigen and positive serum. The standardization study revealed the optimum concentrations of the RVF antigen and positive serum (Sheep H2550) to be 1:80 and 1:27, respectively. Validation of optimized antibody and antigen concentrations using a wide range of samples from different species and localities was recommended.

Keywords: Antigen; Indirect ELISA; Optimization; Rift Valley Fever; Sheep anti-RVF antibody.