Establishment and validation of direct immunofluorescence method to detect rabies virus titer

Objective To establish and validate the direct immunofluorescence method to detect rabies virus (RV) titer. Methods The influences of inoculation method (stepwise and one-step inoculations) on titer of RV were evaluated by direct immunofluorescence assay. The optimized method was verified for inter-precision and specificity, and the results were compared with those of intracerebral titration in mice. Results The cells were inoculated by one-step inoculation.The variation coefficient of 14 test results by two personnel was only 0.04%. Specific fluorescence was observed only in RV but not in non-RV control viruses by the method. The determination results of virus titers by direct immunofluorescence method showed positive correlation with that by intracerebral titration in mice. There is a good linear relationship between the results of the two methods (r=0.918), with linear regression equation: y=0.907x-1.566 (t=12.80, P<0.05). Conclusion The optimized direct immunofluorescence method is precise, specific, easy to handle and time-saving, thus can be used for the quantitative determination of RV titer. Key words: Rabies virus; Direct immunofluorescence assy; Virus titer