Pathogenicity and Cross Protection Studies of Local Rabies Virus Isolates with Cell Culture Anti-Rabies Vaccine Produced in Ethiopia
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Date
2014-07
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Addis Ababa Universty
Abstract
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
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Keywords
Cell Culture Vaccine, Cross protection, Local Isolate, Pathogenicity, Rabies