Evaluation of a Mouse Test for the Standardization of the Immunizing Power of Anti-Rabies Vaccines

Abstract

The Swiss strain of white mice from different dealers gave uniform results. 2-month-old mice developed greater immunity than those aged 1 month or 6 months; [female][female] greater than [male][male]. At least 4 mice tested at each dilution of test dose were necessary for consistent results. The dose of vaccine had to be at least 5 times the relative human dose by wt. to give a definite immunity. Ten daily doses of vaccine gave the greatest immunity, 5 doses every second day next, and one dose gave no immunity when tested on the 10th day. Comparable protection was demonstrated in vaccinated mice to fixed and street virus intracerebrally. Cross protection of fixed strains was shown. The 14th day was the earliest at which definite immunity was demonstrable when vaccine was given every 2d day. In duplicate tests the results were consistent with those vaccines giving a high degree of immunity and variable in those giving borderline immunity. Vaccine showing high protection in the mouse test also protected guinea-pigs infected with street virus then immunized. The recommended technic for testing: 30 [female] Swiss mice 1 month of age are given 0.25 cc of a 0.5% vaccine brain emulsion intraperitoneally every other day for 6 doses. The test dose of homologous fixed virus is given intracerebrally in 10-fold dilutions from 10-1 to 10-5 on the 4th day to 6 mice for each dilution. 6 control mice receive 10-5, 10-8 and 10-7 dilutions to determine the M. L. D. Mice are observed for 21 days and 50% end-points are detd. Protection against 1000 M. L. D. is considered the minimum requirement of an efficient rabies vaccine.