Construction and Production in Pichia Pastoris Fluorescent Single-Chain Antibody Fragments for Rapid Diagnosis of Rabies Virus

In most modern laboratories, rabies is usually diagnosed by the detection of viral antigen in the brain by using a direct Fluorescent Antibody Test (FAT) [1]. The test was first used in 1958, and it became a routine diagnostic method in the 1970s [2]. It is the test currently recommended by the WHO Expert Committee on Rabies [1] and OIE for rabies diagnostics both in animals and humans. The FAT is carried out on brain smears by the application of fluorescein-isothiocyanate labelled antirabies antibodies to the smear followed by incubation and washing steps. The FAT has a sensitivity of 99.78% when carried out in a laboratory by experienced workers [3]. The detection of the rabies antigen using fluorescent antibody conjugate is greatly used for various purposes: i) detection of rabies infection in nervous tissue, ii) conformation of infection in cell culture, and iii) during titration of antibody by neutralization on cellular culture. However, the FAT requires expensive reagents and instruments, and well-trained technicians. In addition, the fluorescent isothiocyanate (FITC)-conjugated antinucleoprotein is commercialised by a limited number of laboratories and has enough high cost. This drawback constitutes a major handicap to intensify the epidemiological monitoring in certain countries in which the rabies is a public health problem and economic means are limited.