Development and evaluation of an anti-rabies virus phosphoprotein-specific monoclonal antibody for detection of rabies neutralizing antibodies using RFFIT

Background: rabies is a major public health problem with a fatality rate close to 100%; however,complete prevention can be achieved through pre- or post-exposure prophylaxis. the rapid fluorescent focus inhibition test (rffit) is one of the recommended testing methods to determine the production of neutralizing antibodies after vaccination. here,we report the development of a new monoclonal antibody (mab) designed to react specifically with rabies virus (rabv) phosphoprotein (p protein),and the evaluation of its applicability to the rffit and its effectiveness as a diagnostic reagent for human rabies. methodology/principal findings: the mab kgh p 16b8 was produced to target the p protein of the korean kgh rabv strain. an indirect immunofluorescence assay (ifa) was conducted to detect various strains of rabv in various cell lines. alexa-conjugated kgh p 16b8 (16b8-alexa) was developed for the rffit. the ifa test could detect rabv up to a 1:2,500 dilution,with a detection limit comparable to that of a commercial diagnostic reagent. the sensitivity,specificity,positive predictive value,and negative predictive value of the rffit using 16b8-alexa in 414 clinical specimens were 98.67%,99.47%,99.55%,and 98.42%,respectively. the results of the rffit with 16b8-alexa were strongly correlated with those obtained using an existing commercial diagnostic reagent (r = 0.995,p<0.001). conclusions/significance: the mab developed in this study shows high sensitivity and specificity,confirming its clinical utility with the rffit to measure the rabies neutralizing antibody titer and establish a diagnosis in human. thus,16b8-alexa is expected to serve as an alternative diagnostic reagent that is widely accessible,with potentially broad applications beyond those of the rffit in korea. further studies with 16b8-alexa should provide insight into the immunological mechanism of the p protein of korean rabv. © 2017 um et al.