Background: Rabbit viral haemorrhagic disease (RVHD) is characterized by high mortality in adult rabbits causing severe economic losses. Vaccination against RHDV is the main preventive method.
Objective: The current study was conducted to investigate the immuno-enhancing effects of some Montanide incomplete seppic adjuvants (ISAs) incorporated within inactivated RHDV vaccine on vaccinated rabbits in comparison to the currently produced aluminum hydroxide (Al (OH)3) gel adjuvanted vaccine. Methods: Four experimental batches of inactivated RHDV oil emulsified (OE) vaccines were prepared using 4 different types of Montanide ISAs (SEPPIC, France) (ISA 70 VG, ISA 71 VG as water-in-oil emulsion (W/O), ISA 206 VG as water-in-oil-in-water emulsion (W/O/W), and ISA 760 VG as water-in-polymer emulsion (W/P)) in addition to another batch adjuvanted with Al (OH); gel. The efficacy of the prepared vaccines was studied in five groups of vaccinated rabbits. The efficacy was based on humoral immune response measured by HI test and ELISA in addition to the resistance to challenge with virulent RHDV.
Results: All of the prepared vaccines induced specific RHDV-antibodies, with variable titers, detected from the 1st week post vaccination (WPV) in vaccinated rabbits. The induced RHDV-antibody titers increased to reach their highest level in 3rd month post vaccination (MPV) for all groups except groups (2) (vaccinated with Montanide ISA 70 adjuvanted vaccine) and (5) (vaccinated with Montanide ISA 760 adjuvanted vaccine) in which the maximum level was attained at 6th WPV and 4th MPV respectively. The vaccinated rabbits resisted the challenge against virulent RHDV as early as at the 3rd WPV and at 6th MPV with 100% protection in contrary to unvaccinated group in which all rabbits get died (0% protection). Conclusion: Montanide ISAs used in this study could be used to produce inactivated RHDV OE vaccine and found to be more preferable than Al (OH)3 gel in enhancing the immune response of vaccinated rabbits achieving higher and longer term protective immune responses with preference of the following order, Montanide ISA 70, 206, 760 and finally 71.