Serological determination of rabies antibodies in vaccinated subjects

This study reports the immunological response in subjects vaccinated against rabies. Four serological methods were compared: the immunoenzymatic test with HDCV virus vaccine (EIA-V) and with purified viral glycoprotein (EIA-P), the neutralizing in vitro rapid fluorescent focus inhibition test (RFFIT) and the indirect immunofluorescent test (IFI). A concordance of 93.3% was found with RFFIT and EIA-V, 86.8% with RFFIT and EIA-P and 80.5% with RFFIT and IFI. The RFFIT is the most sensitive and specific method for rabies antibodies but more expensive and difficult. IFI recognizes late nucleocapsid antibodies but reports more false positive and negative results. The EIA-V and EIA-P methods are efficient, sensitive, specific and inexpensive for routine use to detect protective titres of antibodies above 0.5 IU/ml fifteen days after the inoculation of HDCV vaccine.