Pathogenicity and Cross Protection Studies of Local Rabies Virus Isolates with Cell Culture Anti-Rabies Vaccine Produced in Ethiopia

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Addis Ababa Universty


Rabies is a worldwide problem, and the case is most severe in developing countries where cell culture derived anti-rabies vaccines are unaffordable or the available nervous tissue-derived vaccines are of questionable immunogenicity and may cause neurological complications. The aim of this research was to study pathogenicity and cross protection of local rabies virus isolates with Evenyl Roktincki Abelseth (ERA) based cell culture anti-rabies vaccine produced in Ethiopia. The viruses were isolated from rabid dogs’ brains and human saliva, and adapted on Swiss albino mice brain and cell lines. By titration, a minimum of 106.5TCID50/ml (in vitro) and 104.5MICLD50/0.03ml (in vivo) virus titer were obtained. For pathogenicity study, mice were inoculated intramuscularly with 250MICLD50/0.1ml of each adapted virus isolate and observed for 45 days. Only two virus isolates, human origin sululta (HOS) and dog origin (DO) caused 12.5% death. Cross protection of local isolates with ERA vaccinal strain was studied by in vivo and in vitro methods. For in vivo method, a group of mice were immunized on day zero and seven with 0.5ml (1:5 dilutions) of ERA based cell culture anti-rabies vaccine produced locally. On day fourteenth, mice were challenged with working dilution of each local isolate and one group with challenge virus standard (CVS-11), and observed for further 14 days. Based on the survival rate, high protection was recorded in CVS-11 challenged mice and low protection in all isolates; protection to HOS challenged mice was very low. In vitro test was done by fluorescent antibody virus neutralization (FAVN) test on BHK-21 cell lines. Sera from dog immunized with locally produced vaccine and OIE standard serum were incubated with working dilution of local virus isolates and CVS-11 for 48 hours in the presence of cell lines. Maximum antibody titer (2.74IU/ml) was obtained with CVS-11 challenge virus and minimum antibody titer (1.55IU/ml) was obtained with cow origin (CO) virus isolate. All locally isolated rabies virus show low antibody titer when compared to CVS-11 and PV-12. From the results of this study, it can be concluded that local isolates have some genetic variation from fixed virus strain which can affect efficacy of the candidate vaccine and potency value should be set in-terms of local virus isolates as challenge virus. Generally, the exact genetic relationship should be studied by molecular techniques and canine anti-rabies vaccine should be developed from locally isolated virus. Key Words: Cell Culture Vaccine, Cross protection, Local Isolate, Pathogenicity, Rabies



Cell Culture Vaccine, Cross protection, Local Isolate, Pathogenicity, Rabies