Title : Adaptation of local rabies virus isolates to high growth titer to develop vaccine strain in Ethiopia
Abstract:
Rabies is 100% fatal zoonotic disease with acute encephalitis in humans and animals. 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 complications. The objective of this research was to adapt local rabies virus isolates on cell lines and mice brain, and investigate their attenuation through intramuscular inoculation in order to develop vaccine strain locally.
Methods: Local viruses were isolated from rabid dogs’ brain and human saliva and adapted to Swiss albino mice brain and cell lines (BHK-21 and Vero) by several blind passages to increase viral titer. The viral titer was studied by titration at each blind passage both in vivo and in vitro study. For pathogenicity study, mice were inoculated intramuscularly with 250MICLD50/0.1 ml of each adapted virus isolates and observed for 45 days.
Results: By titration, a minimum of 10 6.5 TCID50/ml (in vitro) and 10 4.5 MICLD50/0.03 ml (in vivo) virus titer were obtained after 20 blind passages. Pathogenicity study result indicate that only two virus isolates, human origin sululta (HOS) and dog origin (DO) caused 12.5% death, 2 out of 14 deaths.
Conclusion: A significant increase in viral titer was observed during in-vitro virus propagation using cell lines. The death in intramuscular inoculation may indicate the two viruses have a rabies-related origin within the phylogroup. The adaptation of these viruses to mice brain and cell lines has significantly increased their infectivity titer, which in turn decrease virulence during intramuscular inoculation. These isolates have been utilized in the production of cell culture vaccines, effectively preventing rabies in both humans and animals. This significant contribution aligns with the one health approach and supports the goal of eliminating rabies by 2030. This study will have significant contribution for one health work force by availing rabies vaccine for human and mass vaccination of dog population in effort to eradicate rabies. This will have significant contribution in strengthening one health work force in rabies elimination by securing effective vaccine supply.
Keywords: Adaptation; Cell culture vaccine; Local virus isolates; Pathogenicity; Virus titer
