Boosting effect of purified chick embryo cell rabies vaccine using the intradermal route in persons previously immunized by the intramuscular route or vice versa.

BACKGROUND: At present, in the event of re-exposure to rabies, 2 booster doses are recommended for people who have been previously vaccinated with cell culture rabies vaccines by the conventional intramuscular route. As the intradermal route of vaccination is likely to be introduced in the future, we investigated the immune response to a cell culture rabies vaccine after crossing over from the intramuscular to the intradermal route and vice versa. METHODS: Twenty healthy adult volunteers who had received a primary course of rabies vaccination with purified chick embryo cell rabies vaccine by either the intramuscular (n = 10) or intradermal (n = 10) route received booster vaccination with the same vaccine by the alternative route. The regimen used was 0.1 ml of vaccine by the intradermal route at two sites (deltoid area) for the intramuscular group, or 1 ml of vaccine by the intramuscular route (deltoid muscle) to the intradermal group on days 0 and 3. RESULTS: There was a 15-fold rise in the rabies virus neutralizing antibody response both by the intradermal and intramuscular routes of booster vaccination (p < 0.0001). Thus, the change of route of purified chick embryo cell booster vaccination did not alter the anamnestic immune response to the vaccine. No side-effects were observed after vaccination with either of the routes. CONCLUSION: Purified chick embryo cell vaccine was found to be safe and immunologically efficacious following booster vaccination after cross-over from the intradermal to the intramuscular route and vice versa.

Development and evaluation of an enzyme immunoassay for rapid diagnosis of rabies in humans and animals.

The presently advocated tests for rapid diagnosis of rabies such as fluorescent antibody test (FAT) is expensive and requires expertise to carry out and interpret the results. In this study we have developed and evaluated a simple enzyme immuno-assay (EIA) to detect rabies antigen in the brain specimens of animals and humans. We have also evaluated the utility of this test in ante mortem diagnosis of human rabies. The brain homogenates of suspected rabid animals (n=250), humans (n=16) and clinical samples like saliva (n=16) and cerebrospinal fluid (CSF, n=16) applied on to ELISA plates coated with rabies antinucleoprotein antibody and the absorbed rabies nucleoprotein antigen was detected using biotinylated anti-nucleoprotein antibody followed by treatment with streptavidin peroxidase conjugate and colour development with OPD. Rabies infected and normal mouse brain homogenates were used as positive and negative controls respectively. The results of this test was evaluated with fluorescent antibody technique (for brain samples) and mice inoculation test (for saliva and CSF samples). A distinct dark brown color was seen in positive control and all positive samples and there was no color development in negative control and samples. The concordance between FAT and EIA was 98.4%. With brain samples, 83.3% with saliva and 91.6% with CSF samples. The specificity of the test was found to be 100%. It can be concluded that the EIA described here is a sensitive, specific and rapid test for post mortem diagnosis of rabies in animals and humans. The utility of this test for ante mortem diagnosis of rabies needs to be further evaluated.