Development and evaluation of NS1 specific monoclonal antibody based antigen capture ELISA and its implications in clinical diagnosis of West Nile virus infection

Background West Nile virus (WNV) is a neurotropic flavivirus that causes viral encephalitis. Recent epidemics of WNV around the world have been associated with significant rates of mortality and morbidity in humans. The early confirmatory diagnosis of WNV infection is important for timely clinical management and epidemiological control in areas where multiple flaviviruses are endemic. Objective The aim of this study is to develop an monoclonal antibody based antigen capture ELISA for early confirmatory diagnosis of WNV infection with high degree of specificity and sensitivity having no cross reactivity with any of the closely related members of other circulating viruses. Study design The gene coding for the NS1 protein of WNV was cloned and expressed in pET-28a expression vector. Purified recombinant protein was then utilized for generation of mice monoclonal antibody (Mab) and hyper immune sera (HIS) in rabbit. The sandwich ELISA was developed using the rabbit HIS and mice Mab as capture and detector antibody respectively and the results were compared with real time RT-PCR by evaluating 105 suspected clinical samples. Results The comparative evaluation of the sandwich ELISA with real time RT-PCR revealed 97% concordance with sensitivity and specificity of 90% and 98% respectively. Conclusion The WN NS1 antigen was detectable in the blood from the first day up to day 9 after the onset of symptoms. The higher sensitivity and specificity of this monoclonal Antibody based sandwich ELISA makes it useful for early diagnosis of WN infection in endemic areas during outbreaks.