Establishment and Preliminary Application of a Rapid Fluorescent Focus Inhibition Test (RFFIT) for Rabies Virus

The World Health Organization (WHO) standard assay for determining levels of the rabies virus neutralization antibody (RVNA) is the rapid fluorescent focus inhibition test (RFFIT), which is used to evaluate the immunity effect after vaccination against rabies. For RFFIT, CVS-11 was used as the challenge virus, BSR cells as the adapted cells, and WHO rabies immunoglobulin (WHO STD) as the reference serum in this study. With reference to WHO and Pasteur RFFIT procedures, a micro-RFFIT procedure adapted to our laboratory was produced, and its specificity and reproducibility were tested. We tested levels of RVNA in human serum samples after immunization with different human rabies vaccines (domestic purified Vero cell rabies vaccine (PVRV) and imported purified chick embryo cell vaccine (PCECV)) using different regimens (Zagreb regimen and Essen regimen). We analyzed the levels of RVNA, and compared the immune efficacy of domestic PVRV and imported PCECV using different immunization regimens. The results showed that the immune efficacy of domestic PVRV using the Zagreb regimen was as good as that of the imported PCECV, but virus antibodies were generated more rapidly with the Zagreb regimen than with the Essen regimen. The RFFIT procedure established in our laboratory will enhance the comprehensive detection ability of institutions involved in rabies surveillance in China.

Comparison of RFFIT Tests with Different Standard Sera and Testing Procedures

The World Health Organization （WHO） standard assay for determining antibody level is the rapid fluorescent focus inhibition test （RFFIT） and is used to determine the degree of immunity after vaccination against rabies. To compare the difference in RFFIT results between the laboratories of The National Institute of Infectious Disease in Japan （NIID） and the Chinese Centre for Disease Control （CCDC） as well the influence of the choice of standard serum （STD） for the detection, the two laboratories detection methods were simultaneously manipulated by RFFIT. The reference serums used in NIID and the WHO standard serum used in CCDC were compared in the same RFFIT detection to determine the titer of four sera samples C1, Sl, S2 and S4 in parallel, and the titers of the detected sera samples were calculated using the standard formula for neutralizing antibody titer. No significant difference was found in RFFIT methods from the two laboratories and the RFFIT testing procedures of the two laboratories have good consistency. However, different titers were obtained with the tentative internal standard serum （TI-STD） produced by adjusting to 2.0 IU of WHO standard serum in NIID and the WHO STD. The titer determined with the TI-STD was higher than that determined with WHO STD, This difference appears to be significant and requires further investigation

The fourth case of rabies caused by organ transplantation in China

In January 2019,the fourth rabies case caused by organ transplantation was noticed in China,with the conditions of one per year for the recent four years.Different from the previous cases,there were no definite epidemiological histories of exposure or rabies-related symptoms from this patient.This case strongly supports the call for the legislation of establishing a national-level management that will incorporate the screening programs on donors prior to the practice of organ transplantation to reduce the risks on rabies caused by organ transplantation.