Development of alternative approaches for In-process quality control of rabies vaccine

Abstract

The present investigation aimed on development of alternative approaches for in process quality control of rabies vaccine. Rabies virus (Pasteur Virus-11 strain) was propagated using 0.1 multiplicity of infection and harvested at 48 hrs. The harvested virus was quantified by fluorescent antibody technique (FAT) and mouse inoculation test (MIT). The results suggested that both tests are equally sensitive for virus infectivity assay. Cell culture propagated virus was inactivated by β propiolactone (BPL) and tested for any residual infectivity in bovine hamster kidney -21 (BHK-21) cells using MIT. MIT revealed absence of residual live virus in vaccine sample. Potency of test vaccine was evaluated using mice by National Institute of Health (NIH) test and compared with reference vaccine (Verorab). Potency of test vaccine was adjusted equal to reference vaccine. Findings with NIH test and rapid fluorescent focus inhibition test (RFFIT) indicated correlation of mean antibody titers with survivability of mice following virulent challenge. Therefore, RFFIT can be used as a backup test for potency estimation in conjunction with NIH test. We adopted post bite immunization schedule using rabbit with 2 different doses and assessment of the humoral immune response by RFFIT. The antibody kinetics of these animals indicated that highest antibody titers (≥300IU) were obtained after 4 initial immunizations (0, 3, 7, 14 days). However, the 5th immunization may be beneficial in cases of vaccines having low antigenic value. This is important in developing countries due to poor storage conditions on account of frequent electric failures and inadequate transportation facilities in rural areas, which may result in vaccine with poor antigenic value.