Evaluation of an animal rabies vaccine by use of two types of potency tests

Abstract

Objective - To evaluate the potency of an inactivated animal rabies vaccine for domestic animals by use of 2 types of potency tests after challenge exposure with a laboratory standard virus or 1 of 5 viruses obtained from various wildlife species. Animals - 384 mice vaccinated twice intraperitoneally; 384 mice vaccinated once IM. Procedure - Mice vaccinated with an inactivated, adjuvanted rabies vaccine for domestic animals were challenge exposed with the common fixed challenge virus or 1 of 5 rabies viruses obtained from wild animal species (street viruses) that most commonly transmit the virus in the United States and Canada. Potency tests included 2 types of antigen extinction tests: the National Institutes of Health (NIH) test and the Centers for Disease Control test. Results - Results of both tests indicated that protection was highest against raccoon and bat viruses. Marked differences were detected in the relative potency ratios for the NIH versus the Centers for Disease Control tests, though the relative potencies themselves (against the street viruses) did not differ markedly. Conclusions - The markedly reduced potency against the street viruses indicated by the NIH test results was suggestive of an inherent bias associated with double intraperitoneal vaccination and intracerebral challenge exposure, whereas the single IM vaccination and IM challenge exposure reduced that bias.