The Comparison of Immunogenicity of a Mono and a Polyvalent Rabies Vaccines by Using the National Institute of Health (NIH) Method and Measuring of Rabies Neutralizing Antibody Titre in Dogs
*Faculty of veterinary medicine, Ferdowsi University, Mashhad, Iran; **Pasteur Institute, Tehran, Iran
Two most common forms of rabies vaccine in market are monovalent and polyvalent forms. In this research, a monovalent and a polyvalent rabies vaccine, both produced by the same company, in terms of potency and induction of antirabies neutralizing antibody, were compared.
First, potency of both vaccines was evaluated via NIH method. Four different dilutions of test (mono1 and polyvalent2) and reference3 vaccines were injected to mice intraperitoneally. Each dilution was injected to 12 mice (total number of mice: 144). After seven days, injections were repeated and mice were challenged with street virus. Relative potency of each vaccine was calculated with a specified formula in the second part. Forty five dogs were randomly assigned to two groups. Group one were inoculated with the monovalent and group two were inoculated with the polyvalent vaccine. Blood sampling was done before vaccination and was repeated in days 14, 60 and 180 after vaccination. The antirabies neutralizing antibody titres were measured by RFFIT (Rapid Fluorescent Focus Inhibition Test) and antibody titres in different days of sampling were compared between groups by Independent t-test.
Calculated potencies of mono and polyvalent vaccines by NIH test were 1.5 IU/ml and 1.01 IU/ml, respectively. According to RFFIT test, the average antirabies neutralizing antibody titres for monovalent vaccine were: 0; 11.3783±6.5966, 7.4095±4.4740 and 6.9±4.3253, and for polyvalent vaccine were: 0, 6.14±7.4968, 5.1857±6.6678 and 4.55±6.0852 on days 0, 14, 16 and 180 respectively. There was seen a statistically significant difference between two groups on day 14, but no significant differences were observed between two groups on the other sampling days.
Calculated potencies of both monovalent and polyvalent test vaccines were higher than defined standard for rabies vaccines (1 IU/dose) in veterinary medicine. The mean of antirabies antibody titre in monovalent vaccine group in day 14 after vaccination was significantly higher than mean titre in polyvalent vaccine group and this difference may be related to antigenic competition mechanism. In contrast with results achieved by some other studies, we would not observe any decline of titre below the protective level, to the end of 6th month. Finally, in view of the results of NIH test and regarding to this fact that a good correlation exists between antirabies antibody titre and protective immunity, we could conclude that mentioned vaccines in terms of potency and immunogenicity have fulfilled the minimum requirements of rabies veterinary vaccines at least in a six-month period.
1. Biocan-R Batch No.266110 Bioveta Co.Scheck Republic
2. Biocan DHPPi-LR Batch No.086009, Bioveta Co.Schech Republic
3. Verorab® Aventis-France
1. Schwartkoff CL, et al. (1993), Aust. Vet. J., 70:123-126
2. Strasser A, et al. (2003), Vet. Immunology and Immunopathy, 94:113-121
3. Sage G. et al. (1993), Trans R Trop Med. Hyg.87 :593-595.